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  • Articles: DFG German National Licenses  (3,456)
  • 1995-1999  (3,456)
  • 1985-1989
  • 1999  (21)
  • 1997  (3,435)
  • Polymer and Materials Science  (3,277)
  • Genetics
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  • Articles: DFG German National Licenses  (3,456)
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  • 1995-1999  (3,456)
  • 1985-1989
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  • 1
    Electronic Resource
    Electronic Resource
    Linkage analysis of candidate myelin genes in familial multiple sclerosis (1999)
    Springer
    Neurogenetics 2 (1999), S. 155-162 
    Details
    ISSN: 1364-6753
    Keywords: Key words Multiple sclerosis ; Genetics ; Myelin basic protein ; Myelin oligodendrocyte glycoprotein ; Proteolipid protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: ABSTRACT Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system. A complex genetic etiology is thought to underlie susceptibility to this disease. The present study was designed to analyze whether differences in genes that encode myelin proteins influence susceptibility to MS. We performed linkage analysis of MS to markers in chromosomal regions that include the genes encoding myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG), oligodendrocyte myelin glycoprotein (OMGP), and myelin oligodendrocyte glycoprotein (MOG) in a well-characterized population of 65 multiplex MS families consisting of 399 total individuals, 169 affected with MS and 102 affected sibpairs. Physical mapping data permitted placement of MAG and PLP genes on the Genethon genetic map; all other genes were mapped on the Genethon genetic map by linkage analysis. For each gene, at least one marker within the gene and/or two tightly linked flanking markers were analyzed. Marker data analysis employed a combination of genetic trait model-dependent (parametric) and model-independent linkage methods. Results indicate that MAG, MBP, OMGP, and PLP genes do not have a significant genetic effect on susceptibility to MS in this population. As MOG resides within the MHC, a potential role of the MOG gene could not be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100480050076
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  • 2
    Electronic Resource
    Electronic Resource
    The neurofibromatoses. An overview (1999)
    Springer
    Italian journal of neurological sciences 20 (1999), S. 89-108 
    Details
    ISSN: 1126-5442
    Keywords: Key words Neurofibromatosis ; Nf1 ; Nf2 ; Mosaic/segmental neurofibromatosis ; Variants ; Classification ; Neurological manifestations ; Genetics ; Childhood ; Adulthood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The last two decades have seen clinical and molecular delineation of the different forms of neurofibromatosis. Differentiation of these forms is not just an academic exercise: their natural history, management and genetic counselling are quite different. Of the numerical classifications of neurofibromatosis proposed in the past, only neurofibromatosis type 1 (Nf1) and neurofibromatosis type 2 (Nf2) are now well delineated clinically and have been shown to be distinct at the molecular level. For both forms of neurofibromatosis, patients with clinical generalised disease have been demonstrated to be mosaic at the molecular level, and features of segmental or mosaic Nf1 and Nf2 have been delineated. Other reported forms of neurofibromatosis are rarer; they include Watson syndrome, hereditary spinal neurofibromatosis, familial intestinal neurofibromatosis, autosomal dominant café-au-lait spots alone, autosomal dominant neurofibromas alone, and schwannomatosis, the latter believed to be a variant of Nf2. Further delineation is neeeded for individuals having overlapping features of Noonan's syndrome and neurofibromatosis (the so-called Noonan/neurofibromatosis syndrome) and the syndrome of “multiple naevi, multiple schwannomas and multiple vaginal leiomyomas”. In this article we review the forms of neurofibromatosis which we believe are true clinical entities. Particular attention is given to the neurological manifestations of neurofibromatosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100720050017
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  • 3
    Electronic Resource
    Electronic Resource
    Insulin resistance and impaired insulin secretion due to phosphofructo-1-kinase-deficiency in humans (1999)
    Springer
    Journal of molecular medicine 77 (1999), S. 96-103 
    Details
    ISSN: 1432-1440
    Keywords: Key words Diabetes ; Genetics ; Phosphofructokinase ; Glycogenosis ; NIDDM ; PFK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The etiology of non-insulin-dependent diabetes mellitus (NIDDM) is usually explained as a combination of peripheral insulin resistance and impaired beta-cell function. Phosphofructo-1-kinase (PFK1) is a rate limiting enzyme in glycolysis, and its muscle subtype (PFK1-M) deficiency leads to an autosomal recessively inherited disorder known as glycogenosis type VII or Tarui’s disease. It was evaluated whether PFK1-M deficiency leads to NIDDM in humans. A core family of four was evaluated for PFK1-M deficiency by DNA- and enzyme-activity-analyses. All members underwent oral and intravenous glucose tolerance test (oGTT/ivgtt), as well as an insulin sensitivity test (IST) using octreotide. Results: Father (46 years, BMI 22.4 kg/m2) and older son (19 years, BMI 17.8 kg/m5) showed homozygous PFK1-M deficiency, while mother (47 years, BMI 28.4 kg/m5) and younger son (13 years, BMI 16.5 kg/m5) were shown to be heterozygously PFK1-M-deficient on enzyme activity levels. DNA analysis revealed an exon 5-missense-mutation at one allele of all four members, and an exon 22-frameshift-mutation at the other allele of the two homozygously affected individuals. By oGTT the father showed impaired glucose tolerance, and the mother clinical diabetes. By ivGTT both parents and the older son had a decreased first phase insulin secretion, and a diminished glucose disappearance rate. The IST showed marked insulin resistance in both parents and the older son, and moderate resistance in the younger son, previously not described. Conclusion: PFK1-M-deficiency leads to a metabolic state typical for early NIDDM in homozygously affected humans, especially concerning insulin resistance and loss of first phase beta-cell insulin secretion, and may contribute to the manifestation of NIDDM in a subgroup of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050311
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  • 4
    Electronic Resource
    Electronic Resource
    Erbliche Ursachen und Risikofaktoren der Alzheimer-Krankheit (1999)
    Springer
    Der Nervenarzt 70 (1999), S. 195-205 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Alzheimer-Krankheit ; Genetik ; Risikofaktoren ; Genetische Beratung ; Key words Alzheimer’s disease ; Genetics ; Risk factors ; Genetic counseling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A multifactorial etiology underlies the majority of cases of Alzheimer’s disease (AD). Both ill-defined environmental and genetic factors contribute to the development of the disease. Allele ɛ4 of ApoE is a genetic risk factor. Its presence increases the risk of developing AD. However, presence of e4 is neither necessary nor sufficient for the disease to arise. Apart from the common multifactorial forms of the disease, there are rare variants which are inherited as Mendelian traits. To date three genes are known that can be mutated in these rare forms of AD. Of these, mutations in the gene presenilin 1 on chromosome 14 are most frequent. In addition, mutations in the gene presenilin 2 on chromosome 1 and in the amyloid precursor protein gene (APP on chromosome 21) occur in autosomal dominant AD. This article reviews our present knowledge of the genetics of AD and discusses its relevance for patients with AD and their relatives.
    Notes: Zusammenfassung Der Großteil der Fälle von Alzheimer-Krankheit (AK) hat eine multifaktorielle Ätiologie. Das bedeutet, bisher nicht genauer bekannte Umwelteinflüsse und genetische Faktoren spielen bei der Entwicklung der Krankheit eine wesentliche Rolle. Von seiten der Genetik unterscheidet man bei der AK gegenwärtig genetische Risikofaktroren und Mutationen. Der einzige bisher gesicherte genetische Risikofaktor ist das Allel ɛ4 des Gens für Apolipoprotein E auf Chromosom 19. Dieses Allel erhöht die Wahrscheinlichkeit, an der AK zu erkranken, ist jedoch weder eine notwendige noch eine hinreichende Bedingung. Neben den häufigen Formen mit multifaktorieller Ätiologie kommen seltene Varianten der Krankheit vor, die nach Mendelschen Regeln vererbt werden. Bisher sind 3 Gene bekannt, die bei diesen seltenen, in der Regel früh auftretenden und autosomal dominant vererbten Formen mutiert sein können. Am häufigsten findet sich bei den autosomal-dominanten Fällen eine Mutation im Gen präsenilin 1 auf Chromosom 14, seltener liegen Mutationen im Gen präsenilin 2 auf Chromosom 1 und im Gen des Amyloid- Vorläuferproteins auf Chromosom 21 vor. In diesem Beitrag geben wir eine Übersicht über gegenwärtige Befunde zur Genetik der AK und diskutieren die Bedeutung dieses Wissens für Patienten und deren Verwandte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050423
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  • 5
    Electronic Resource
    Electronic Resource
    Genetik schizophrener Störungen Neuere Konzepte und Befunde (1999)
    Springer
    Der Nervenarzt 70 (1999), S. 955-969 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Schizophrenie ; Genetik ; Schizophrenes Spektrum ; Kopplungsuntersuchungen ; Assoziationsuntersuchungen ; Key words Schizophrenia ; Genetics ; Schizophrenia spectrum ; Linkage studies ; Association studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Schizophrenia is a genetic complex disease as it does not follow monogenic transmission while non-familial environmental factors have a strong additional impact. A heterogenous, continuous phenotype is transmitted in families which can now be more precisely characterized. Genes coding for proteins with presumed pathophysiological relevance are apparently not playing a major causal role. However, in the last three years several (currently seven) candidate regions have been identified in a replicable manner by linkage studies. These regions are likely to host susceptibility genes for schizophrenia, but none of them has been identified up to now. Given these findings, polygenic transmission has now become very likely. The candidate regions are currently being narrowed down by various promising techniques.
    Notes: Zusammenfassung Die Schizophrenie gehört zu den genetisch komplexen Erkrankungen, die keinem monogenen Erbgang folgen und bei denen auch nichtfamiliäre Umgebungsfaktoren eine wichtige Rolle spielen. Dabei wird intrafamiliär ein heterogener, quantitativ variierender Phänotyp übertragen, der zunehmend genauer charakterisiert werden kann. Keines der bekannten Gene mit vermuteter pathophysiologischer Relevanz spielt nach den bisherigen Erkenntnissen eine substantielle Rolle. In den vergangenen drei Jahren ist es aber erstmals durch Kopplungsuntersuchungen gelungen, mehrere replizierbare Kandidatenregionen (derzeit sieben) auf dem Genom zu identifizieren, in denen vermutlich Suszeptibilitätsgene für Schizophrenie liegen. Keines dieser Gene wurde jedoch bislang identifiziert. Mit diesen Befunden ist eine polygene Übertragung der Schizophrenie sehr wahrscheinlich geworden. Verschiedene Techniken zur Eingrenzung der Kandidatenregionen werden derzeit erfolgreich angewandt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050524
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  • 6
    Electronic Resource
    Electronic Resource
    A mutation at codon 279 (N279K) in exon 10 of the Tau gene causes a tauopathy with dementia and supranuclear palsy (1999)
    Springer
    Acta neuropathologica 98 (1999), S. 62-77 
    Details
    ISSN: 1432-0533
    Keywords: Key words Frontotemporal dementia ; Genetics ; Progressive supranuclear palsy ; Tauopathy ; Exon ; amplifcation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently intronic and exonic mutations in the Tau gene have been found to be associated with familial neurodegenerative syndromes characterized not only by a predominantly frontotemporal dementia but also by the presence of neurological signs consistent with the dysfunction of multiple subcortical neuronal circuitries. Among families, the symptomatology appears to vary in quality and severity in relation to the specific Tau gene mutation and often may include parkinsonism, supranuclear palsies, and/or myoclonus, in addition to dementia. We carried out molecular genetic and neuropathological studies on two patients from a French family presenting, early in their fifth decade, a cognitive impairment and supranuclear palsy followed by an akinetic rigid syndrome and dementia. The proband died severely demented 7 years after the onset of the symptoms; currently, his brother is still alive although his disease is progressing. In both patients, we found a Tau gene mutation in exon 10 at codon 279, resulting in an asparagine to lysine substitution (N279K). Neuropathologically, widespread neuronal and glial tau accumulation in the cortex, basal ganglia, brain stem nuclei as well as in the white matter were the hallmark of the disease. These deposits were shown by immunohistochemistry and immunoelectron microscopy, using a battery of antibodies to phosphorylation-dependent and phosphorylation-independent epitopes present in multiple tau regions. In the neocortex, tau-immunopositive glial cells were more numerous than immunopositive neurons; the deeper cortical layers as well as the white matter adjacent to the cortex contained the largest amount of immunolabeled glial cells. In contrast, some brain stem nuclei contained more neurons with tau deposits than immunolabeled glial cells. The correlation of clinical, neuropathological and molecular genetic findings emphasize the phenotypic heterogeneitiy of diseases caused by Tau gene mutations. Furthermore, to test the effect of the N279K mutation and compare it with the effect of the P301L exon 10 mutation on alternative splicing of Tau exon 10, we used an exon amplification assay. Our results suggest that the N279K mutation affects splicing similar to the intronic mutations, allowing exon 10 to be incorporated more frequently in the Tau transcript.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010051052
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  • 7
    Electronic Resource
    Electronic Resource
    Management of mantle cell lymphoma (1999)
    Springer
    Annals of hematology 78 (1999), S. 485-494 
    Details
    ISSN: 1432-0584
    Keywords: Key words Mantle cell lymphoma ; Classification ; Pathology ; Prognosis ; Immunology ; Genetics ; Antineoplastic agents ; Combined ; Therapeutic use ; Radiotherapy ; Hematopoietic stem cell transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002770050545
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  • 8
    Electronic Resource
    Electronic Resource
    Why is acute leukemia more common in males? A possible sex-determined risk linked to the ABO blood group genes (1999)
    Springer
    Annals of hematology 78 (1999), S. 233-236 
    Details
    ISSN: 1432-0584
    Keywords: Key words Acute leukemia ; Genetics ; Sex ; ABO Blood group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Acute leukemia is more common in males at almost every age, and this fact remains unexplained. A study was carried out in northeast peninsular Malaysia, where the population is predominantly Malay, to examine whether there was a difference in ABO blood group distribution between males and females with acute leukemia (AL). The ABO blood groups of 109 male and 79 female patients with AL (98 ALL, 90 AML) were compared with those of 1019 controls. In the control population, 39.7% were group O. Among males with AL, 39.4% were group O, whereas among females with AL, the proportion was 24.1% (p=0.03). The same trend to a lower proportion of group O among females was seen if the group was divided into adult/pediatric or lymphoblastic/myeloblastic groups, though these differences were not statistically significant. If these findings can be confirmed, they suggest the presence of a "sex-responsive" gene near to the ABO gene locus on chromosome 9, which relatively protects group O women against AL, at least in our population. The existence of such a gene might also partly explain why acute leukemia, and possibly other childhood cancers, are more common in males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002770050507
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of potential phosphorylation sites in human T cell leukemia virus type 1 Tax (1999)
    Springer
    Journal of biomedical science 6 (1999), S. 206-212 
    Details
    ISSN: 1423-0127
    Keywords: Tax ; HTLV-1 ; Trans-activation ; Phosphorylation ; Mutagenesis ; Transcription ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The human T cell leukemia virus type 1 (HTLV-1) Tax is a phosphoprotein, however, the contribution of phosphorylation to Tax activity is unknown. Previous studies have shown that phosphorylation of Tax occurs on serine residue(s), within one tryptic fragment, in response to 4β-phorbol-12β-myristate-13α-acetate, in both mouse and human cells. Studies were conducted in multiple cell lines to identify the specific phosphorylated serines as a prelude to functional analysis. The phosphorylation pattern of Tax was found to be different in 293T and COS-7 cells in comparison with MT-4 and Px-1 cells. However, one tryptic fragment remained consistent in comigration analyses among all cell lines. Using selected Tax serine mutants a tryptic fragment containing a serine at residue 113 believed to be the site of phosphorylation of Tax did not comigrate with the common phosphorylated tryptic fragment. Analysis of selected Tax mutants for ability totrans-activate the cytomegalovirus promoter demonstrated mutation of serine 77 to alanine reducedtrans-activation by 90% compared to wild-type Tax. However, examination of the phosphorylation pattern of the serine 77 mutant demonstrated that it is not the site of phosphorylation. These studies demonstrate the importance of using relevant cell lines to characterize the role of phosphorylation in protein function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255904
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  • 10
    Electronic Resource
    Electronic Resource
    Pathologie der Rhabdo- myosarkome des Kindes- und Adoleszentenalters Ein Bericht des Kindertumorregisters bei der Gesellschaft für Pädiatrische Onkologie und Hämatologie (GPOH) (1999)
    Springer
    Der Pathologe 20 (1999), S. 87-97 
    Details
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Rhadomyosarkom ; Klassifizierung ; Immunhistochemie ; Genetik ; Prognose ; Key words Rhabdomyosarcoma ; Classification ; Immunohistochemistry ; Genetics ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Rhabdomyosarcoma (RMS) is the most important and a very heterogeneous group of malignant soft tissue tumors of childhood and adolescence.The two major subtypes (embryonal and alveolar) share a common myogenic differentiation, but seem to be histogenetically not related. The so-called ’International Classification of Rhabdomyosarcoma’ includes, besides the two major subtypes, the botryoid and leiomyomatous subtypes of embryonal RMS which are associated with a better prognosis and are treated less aggressively according to current protocols. In addition, the solid variant of alveolar RMS is included in the alveolar group of RMS. The identification of the various subtypes is necessary and important because the treatment with the current protocols is also related to histology. Using conventional stains and immunohistochemistry, these subtypes are distinguishable. Genetic analysis can be helpful in the demonstration of t(2;13) or t(1;13) translocations in alveolar RMS. The identification of alveolar RMS with t(1;13) translocation might become important in the future, because this type of translocation seems to be related to a better prognosis as compared to tumors with a t(2;13) translocation.
    Notes: Zusammenfassung Rhabdomyosarkome stellen eine heterogene Gruppe von ganz verschiedenartigen, histogenetisch wohl nicht zusammengehörenden Tumoren dar. Nach der heute verwendeten „Internationalen Klassifikation” der Rhabdomyosarkome werden neben der Unterteilung in embryonalen und alveoläre Rhabdomyossarkome auch Subtypen des embryonalen RMS identifiziert (botryoider und leiomyomatöser Subtyp), die durch eine günstigere Prognose und durch die Notwendigkeit einer weniger aggressive Therapie gekennzeichnet sind. Durch Einsatz von verschiedenen histologischen und immunhistochemischen Färbungen ist die Identifizierung der verschiedenen Typen der RMS heute möglich und auch zwingend notwendig, da die einzelnen Entitäten nach ganz unterschiedlichen Therapieprotokollen behandelt werden. Der Nachweis typischer molekulargenetischer Veränderungen kann in der Unterscheidung insbesondere von embryonalen und alveolären RMS hilfreich sein. In der Regel ist die Abgrenzung zwischen diesen beiden Entitäten auch an konventionell gefärbten Schnittpräparaten möglich. Die Identifizierung von alveolären RMS mit einer t(1;13)-Translokation könnte in Zukunft eine große Bedeutung haben, da diese genetische Veränderung möglicherweise mit einer günstigeren Prognose assoziert sein könnte als die t(2;13)-Translokation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002920050326
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  • 11
    Electronic Resource
    Electronic Resource
    Clinical relevance of monosomy 22q11.2 in children with pulmonary atresia and ventricular septal defect (1999)
    Springer
    European journal of pediatrics 158 (1999), S. 302-307 
    Details
    ISSN: 1432-1076
    Keywords: Key words Congenital heart disease ; Pulmonary atresia and ventricular septal defect ; Genetics ; Monosomy 22q11.2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of our study was to describe the prevalence and the clinical spectrum of monosomy 22q11.2 in a population of patients with pulmonary atresia and ventricular septal defect. We examined all 44 patients with this conotruncal cardiac malformation who presented to our institution from January 1994 until December 1997. The type of collateral lung perfusion was recorded including anomalies of the pulmonary arteries as well as facial and immunological abnormalities. Molecular-cytogenetic testing for a 22q11.2 microdeletion was performed using the probes D22S75 and cHKAD26. Statistical differences were evaluated with the Fisher's Exact Test. Monosomy 22q11.2 was present in ten children (23%) with major aortopulmonary collateral arteries (group 1). The remaining 13 children (29%) with major aortopulmonary collateral arteries (group 2) and all 21 children (48%) with ductus arteriosus (group 3) were negative for this microdeletion. All children in group 1 had facial anomalies, six had mild immunological abnormalities including decreased CD 4+ or CD 8+ cells. Anomalies of the pulmonary vascular bed were significantly more frequent in children of group 1 (9/10) than in children of group 2 (4/13) or group 3 (0/21). Due to these pulmonary vascular anomalies, corrective surgery had been accomplished in fewer children with monosomy 22q11.2 (none in group 1) as compared to 7/13 children in group 2 and 14/21 children in group 3. Conclusion In children with pulmonary atresia and ventricular septal defect, monosomy 22q11.2 is preferentially associated with major aortopulmonary collateral arteries. Due to the higher incidence of pulmonary arterial abnormalities, successful surgical repair will require a different therapeutic approach in most patients with this microdeletion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004310051077
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  • 12
    Electronic Resource
    Electronic Resource
    Controlling septation in fission yeast: finding the middle, and timing it right (1999)
    Springer
    Current genetics 35 (1999), S. 571-584 
    Details
    ISSN: 1432-0983
    Keywords: Key words Cytokinesis ; Kinase ; Mitosis ; Schizosaccharomyces pombe ; Cell division ; Phosphatase ; Mutant ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fission yeast Schizosaccharomyces pombe provides a simple eukaryotic model for the study of cytokinesis. S. pombe cells are rod-shaped, grow mainly by elongation at their tips, and divide by binary fission after forming a centrally placed division septum. Analysis of mutants has begun to shed light upon how septum formation and cytokinesis are regulated both spatially and temporally. Some of the proteins involved in these events have been functionally conserved throughout eukaryotic evolution, suggesting that aspects of this control will be common to all eukaryotic cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050455
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  • 13
    Electronic Resource
    Electronic Resource
    Polymorphisms in the glutamate transporter gene EAAT2 in European ALS patients (1999)
    Springer
    Journal of neurology 246 (1999), S. 1140-1144 
    Details
    ISSN: 1432-1459
    Keywords: Key words Amyotrophic lateral sclerosis ; Genetics ; Glutamate transporter gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder characterised by degeneration of upper and lower motor neurons. Whilst the primary pathogenic trigger is unknown in most cases, evidence is mounting to implicate a role for glutamate-mediated neurotoxicity in the disorder. Recent studies have shown reduced levels of the mainly astroglial glutamate transporter EAAT2 in ALS motor cortex and spinal cord and multiple abnormal EAAT2 mRNA species in ALS brain tissue. One cause of the low EAAT2 levels may be that point mutations in the EAAT2 gene, EAAT2, result in an abnormal unstable protein. To test this hypothesis we analysed EAAT2 in 128 sporadic and 23 familial European ALS cases. No variants within the coding sequence of EAAT2 to affect the protein sequence nor in the consensus splice sites of the flanking intronic sequences were found in any cases, similar to findings in other reports. Frequent polymorphisms within the flanking intronic sequences of both exons 2 and 4 were seen but at similar frequencies in controls. Mechanisms other than mutations within the coding region of EAAT2 must therefore be responsible for the low levels of EAAT2 seen in most cases of ALS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050532
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  • 14
    Electronic Resource
    Electronic Resource
    Etiology of the inflammatory bowel diseases (1999)
    Springer
    International journal of colorectal disease 14 (1999), S. 2-9 
    Details
    ISSN: 1432-1262
    Keywords: Key words Inflammatory bowel disease ; Crohn's disease ; Ulcerative colitis ; Epidemiology ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Inflammatory bowel diseases (IBD) are complex disorders. While the exact etiology of these diseases remains unknown, recent progress in the epidemiology and genetics of IBD has clearly demonstrated both environmental and genetic factors to play a role in the development of the disease, and it is expected that some risk factors are common for both Crohn's disease (CD) and ulcerative colitis (UC). The environmental factor(s) are associated with the Western way of life in the second half of the twentieth century. Cigarette smoking is presently the best known environmental factor. However, the effect of tobacco is opposite in CD and UC. A familial history of IBD is the most important risk factor for developing the disease, suggesting a genetic predisposition to IBD. This hypothesis has recently been confirmed by the localization of at least two susceptibility loci on chromosomes 12 and 16. These genes seem to play a role in both CD and UC. They must now to be identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003840050175
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  • 15
    Electronic Resource
    Electronic Resource
    Craniosynostosis: from a clinical description to an understanding of bone formation of the skull (1999)
    Springer
    Child's nervous system 15 (1999), S. 676-680 
    Details
    ISSN: 1433-0350
    Keywords: Key words Craniosynostosis ; Genetics ; FGFR ; Msx2 ; Development ; Skull
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The genetic studies of syndromic craniosynostoses lead to the characterisation of genes that regulate the correct development of the bones of the skull. From these studies, it appears that FGF/FGFR signalling has a crucial role in this problem. Numerous mutations affecting the genes coding for FGFR1, 2 or 3 are responsible for these syndromes. It is interesting to note that some identical mutations produced various different phenotypes, suggesting that other genes modulate the phenotypic expressivity. The other involved genes in these syndromes code for such proteins as Msx2 or Twist that interact in the cellular pathways responsible for FGF action. From these genetic studies, it is now important to establish the role of these proteins during the development of the skull. Msx2 plays a repressive role in osteogenesis, whereas FGFRs act as promoting proteins. In the near future, it will be very important to improve our understanding of these phenomena in order to test specific treatments to prevent the development of such syndromes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003810050457
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  • 16
    Electronic Resource
    Electronic Resource
    Early diagnosis and the clinical genetics of Alzheimer’s disease (1999)
    Springer
    Journal of neurology 246 (1999), S. 69-72 
    Details
    ISSN: 1432-1459
    Keywords: Key words Alzheimer’s disease ; Genetics ; Genetic counseling ; Predictive testing ; Diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Alzheimer’s disease (AD) has a significant genetic background manifested as autosomal dominant inheritance in some early-onset families and as familial risk in late-onset cases. Three genes responsible for early-onset autosomal dominant AD have been identified, and one gene, apolipoprotein E, has been confirmed as a susceptibility gene for late-onset forms of the disorder. These findings raise the possibility of genetic testing, either for early diagnosis or prediction. For early-onset autosomal dominant AD genetic testing will have a limited but useful role in confirming diagnosis in established cases and in predictive counselling for relatives; a situation analogous to that for Huntington’s disease. For late-onset AD significant problems remain to be overcome before the advances in molecular genetics have a direct clinical application
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050310
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  • 17
    Electronic Resource
    Electronic Resource
    Mitochondrial DNA mutation at np 3243 in a family with maternally inherited diabetes mellitus (1999)
    Springer
    Acta diabetologica 36 (1999), S. 163-167 
    Details
    ISSN: 1432-5233
    Keywords: Key words Mitochondrial DNA ; Genetics ; Maternally inherited diabetes mellitus ; Deafness ; np 3243 mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Mitochondrial DNA (mtDNA) gene defects may play a role in the development of maternally inherited diabetes mellitus and deafness (MIDD). A family from Southern Italy who showed maternal transmission of type 2 diabetes mellitus with three individuals affected is described. A 10.4 kb deletion and mutations at nucleotide positions (np) 3243, 7445 and 11778 in the mtDNA of six relatives were sought. The mitochondrial np 3243 mutation of the tRNA Leu (UUR) gene was identified in a boy affected by optic atrophy and mental retardation, as well as in his diabetic mother. No other mutations or deletions were found. Our study points out the variable phenotypic expression of the np 3243 mtDNA mutation. This may suggest the presence of other mitochondrial or nuclear mutations required to modulate the phenotype. A clinical and metabolic follow-up of all family members was necessary to understand the role of the np 3243 mutation, especially in one child affected by optic atrophy and mental retardation. Further studies will be aimed at investigating the prevalence of mutations and deletions of mtDNA in type 2 diabetes mellitus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005920050161
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  • 18
    Electronic Resource
    Electronic Resource
    Self-incompatibility in passion fruit: evidence of two locus genetic control (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 564-568 
    Details
    ISSN: 1432-2242
    Keywords: Key words Passiflora ; Self-incompatibility ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The self-incompatibility in yellow passion fruit was previously described as homomorphic sporophytic with monofactorial inheritance. Five progenies were obtained by bud-selfing. The plants of these progenies were selfed, reciprocally crossed within each progeny and crossed with known incompatible phenotypes to identify their phenotypic group. Fruit set was evaluated at the 7th day after pollination. Two progenies consisted of two self-incompatible groups, the other three formed three suck groups. The groups were identified as S1, S2, S3, S4, S5 and S6. The results provide evidence that the self-incompatibility of passion fruit is controlled by two loci, the S-gene and another, whose expression needs to be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051105
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  • 19
    Electronic Resource
    Electronic Resource
    AC/GT and AG/CT microsatellite repeats in peach [Prunus persica (L) Batsch]: isolation, characterisation and cross-species amplification in Prunus (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 65-72 
    Details
    ISSN: 1432-2242
    Keywords: Key words Simple sequence repeat (SSR) ; Microsatellites ; Molecular markers ; Genetics ; Fingerprinting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We report the sequences of 17 primer pairs of microsatellite loci, which we have cloned and sequenced from two genomic libraries of peach [Prunus persica (L) Batsch] ‘Redhaven’, enriched for AC/GT and AG/CT repeats respectively. For ten of these microsatellite loci we were able to demonstrate Mendelian inheritance in a segregating back-cross population; the remainder did not segregate. The polymorphism of the microsatellites was evaluated in a panel of ten peach genotypes, including true-to-type peaches, nectarines and one canning-peach. Fifteen microsatellites (88%) were polymorphic showing 2–4 alleles each. The mean heterozygosity, averaged over all loci, was 0.32 and significantly higher than that reported in the literature for isozymes and molecular markers, such as RFLPs and RAPDs. We have also assayed the cross-species transportability and found that ten microsatellite (59%) gave apparently correct amplification in all Prunus species surveyed, namely P. domestica (European plum), P. salicina (Japanese plum), P. armeniaca (apricot), P. dulcis (almond), P. persica var. vulgaris (peach), P. persica var. laevis (nectarine), P. avium (sweet cherry) and P. cerasus (sour cherry), with three of them also being amplified in Malus (apple). The remaining microsatellites gave less-extensive amplification. Because of their appreciable polymorphism and wide cross-species transportability, most of these new markers can be integrated into the linkage maps which are currently being constructed in peach, as well as in other stone fruit crops, such as almond, apricot, cherry and plum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051209
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  • 20
    Electronic Resource
    Electronic Resource
    A stylar ribonuclease assay to detect self-compatible seedlings in almond progenies (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 800-810 
    Details
    ISSN: 1432-2242
    Keywords: Key words Almond ; Compatibility ; Genetics ; Prunus dulcis ; Ribonucleases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Six almond progenies, each the product of a cross between a self-compatible and a self-incompatible parent, were analysed for stylar ribonucleases. Proteins were extracted and separated using non-equilibrium pH gradient electrofocusing (NEPHGE), and the gels were stained for ribonuclease activity. Most seedlings showed either two principal bands, interpreted as corresponding to two incompatibility alleles, or a single band. The seedlings were also bagged in the field at flowering time to determine fruit set after selfing, and some were also examined for the growth of pollen-tubes in selfed styles using UV fluorescence microscopy. With very few exceptions, those seedlings showing single-banded zymograms were found to be self-compatible according to field and microscope studies, and those with two bands were found to be self-incompatible. We conclude that the allele for self-compatibility in almond does not code for ribonuclease activity and that the ribonuclease isoenzyme assay is a convenient technique for predicting self-compatibility in segregating progenies. A novel band in two derivatives of ’Ferrastar’ was ascribed to a new incompatibility allele, S 10 .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051299
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  • 21
    Electronic Resource
    Electronic Resource
    Division of labor in a dynamic environment: response by honeybees (Apis mellifera) to graded changes in colony pollen stores (1999)
    Springer
    Behavioral ecology and sociobiology 46 (1999), S. 171-179 
    Details
    ISSN: 1432-0762
    Keywords: Key words Honeybee ; Apis mellifera ; Division of labor ; Genetics ; Pollen foraging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A fundamental requirement of task regulation in social groups is that it must allow colony flexibility. We tested assumptions of three task regulation models for how honeybee colonies respond to graded changes in need for a specific task, pollen foraging. We gradually changed colony pollen stores and measured behavioral and genotypic changes in the foraging population. Colonies did not respond in a graded manner, but in six of seven cases showed a stepwise change in foraging activity as pollen storage levels moved beyond a set point. Changes in colony performance resulted from changes in recruitment of new foragers to pollen collection, rather than from changes in individual foraging effort. Where we were able to track genotypic variation, increases in pollen foraging were accompanied by a corresponding increase in the genotypic diversity of pollen foragers. Our data support previous findings that genotypic variation plays an important role in task regulation. However, the stepwise change in colony behavior suggests that colony foraging flexibility is best explained by an integrated model incorporating genotypic variation in task choice, but in which colony response is amplified by social interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050607
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  • 22
    Electronic Resource
    Electronic Resource
    Preliminary report on the Mount Sinai Hospital Inflammatory Bowel Disease Genetics Project (1997)
    Springer
    Diseases of the colon & rectum 40 (1997), S. 553-557 
    Details
    ISSN: 1530-0358
    Keywords: Inflammatory bowel disease ; Crohn's disease ; Ulcerative colitis ; Genetics ; Family history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract BACKGROUND: Although the etiology of inflammatory bowel disease (IBD) is unknown, there is increasing evidence that genetic predisposition plays a major etiologic role. To provide the framework for gene identification using a positional cloning approach, ascertainment of families with multiple affected members and careful documentation of pedigrees are essential. Objective: To report the initial findings of the IBD Genetics Project of the Mount Sinai Hospital IBD Research Unit. METHODS: All records of patients with ulcerative colitis and Crohn's disease followed at the Mount Sinai Hospital IBD Unit were reviewed. A questionnaire was sent to all patients to ascertain those with a family history of IBD. Patients with a presumed family history were contacted by a research assistant, and after confirmation of diagnosis, relevant clinical information, pedigrees, and consent to contact family members were obtained. Blood for DNA and cell line preparation were collected from affected and nonaffected family members. RESULTS: Of 2,504 patients registered in the IBD database, 231 (9.2 percent) were found to have an affected family member: 96 of 964 (10 percent) with Crohn's disease (CD) and 135 of 1,540 (8.8 percent) with ulcerative colitis (UC). A mean of 2.4 family members were affected. In families in which the proband had CD, 82.3 percent had only two affected family members, 78.1 percent had only family members affected with CD, and 82.3 percent had only first-degree family members affected. In families in which the proband had UC, 70.4 percent had only two affected family members, 71.1 percent had only family members affected with UC, and 65.2 percent had only first-degree family members affected. In the 231 families, there were 103 sibling pairs: 46 percent with CD, 28 percent with UC, and 26 percent with CD/UC. CONCLUSION: These data suggest that approximately 10 percent of IBD patients have affected family members, with the rate being similar in UC and CD. Future research is directed to genome scanning and linkage analysis in this cohort of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02055377
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  • 23
    Electronic Resource
    Electronic Resource
    Genetic control of Interleukin 12 responsiveness: implications for disease pathogenesis (1997)
    Springer
    Journal of molecular medicine 75 (1997), S. 502-511 
    Details
    ISSN: 1432-1440
    Keywords: Key words T helper 1/T helper 2 ; Genetics ; Interleukin 12 ; Allergy ; Autoimmunity ; Leishmania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We examined the effect of genetic background on Th1/Th2 development. We discuss data demonstrating that genetic background is an important determinant of interleukin-12 (IL-12) responsiveness and the potential implications for disease progression in murine experimental leishmaniasis. Genetic analysis of the differential control of IL-12 responsiveness led to the identification of a controlling locus on the middle portion of murine chromosome 11. This genetic region (or its human counterpart, 5q31) has been associated with increased disease susceptibilities for several atopic, infectious, and autoimmune disorders. We discuss potential roles for genetic control of IL-12 responsiveness in the development of these diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050135
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  • 24
    Electronic Resource
    Electronic Resource
    Familial Hodgkin's disease: a disease of young adulthood? (1997)
    Springer
    Annals of hematology 74 (1997), S. 131-134 
    Details
    ISSN: 1432-0584
    Keywords: Key words Hodgkin's disease ; Sex ; Age ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Familial Hodgkin's disease (FHD) is estimated to represent approximately 4.5% of all cases of Hodgkin's disease (HD). Shared environmental factors, such as Epstein-Barr virus and other viral agents, and genetic determinants have all been proposed to explain familial aggregation of HD. In order to compare the characteristic features of FHD with those of the much more common sporadic form, we reviewed 28 articles on FHD, published between 1972 and 1995, and analyzed in further detail data from 18 papers, reporting on a total of 328 patients. The male-to-female ratio of the FHD population examined was 1.5, similar to that reported for sporadic HD, and lower than the one suggested for FHD by some authors. On the other hand, a significant difference was found between sporadic and familial HD according to age at diagnosis; that is, only one major peak between 15 and 34 years was present in the group of patients with FHD. Further investigation of FHD in young adulthood may provide insight into the hypothesis of a genetic or infectious etiology of the disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002770050270
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  • 25
    Electronic Resource
    Electronic Resource
    Genetics and cytology of a new genic male-sterile soybean [Glycine max (L.) Merr.] (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 13-21 
    Details
    ISSN: 1432-2145
    Keywords: Key words Soybean ; Male sterility ; Genetics ; Callase ; Callose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic and cytological studies were conducted with a new male-sterile, female-fertile soybean [Glycine max (L.) Merr.] mutant. This mutant was completely male sterile and was inherited as a single-recessive gene. No differences in female or male gamete transmission of the recessive allele were observed between reciprocal cross-pollinations in the F1 or F2 generations. This mutant was not allelic to any previously identified soybean genic male-sterile mutants: ms1, ms2, ms3, ms4, ms5, or ms6. No linkage was detected between sterility and flower color (W1 locus), or between sterility and pubescence color (T1 locus). Light microscopic and cytological observations of microsporogenesis in fertile and sterile anthers were conducted. The structure of microspore mother cells (MMC) in male-sterile plants was identical to the MMCs in male-fertile plants. Enzyme extraction analyses showed that there was no callase activity in male-sterile anthers, and this suggests that sterility was caused by retention of the callose walls, which normally are degraded around tetrads at the late tetrad stage. The tapetum from male-sterile anthers also showed abnormalities at the tetrad stage and later stages, which were expressed by an unusual formation of vacuoles, and by accumulation of densely staining material. At maturity, anthers from sterile plants were devoid of pollen grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050062
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  • 26
    Electronic Resource
    Electronic Resource
    Effect of naltrexone on subjective alcohol response in subjects at high and low risk for future alcohol dependence (1997)
    Springer
    Psychopharmacology 129 (1997), S. 15-22 
    Details
    ISSN: 1432-2072
    Keywords: Key words Naltrexone ; Alcohol ; Genetics ; Social drinkers ; Family history of alcoholism ; Biphasic Alcohol Effects Scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated specific subjective effects of naltrexone pretreatment or placebo during various intervals on the breath alcohol level (BAL) curve in nonalcoholic volunteers. Fifteen high-risk (social drinkers with an alcoholic father) and 14 low-risk (no alcoholic relatives in at least two generations) subjects were tested in a double-blind, placebo-controlled study of the effects of 50 mg oral naltrexone on response to a moderate dose of alcohol. Dependent measures included subjective stimulation and sedation subscales from the Biphasic Alcohol Effects Scale (BAES) and mood subscales from the Profile of Mood States (POMS). At rising BALs, high-risk subjects showed a naltrexone-related attenuation of BAES stimulation. This effect was not evident in low-risk subjects, who directionally showed the opposite effect, although nonsignificant. For both groups, there were no significant naltrexone-related effects for BAES sedation; however, naltrexone did affect several POMS scales on alcohol response, such as decreased vigor, and increased fatigue, tension, and confusion. Confusion was significantly elevated for the high-risk group during rising BALs of the naltrexone session. The results suggest a differential response to naltrexone, based on paternal history of alcoholism and level of stimulation experienced during alcohol drinking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050156
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  • 27
    Electronic Resource
    Electronic Resource
    Mitochondrial DNA polymorphisms in pathologically proven Parkinson’s disease (1997)
    Springer
    Journal of neurology 244 (1997), S. 262-265 
    Details
    ISSN: 1432-1459
    Keywords: Key words Parkinson’s disease ; Genetics ; Mitochondrial DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To date, five single base pair changes of the mitochondrial DNA have been reported to occur either exclusively or with increased frequency in Caucasian patients with Parkinson’s disease (PD) and it has been postulated that these mutations might be causally related to the observed inhibition of mitochondrial respiratory chain function in PD. To evaluate these findings, we analysed the frequency of all five polymorphisms in 100 cases of pathologically proven cases of PD. We were either unable to detect the previously described polymorphisms in our series or found them to be present with the same frequency among controls. Our data do not support the hypothesis of an involvement of the mitochondrial DNA in the pathogenesis of PD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050082
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  • 28
    Electronic Resource
    Electronic Resource
    Genetics, haloperidol-induced catalepsy and haloperidol-induced changes in acoustic startle and prepulse inhibition (1997)
    Springer
    Psychopharmacology 134 (1997), S. 131-139 
    Details
    ISSN: 1432-2072
    Keywords: Key words Startle ; Prepulse inhibition ; Inbred strains ; Haloperidol ; Catalepsy ; Schizophrenia ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The acoustic startle response (ASR), prepulse inhibition (PPI) of the ASR and the effects of haloperidol on the ASR and PPI were examined in C57BL/6J (B6) and DBA/2 (D2) inbred mouse strains and their F1 and F2 progeny. The startle stimulus was a 60-ms, 110-dB, 10-kHz tone; the prepulse stimuli were 20-ms white noise bursts at 56, 68 and 80 dB against a 50-dB background presented 100-ms before the startle pulse. The B6 strain showed modest PPI (25–40%); in contrast, the D2 strain showed on average no PPI and numerous individuals showed prepulse augmentation (PPA). The F2 progeny showed an intermediate PPI; however, the extreme values ranged from 200% PPA to essentially 100% PPI. Haloperidol in dose-dependent fashion, increased PPI in both the B6 and D2 strains; the threshold dose was in the range of 0.1–0.2 mg/kg. Raclopride (0.3 mg/kg), clozapine (2 mg/kg) and risperidone (0.4 mg/kg) also increased PPI in both strains. The effects of haloperidol (0.4 mg/kg) on PPI in 140 F2 progeny were examined. For all prepulse intensities, there were highly significant (r 〉 0.80) and negative correlations between baseline PPI and the haloperidol-induced change in PPI. Thus, those animals that showed the greatest PPA showed the greatest haloperidol-induced increase in PPI. There was, however, significant variance in the haloperidol response; plots of the regression residuals showed the most and least responsive animals differed by almost 100% in effect on PPI. The F2 progeny were subsequently phenotyped for haloperidol-induced catalepsy. There was no association between the variation in effects on catalepsy and PPI. However, it was observed that those individuals with the poorest baseline PPI were catalepsy non-responsive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050434
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  • 29
    Electronic Resource
    Electronic Resource
    Behavioral phenotypes of inbred mouse strains: implications and recommendations for molecular studies (1997)
    Springer
    Psychopharmacology 132 (1997), S. 107-124 
    Details
    ISSN: 1432-2072
    Keywords: Key words Mouse ; Inbred strains ; Behavior ; Genetics ; Locomotion ; Open field activity ; Learning ; Memory ; Aggression ; Parental behaviors ; Acoustic startle ; Prepulse inhibition ; Alcohol ; Nicotine ; Cocaine ; Opiates ; Haloperidol ; Diazepam ; Breeding ; Embryonic stem cell lines ; Transgenic ; Knockouts ; Null mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Choosing the best genetic strains of mice for developing a new knockout or transgenic mouse requires extensive knowledge of the endogenous traits of inbred strains. Background genes from the parental strains may interact with the mutated gene, in a manner which could severely compromise the interpretation of the mutant phenotype. The present overview summarizes the literature on a wide variety of behavioral traits for the 129, C57BL/6, DBA/2, and many other inbred strains of mice. Strain distributions are described for open field activity, learning and memory tasks, aggression, sexual and parental behaviors, acoustic startle and prepulse inhibition, and the behavioral actions of ethanol, nicotine, cocaine, opiates, antipsychotics, and anxiolytics. Using the referenced information, molecular geneticists can choose optimal parental strains of mice, and perhaps develop new embryonic stem cell progenitors, for new knockouts and transgenics to investigate gene function, and to serve as animal models in the development of novel therapeutics for human genetic diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050327
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  • 30
    Electronic Resource
    Electronic Resource
    The effects of cocaine on operant responding for food in several strains of mice (1997)
    Springer
    Psychopharmacology 132 (1997), S. 202-208 
    Details
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Operant behavior ; Genetics ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The availability of numerous genetically homogenous mouse strains permits the analysis of genetic influences on behavior and also behavioral sensitivity (responsivity) to drugs of abuse. The current study was conducted to characterize discriminated operant responding for food in four inbred strains (Balb/cByJ, DBA/2J, C57BL/6J, SJL/J), an F1 Hybrid (C57BL/6×SJL), and one outbred strain (CD1) of mouse. The effect of cocaine on this operant behavior was also examined. Initially, all animals were trained to nosepoke for food on a continuous reinforcement schedule. The minimum response requirement for reinforcement was increased every 5 days until the animals were responding on an FR-15 schedule of reinforcement. All strains increased operant responding as the schedule of reinforcement was raised. However, significant differences in response rate and discrimination learning were observed among the various strains of mice. Cocaine administration reduced operant responding for food in Balb/cByJ, C57BL/6J, C57BL/6×SJL/J and CD1 mice at a dose of 15.0 mg/kg, whereas higher doses were required in DBA/2J mice (30.0 mg/kg) and SJL/J mice (56.0 mg/kg). These results suggest that operant performance and the effect of cocaine on this behavior is differentially influenced by genetic make-up.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050337
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  • 31
    Electronic Resource
    Electronic Resource
    Homoclinic chaos in a model of natural selection (1997)
    Springer
    Journal of mathematical biology 35 (1997), S. 294-320 
    Details
    ISSN: 1432-1416
    Keywords: Key words: Natural selection ; Homoclinic chaos ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract.  We modify a simple mathematical model for natural selection originally formulated by Robert M. May in 1983 by permitting one homozygote to have a larger selective advantage when rare than the other, and show that the new model exhibits dynamical chaos. We determine an open region of parameter space associated with homoclinic points, and prove that there are infinite sequences of period-doubling bifurcations along selected paths through parameter space. We also discuss the possibility of chaos arising from imbalance in the homozygote fitnesses in more realistic biological situations, beyond the constraints of the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002850050053
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  • 32
    Electronic Resource
    Electronic Resource
    Expression of a unique plastid-localized heat-shock protein is genetically linked to acquired thermotolerance in wheat (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 834-841 
    Details
    ISSN: 1432-2242
    Keywords: Key words Stress proteins ; Heat tolerance ; Chloroplast ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have used a combination of molecular and classical genetic approaches to delineate the relationship between a specific HSP member and cell viability under heat stress. Using recombinant inbred lines (RILs) of wheat, derived from a cross of the thermotolerant cultivar ‘Mustang’ and the thermosusceptible cultivar ‘Sturdy,’ we have identified a unique HSP and a differentially expressed cDNA sequence, both related to the plastid-localized HSP26 gene family, that are closely associated with acquired thermotolerance in wheat. An isoform of HSP26 was synthesized under heat stress in all examined thermotolerant RILs and ‘Mustang’, and was absent in all examined thermosusceptible RILs and ‘Sturdy.’ Using a modified differential-display method, we have also identified a gene-specific cDNA sequence that is similar to other known members of the wheat HSP26 gene family and is selectively expressed in ‘Mustang’ and most of the examined thermotolerant RILs, but not expressed in ‘Sturdy’ and all the thermosusceptible RILs. These results suggest a genetic linkage between the acquired thermotolerance trait and the differential expression of a unique member of the HSP26 gene family.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050633
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  • 33
    Electronic Resource
    Electronic Resource
    Extreme resistance to potato virus V in clones of Solanum tuberosum that are also resistant to potato viruses Y and A: evidence for a locus conferring broad-spectrum potyvirus resistance (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 1258-1262 
    Details
    ISSN: 1432-2242
    Keywords: Key words Extreme virus resistance ; Potyviruses ; Genetics ; Genes Rysto and Ra ; Broad-spectrum resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Extreme resistance to the potato V potyvirus (PVV) was found in four potato cultivars that contain Ry genes from Solanum stoloniferum. When plants of these cultivars, were inoculated by grafting in shoot tips from PVV-infected tomato plants, necrotic symptoms developed in some cultivars, although a full hypersensitive reaction was not elicited, while other cultivars were symptomless. PVV replication was not detected in any of the inoculated plants by ELISA, an infectivity assay of leaf extracts by manual inoculation to Nicotiana benthamiana indicator plants, or by ‘return grafting’ of shoot tips taken from newly developed shoots of the potato plants to virus-free indicator plants of tomato. These methods readily detected PVV infection in inoculated plants of cv ‘Flourball’, which does not contain an Ry gene and is susceptible, and in cvs ‘Maris Piper’ and ‘Dr Macintosh’, which contain gene Nv conditioning a hypersensitive reaction to inoculation. One of the Ry-containing cultivars, ‘Barbara’, has been previously shown to contain two genes that control extreme resistance, defined as no viral replication in intact plants, to the potyviruses potato viruses Y and A (PVY and PVA). These genes are: Ry sto , which conditions resistance to PVY and PVA, and gene Ra, which conditions resistance to PVA only. It was found that in genotypes from a progeny of the cross ‘Barbara’ (Ry sto /Ra)בFlourball’ (ry/ra), extreme resistance to PVV segregated with gene Ry sto . It is proposed that either gene Ry sto conditions broad-spectrum extreme resistance to the distinct potyviruses PVY, PVA, and PVV or that Ry sto represents a family of genetically closely linked genes each controlling resistance to a specific virus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050690
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  • 34
    Electronic Resource
    Electronic Resource
    Resistance to Phytophthora fragariae var. fragariae in strawberry: the Rpf2 gene (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 1092-1096 
    Details
    ISSN: 1432-2242
    Keywords: Key words Fragaria×ananassa ; Genetics ; Inheritance ; Red core ; Red stele
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   Phytophthora fragariae var. fragariae is the causal agent of red stele (red core) root rot in strawberry (Fragaria spp.). The inheritance of resistance to one isolate of this fungus was studied in 12 segregating populations of F.×ananassa derived from crosses between four resistant cultivars (‘Climax’, ‘Redgauntlet’, ‘Siletz’, and ‘Sparkle’) and three susceptible cultivars (‘Blakemore’, ‘Glasa’, and ‘Senga’ Sengana’). The analysis clearly supports the hypothesis of a single segregating dominant resistance gene. It is proposed that this gene be designated Rpf2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050520
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  • 35
    Electronic Resource
    Electronic Resource
    Genetic aspects of childhood behavioral disorders (1997)
    Springer
    Child psychiatry & human development 27 (1997), S. 139-150 
    Details
    ISSN: 1573-3327
    Keywords: ADHD ; Tourette Syndrome ; Genetics ; Gene Selection ; Conduct Disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The evidence is reviewed to support the concept that many disruptive, childhood and adolescent behavioral disorders including ADHD, Tourette syndrome, learning disabilities, substance abuse, oppositional defiant disorder and conduct disorder, are part of a spectrum of inter-related behaviors that have a strong genetic component, are polygenically inherited, share a number of genes in common that affect dopamine, serotonin and other neurotransmitters, and are transmitted from both parents. Some of the implications of this hypothesis in relation to diagnosis and treatment are reviewed, including the possibility that the genes involved may be increasing in frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02353694
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  • 36
    Electronic Resource
    Electronic Resource
    Computerized EEG topography of normal preadolescent twins—Correlating similarity of background activity with genetic relatedness (1997)
    Springer
    Brain topography 9 (1997), S. 303-311 
    Details
    ISSN: 1573-6792
    Keywords: EEG normality ; Brain topography ; Twins ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of genetic relatedness on the similarity degree of topographical EEG parameters was studied in a sample of 26 sets of monozygotic (MZ) and 46 sets of dizygotic (DZ) twins. All 144 subjects were healthy, primary school children, aged 7–15 years, 69 boys and 75 girls. Correlation coefficients were calculated for 50 quantitative EEG parameters of paired values obtained at each of 16 active electrode sites, in four groups of paired tracings: 1. MZ twins, 2. DZ twins, 3. The autocorrelated (A) group formed by correlating the spectral parameters from the same subjects in two different analyzed sequences, 4. The random (R) control group of 1200 unrelated pairs formed from DZ twin pairs. Sets of MZ twins and A group showed the highest degrees of similarity of spectral parameters over all brain areas except for significant differences only for some background features over posterior regions. In contrast, highly significant differences in topographic parameters were evident in comparison of MZ sets with DZ sets, particularly when MZ sets were compared with DZ subsets of opposite sex. Both number and degree of significant differences increased progressively in comparisons with groups 3 vs 2,1 vs 4, and 3 vs 4. The data gave strong evidence for a complex polygenic determination of normal human EEG topography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01464485
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  • 37
    Electronic Resource
    Electronic Resource
    Polycarbonat-ein vielseitiger werkstoff mit zukunft (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 244 (1997), S. 43-66 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The market development of bisphenol-A-polycarbonate has shown higher growth than any other engineering thermoplastic. The reasons can be found in the permanent improvement of the cost/performance-relationship and in the technical use of the variability of the basic structure. Incorporation of specific monomer units leads to tailor-made properties for a wide range of applications, as for example medical devices, electronic parts and glazing.This process has not yet slowed down, rather it is accelerated by new results from research and development. The improvement of flaw behavior and pit replication for new grades of materials for the next generation of compact discs, new grades that can be sterilized by γ-radiation without degradation and the microstructuring by low-energy laser systems are examples for the ongoing expansion of polycarbonate applications. Surface modification by hardcoatings with nanosized particles will allow to enter the fast growing market of glazing.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052440103
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  • 38
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    Electronic Resource
    Polyamide, polyester und polyoxymethylen. Die klassischen technischen kunststoffe und ihre perspektiven (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 244 (1997), S. 67-92 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyamide, Polyester und Polyoxymethylen sind mit einem weltweiten Verbrauch von derzeit 2,4 Mio t pro Jahr wichtige technische Kunststoffe. Sie werden aufgrund ihrer besonderen Eigenschaftsprofile überwiegend im Fahrzeugbau und in der Elektroindustrie für hochbelastete Funktionsbauteile eingesetzt. Der vorliegende Beitrag behandelt Polymerisationswege, Eigenschaften und ausgewählte neue Entwicklungen dieser Polymerklassen.Teilaromatische Polyamide stoßen durch ihre Dimensionsstabilität und thermische Belastbarkeit in Anwendungen vor, die bisher Duromeren oder Metallen vorbehalten waren. Glasfaserverstärkte Polyamide mit besonders hoher Dauerwärmebeständigkeit übemehmen wichtige Funktionen im Motorbereich von Fahrzeugen. Polyamid-Blends sind als Karosseriewerkstoffe ein Schlüssel zu leichten Autos mit niedrigem Treibstoffverbrauch. Halogenfrei flammgeschützte Polyamide erhöhen Sicherheit und Umweltverträglichkeit in brandgefährdeten Anwendungsbereichen.Polybutylenterephthalat als technisch wichtigster Polyester eröffnet in Mischung mit amorphen Polymeren neue Perspektiven durch geringerenVerzug und bessere Oberfläche bei glasfaserverstärkten Teilen. Polybutylennaphthalat erweitert den Anwendungsbereich zu höheren Temperaturen. Von Polybutylenterephthalat abgeleitete Copolyester sind biologisch abbaubar und daher vielversprechend für kompostierbare Folien.Polyoxymethylen-Copolymere haben ihre Stärke in der günstigen Kombination aus Steifigkeit, Dimensionsstabilität, Gleit/Reibe-Verhalten und Beständigkeit gegen heißes Wasser und Kraftstoff.Aufgrund ihres hohen und noch weiter steigerungsfähigen Leistungsvermögens werden Polyamide, Polyester und Polyoxymethylen das in den letzten Jahren gezeigte Wachstum in Zukunft weiter ausbauen können.
    Notes: Polyamide, polyester and polyoxymethylene having presently a worldwide sales volume of 2,4 million tons a year are important engineering thermoplastics. Based on their special property profiles they are mainly used in the automotive and electronic industry for high performance functional parts. This contribution presents polymerisation processes, properties, and selected new developments for these polymer classes.Semiaromatic polyamides due to their dimensional stability and thermal resistance lend themselves to applications which were so far reserved for thermosets or metals. Glass fiber reinforce polyamides designed to have the highest possible heat ageing resistance can take important functions under the hood. A polyamide blend used as a material for exterior body parts is key to light weight cars with strongly reduced fuel consumption. Halogene free flame retardant polyamide increases fire safety and environmental safety in flame sensitive applications.Polybutyleneterephthalate as the technically most important polyester offers new perspectives in blends with amorphous polymers leading to lower distortion and better surface quality in glass fiber reinforced parts. Polybutylenenaphthalate is widening the range of application of polyesters towards higher temperatures. Copolyesters derived from polybutyleneterephthalate are biologically degradable and are therefore promising materials for fermentable foils.Polyoxymethylene copolymers show an outstanding combination of stiffness, dimensional stability, friction and wear as well as resistance against hot water and fuel.As a result of their excellent properties and the existing potential for further improvements polyamide, polyester and polyoxymethylene will continue to grow above average in the future.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052440104
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  • 39
    Electronic Resource
    Electronic Resource
    Sind polyurethanwerkstoffe ein reifes gebiet? (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 244 (1997), S. 121-133 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The world-wide production of polyurethanes has exceeded 6 mio. metric tons in 1994. Compared with the produced amounts of large-scale thermoplastics such as PE, PVC, PP and PS, polyurethanes keep the 5th place.Polyurethanes (PUR) are segmented polymers, which can be synthesized from preformed building blocks in a modular unit construction system. The chemical modules and the various possibilities of combination will be discussed here.Tailor-made polyurethane materials can be divided into two main-fields of application: foams and compact PUR.The main constituents of polyurethane materials are diisocyanates and polyols. These key- chemicals are well characterised with respect to their technological, economical and ecological properties. Taking into account the availability, the masses of production and the experiences that have been collected with the PUR main constituents, these PUR precursors seem to be very mature already.In contrast to this, the PUR-materials made from these building blocks still offer numerous novel problem-solutions, resulting from the variability of the diisocyanate-poly-addition reaction: PUR materials are most commonly segmented into several phases. The formation of hard- and softsegments can be easily demonstrated by looking at thermoplastic polyurethanes (TPU). A deeper understanding of this phase separation and the molecular organisation within these materials promises to realize prospectic polymeric architectures with new and improved properties. PUR materials will still be able to offer new answers to future requirements in balancing economical and ecological needs. By looking at the life-cycles of soft and hard-foams, polyurethane-coatings and thermoplastic PUR-elastomers, this contribution will adress the question: “Is PUR-chemsitry still a challenging field?”
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052440106
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  • 40
    Electronic Resource
    Electronic Resource
    Fire-retardant action of potassium nitrate in polyamide 6 (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 23-35 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Zugabe von 10-20 Gew.-% Kaliumnitrat (KN03) zu Polyamid 6 (PA 6) vermindert die Brennbarkeit des Polymeren. Das thermische Verhalten der KN03/PA 6-Mischung wurde mittels Thermogravimetrie, Differentialkalorimetrie und Analyse der fluchtigen Anteile untersucht. Feste Zersetzungsprodukte der Mischung wurden mittels Infrarotspektroskopie, Rontgendiffraktometrie und Elektronenresonanzspek-'troskopie analysiert. Es wurde gefunden, daß KNO3 dem Flielßen und Tropfen der Schmelze vorbeugt und die Karbonisierung auf der Oberflache des Polymeren fordert. Das verringert die Brandgefahr und verbessert die Feuerbestandigkeit. Andererseits geht KNO3 mit PA 6 in der kondensierten Phase eine exotherme Reaktion ein und setzt Sauerstoff frei, der wiederum die Brennbarkeit von PA 6 begiinstigt. Der Mechanismus der chemischen Wechselwirkung van KNO3 mit PA 6 wird diskutiert.
    Notes: The addition of 10-20 wt.-% of potassium nitrate (KNO3) to polyamide 6 (PA 6) improves the fire retardance of the polymer. The thermal decomposition behaviour of the PA 6/KN03-mixture was studied using thermogravimetry, differential scanning calorimetry and thermal volatilisation analysis. Solid products of the thermal decomposition of the mixture were analysed by infrared spectroscopy, X-ray diffraction and electron paramagnetic resonance. It was found that KNO, prevents flowing and dripping of the melt and promotes charring on the surface of the polymer which decreases its fire hazard and improves its fire retardance. On the other hand, KNO3 exothermally reacts with PA 6 in the condensed phase and supplies oxygen to the gas phase which increases the combustibility of PA 6. The mechanism of the chemical interaction of KN03 with PA 6 is discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450103
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  • 41
    Electronic Resource
    Electronic Resource
    Effect of tricalcium phosphate, hydroxyethyl methacrylate, and ethylene glycol dimethacrylate on the mechanical properties of acrylic bone cement (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 49-62 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß einer Beimischung von Tricalciumphosphat (TCP), Hydroxyethylmethacrylat (HEMA) und Ethylenglycoldimethacrylat (EGDMA) auf die Eigenschaften eines chirurgischen Knochenzements wurde untersucht. Die in Zugversuchen entstandenen Bruchflächen wurden mittels Rasterelektronenmikroskopie charakterisiert. Der Einfluß der Additive auf den Temperaturanstieg während der Polymerisation wurde geprüft. Zug-, Biege- und Druckfestigkeit des ausgehärteten Zements nahmen mit zunehmendem TCP-Gehalt ab, der Elastizitätsmodul stieg dagegen an. Die Zugfestigkeit nahm mit steigendem HEMA-Gehalt geringfügig zu und blieb oberhalb 15 Gew.-% HEMA konstant. Zug-, Biege- und Druckfestigkeit zeigten bei einem EGDMA-Gehalt von 2 Gew.-% (in HEMA) ein Maximum. HEMA und EGDMA beschleunigten die Polymerisation, wogegen TCP retardierend wirkte.
    Notes: The effects of the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) on the properties of standard surgical Simplex-P radiopaque bone cement have been investigated. The fracture surface after tensile test was studied by scanning electron microscopy. The influence of these components on the temperature rise during polymerization was investigated. It was found that the tensile strength, the bending strength, and the compressive strength decreased with increasing TCP content, whereas the inverse was observed for the Young's modulus. The tensile strength slightly increased with increasing HEMA content and then it levelled off when the HEMA content was higher than 15 wt.-%. It seemed that there were maximum tensile, bending and compressive strengths when 2 wt.-% EGDMA (in HEMA) was added. Polymerization occurred more rapidly when HEMA and EGDMA were added, whereas the inverse result was found with TCP.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450105
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  • 42
    Electronic Resource
    Electronic Resource
    The relative physical and thermal properties of polyurethane elastomers. Effect of chain extenders derived from dihydroxynaphthalene (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 89-104 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyurethanelastomere wurden in Gegenwart von zwei Dihydroxynaphthalin(DHN)-Verbindungen und deren bromierter Derivate als Kettenverlängerer hergestellt. Als Polyole wurden Polycaprolactondiol und Polytetramethylenglykol und als Diisocyanat-Komponenten Diphenylmethandiisocyanat (MDI) und Dicyclohexylmethan-4,4′-diisocyanat (HMDI) eingesetzt. Der Einfluß der Struktur der Kettenverlängerer auf die physikalischen und thermischen Eigenschaften der Polyurethane wurde untersucht. Wegen der besseren Phasenmischungswirkung der 1,5-DHN-Segmente haben die damit hergestellten Polyurethane höhere Glasübergangstemperaturen und bessere dynamische Eigenschaften als die Polyurethane auf 2,7-DHN-Basis. Der Einbau von bromierten DHN-Einheiten erschwert die Entflammbarkeit. Durch das große freie Volumen der Bromatome wird jedoch die Rotation der DHN-Einheiten eingeschränkt, was zu Polyurethanen mit verringerten Phasenmischungs- und Kristallisationsgraden führt. Die bromhaltigen Polyurethane zeigen zudem eine Verschlechterung der mechanischen und physikalischen Eigenschaften und eine erhöhte Löslichkeit.
    Notes: Polyurethane elastomers were synthesized based on polyols such as poly(caprolactonediol) and poly(tetramethylene glycol), diisocyanates such as diphenylmethane-4,4′-diisocyanate (MDI) and dicyclohexylmethane-4,4′-diisocyanate (HMDI), and two dihydroxynaphthalenes (DHNs) and their brominated derivatives used as chain extenders. The effects of the chemical structures of the chain extenders on the physical and thermal properties of the polyurethanes were investigated. Because of the higher degree of phase mixing of the 1,5-DHN unit, the 1,5-DHN-based polyurethanes have higher Tg values and higher dynamic properties than 2,7-DHN-based polyurethanes. Introduction of bromine atoms increased the flame retardance. However, the large free volume of bromine atoms restricted the rotation of DHNs, thus, directly decreasing the degree of phase-mixing and crystallinity of the polyurethanes. Introducing bromine atoms also decreased the mechanical and dynamic properties and increased the solubility of the polyurethanes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450108
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  • 43
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of polypyrrolepolyurethane cationomer composites (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 139-147 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Poly(oxytetramethylen), 4,4′-Bibenzyldiisocyanat, N-Methyldiethanolamin als Kettenverlängerer und Acrylsäure/Polyacrylsäure als Quaternisierungsagens wurden Poly(etherurethan)-Kationomere hergestellt. In aus diesen Kationomeren hergestellten Filmen wurde Pyrrol (15 Gew.-%) in Gegenwart von CuCl2 polymerisiert. Die Filme wurden mittels dynamisch-mechanischer Analyse, Thermogravimetrie und Differentialthermoanalyse charakterisiert. Die elektrische Leitfähigkeit beträgt für den Film ohne Polypyrrol 7.5 · 10-12 Ω-1 cm-1 und mit Polypyrrol 4.5 · 10-6 Ω-1 cm-1.
    Notes: Poly(ether urethane) cationomers based on poly(oxytetramethylene), 4,4′-bibenzyldiisocyanate, N-methyldiethanolamine as chain extender, and acrylic acid/poly(acrylic acid) as quaternization agent were synthesized. Pyrrole (15 wt.%%) was polymerized in films of the ionomer containing CuCl2. The films were characterized by dynamic mechanical analysis, thermogravimetry and differential scanning calorimetry. The electric conductivity of the film without polypyrrole is 7.5 · 10-12 Ω-1 cm-1, while incorporation of polypyrrole increases the conductivity to 4.5 · 10-6 Ω-1 cm-1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450112
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  • 44
    Electronic Resource
    Electronic Resource
    Synthesis, characterization and polymerization of waxy monomers (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 155-164 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Wachsartige Monomere und Vernetzer wurden aus kommerziellen Wachsen durch Veresterung mit 2-Hydroxyethylmethacrylat, Glycerindimethacrylat oder Glycidylmethacrylat oder durch Funktionalisierung mit 2-Isocyanatoethylmethacrylat synthetisiert. Die erhaltenen opaken Methacrylate mit Schmelzpunkten zwischen 45 und 80°C wurden in Substanz bzw. Toluollösung in Gegenwart von Radikalinitiatoren polymerisiert. Die Polymeren zeichnen sich durch eine breite Molmassenverteilung aus. Im Gegensatz zur Substanzpolymerisation ist der Doppelbindungsumsatz nach der Lösungspolymerisation nahezu vollständig. Aufgrund der hohen Molmasse der Monomeren ist der beobachtete Polymerisationsschrumpf sehr gering. Polymerisate mit Vernetzermonomeren zeigen eine verbesserte mechanische Stabilität.
    Notes: Waxy monomers and crosslinkers, respectively, were synthesized from commercially available waxes by esterification with 2-hydroxyethyl methacrylate, glycerol dimethacrylate, or glycidyl methacrylate or by functionalization with 2-isocyanatoethyl methacrylate. The resulting opaque methacrylates with melting points between 45 and 80°C were polymerized in bulk and in toluene solution in presence of free radical initiators. The obtained polymers were characterized by a broad molecular weight distribution. Opposite to the bulk polymerization, the double bond conversion in solution polymerization is nearly quantitative. The observed volume shrinkage during polymerization is very low due to the high molecular weight of the monomers. Polymerizates containing crosslinking comonomers exhibit improved mechanical stability.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450114
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  • 45
    Electronic Resource
    Electronic Resource
    Zur Kinetik der stabilisierten Fällungs-polymerisation eines Kationischen Monomeren in wäßrigen Natriumchlorid-Lösungen (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 245 (1997), S. 165-181 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The stabilized free-radical precipitation polymerization of the cationic monomer N-(2-methacryloyloxyethyl)-N,N-dimethylbenzylammonium chloride (MADAMBQ) in aqueous solutions of sodium chloride was studied by reaction calorimetry. Poly(ethylene oxide) was used as stabilizer. The rate of polymerization reaches its maximum immediately after initiation and remains nearly constant up to 50 % conversion followed by a decrease that could be described by a first order kinetics. The particles formed are approximately 1 to 30 μm in diameter and are stable over a period of several months.A model based on the theory of homogeneous particle nucleation is suggested to describe the kinetic course of polymerization, taking into account the rate of polymerization in both phases. With the assumption that the concentration of monomer in the phases is determined by a Nernst distribution law, the kinetics of the early stage of polymerization can be modelled reasonably well.The solution polymerization and the unstabilized precipitation polymerization of MADAMBQ was also studied.
    Notes: Die Kinetik der stabilisierten Fällungspolymerisation des kationischen Monomeren N-(2-Methacryloyloxyethyl)-N,N-dimethylbenzylammoniumchlorid (MADAMBQ) in wäßrigen Natriumchlorid-Lösungen wurde mittels Reaktionskalorimetrie untersucht. Polyethylenoxid höherer Molmasse wurde als Stabilisator eingesetzt. Die Reaktionsgeschwindigkeit ist über einen größeren Umsatzbereich nahezu konstant und fällt anschließend mit dem Umsatz annähernd linear ab. Die Teilchengrößenverteilung der gebildeten Dispersion ist bimodal mit Teilchen von etwa 1 bis 30 μm Durchmesser.Zur Beschreibung des Geschwindigkeitsverlaufs der Fällungspolymerisation wird ein Modell vorgeschlagen, das die Polymerisation in der Wasser- sowie in der Polymerphase berücksichtigt. Die Teilchenbildung soll durch homogene Nukleierung erfolgen. Es wird angenommen, daß die Konzentration des Monomeren in den Phasen durch ein Nernstsches Verteilungsgleichgewicht bestimmt wird. Zu Vergleichszwecken wurde auch die Polymerisation von MADAMBQ in Lösung und als nicht stabilisierte Fällungspolymerisation durchgeführt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052450115
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  • 46
    Electronic Resource
    Electronic Resource
    An investigation of the grafting of cellulose powder with acrylamide under a magnetic field (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 246 (1997), S. 1-9 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Cellulosepulver, hergestellt durch Nitrierung von Eichen-Furfural-Lignocellulose, wurde mit Acrylamid radikalisch gepfropft. Die Pfropfreaktion wurde sowohl in Gegenwart eines äußeren Magnetfeldes (0,15-0,35 T) als auch ohne Magnetfeld durchgeführt. Der Einfluß von Monomerkonzentration, Initiatorkonzentration, Polymerisationszeit und temperatur sowie der magnetischen Feldstärke auf den Polymerisationsverlauf wurde untersucht. Es wurde festgestellt, daß der Pfropfumsatz mit zunehmender Feldstärke signifikant ansteigt.
    Notes: Cellulose powder obtained from oak furfural lignocellulose by nitration reaction was grafted with acrylamide using a radical initiation. The grafting reactions were carried out and compared both in presence and in absence of a continuous external magnetic field with the intensity extended between 0.15-0.35 T. The effect of monomer and initiator concentration, time and temperature of reaction and magnetic field intensity onto the grafting process were examined. It was observed that the presence of a magnetic field leads to a significant increase of the graft conversion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052460101
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  • 47
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    Electronic Resource
    Radical polymerization of poly(butyl acrylate) in the presence of poly(L-lactic acid), 1. Synthesis, characterization and properties of blends (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 246 (1997), S. 49-63 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(L-milchsäure) ist ein biokompatibler, semikristalliner, thermoplastischer Polyester mit ungünstigen mechanischen Eigenschaften. Daher wurde in einem “reactive blending”-Prozeß ein Acrylkautschuk, n-Butylacrylat, mittels einer Suspensionspolymerisation in Wasser auf in einem organischen Lösungsmittel gelöste Poly(L-milchsäure) gepfropft. Die gebildeten Copolymeren konnten isoliert und durch NMR-Spektroskopie und DSC-Messungen charakterisiert werden. Die Untersuchung der mechanischen Eigenschaften ergab keine befriedigenden Ergebnisse, weil die Kautschukphase wahrscheinlich aus viskosen linearen Makromolekülen besteht und daher keine elastischen Eigenschaften besitzt. In weiteren Arbeiten soll der Syntheseweg so modifiziert werden, daß durch den Einbau von Diacrylaten eine zumindest partielle Vernetzung der Kautschukphase erreicht wird.
    Notes: Poly(L-lactic acid) is a biocompatible polyester, semicrystalline, thermoplastic, with low versatility in mechanical properties. To overcome this problem, a reactive blending procedure was performed by grafting an acrylic rubber, n-butyl acrylate, via water suspension polymerization onto poly(L-lactic acid) dissolved in an organic solvent. It was possible to isolate the copolymeric phase formed from the two polymers and characterize it by using NMR and DSC techniques. Mechanical tests on blends gave no satisfactory response, probably because the rubbery phase is composed essentially of viscous linear macromolecules, not able to perform elastic properties. Work is in progress to modify the synthetic pathway to incorporate diacrylates in order to realize a rubbery phase at least partially cross-linked.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052460104
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    Tin-coupled styrene-butadiene rubbers (SBRs). Relationship between coupling type and propertiesBased on a paper presented at the 148th Meeting of the Rubber Division, American Chemical Society, Cleveland, Ohio, 17-20 October 1995. (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 246 (1997), S. 85-96 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Entwicklung von neuen Styrol-Butadien-Kautschuken (SBRs) für Reifenanwendungen sind mehrere Arten von Zinn-Polymer-Bindungen (Styryl-, Butadienyl-, Isoprenyl- and α-Methylstyryl-Zinn) sowohl in linearen als auch in verzweigten Ketten untersucht worden. Die dynamisch-mechanischen Eigenschaften von Vulkanisaten mit Ruß wurden analysiert, um eine Beziehung zwischen den Strukturparametern der Polymeren und den Materialeigenschaften herzustellen. Der Polymer-Füll-stoff-Wechselwirkungsparameter, der durch das Verhältnis von mechanischen und dynamischen Termen definiert ist, wurde zur Charakterisierung der Verbindungen herangezogen. Der Einbau von verschiedenen Zinn-Polymer-Bindungen in lineare und in verzweigte SBR-Ketten bewirkte eine Verbesserung der Hystereseeigenschaf-ten der Vulkanisate und eine Veranderung des Wechselwirkungsparameters.
    Notes: Following the development of new SBRs for tyre applications, several kinds of tin-polymer bonds (styryl-, butadienyl-, isoprenyl- and α-methylstyryltin) have been studied, in both branched and linear chains.Dynamic-mechanical properties of the carbon black vulcanizates have been analyzed to establish a relationship between structural parameters of polymers and compound properties. The filler-polymer interaction parameter, defined by a ratio of mechanical and dynamic terms, has been used for the evaluation of the compounds. The introduction of different types of tin-polymer bonds, in branched and linear chains of the SBRs, implies an improvement in the hysteresis properties of the vulcanizates as well as a modification of the interaction parameter.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052460107
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    A novel spin-finishing method for antistatic modification of polyester fiber. Surface reaction onto amine-containing copoly(amide-ethers) blended with polyester fiber (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 246 (1997), S. 109-123 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Copoly (amid-ether) rnit zwei unteschiedlichen Aminfunktionalitäten wurden als antistatische Modifikatoren für Polyethylenterephthalatfasern (PET) eingesetzt. Die tertiären Aminogruppen schmelzegesponnener Copolymerfilamente wurden rnit drei Alkylierungsmitteln umgesetzt, wobei ein Sulfobetain, ein Carbobetain bzw. Ammoniumionen gebildet wurden. Dadurch wurde der scheinbare spezifische Widerstand der Filamente auf größfienordnungsmäßfiig 106 bis 108 Ω/cm verringert. Da sich die quaternisierten Copolymeren beim Blend-Spinnen rnit PET zersetzen, wurden Blendfasern von PET mit einem Copolymeren nach dem Schmelzespinnen einer Quaternisierung oder Vernetzung rnit Alkylierungsmitteln bzw. Epoxyvernetzern unterzogen, was die antistatischen Eigenschaften der Fasern im Vergleich rnit der unbehandelten Faser verbesserte. Insbesondere die mit Epoxiden vernetzten Fasern wiesen antistatische Eigenschaften auf, wie sie mit dieser Modifizierungsmethode bislang nicht erreicht wurden. Die antistatischen Eigenschaften blieben nach dem Fkben erhalten, da sowohl die hydrophilen als auch die ionischen Gruppen auf der Faseroberflache immobilisiert waren. Da Quaternisierung bzw. Vernetzung in einem Arbeitsgang rnit dem Verspinnen und Verstrecken der Fasern innerhalb einer kurzen Reaktionszeit erfolgen, sollte diese “spin-finishing„ genannte Methode konventio- nellen Verfahren bezuglich Kosten und Produktivitat uberlegen sein.
    Notes: Copoly(amide-ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt-spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo-betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide-ether) was melt-spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on-line with spinning and drawing within a short reaction time, this modification technique is called “spin-finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052460109
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    Etching of a low-density polyethylene film by fuming nitric acid (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 249 (1997), S. 33-46 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Filme aus Polyethylen niedriger Dichte (LDPE) wurden mit rauchender Salpetersäure behandelt. Die Oberflächeneigenschaften sowie die Bildung polarer Gruppen wie auf der geätzten Filmoberfläche wurden mit SEM-, IR- und XPS-Methoden analysiert. Die mechanische Festigkeit eines aus dem geätzten LDPE-Film und einem Epoxidharz hergestellten Laminats sowie die Bedruckbarkeit der geätzten Oberflächen wurden untersucht und mit einer unbehandelten Probe verglichen. Die Oberflächenrauhigkeit und die Gegenwart polarer Gruppen erhöhen die mechanische Festigkeit des Laminats aus dem geätzten Film durch mechanische Verankerung und chemischer Wechselwirkungen. Die Oberfläche des behandelten LDPE-Films ist besser bedruckbar als die des unbehandelten Films.
    Notes: Low-density polyethylene (LDPE) films were treated with fuming nitric acid (FNA). The surface characteristics and also the insertion of polar groups like on the etched LDPE film surface were measured by SEM, IR and XPS analyses, respectively. The mechanical performance of a laminate of the etched film with epoxy resin and also the printability of the etched film surface were tested and compared with the unetched sample. The surface roughening and the presence of polar groups enhance the mechanical strength of the laminate of FNA-treated film due to mechanical interlocking and chemical interaction. The printability of the treated film surface is also superior to that of the untreated LDPE film surface.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052490103
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    Celluloseether als Trennschichten hydrophiler Polymermembranen (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 249 (1997), S. 11-32 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: This paper reports on polymer membranes characterized by a surface layer of hydroxyalkyl derivatives of cellulose. Water compatible polymers like hydroxyalkyl derivatives of cellulose are preferably those exhibiting good chemical stability and desired membrane characteristics. Normally, water-compatible polymers used in the coating solutions must be rendered water-insoluble after coating. By adapting crosslinking conditions on separation problems, the membranes are useful for many processes in the fields of biotechnology, food and chemical industry.The membranes presented here possess the advantage of being highly resistant to chemical and biological degradation and, hence, have long lifetimes under many process conditions.
    Notes: Es wird die Entwicklung hydrophiler Polymermembranen diskutiert, die nach Beschichtung mit Celluloseethern und anschließender Vernetzung auf den asymmetrischen Trägermembranen interessante Permeations- und Trenneigenschaften bei hervorragenden chemischen Stabilitäten, vor allem beim Membrantrennverfahren der Nanofiltration, aufzeigen. Weiterhin werden Aussagen zu den Gastrenneigenschaften der Celluloseetherkompositmembranen getroffen.Erläutert werden die Permeations- und Trenndaten der Kompositmembranen in Korrelation zur Vernetzung der Celluloseether anhand verschiedener Einflußgrößen, was qualitative und gegebenenfalls quantitative Aussagen zum Vernetzungsmechanismus der Celluloseetherderivate erlaubt. Dabei stehen die Vernetzungstemperatur, der Einfluß der katalysierenden Wasserstoffionen und bedingt die Vernetzungszeit im Vordergrund. Abgerundet werden die Arbeiten durch Ermittlungen rheologischer Daten, die in Zusammenhang zu den Vernetzungsreaktionen und damit zu membranspezifischen Größen stehen.Infolge der hervorragenden chemischen Stabilität der Celluloseether werden Einsatzmöglichkeiten der Kompositmembranen zur Nanofiltration niedermolekularer Verbindungen aus organisch hochbelasteten Systemen beschrieben.
    Additional Material: 30 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052490102
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    Products of polycondensation of 4,4′-biphenyldithiol with some hydrocarbon dihalides (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 13-21 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polysulfide wurden mit hoher Ausbeute durch Hochtemperatur-Lösungspolykondensation von 4,4′-Dimercaptobiphenyl mit ausgewählten aliphatischen und aromatisch-aliphatischen Dihalogenkohlenwasserstoffen hergestellt. Um die optimalen Polykondensationsbedingungen zu bestimmen, wurde der Einfluß folgender Faktoren auf die reduzierte Viskosität und die Ausbeute der Polysulfide ermittelt: Art des organischen Lösungsmittels, Art des Halogenwasserstoff-Akzeptors, Konzentration der organischen Reagenzien, Reaktionstemperatur und -zeit. Die Polykondensation des Dithiols mit Bis(4-chlormethylphenyl)methan wurde als Modellsystem eingehender untersucht. Die Polysulfidstrukturen wurden mittels Elementaranalyse, IR-Spektroskopie und Röntgenstrukturanalyse bestätigt. Aus der thermogravimetrischen Analyse wurden die Zersetzungstemperatur, der Gewichtsverlust bei dieser Temperatur und das Maximum der Zersetzungsgeschwindigkeit erhalten. Weiterhin wurden einige physikalisch-chemische, mechanische und dielektrische Eigenschaften ermittelt. Die beste thermische und chemische Bestandigkeit zeigt das aus dem Dithiol und 4,4′-Bis(chlormethyl)biphenyl hergestellte Polysulfid, was auf dessen vorwiegend aromatische Struktur zuriickgefuhrt werden kann.
    Notes: Polysulfides were synthesized with high yield by high-temperature solution polycondensation of 4,4′-biphenyldithiol with selected aliphatic and aromatic-aliphatic hydrocarbon dihalides. To determine the optimum polycondensation conditions, the influence of the following factors on reduced viscosity and yield was studied: type of organic solvent, type of hydrogen halide acceptor, concentration of reagents, reaction temperature, and reaction time. A thorough examination was carried out only for the polycondensation of dithiol with bis(4-chloromethylphenyl)methane chosen as model system. The structures of the polysulfides were confirmed by elemental analysis, X-ray analysis, and infrared spectroscopy. The temperature of initial decomposition, the percentage of mass loss, and the temperature of the fastest decomposition, process were determined from curves of differential thermal and thermogravimetric analysis. Some physicochemical, mechanical and electrical properties were determined. The highest thermal and chemical resistance has been found for the polysulfide obtained from 4,4′-biphenyldithiol and 4,4′-bis(chloromethyl)biphenyl, probably because of the predominantly aromatic structure.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510102
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    Organic-inorganic hybrid sol-gel materials, 2. Application for dental composites (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 61-72 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Drie organisch-anorganische Hybridmaterialien wurden nach dem Sol-Gel-Verfahren durch kovalenten Einbau von Poly(styrol-co-methylmethacrylat)(Poly(St-co-MMA))-, Polymethylmethacrylat(PMMA)- und Polystyrol(PS)-Struktureinheiten in ein SiO2-Netzwerk hergestellt und als Füllstoffe (bis zu 60 Gew.-%) in Dentalharzen verwendet. Der Einfluß der Füllstoffe auf einige mechanische Eigenschaften der Harze wurde untersucht. Die Härte der gefüllten Dentalharze nahm mit steigendem Füllstoffgehalt zu, wogegen die Biegefestigkeit abnahm. Die Druckfestigkeit der gefüllten Harze war besser als die des ungefüllten Harzes, nahm jedoch mit steigendem Füllstoffgehalt ab.
    Notes: By incorporating poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(styrene-co-methyl methacrylate) (poly(St-co-MMA)) structure units covalently into the SiO2 glass network via a sol-gel approach, three organic-inorganic hybrid materials (PMMA-SiO2, PS - SiO2, and poly(St-co-MMA) - SiO2) have been prepared. The three hybrid sol-gel materials were used as filler (up to 60 wt.-%) for dental composite resins. The effect of the three filler materials on several mechanical properties of the dental composite resins was investigated. The hardness of the filled dental composites increased with increasing filler content, whereas the bending strength decreased. The compressive strength of the composites was improved, compared with the unfilled resin, but decreased with inreasing filler content.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510106
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    Adsorption of BTX compounds from aqueous solutions by water-insoluble starch (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 107-116 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Adsorption von Benzol, Toluol und p-Xylol (BTX) aus wäßrigen Lösungen mittels hochvernetzter kationischer Stärke mit tertiären Amingruppen wurde untersucht. Der endotherme Adsorptionsvorgang ist vom Anfangs-pH-Wert und der Anfangskonzentration abhängig und kann mit einer Langmuir-Isotherme beschrieben werden.Die Adsorptionswärme (Δ) bei pH 4 beträgt für Benzol, Toluol und Xylol 29,45 kJ mol-1, 34,41 kJ mol-1 bzw. 35,58 kJ mol-1, bei pH 10 30,17 kJ mol-1, 35.56 kJ mol-1 bzw. 39,39 kJ mol-1. Die adsorbierte Menge nimmt in der Reihenfolge Benzol 〉 Toluol 〉 Xylol ab.
    Notes: The removal of benzene, toluene and p-xylene (BTX) compounds from aqueous solutions with highly crosslinked cationic starch containing tertiary amine groups was investigated. The adsorption process has found to be initial pH- and initial concentration-dependent, endothermic, and follows the Langmuir isothermal adsorption.The heats of adsorption (ΔH) at initial pH = 4 of benzene, toluene and p-xylene compounds are 29.45 kJ mol-1, 34.41 kJ mol-1, and 35.58 kJ mol-1, respectively, those at initial pH = 10 are 30.17 kJ mol-1, 35.56 kJ mol-1, and 39.39 kJ mol-1, respectively. The order of the amount of adsorbed BTX compounds on the adsorbent is benzene 〉 toluene 〉 p-xylene.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510110
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    Thermogravimetric and ESR studies of polymer/metal precursors for high-temperature superconductors (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 157-170 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bi-Sr-Ca-Cu-Komplexverbindungen von Polymethacrylsäure (PMAA) und Kresolnovolaken, die als Precursoren für Hochtemperatursupraleiter (HTSL) eingesetzt werden, sowie deren Cu-Komplexsalze wurden ESR-spektroskopisch und thermogravimetrisch untersucht. In den PMAA-Proben wurden drei verschiedene Cu2+-Spezies nachgewiesen: i) Cu2+-Paare, ii) isolierte Cu2+-Ionen und iii) Cu2+-Cluster. Bei niedrigem Cu-Gehalt der Proben bilden die Cu2+-Paar-Bindungen den Hauptanteil, bei hohem Cu-Gehalt überwiegen die Clusterbindungen. In den Novolakproben wurden nur isolierte Cu2+-Ionen und Cu2+-Cluster nachgewiesen. Die Einführung der Cu-Ionen erniedrigt die thermische Stabilität der Polymeren, der thermische Abbau erfolgt stufenweise. In den PMAA-Proben wird die erste Abbaustufe bei ≈ 220°C durch die Cu2+-Paar-Komplexe verursacht.
    Notes: Bi-Sr-Ca-Cu complexes of poly(methacrylic acid) (PMAA) and cresol novolac, which are precursors for high-temperature superconductors (HTSC) and Cu complexes of those polymers were investigated by ESR spectroscopy and thermogravimetry. In the PMAA samples three different kinds of Cu2+ species were detected: i) Cu2+ pairs, ii) isolated Cu2+ ions and iii) Cu2+ clusters. While Cu2+ pairs are the main species at low Cu concentrations, clusters become dominant at high Cu contents. In the novolac samples Cu2+ was only detected in isolated sites and clusters. The introduction of Cu ions lowered the thermal stability of the polymers and led to a stepwise decomposition. In the PMAA samples the first decomposition step at ≈ 220°C is caused by the Cu2+ pair complexes.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510114
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    Polymerization of 1,3-butadiene with neodymium chloride/2-ethylhexanolate/triethylaluminium catalyst systemIPCL communication No. 325. (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 193-205 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Neodymchlorid-2-ethylhexanolate mit der allgemeinen Formel NdCl3 · nL wurden durch eine Liganden-Austauschreaktion zwischen Neodymchloridisopropanolat (I) und 2-Ethylhexanol (EH) hergestellt. Die Hexanolate NdCl3 · 1,5 EH (II) und NdCl3 · 2,5 EH (III) wurden durch Elementaranalyse und Gravimetrie charakterisiert. Die katalytische Aktivität der Hexanolate bei der Homopolymerisation von 1,3-Butadien in Gegenwart von Triethylaluminium wurde untersucht. Die Verbindung III zeigte eine höhere Aktivität als die Verbindung II. Höhere Katalysator- und Cokatalysatorkonzentrationen sowie eine höhere Temperatur steigerten den Umsatz, wogegen die Viskosität der Produkte abnahm. Mit zunehmender Reaktionszeit erhöhten sich sowohl der Umsatz als auch die Viskosität. Die cis-1,4-Konformation wurde durch die Variation von Temperatur und Cokatalysatorkonzentration beeinflußt. Der gesamte Anteil der cis-1,4-Stuktur lag jedoch in allen Fällen über 99%, während die Produkte nur einen sehr geringen Vinyl-Anteil von 〈1% enthielten. Die Zugabe einer elektronenspendenden Verbindung verringerte den cis- 1,4-Gehalt aber auf 87%.
    Notes: Neodymium chloride 2-ethylhexanolates of the general formula NdCl3 · nL were prepared by ligand exchange reaction between neodymium chloride ispropanolate (I) and 2-ethylhexanol (EH). These hexanolates, NdCl3 · 1.5 EH (II) and NdCl3 · 2.5 EH (III), were characterized by elemental analysis and gravimetry. The catalytic activity of these hexanolates in combination with triethyl aluminium in the homopolymerization of 1,3-butadiene was studied, and the activity was found to be higher with III than II. The conversions increased with increasing the catalyst and co-catalyst concentrations and the temperature, whereas the intrinsic viscosity decreased. The conversions and the intrinsic viscosity decreased. The conversions and the intrinsic viscosity increased with reaction time. The cis-1,4 structure was influenced by variation in temperature and co-catalyst concentration, however, the total cis-1,4 structure was always more than 99% with very low vinyl content (〉1%). Addition of an external electron donor decreased the cis-1,4 content to 87%.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510117
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    The effects of desolvation methods of the recrystallized MgCl2-alcohol adduct on catalyst characteristics and the bulk density of polyethylene (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 17-25 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: MgCl2-Träger für einen Ethylenpolymerisationskatalysator wurden mit Hilfe der Rekristallationsmethode hergestellt, wobei Methanol als Lösungsmittel diente. Der Einfluß verschiedener Lösungsmethoden des rekristallisierten MgCl2-Alkohol-Adduktes auf die morphologischen Charakteristika der Katalysatoren wurde untersucht. Die Lösungsmethode beeinflußt die Eigenschaften der Katalysatoren beträchtlich. Die dargestellten Katalysatoren wiesen unterschiedliche Ti/Mg-Verhältnisse auf, sowohl was die Oberfläche als auch die gesamten Katalysator-Partikel betrifft. Betrachtet man die Ti-Verteilung und Aktivitätsprofile, dann erweisen sich nicht nur die Polymerisationsbedingungen, sondern auch die Ti-Verteilung auf dem Katalysator als wichtige Faktoren, welche die Dichte der Polymeren beeinflussen.
    Notes: The MgCl2 supports for an ethylene polymerization catalyst were prepared by the recrystallization method using methanol as a solvent. The effects of different desolvation methods of the recrystallized MgCl2-alcohol adduct on the morphological characteristics of the catalysts were examined. The desolvation method greatly affects the characteristics of the catalyst. The prepared catalysts had different Ti/Mg ratios with respect to both surface content and entire catalyst particles. Considering Ti distribution and activity profiles, not only the polymerization conditions but also the Ti distribution on the catalyst appear to be an important factor which affects the bulk density of the polymers.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052530102
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    Synthesis of aromatic poly(ether ketone)s with ferrocene units in the main chain (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 89-97 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aromatische Poly(etherketon)e mit Ferrocen-Einheiten in der Hauptkette wurden durch direkte Polykondensation von 1,1′-Ferrocendicarbonsäure mit Diphenylether oder 1,4-Diphenoxybenzol hergestellt. Als Katalysatoren wurden Trifluormethansulfonsäure, Methansulfonsäure/P2O5 (Eatons Reagens) oder Trifluormethansulfonsäure/P2O5 verwendet. Polykondensationen bei Raumtemperatur für 24 h ergaben Poly(arylenetherketon)e mit Grenzviskositäten bis zu 40 mL g-1. Die Monoacylierung von Diphenylether mit Ferrocencarbonsäure wurde im Hinblick auf die Effektivität von Eatons Reagens als Katalysator und Lösungsmittel eingehender untersucht.
    Notes: Aromatic poly(ether ketone)s with ferrocene units in the main chain were prepared by direct polycondensation of 1,1′-ferrocenedicarboxylic acid with diphenyl ether or 1,4-diphenoxybenzene using various catalysts such as trifluoromethanesulfonic acid (triflic acid), a combination of methanesulfonic acid/P2O5 (Eaton's reagent) or a combination of triflic acid/P2O5. Polycondensations at room temperature for 24 h gave poly(arylene ether ketone)s with inherent viscosities up to 40 mL g-1. Monoacylation of diphenyl ether with ferrocenecarboxylic acid was studied in detail in order to show the efficiency of polymer formation employing Eaton's reagent as catalyst and solvent.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052530107
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    Mechanical and structural characteristics of phenolphthalein poly(ether sulfone)/ultra-high molecular weight polyethylene blends (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 73-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die mechanischen und strukturellen Eigenschaften von Blends aus Phenolphthalein-Polyethersulfon und ultrahochmolekularem Polyethylen (UHMWPE) wurden anhand von Zug- und Biegeversuchen, Raster- und Transmissionselektronenmikroskopie untersucht. Die Zugabe einer geringen Menge UHMWPE (2 Gew.-%) führt zu einer Verstärkung der PES-C-Matrix. Höhere UHMWPE-Konzentrationen verschlechtern die mechanischen Eigenschaften. Die Strukturuntersuchungen zeigen, daß die Blends im gesamten Zusammensetzungsbereich mehrphasig sind. Bei geringen UHMWPE-Konzentrationen ist die UHMWPE-Phase gleichmäßig verteilt und entlang der Fließrichtung orientiert, was mit der starken Grenzflächenadhäsion zur Verbesserung des mechanischen Verhaltens beiträgt. Mit steigender UHMWPE-Konzentration nimmt die Domänengröß der UHMWPE-Phase zu.
    Notes: Mechanical and structural properties of blends of phenolphthalein poly(ether sulfone) (PES-C) with ultra-high molecular weight polyethylene (UHMWPE) were investigated using tensile and bending testing, scanning electron microscopy and transition electron microscopy. The incorporation of minor amounts of UHMWPE (2 wt.-%) into PES-C has a reinforcement effect. With higher concentrations of UHMWPE, the mechanical properties decrease gradually. Structural studies demonstrated that the blends are multiphasic in the whole composition range. The minor UHMWPE, dispersed uniformly and oriented along the flow direction, as well as the strong interfacial adhesion contribute to the increase of the mechanical performance of the blends. The domain size of the UHMWPE phase was found to increase with the increase of its concentration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052510107
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    Redox copolymer with N-bromosulfonamide groups for the decomposition of cyanide ions in dilute aqueous solutions (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 117-130 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Redoxcopolymeres, ein makroporöses Poly(Styrol-co-Divinylbenzol) (S/DVB)-Harz mit N-Bromsulfonamidgruppen, wurde angewandt, um Cyanide aus wäßrigen Lösungen zu entfernen. Dieses Harz enthält aktives Brom in den funktionellen Gruppen (1.86 mmol g-1, 3.72 meq g-1) und weist Oxidationseigenschaften auf. Es wurde sowohl in statischen als auch in dynamischen Systemen für die Oxidation von Cyanidionen zu nichttoxischen Verbindungen angewandt. Die Reaktionen wurden in wäßrigen Lösungen mit 26-2600 mg L-1 CN- bei unterschiedlichen pH-Werten durchgeführt. Die Ergebnisse zeigten, daß dieses Harz die Cyanide leicht zu Cyanaten oxidiert, die ca. 1000 mal weniger toxisch sind. Bei Kontakt mit dem Harz fiel die Cyanidkonzentration in den Lösungen unter 0.05 mg L-1 CN-. Die —SO2NBrNa-Gruppen gingen dabei in —SO2NH2-Gruppen über. Diese konnten wiederum mit Natriumhypochlorit- und Natriumbromid-Lösungen reaktiviert werden. Es wurde auch eine Alternative zu der Cyanidionenoxidation mit N-Bromsulfonamid-Harz untersucht, indem ein analoges N-Chlorsulfonamid-Harz in Gengenwart von katalytischen Mengen von Bromiden angewandt wurde.
    Notes: A redox copolymer, macroporous poly(styrene-co-divinylbenzene) (S/DVB) resin having N-bromosulfonamide groups, was used for removal of cyanide ions from aqueous solutions. This resin contains active bromine in functional groups (1.86 mmol g-1, i. e. 3.72 meq g-1) and shows oxidative properties. It was employed in static and flow system for oxidation of cyanide ions to non-toxic compounds. The reactions were carried out in aqueous media containing 26-2600 mg L-1 CN- at different pH values. The data showed that the resin having active bromine easily oxidized cyanides, forming cyanates being 1000-times less toxic than cyanides. In contact with the resin the concentration of cyanides in tested solutions dropped below 0.05 mg L-1 CN-. During the oxidation processes the —SO2NBrNa groups transform to —SO2NH2 groups. They can be reactivated by use of sodium hypochlorite and bromide solutions. As an alternative to oxidation of cyanides by N-bromosulfonamide resin, the oxidation of these ions by N-chlorosulfonamide resin with addition of a small amount of bromides was examined.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052510111
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    Mitteilungen/Announcements (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 251 (1997), S. 207-208 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052510118
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    Hydrolytic and thermal stability of novel polyurethane elastomers (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 33-43 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel Polyester glycols with alkyl side groups were used for the improvement of thermal stability and hydrolytic stability of polyester urethane elastomers. The novel polyester glycols used are poly( β -methyl- δ -valerolactone)glycol (PMVL), poly(3-methyl pentamethylene adipate) glycol (PMPA), poly(nonamethylene-co-2-methyl octamcthylene carbonate) gycol (PNCO). A mixture of PNCO and poly(dimethyl siloxane)gycol (PNCO/PDMS) was also used. Polyurethane network elastomers were prepared from 4,4′-diphenylmethane diisocyanate (or 2,4-tolylene diisocyanate), and a mixture of 1,4-butane diol and trimethylol propane by a prepolymer method. Mechanical properties, Tg, thermal stability, and hydrolytic stability were measured. Morphology were also measured by means of polarizing microscopy, dynamic viscoelastometer, and ESR. The properties of novel polyurethane elastomers have good mechanical properties comparable to those of the general purpose polyester urethanes, and better thermal and hydrolytic stability than PTMG-based polyurethane. These polyurethane elastomers were exposed in out door during 2 year in Nagasaki, JAPAN. The novel polyurethane clastomers held alomost constant values for gel fraction, swelling ratio, relative modulus during 12 months, while poly(oxytetramethylene oxide)-based polyurethane as a control decreased the these values. Relationship of degradation behaviors with chemical structure and morphology were discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052520103
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    Oxidizability of lactams and lactam-based polyamidesDedicated to Dr Jan Šebenda on the occasion of his 70th birthday (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 139-151 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the chain oxidation of N-alkylamides with molecular oxygen, propagation is the ratedetermining step under conditions when the oxidation rate is independent of oxygen pressure. The oxidizability of lactams and lactam-based polyamides correlates with the energy of the formation of N-alkylamide radical by abstraction of hydrogen from the methylene group adjacent to nitrogen. While for lactams this energy depends on the number of carbons in the lactam ring, for N-alkylamides and polylactams such dependence is not observed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052520110
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    Use of EPR to image nitroxyl radicals in hals stabilized polymers (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 179-193 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An X-band EPR-Imaging apparatus which allowed us to determine the distribution of nitroxyl radicals within solid samples of polymeric materials containing hindered amine stabilizers, is described. It is shown that EPR Imaging represents a powerful tool for investigating the growth and decay of nitroxyls formed in polymers irradiated under air for long periods. Since the variations of the radical concentration can be monitored both in time and in the space, this technique provides valuable information not easily attainable by means of other methods.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052520113
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    Photo-oxidation mechanisms of poly(2,6-dimethyl-1,4-phenylene oxide). (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 237-256 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A re-examination of the photo-oxidation mechanism of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at both long and short irradiation wavelengths under accelerated conditions is reported. The formation rate of poly-2,6-dimethylphenoxy (PDMP) radicals, have been observed by esr spectroscopy, while benzylic-type radicals have been detected by spin trapping experiments using nitrosodurene under UV irradiation conditions. The changes of FTIR spectra obtained under accelerated photo-oxidative conditions show the formation of primary oxidation products such as aromatic aldehydes and quinones. The direct formation of radical cations and superoxide anions by a photo-induced electron-transfer reaction is suggested under our conditions. In addition, some results on the of photo-oxidation PPO/PS blends as a function of polystyrene tacticity are also reported. In the case of syndiotactic polystyrene the blend photostability shows some differences in comparison with the blend containing atactic polystyrene. This effect has been ascribed to the absence of excimers in syndiotactic polystyrene which are not revealed by fluorescence measurements. Finally, the chemical modification of PPO with bromine gave a bromomethylated PPO with different amounts of CH2 Br groups, which has been used for further substitution reactions with alkoxy sodium salts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine (PMPP). The accelerated photo-oxidation of a modified copolymer PPO-PMPP containing a 60% PMPP moieties as side groups and its blends with pure PPO has been followed by FTIR and esr spectroscopies. Some comparisons with a commercially available hindered amine light stabilizers (HALS) and a modified copolymer PPO-PMPP are also reported under the same photo-oxidative conditions.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052520116
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    Zähigkeit und Relaxationsverhalten von Polymethylmethacrylat, Polystyrol und Polycarbonat (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 27-49 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: For innovative applications of plastics, which take advantage of special properties of polymeric materials, comprehensive understanding on strengthening and toughening mechanisms is required. The temperature-dependent mechanical behaviour of PMMA, PS and PC under dynamic loading conditions were investigated by means of an instrumented Charpy impact tester. The elastic-plastic fracture mechanics parameters, the energy-determined J-integral, and the deformation-determined crack opening displacement, δ, enable to do structure-related quantification of micromechanical processes. The J-integral values showed a maximum, resulting from an energy-dissipative process. The maximum values for PMMA occurred at 50°C and for PC at 40°C , which is related to the secondary(β) relaxation as evaluated from the frequency dependence of the mechanical loss factor. The 0-relaxation initiated shear deformation mechanisms, which led to a local increase of toughness. In polycarbonate, toughness is strongly increased due to a stress-induced shear flow process at temperatures higher than -25°C. Correlations between morphology and toughness can be derived with the help of optical investigations of stable crack propagation on fracture surfaces.
    Notes: Innovative Kunststoffanwendungen, die die speziellen Eigenschaften polymerer Werkstoffe gezielt ausnutzen, erfordern vertiefte Kenntnisse über festigkeits- und zähigkeitsbestimmende Mechanismen. Das sich in Abhängigkeit von der Temperatur ändernde Werkstoffverhalten von PMMA, PS und PC wurde bei dynamischer Beanspruchung mittels instrumentierter Kerbschlagbiegeprüfung bestimmt. Mit der verformungsbestimmten Rißöffnungsverschiebung δ und dem energiebestimmten J-Integral stehen Kenngrößen der Fließbruchmechanik zur Verfügung, die eine strukturbezogene Quantifizierung der temperaturabhängigen mikromechanischen Prozesse erlauben. Die J-Integralwerte zeigen für PMMA bei 50°C und für PC bei -60°C ein durch einen energiedissipativen Prozeß verursachtes Maximum. Dieses Maximum steht, wie sich aus der Interpretation der Frequenzabhängigkeit des mechanischen Verlustfaktors ergibt, mit der Neben(β)-Relaxation in Beziehung. Dabei initiiert die β-Relaxation Scherdeformationsmechanismen, die ihrerseits die lokale Zähigkeitserhöhung bewirken. Ab -25°C führt für PC ein spannungsinduzierter Scherfließprozeß zu einer erheblichen Zähigkeitssteigerung. Durch die Einbeziehung lichtmikroskopischer Untersuchungen des stabilen Rißfortschritts auf der Bruchfläche können Morphologie-Zähigkeits-Korrelationen abgeleitet werden.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052530103
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    Thermostable block copolymers, 2Part 1 cf. 16.. Preparation and characterization of soluble blockcopolyimides (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 71-88 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe von Polyamidimid-Polyimid-Blockcopolymeren (PAI-PI-BCPs) wurde durch Polykondensation von PAI-Blöcken mit Amino-Endgruppen und PI-Blöcken mit Anhydrid-Endgruppen hergestellt. Zur Synthese der Blöcke mit Molekulargewichten im Bereich von ca. 2000 bis 15000 wurden nur technisch leicht zugängliche Monomere, wie Trimellitsäureanhydridchlorid, Benzophenontetracarbonsäuredianhydrid, 4,4′-Diaminodiphenylmethan, 2,4-Toluylendiamin und 4,4′-Diaminodiphenylsulfon eingesetzt. Dabei zeigte sich, daß durch den blockartigen Aufbau die Löslichkeit-und damit die Verarbeitbarkeit-im Vergleich zu den reinen, unlöslichen Polyimiden wesentlich verbessert werden konnte, bei nahezu gleichbleibender Thermostabilität. So wurden BCPs mit guten mechanischen Eigenschaften, Thermostabilitäten bis ca. 480°C (Thermogravimetrie, 5% Gewichtsverlust) und guten Löslichkeiten in Dimethylacetamid und anderen polaren aprotischen Lösungsmitteln erhalten.
    Notes: New poly(amide-imide)-poly(imide) block copolymers (PAI-PI-BCPs) were prepared by polycondensation of amino-terminated PAI-blocks with anhydride-terminated PI-blocks. For the syntheses of the blocks with molecular weights from 2000 to 15000 only commercially available monomers were used, e.g. trimellitic acid anhydride chloride, benzophenone tetracarboxylic acid dianhydride, 4,4′-diaminodiphenylmethane, 2,4-toluenediamine and 4,4′-diaminodiphenylsulfone. The BCPs were shown to have better solubility compared to the pure, insoluble PIs with only minor decrease of the thermostability. Thus, BCPs with good mechanical properties, thermostabilities up to 480°C (thermogravimetric analysis, 5% weight loss) and good solubility in dimethylacetamide and other polar aprotic solvents were obtained.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052530106
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    Block and graft copolymers with polysiloxane and poly(N-acyliminoethylene) sequences (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 139-149 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe von Polysiloxan/Poly(N-acetyliminoethylen)-(PSiO/PNAI)-Block- und -Pfropfcopolymeren wurde durch Polymerisation von 2-Methyl-2-oxazolin (MeOZO) mit funktionellen Polysiloxan-Prepolymeren als Initiatoren synthetisiert. Die Copolymeren wurden mit IR- und 1H NMR-Spektroskopie sowie Elementaranalyse, Differentialkalorimetrie und Thermogravimetrie charakterisiert. Der Einbau sowohl von hydrophoben als auch von hydrophilen Sequenzen verleiht den Polymeren amphiphile Eigenschaften. Ihre Eigenschaften in Lösung und als Feststoffe lassen die Produkte für Anwendungen als nichtionische Emulgatoren, Oberflächenmodifikatoren, Gele, usw. geeignet erscheinen.
    Notes: A series of polysiloxane/poly(N-acetyliminoethylene) (PSiO/PNAI) block and graft copolymers were synthesized by the initiation of 2-methyl-2-oxazoline (Me-OZO) polymerization with functional polysiloxane prepolymers. The copolymerization products were characterized by IR- and 1H NMR spectroscopy, elemental analysis, DSC and thermogravimetry. The insertion of both hydrophobic and hydrophilic sequences in the macromolecular structure induces a behavior characteristic of amphiphilic compounds. Their solution and solid state behavior evidenced peculiarities which make them able to act as nonionic emulsifiers, surface modifiers, gels, etc.
    Additional Material: 4 Ill.
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    The state of water in styrene-grafted and sulfonated poly(vinylidene fluoride) membranes (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 151-167 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Zustand von Wasser in Protonenaustausch-Membranen, hergestellt durch Pfropfen von Styrol auf Polyvinylidenfluorid-Filme (PVDF-g-PS) mittels Elektronenstrahlen und anschließendes Sulfonieren (PVDF-g-PSSA), wurde mittels Differentialkalorimetrie (DSC), Raman-Spektroskopie und Rontgen-Diffraktion (SAXS) ermittelt. Die Raman-Untersuchungen zeigten, daß einzelne Wassermolekule durch hydrophobe Wechselwirkungen an die Polymerketten gebunden sind. Die DSC-Untersuchungen zeigten, daß Wasser in den Membranen in drei verschiedenen Umgebungen vorliegt: nicht gefrierendes ionisch gebundenes Wasser, gefrierendes freies Wasser und gefrierendes gebundenes Wasser. Die Menge an nicht gefrierendem Wasser betragt unabhangig vom Pfropfungsgrad etwa 10 H2O/SO3H (mol/mol). Die Menge an gefrierendem Wasser ist stark vom Pfropfungsgrad abhangig. Oberhalb eines Pfropfungsgrades von 50% werden Werte von 40 H20/S03H (mol/mol) erreicht. Die Leitfahigkeit von nur nicht gefrierendes Wasser enthaltenden Membranen ist gering, d. h., das ionisch gebundene Wasser kann nicht allein die fur den Transport von Protonen und Wasser notwendigen Kanale bilden. Die SAXS Untersuchungen zeigten, daß Wasser/Sulfonsaure-Cluster in Membranen aus hydratisiertem PVDF-g-PSSA mit einem Bragg-Abstand von 25 Å gebildet werden. Diese Cluster formen die Kanale fur den Ionentransport und die Leitfähigkeit.
    Notes: The state of water in proton exchange membranes prepared by pre-irradiation (electron beam, 100 kGy) grafting of styrene onto poly(vinylidene fluoride) films (PVDF-g-PS), followed by sulfonation (PVDF-g-PSSA), has been studied with thermal analysis, Raman spectroscopy and small angle X-ray diffraction (SAXS). Raman spectra show that, in addition to free liquid water in the membranes, single water molecules are weakly bound to the polymer backbone. Thermal analysis shows that there are three types of water molecules in the membrane; non-freezable water associated with the ionic sites, freezable free water, and freezable bound water. The amount of non-freezable water is around 10 H2O/SO3H (mol/mol), and is independent of the degree of grafting (d.o.g.). The amount of freezable water is strongly dependent on the d.o.g. as long as the grafting has not penetrated the whole of the film, and reaches a value of around 40 H2O/SO3H (mol/mol) above a d.o.g. of 50%. The conductivity of membranes containing only the non-freezable water is low, i. e. the ionically bound water alone does not form the domains necessary for proton and water transport. SAXS measurements show that water/sulfonic acid clusters in hydrated PVDF-g-PSSA membranes with a Bragg distance of 25 Å are formed; these form the ion conducting channels in the membrane.
    Additional Material: 9 Ill.
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    MITTEILUNGEN/ANNOUNCEMENTS (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 211-211 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052530117
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    Tensile and flexural behavior of polypropene sheets with different crystallinities of surface layer (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 253 (1997), S. 201-210 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Zug- und Biegemoduli von preßgeformten Polypropen-Probekörpern mit unterschiedlichen Oberflächenkristallinitäten wurden basierend auf der Annahme eines Schicht-Verbund-Modells untersucht. Es zeigte sich, daß die Spannungs-Dehnungs-Kurven der Zugversuche und die Werte der Biegeablenkung im wesentlichen von der Oberfächenkristallinität abhängen, jedoch erwiesen sich die Bruchspannungen als von der Oberflächenkristallinität unabhängig. Es wird angenommen, daß das beobachtete Zug- und Biegeverhalten der Proben auf der Grundlage eines Schicht-Verbund-Modells, bei dem eine massive, starre Platte zwischen zwei weichen Schichten eingebettet ist, charakterisiert werden kann.
    Notes: The tensile and flexural moduli of the compression-molded sheets of polypropene with different surface layer crystallinity were investigated based on a layered composite model. It was found that the tensile stress-strain curve and flexural deflection depended largely on the surface layer crystallinity, but the ultimate strain-at-break values were independent of the surface layer crystallinity. It is suggested that the tensile and flexural behavior can be characterized using a layered composite model in which a bulk plate was sandwiched between two surface layers.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052530116
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    The role of charge transfer complexes in the photodegradation of polyolefins (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 45-54 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Addition of HALS-stabilisers, the cut-off wavelength of the light source, the temperature and the oxygen pressure have an influence on the UV-degradation mechanism of polyolefins. All these parameters influences the conversion of oxygen into polymeric carbonyls. The results are explained assuming that the initiation of the UV-degradation of pololefins is due to substrate-oxygen charge transfer complexes (CTCs).
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    URL: http://dx.doi.org/10.1002/apmc.1997.052520104
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    Fracture behavior of exposed HDPE specimens with an embrittled layer due to UV-exposure (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 69-88 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The applicability of fracture mechanics was studied on UV-exposed HDPE Charpy specimens. The failure distribution of the stress at failure measured in three-points bending tests showed a bifurcation in failure processes. At high stresses yielding occurs, resulting in large strain at failures. At lower stresses crack propagation causes low strain at failures. Due to the bifurcation in failure processes the ductile-brittle transition temperature of exposed specimens is hard to determine.Specimens notched after exposure showed a decrease in the critical stress intensity values. The effective notch depth of exposed specimens was found to be larger than the thickness of the oxidized layer measured by FT-IR and density measurements.
    Additional Material: 21 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052520106
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    Deactivation processes of 2-hydroxyphenyl-1,3,5-triazines  -  polymeric and monomeric UV absorbers of the benzotriazole and triazine class (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 119-138 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the 2-hydroxyphenyl-1,3,5-triazines, the intramolecular hydrogen bond is stronger than in the corresponding 2-hydroxyphenylbenzotriazoles. Compounds with only one aryl group in the 2-hydroxyphenyl-1,3,5-triazine series show proton-transferred fluorescence with large Stokes shift and high quantum yield. No such fluorescence is observed, in contrast, for compunds with three aryi groups bearing no electrondonating groups on the aryl moieties. When the hydrogen atom of the intramolecular hydrogen bond is replaced by CH3, the respective derivative shows fluorescence with a normal Stokes shift.Various copolymers of MA-TIN 1 (2-[2-hydroxy-3-tert.-butyl-5-(O-[2-hydroxy-3-(2-methylpropenoyloxy)propyl]-2-carbonyloxyethyl)phenyl]benzotriazole), and MA-TZ 1 (2,4-Bis(2,4-dimethyl-phenyl)-6-[2-hydroxy-4-(2-hydroxy-3-[2-methylpropenoyloxy])propoxyphenyl]-1,3,5-triazine) with styrene, methyl methacrylate, and methacrylic acid have been synthesized by radical polymerization. The absorption spectra in the longwavelength UV region appear unchanged compared to those of the monomeric UV absorbers indicating that the stabilizer chromophores are conserved intact in the polymer. Both the monomeric and the polymeric stabilizers exhibit a strongly Stokesshifted, temperature-dependent, low-quantum-yield, proton-transferred fluorescence. This may be taken as evidence that the intramolecular hydrogen bond, which is essential for the photostability of this type of UV absorber, remains intact also in the copolymers. Activation energies of the radiationless deactivation process can be evaluated from the temperature dependence of this fluorescence. These energies lie between 4 and 5 kJ/mol for most of the benzotriazole and triazine stabilizers investigated.Fluorescence-decay measurements with crystalline MA-TIN 1 at different temperatures reveal a close correspondence of the temperature dependence between decay times and relative quantum yields. The radiationless process is thence concluded to originate from the proton-transferred level S1'. The decay time at room temperature is estimated at 70 ps, close to the value for crystalline TIN P (2-(2-hydroxy-5-methylphenyl)benzotriazole). The proton-transferred fluorescence of MA-TIN 1 exhibits a biexponential decay profile whereas solid TIN P, in contrast, displays only one single lifetime.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1997.052520109
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    Buckling transitions in superhelical DNA: Dependence on the elastic constants and DNA size (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 5-25 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Buckling transitions in superhelical DNA are sudden changes in shape that accompany a smooth variation in a key parameter, such as superhelical density. Here we explore the dependence of these transitions on the elastic constants for bending and twisting, A and C, important characteristics to DNA's bending and twisting persistence lengths. The large range we explore extends to other elastic materials with self-contact interactions, modeled here by a Debye-Hückel electrostatic potential.Our collective description of DNA shapes and energies over a wide range of ρ = A/C reveals a dramatic dependence of DNA shape and associated configurational transitions on ρ: transitions are sharp for large ρ but masked for small ρ. In particular, at small ρ, a nonplanar circular family emerges, in agreement with Jülicher's recent analytical predictions; a continuum of forms (and associated writhing numbers) is also observed.The relevance of these buckling transitions to DNA in solution is examined through studies of size dependence and thermal effects. Buckling transitions smooth considerably as size increases, and this can be explained in part by the lower curvature in larger plasmids. This trend suggests that buckling transitions should not be detectable for isolated (i.e., unbound) DNA plasmids of biological interest, except possibly for very large ρ. Buckling phenomena would nonetheless be relevant for small DNA loops, particularly for higher values of ρ, and might have a role in regulatory mechanisms: a small change in superhelical stress could lead to a large configurational change.Writhe distributions as a function of ρ, generated by Langevin dynamics simulations, reveal the importance of thermal fluctuations. Each distribution range (and multipeaked shape) can be interpreted by our buckling profiles. Significantly, the distributions for moderate to high superhelical densities are most sensitive to ρ, isolating different distribution patterns. If this effect could be captured experimentally for small plasmids by currently available imaging techniques, such results suggest a slightly different experimental procedure for estimating the torsional stiffness of supercoiled DNA than considered to date. © 1997 John Wiley & Sons, Inc.
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    Conformational analysis and molecular dynamics simulation of α-(1 → 2) and α-(1 → 3) linked rhamnose oligosaccharides: Reconciliation with optical rotation and NMR experiments (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 83-96 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular mechanics and dynamics calculations were carried out on the disaccharides α-L-Rhap-(1 → 2)-α-L-Rhap-(1 → OMe) (1) and α-L-Rhap-(1 → 3)-α-L-Rhap-(1 OMe) (2), and the trisaccharide α-L-Rhap-(1 → 2)-α-L-Rhap-(1 → 3)-α-L-Rhap-(1 → OMe) (3). The semiflexible conformational behavior of these molecules was characterized by the occupation of a combination of different glycosidic linkage and side-chain conformational positions whose relative occupations were sensitive to dielectric screening. Molecular dynamics simulations of the trisaccharide 3 showed little difference between the linkage conformations in the trisaccharide and the component disaccharides 1 and 2.Experimental optical rotation data of 1 and 2 were obtained as a function of temperature in varying solvents. The molecular models were combined with the semiempirical theory of Stevens and Sathyanarayana to yield calculated optical rotations. Interpretation of the data of both 1 and 2 implied that a combination of conformations, both in glycosidic and side-chain positions, could explain the experimental data. Solvents effects were important in influencing the conformational mix and averaged optical rotation.Three-bond heteronuclear coupling constants 3JC, H were obtained for the glycosidic linkages of 1 and 2 in D2O and DMSO. Analysis of the coupling constants with a Karplus curve showed that small reductions in the glycosidic torsion angles of the conformations of the models used here of ca. 10°-15° in φ and 5°-10° in ψ were required to give better agreement with experiment; a combination of conformations for both 1 and 2 was consistent with the data. There was a negligible influence on the coupling constants of 1 on changing the solvent from D2O to DMSO. © 1997 John Wiley & Sons, Inc.
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    Protein folding: Optimized sequences obtained by simulated breeding in a minimalist model (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 165-180 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For a minimalist model of protein folding, which we introduced recently, we investigate various methods to obtain folding sequences. A detailed study of random sequences shows that, for this model, such sequences usually do not fold to their ground states during simulations. Straightforward techniques for the construction of folding sequences, based solely on the target structure, fail. We describe in detail an optimization algorithm, based on genetic algorithms, for the “simulated breeding” of folding sequences in this model. We find that, for any target structure studied, there is not only a single folding sequence but a patch of sequences in sequence space that fold to this structure. In addition, we show that, much as in real proteins, nonhomologous sequences may fold to the same target structure. © 1997 John Wiley & Sons, Inc.
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    Fourier transform IR studies of the self-association of N-tert-butoxycarbonyl-α-amino acids (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 205-212 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The self-association of several N-urethanyl-L-amino acids (N-t-Boc-glycine, N-t-Boc-L-alanine, N-t-Boc-L-methionine, and N-t-Boc-O-Bz-L-tyrosine has been investigated in carbon tetrachloride by Fourier transform (FTIR) spectrometry. The fractions of nonbonded OH and NH groups have been determined from the intensities of the free OH and NH-stretching vibrations. The FTIR spectra have been examined in the carbonyl stretching regions by using Fourier self-deconvolution techniques. The results show that intermolecular hydrogen bonds are formed between the carboxylic acid group of one molecule and the urethane group of another molecule, suggesting that the leading factor for the self-association of N-t-Boc amino acids is the acidity of the OH groups. In N-t-Boc glycine, more heterodimers are formed than in the other amino acids. In N-t-Boc-O-Bz-L-tyrosine where the steric hindrance of the substituent implanted on the Cα atom is higher, the concentration of homodimers and heterodimers is lower than in N-t-Boc-L-alanine or N-t-Boc-L methionine. © 1997 John Wiley & Sons, Inc.
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    A heteropolymer model study for the mechanism of protein folding (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 239-250 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A heteropolymer model of randomly self-interacting chains in two dimensions is studied with numerical simulations in order to elucidate the folding mechanism of protein. We find that the model occasionally shows folding propensity depending on the sequence of random numbers given to the chain. We study the thermodynamic and kinematic roles in the folding mechanism by grouping the local energy minima found in the simulations into clusters according to the similarity of their conformations. It is suggested that the local minima to which some heteropolymers show a folding tendency are always the lowest energy states of the energy spectrum within a cluster, though which cluster is selected depends on the sequence. For the eight random sequences we study, we find that the energy gap between the ground state and excited states is little correlated with folding or nonfolding. We rather find that folding propensities are correlated with the global structure of the average energy surface, implying a dominant kinetic role in the folding mechanism, although thermal factors cannot be ignored as the mechanism of choosing the ground state within a cluster of states connected by small deformations. We suggest that a hierarchical cluster structure plays an important role in selecting a unique folded state out of the huge number of local minima of heteropolymers. © 1997 John Wiley & Sons, Inc.
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    Ordered aggregation of ribonucleic acids by the human immunodeficiency virus type 1 nucleocapsid protein (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 301-312 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nucleocapsid protein NCp7, which is the major genomic RNA binding protein of human immunodeficiency virus type 1, plays an important role in several key steps of the viral life cycle. Many of the NCp7 activities, notably the nucleic acid annealing and the genomic RNA wrapping ones, are thought to be linked to a nonspecific binding of NCp7 to its nucleic acid targets. The mechanism of these activities is still debated but several clues are in favor of an intermediate aggregation of nucleic acids by NCp7. To check and characterize the nucleic acid aggregating properties of NCp7, we investigated the interaction of NCp7 with the model RNA homopolymer, polyA, by quasielastic light scattering and optical density measurements. The ordered growth of monodisperse large particles independently of the nucleic acid size and the almost complete covering of polyA by NCp7 strongly suggested an ordered aggregation mechanism. The aggregate kinetics of growth in the optimum protein concentration range (≥2 μM) were governed by a so-called Ostwald ripening mechanism limited by transfer of NCp7-covered polyA complexes from small to large aggregates. The aggregation process was strongly dependent on both Na+ and Mg2+ concentrations, the optimum concentrations being in the physiological range. Similar conclusions held true when polyA was replaced by 16S + 23S ribosomal RNA, suggesting that the NCp7 aggregating properties were only poorly dependent on the nucleic acid sequence and structure. Finally, as in the NCp7 annealing activities, the basic regions of NCp7, but not the zinc fingers, were found critical in nucleic acid aggregation. Taken together, our data indicate that NCp7 is a highly efficient nucleic acid aggregating agent and strengthen the hypothesis that aggregation may constitute a transient step in various NCp7 functions. © 1997 John Wiley & Sons, Inc.
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    NMR three-dimensional solution structure of the serine protease inhibitor cyclotheonamide A (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 349-358 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nmr solution conformation of cyclotheonamide A (CtA) was determined in aqueous media. The data produced 15 distance and 10 torsional constraints which were used to generate conformations using restrained simulated annealing (SA) and distance geometry/simulated annealing (DG/SA) calculations. Two different calculation protocols were performed to ensure proper sampling of conformational space and even though the torsional restraints were input differently, both calculation methods yielded the same conformation of CtA. In the structure calculations, all solutions of the Karplus equation were sampled simultaneously using the restrained SA protocol and large ranges were used for the dihedral restraints in the DG/SA protocol because all solutions to the Karplus equation could not be sampled simultaneously. The solution conformation was also compared to the solid state x-ray conformations of CtA bound to thrombin and trypsin. The conformation of the residues important for active site binding (d-Phe, h-Arg, and Pro) are nearly identical in aqueous solution and solid state with largest differences at the a-Ala and v-Tyr residues. CtA appears to be preordered in structure and does not undergo a significant conformational change upon binding to the enzyme active site. © 1997 John Wiley & Sons, Inc.
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    The reconstruction of a protein backbone from Cα coordinates (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 381-389 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Monte Carlo Protein Building method to construct the backbone and Cβ atomic coordinates from known Cα coordinates is reported. The method selects values of dihedral angles from ranges established from a statistical analysis of the relationship between dihedral angles of the backbone and Cα coordinates for a protein data base. The averaged coordinates from ten backbone models of a protein were used to define a mean structure that was refined by energy minimization using the AMBER force field (GB/SA). By the latter method the average atomic deviation and rmsd of the backbone and Cβ atoms for 24 proteins is between 0.14 and 0.32 Å (average 0.22 Å) and 0.22 and 0.61 Å (average 0.43 Å), respectively. A comparison with other methods is made. © 1997 John Wiley & Sons, Inc.
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    The reconstruction of side-chain conformations from protein Cα coordinates (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 391-405 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model of nine proteins including side-chain atoms have been built from the known Cα coordinates and amino acid sequences using a Monte Carlo Protein Building Annealing method. The Cartesian coordinates for the side-chain atoms were established with bond lengths and angles selected randomly from within previously determined ranges. A simulated annealing technique is used to generate some 300 structures with differing side-chain conformations. The atomic coordinates of the backbone atoms are fixed during the simulated annealing process. The coordinates of the side-chain atoms of 300 low energy conformations are averaged to obtain a mean structure that is minimized with the Cα atoms constrained to their position in the x-ray structure using the OPLS/AMBER force field with the GB/SA water model. The rms deviation of the main-chain atoms (without Cβ) compared with the corresponding crystal structures is in the range 0.20-0.64 Å. The rms deviation of the side-chain atoms is between 1.72 and 2.71 Å and for all atoms is between 1.19 and 1.99 Å. The method is insensitive to random errors in the Cα positions and the computational requirement is modest. © 1997 John Wiley & Sons, Inc.
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    Simulation of electrostatic and hydrodynamic properties of Serratia endonuclease (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 443-450 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We analyze the electrostatic and hydrodynamic properties of a nuclease from the pathogenic gram-negative bacterium Serratia marcescens using finite-difference Poisson-Boltzmann methods for electrostatic calculations and a bead-model approach for diffusion coefficient calculations.Electrostatic properties are analyzed for the enzyme in monomeric and dimeric forms and also in the context of DNA binding by the nuclease. Our preliminary results show that binding of a double-stranded DNA dodecamer by nuclease causes an overall shift in the charge of the protein by approximately three units of elementary charge per monomer, resulting in a positively charged protein at physiologic pH. In these calculations, the free enzyme was found to have a negative (-1 e) charge per monomer at pH 7. The most dramatic shift in pKa involves His 89 whose pKa increases by three pH units upon DNA binding. This shift leads to a protonated residue at pH 7, in contrast to the unprotonated form in the free enzyme. DNA binding also leads to a decrease in the energetic distances between the most stable protonation states of the enzyme. Dimerization has no significant effect on the electrostatic properties of each of the monomers for both free enzyme and that bound to DNA.Results of hydrodynamic calculations are consistent with the dimeric form of the enzyme in solution. The computed translational diffusion coefficient for the dimer model of the enzyme is in very good agreement with measurements from light scattering experiments. Preliminary electrooptical calculations indicate that the dimer should possess a large dipole moment (approximately 600 Debye units) as well as substantial optical anisotropy (limiting reduced linear electric dichroism of about 0.3). Therefore, this system may serve as a good model for investigation of electric and hydrodynamic properties by relaxation electrooptical experiments. © 1997 John Wiley & Sons, Inc.
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    Structural characterization (shape and dimensions) and stability of polysaccharide/lipid nanoparticles (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 511-520 
    Details
    ISSN: 0006-3525
    Keywords: biovector ; light scattering ; lipid ; microgel ; polysaccharide ; soft sphere ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of a new supramolecular drug carrier (named Biovectors - BV) was studied using light scattering and scanning electronic microscopy techniques. This system consists of a polysaccharide core of chemically cross-linked maltodextrins to which phospholipids (and, in some cases, cholesterol) are added. Both polysaccharide cores and BV cross-linked with phosphate (negatively charged) and epichlorhydrin (no net charge) are spherical particles. The increase in the ionic strength of the medium increases the density of the charged polysaccharide cores. The lipid strongly interacts with neutral and negatively charged cores, decreasing both intra- and interparticle interactions. The results (mainly, ρ = Rg/Rh 〈 0.775 in some cases) suggest that BV are gel-like particles of variable density, referred to as microgels or soft spheres. Neutral polysaccharides have a strong tendency to self-aggregate. This self-aggregation of polysaccharide neutral cores is prevented by the addition of lipid or dimethylsulfoxide. © 1997 John Wiley & Sons, Inc. Biopoly 41: 511-520, 1997
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    Protein hinge bending as seen in molecular dynamics simulations of native and M61 mutant T4 lysozymes (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 533-544 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dynamical model of interdomain “hinge bending” of T4 lysozyme in aqueous solution has been developed on the basis of molecular dynamics (MD) simulation. The MD model study provides a description of the conformational reorganization expected to occur for the protein in aqueous solution as compared to the crystalline environment. Three different 500 ps molecular dynamics simulations were calculated, each using a distinctly different crystal conformation of T4 lysozyme as the starting points of the MD simulations. Crystal structures of wild-type lysozyme and “open” and “closed” forms of M6I variant structures were analyzed in this study. Large-scale, molecular-conformational rearrangements were observed in all three simulations, and the largest structural change was found for the open form of the M6I allomorph. All three simulated proteins had closed relative to the wild-type crystal structure, and the closure of the “jaws” of the active site cleft occurred gradually over the time course of the trajectories. The time average MD structures, calculated over the final 50 ps of each trajectory, had all adapted to conformations more similar to each other than to their incipient crystal forms. Using a similar MD protocol on cytochrome P450BM-3 [M. D. Paulsen and R. L. Ornstein (1995) Proteins: Structure Function and Genetics, Vol. 27, pp. 237-243] we have found that the opposite type of motion relative to the starting crystal structure, that is, the open form of the crystal structure, had opened to a greater degree relative to the incipient crystal structure form. Therefore we do not believe that either result is merely a simulation artifact, but rather the protein dynamics are due to protein relaxation in the absence of crystal packing forces in the simulated solution environments. © 1997 John Wiley & Sons, Inc. Biopoly 41: 533-544, 1997
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    Structural comparison between retro-inverso and parent peptides: Molecular basis for the biological activity of a retro-inverso analogue of the immunodominant fragment of VP1 coat protein from foot-and-mouth disease virus (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 569-590 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibodies induced against intact foot-and-mouth disease Virus (FMDV) particles bind to the retro-inverso analogue of fragment 141-159 of the viral coat protein VP1 of FMDV, variant A, equally well as to the parent peptide. A conformational investigation of this retro-inverso peptide was carried out by nmr spectroscopy and restrained molecular modeling in order to identify the structural basis for the antigenic mimicry between these retro-inverso and parent peptides. In 100% trifluoroethanol a well-defined left-handed α-helical region exists from residue 150 to residue 159, which is consistently present in all conformational families obtained from restrained modelling. A less-defined left-handed helical region is present in the tract 144-148, which is also consistent for all structures. Conformational flexibility exists about Gly149, which leads to two types of structures, either bent or linear. In the bent structures, a three-residue inverse tight turn is found, which can be classified as an inverse γ-turn centered at Gly149. The overall structural features of the retro-inverso peptide are shown to be similar to those of the parent L-peptide. The two molecules, however, are roughly mirror images because they share inherently chiral secondary structure elements. By comparing these conformational conclusions with the x-ray structure of the Fab complex of a corresponding VP1 antigenic fragment, a rationale is proposed to account for the topological requirements of specific recognition that are implied by the equivalent antigenic activity of the natural and retro-inverso compounds. © 1997 John Wiley & Sons, Inc. Biopoly 41: 569-590, 1997.
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    Conformational preferences of Leu-enkephalin in reverse micelles as membrane-mimicking environment (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 591-606 
    Details
    ISSN: 0006-3525
    Keywords: Leu-enkephalin ; [13C, 15N]-backbone-labeled ; reverse micelles ; conformation ; CD ; FTIR ; nmr ; distance geometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enkephalin represents one of the bioactive peptide molecules most extensively investigated both in solution and in the crystal state. Depending upon the environment chosen for such studies, three main conformational states were identified for this flexible, linear pentapeptide - i.e., an extended conformation, a single-bend, and a double-bend structure. Since CD and Fourier transform ir (FTIR) spectra of Leu-enkephalin solubilized in negatively charged reverse micelles of bis (2-ethylhexyl)sulfosuccinate sodium salt/isooctane/water were supportive of a restricted conformational space of the aromatic side chains and of a bended type fold, we have analyzed by nmr the conformational preferences of Leu-enkephalin in reverse micelles using a synthetic [13C, 15N]-backbone-labeled sample. The overall conformation derived from nuclear Overhauser effect spectroscopy (NOESY) and 15N-filtered rotating frame NOESY (ROESY) spectra and by distance geometry calculations is a double-bend fold of the backbone that is comparable to one of the known x-ray structures. Thereby the tyrosine side chain is inserted into the hydrophobic core of the reverse micelles in a restrained conformational space as well evidenced by NOEs between the aromatic ring protons and the surfactant. The proximity of the aromatic rings of tyrosine and phenylalanine indicate a preferred structure consistent with the postulated conformation of the opioid peptide in the δ-receptor-bound state. These results confirm the interesting and promising properties of reverse micelles as membrane mimetica. © 1997 John Wiley & Sons, Inc. Biopoly 41: 591-606, 1997
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  • 89
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    Electronic Resource
    Prediction of β-turns in proteins by 1-4 and 2-3 correlation model (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 673-702 
    Details
    ISSN: 0006-3525
    Keywords: protein folding ; coupling effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 1-4 and 2-3 residue-correlation model is proposed to predict the β-turns in proteins. The average rate of correct prediction for the 455 β-turn tetrapeptides and 4018 non-β-turn tetrapeptides in the training data base is 80.1%, and that for the 223 β-turn tetrapeptides and 12562 non-β-turn tetrapeptides in the testing data base is 80.9%. Compared with the rates of correct prediction based on the residue-independent model reported previously, the quality of prediction is significantly improved by the new model, implying that the correlation effect between the 1st and the 4th residues and that between the 2nd and 3rd residues along a tetrapeptide are important for forming a β-turn in a protein during the process of its folding. © 1997 John Wiley & Sons, Inc. Biopoly 41: 673-702, 1997
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  • 90
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    Electronic Resource
    Effect of the side group on the helix-forming tendency of α-alkyl-β-L-aspartamyl residues (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 721-729 
    Details
    ISSN: 0006-3525
    Keywords: Poly(β-L-aspartate)s ; helical conformations ; quantum mechanical calculations ; cooperative energy effects ; helix stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational preferences of the monomeric units of a series of poly(α-alkyl-β-L-aspartate)s were examined by quantum mechanical calculations. α-Alkyl-β-aspartamyl m-oligopeptides with a number of residues m ranging from 1 to 7 and arranged in the conformations experimentally observed for their corresponding polymers were computed. Both their total relative energies and their cooperative energy differences were compared as a function of the length of the oligopeptide and the nature of the alkyl side group. Results revealed that the 13/4 helical arrangement is the most stable structure for the isolated polymer chain for any side group, although a 17/4 helix becomes favored in the case of methyl and ethyl groups due to the packing effects. On the other hand, the stability of the 4/1 helix appears to be the preferred conformation for side groups with a branched constitution. © 1997 John Wiley & Sons, Inc. Biopoly 41: 721-729, 1997
    Additional Material: 5 Ill.
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  • 91
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    Electronic Resource
    Experimental evidence at atomic resolution for intramolecular N(SINGLEBOND)H · · · π (phenyl) interactions in a family of amino acid derivatives (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 1-6 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 2 Ill.
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  • 92
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    Electronic Resource
    Mapping of ligand binding sites of the cholecystokinin-B/gastrin receptor with lipo-gastrin peptides and molecular modeling (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 799-817 
    Details
    ISSN: 0006-3525
    Keywords: gastrin ; lipo-gastrin derivatives ; cholecystokinin-B/gastrin receptor ; molecular modeling ; ligand binding sites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double-tailed lipo-tetragastrin derivatives of increasing fatty acid chain length were used to identify the minimum size of the fatty acid moieties (≥C10) that restricts the access to the CCK-B/gastrin (CCK: cholecystokinin) receptor via a membrane-bound pathway. Then dimyristoyl-mercaptoglycerol/maleoyl-gastrin adducts of increasing peptide chain length were synthesized to define the minimal peptide size required for receptor binding affinities comparable to those of underivatized gastrin peptides despite anchorage of the lipid tails in the membrane bilayer. The experimental results indicated that most of the little-gastrin sequence, i.e., 2-17, is needed for optimal interaction of the molecule with the binding cleft of the receptor. From these data experimentally based restraints could be derived for docking of lipo-gastrin onto a CCK-B/gastrin receptor model applying molecular dynamics simulations and energy minimizations. In the receptor-bound state some of the secondary structure elements of gastrin as determined by nmr analysis of gastrin-peptides in low dielectric constant media are retained. The N-terminal gastrin portion interacts in a more or less extended conformation with the receptor surface, and upon a sharp kink at the Ala-Tyr dipeptide portion the C-terminal pentapeptide amide part inserts deeply into the helix bundle. Besides Arg-57 on top of helix 1 of the receptor, for which no potential interaction with the ligand could be detected, the other amino acid residues identified by mutagenesis studies as involved in gastrin recognition were found to interact with the C-terminal portion of gastrin. Even taking into account the strong limitations of such a model system, it represents an interesting tool for rationalizing the experimental results of the extensive structure-function studies performed previously on gastrin and to delineate more precisely the putative ligand binding site on the extracellular face of the receptor. © 1997 John Wiley & Sons, Inc. Biopoly 41: 799-817, 1997
    Additional Material: 10 Ill.
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  • 93
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    Electronic Resource
    FKBP-like catalysis of peptidyl-prolyl bond isomerization by micelles and membranes (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 49-60 
    Details
    ISSN: 0006-3525
    Keywords: micellar catalysis ; cis/trans isomerization ; peptidyl-prolyl cis/trans isomerase ; proline ; FKBP12 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under physiological conditions, peptidyl-prolyl cis/trans isomerases catalyze powerfully the cis/trans isomerization of the -Xaa-Pro- bond (Xaa: natural amino acids) in oligopeptides and proteins (PPIases; EC 5.2.1.8). However, incorporation of proline containing tetrapeptide-4-nitroanilides in micelles and phospholipid vesicles also leads to increased rates of this unimolecular conformational interconversion. The isomerization rate was dependent on the detergent and vesicle concentration, respectively. The observed rate constants fit the pseudophase model of micellar catalysis allowing the calculation of micellar turnover numbers (kcismic) and dissociation constants (KCmic). Comparing kcismic values to the rate constants of the uncatalyzed cis to trans isomerization, an acceleration factor of about 20-fold was obtained for Suc-Ala-Phe-Pro-Phe-4-nitroanilide (Suc: succinyl) bound to zwitterionic SB12 (N-dodecyl-N,N-dimethylammonium-3-propanesulfonate) micelles. In addition, a marked increase in the population of the trans conformer relative to cis was noted for all investigated combinations of peptides and detergents. In a series of tetrapeptides, Suc-Ala-Xaa-Pro-Phe-4-nitroanilide kcismic/KCmic as well as kcismic values are linearly correlated with the high performance liquid chromatography capacity factor R′ describing the hydrophobicity of the amino acid Xaa. The same correlation can describe quantitatively the dependency of kcar/Km on substrate hydrophobicity for the FKBP12-catalyzed isomerization. Despite the great differences in catalytic power, these results confirm the suspicion that micelles and FKBP12 may share a common component in the catalytic mechanism of peptidyl-prolyl bond isomerization. © 1997 John Wiley & Sons, Inc. Biopoly 42: 49-60, 1997
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  • 94
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    Electronic Resource
    Tapping mode atomic force microscopy of scleroglucan networks (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 89-100 
    Details
    ISSN: 0006-3525
    Keywords: tapping mode atomic force microscopy ; scleroglucan networks ; denaturation-renaturation ; fractal dimension ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tapping mode Atomic Force Microscopy (TmAFM) has been used to study the fungal polysaccharide scleroglucan deposited from aqueous solution and dimethyl sulfoxide (DMSO) onto a mica surface. The solutions from which the microscope samples were produced were prepared by first dissolving the solid scleroglucan in 0.1M NaOH, then neutralizing the solution with HCl, followed by dilution to the required concentration in either water or DMSO. It was found that from the aqueous solution described above, scleroglucan forms networks. Based on a comparison of the denatured-renatured and aqueous solution samples, network formation is due to the imperfect registration between the chains forming the triple helices. The relatively large stiffness of the scleroglucan triple helix is also assumed to contribute to the formation of the extended networks. The triple helix diameter was measured to be 0.92 ± 0.27 nm, which is in the same range as that obtained by other researchers using similar techniques. Denatured scleroglucan, deposited from DMSO onto mica, forms a web-like layer on top of which there are sphere-like structures. These morphologies are believed to be due to triple helix denaturation yielding highly flexible single chains in DMSO, which results in coiling and web-like dense packing of scleroglucan upon deposition onto mica. Most interestingly after addition of water to the samples deposited from DMSO, some of the chains can be renatured into short, stiff rod-like structures which are similar to the structures observed by other researchers. The imaging data for aqueous solution deposition can be analyzed by plotting maximum end-to-end distance versus the perimeter of the networks deposited onto mica. This yields a Flory-like exponent of 0.67, which is almost similar in value to that obtained by other researchers for linear structures of scleroglucan but less than that expected for a polymer chain following a self-avoiding walk (v = 0.75) model on a two-dimensional surface. The fractal dimension that can be used to characterize the networks was determined graphically to be 1.22 ± 0.06. © 1997 John Wiley & Sons, Inc. Biopoly 42: 89-100, 1997
    Additional Material: 11 Ill.
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  • 95
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    Electronic Resource
    Binding geometries of triple helix selective benzopyrido [4,3-b]indole ligands complexed with double- and triple-helical polynucleotides (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 101-111 
    Details
    ISSN: 0006-3525
    Keywords: triple helix stabilization ; intercalation ; DNA ligands ; benzo[4,3-b]indole ; polynucleotides ; linear dichroism ; CD ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding modes of three benzopyrido [4,3-b]indole derivatives (and one benzo[-f]pyrido [4-3b] quinoxaline derivative) with respect to double helical poly(dA) · poly(dT) and poly[d(A-T)]2 and triple-helical poly(dA) · 2poly(dT) have been investigated using linear dichroism (LD) and CD: (I) 3-methoxy-11-amino-BePI where BePI = (7H-8-methyl-benzo[e]pyrido [4,3-b]indole), (II) 3-methoxy-11-[(3′-amino) propylamino]-BePI, (III) 3-methoxy-7-[(3′-diethylamino)propylamino] BgPI where BgPI = (benzo[g]pyrido[4,3-b]indole), and (IV) 3-methoxy-11-[(3′-amino)propylamino] B f P Q where B f P Q = {benzo[-f]pyrido[4-3b]quinoxaline}. The magnitudes of the reduced LD of the electronic transitions of the polynucleotide bases and of the bound ligands are generally very similar, suggesting an orientation of the plane of the ligands' fused-ring systems preferentially perpendicular to the helix axis. The LD results suggest that all of the ligands are intercalated for all three polynucleotides. The induced CD spectrum of the BePI chromophore in the (II-BePI)-poly[d(A-T)]2 complex is almost a mirror image of that for the (I-BePI)-poly(dA) · poly(dT) and (I-BePI)-poly(dA) · 2poly(dT) complexes, suggesting an antisymmetric orientation of the BePI moiety upon intercalation in poly[d(A-T)]2 compared to the other polynucleotides. The induced CD of I-BePI bound to poly(dA) · 2poly(dT) suggests a geometry that is intermediate between that of its other two complexes. The concluded intercalative binding as well as the conformational variations between the different BePI complexes are of interest in relation to the fact that BePI derivatives are triplex stabilizers. © 1997 John Wiley & Sons, Inc. Biopoly 42: 101-111, 1997
    Additional Material: 5 Ill.
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  • 96
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    Electronic Resource
    Molecular modeling of c-erbB2 receptor dimerization: Coiled-coil structure of wild and oncogenic transmembrane domains - Stabilization by interhelical hydrogen bonds in the oncogenic form (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 157-168 
    Details
    ISSN: 0006-3525
    Keywords: molecular modeling ; c-erbB2 receptor ; dimerization ; coiled-coil structure ; wild transmembrane helices ; oncogenic transmembrane helices ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimerization models of c-erbB2 transmembrane domains (Leu651-Ile675) are studied by molecular mechanics and molecular dynamics simulations. Both wild and Glu mutated transmembrane helices exhibit the same relative orientation for favorable associations and dimerize preferentially in left-handed coiled-coil structures. The mutation point 659 belongs to the interfacing residues, and in the transforming domain, symmetric hydrogen bonds between Glu carboxylic groups stabilize the dimeric structure. The same helix packing found for the wild dimers, except side-chain - side-chain hydrogen bonds, suggests that the transmembrane domains dimerize according to similar process. Structural and energetical characterization of the models are presented. © 1997 John Wiley & Sons, Inc. Biopoly 42: 157-168, 1997
    Additional Material: 6 Ill.
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  • 97
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    Electronic Resource
    Electrophoresis of proteins in semidilute polyethylene glycol solutions: Mechanism of retardation (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 183-189 
    Details
    ISSN: 0006-3525
    Keywords: electrophoresis ; retardation ; native proteins ; semidilute polymer solution ; scaling theory ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The retardation of proteins in the Mt range of 15-500 kDa in capillary electrophoresis conducted in semidilute solutions of the polymer polyethylene glycol (Mt range 0.2-8.0 × 106), was measured. The purpose was to test the predictions of the scaling theory with regard to the relation of retardation to (a) the Mt of the polymer, (b) the concentration of the polymer, and (c) the radius of the protein particles. These predictions derive from a mechanism that relates retardation to the screening length of the polymer solution, viewed as the average distance between the entanglement points of polymer chains.For the molecular weight range from 60 to 500 kDa of (near) spherical proteins, the retardation was found to be related to polymer concentration c asμ/μo = exp(-Ac0.69)where μ/μ0 is the retardation expressed as the ratio between the mobility in polymer solution and that in free solution. The value of the exponent of 0.69 is in close agreement with the value of 0.75 predicted by the scaling theory. Parameter A was found (a) to scale as the 0.04th power of Mt (polymer), approximating the predicted value of 0; and (b) to be proportional to particle radius as predicted. All measured values of retardation were independent of electric field strength in the range of 37-370 V/cm. Thus, experimental findings are consistent with the mechanism relating electrophoretic retardation to the screening length of the polymer network in the specified molecular weight range of proteins.Under the same conditions, log(μ/μ0) of proteins with Mt's less than 60 kDa (a) scales as the -0.06th power of Mt (polymer), and (b) is proportional to polymer concentration, suggesting a retardation mechanism that is not related to the screening length. © 1997 John Wiley & Sons, Inc. Biopoly 42: 183-189, 1997
    Additional Material: 5 Ill.
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  • 98
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    Electronic Resource
    Comparison of van der Waals and semiempirical calculations of the molecular volumes of small molecules and proteins (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 191-202 
    Details
    ISSN: 0006-3525
    Keywords: molecular volume ; van der Waals radius ; molecular orbital calculation ; accessible surface area ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular volumes for hydrocarbons, amino acids, peptides, and 14 globular proteins were calculated by techniques using van der Waals radii and by semiempirical molecular orbital methods. The resulting values were compared to experimentally determined volumes. The values obtained by methods employing van der Waals radii were found to be up to three times smaller than the experimentally determined values in the case of proteins, 25% smaller than the experimental values for peptides, and up to 50% greater than experimental values for simple hydrocarbons. For the semiempirical calculations, neither the type nor precision of the calculation altered the percentage of the electron density required to reproduce the experimentally observed volumes for any of the different types of molecules tested. For molecules en vacuo, the amount of electron density included was approximately 98.5% of the total calculated value. For solvated molecules, the percentage was closer to 99.5%. From the results of our studies, we conclude that semiempirical techniques are more reliable, less arbitrary, and hence are more accurate for the determination of molecular volumes. The methods by which we employ semiempirical techniques for determination of molecular volume will be described in detail. © 1997 John Wiley & Sons, Inc. Biopoly 42: 191-202, 1997
    Additional Material: 7 Ill.
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  • 99
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    Electronic Resource
    Qualitative and quantitative analysis of the secondary structure of cytochrome C Langmuir-Blodgett films (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 227-237 
    Details
    ISSN: 0006-3525
    Keywords: fourier transform ir spectroscopy ; protein conformations ; cytochrome C ; Langmuir-Blodgett film ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A qualitative and quantitative analysis of the conformation of Langmuir-Blodgett (LB) dried films of cytochrome C on silicon wafers was performed by Fourier transform ir (FTIR) spectroscopy. A deconvolution procedure was applied to the amide I band analysis, in order to determine the percentage of the different secondary structures. Qualitative analysis was performed by examining difference spectra.Films obtained by spreading protein solutions at pH 7.4 and 1, dried at 25 and 100°C, on silicon wafers were also examined in order to detect spectral components associated with denatured protein domains, and to compare them with cytochrome C LB films.FTIR spectroscopy showed that the following important changes characterise LB film spectra: (a) the α-helix component is higher (its percentage is 57 and 54%) than the one estimated in dried film obtained by spreading the solutions at pH 7.4 on a silicon substrate (43%), (b) there is an increase in the intensity of bands attributed to protonated carboxy group bands, involved and not involved in the formation of hydrogen bonds, and a decrease in those attributed to deprotonated carboxy groups, (c) the intensity of several bands attributed to aromatic amino acids and aliphatic chains increases, and (d) bands due to O(SINGLEBOND)H stretching vibrations of crystallization water are present.These conformational changes could be induced by protein-protein interaction caused by the close packing of molecules that occurs during LB film formation; it cannot be excluded that they may be accompanied by partial changes in the tertiary structure of the protein. A preferential orientation of protein molecules in LB films is also a possibility. © 1997 John Wiley & Sons, Inc. Biopoly 42: 227-237, 1997
    Additional Material: 4 Ill.
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  • 100
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    Electronic Resource
    DNA recognition by Zn [Cysteinyl-His-OMe]2: A minimal zinc finger docking unit (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 407-418 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zinc fingers, 30-residue peptides anchored on Zn(II) coordinated to pairs of cysteines and histidines, recognize DNA triplets and, as tandem modules, effect sequence read out. The focus of zinc finger-DNA interaction studies thus far has been to probe the nature of the binding of the 12-residue recognition element of the finger with DNA code bases. To understand the possible role of the Zn(II) ligand and to assess its own DNA interaction profile, [(CH)2Zn] (C: cysteine; H: histidine; Figure 1) was constructed from bis-t Boc-cystinyl-di-His-OMe via thiol-disulfide exchange, Zn(II) complexation, and deprotection. [(CH)2Zn] binds with polyd- (G·C)·polyd(G·C) with association constants - 1.8 × 107 M-1 (specific DNA-phosphate) and 3.3 × 103 M-1 (nonspecific DNA-phosphate); perturbs its B-DNA profile; and enhances the Tm from 62.5 to 70.15°C in a concentration-independent manner, with an ideal reversal profile on cooling, not observed in the DNA alone; releases polyd(G·C)·polyd(G·C)-bound ethidium bromide; enhances the fluorescence of polyd(G·C)·polyd(G·C)-bound ethidium bromide at low concentrations; and quenches it at higher ranges. [(CH)2Zn] also binds to d(ACGCTGGGCGT), the sequence associated with Zif-268, 3-finger binding site. Such interactions were not seen in parallel studies with (a) polyd(A·T)·polyd(A·T) and [(CH)2Zn] and (b) {[C′H2] (C′: cystine; H: histidine; the direct metal-free precursor of [(CH)2Zn]}, ionic zinc nitrate, and covalent zinc acetyl acetonate Zn(AcAc)2, with poly[d(G·C)·polyd(G·C)].The results are rationalized on the basis of two types of association between [(CH)2Zn] and polyd(G·C)·polyd(G·C), a nonspecific recognition of the sugar phosphate backbone, by an imidazole of [(CH)2Zn] and a specific one involving the amino group of [(CH)2Zn] and the guanine base of DNA. Control experiments show that the latter greatly promotes DNA recognition. The possibility for such specific interactions with relatively small structures of the type [(CH)2Zn] would be of use in the design of DNA recognition elements and also provide an explanation for the experimentally found variation in the placement of the zinc finger docking unit around the major groove of DNA. © 1997 John Wiley & Sons, Inc.
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