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  • 1985-1989  (8,612)
  • 1965-1969
  • 1960-1964
  • 1890-1899
  • 1988  (8,612)
  • Chemistry  (8,591)
  • Polymer and Materials Science  (3,199)
  • Biochemistry and Biotechnology  (680)
  • Insulin
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  • 1985-1989  (8,612)
  • 1965-1969
  • 1960-1964
  • 1890-1899
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Plasma growth hormone-releasing hormone levels in type 1 (insulin-dependent) diabetic children following a mixed meal (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 257-260 
    Details
    ISSN: 1432-1440
    Keywords: Growth hormone-Releasing hormone ; Somatostatin ; Insulin ; Type 1 diabetic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following a mixed meal, plasma hormone responses were measured in four type 1 diabetic children and in eight short normal children. Between 60 and 150 min after ingestion of the mixed meal there was a significant increase in circulating growth hormone-releasing hormone values both in diabetic and in normal children. Mean plasma GHRH peak values were not different between diabetic patients (27.0±3.9 ng/l) and controls (24.6±4.9 ng/l). No time relationship to spontaneous growth hormone peaks was observed. Whereas normal children showed a characteristic biphasic plasma somatostatin response, somatostatin plasma levels in diabetic children did not change. In normal children plasma insulin values increased between 30 and 150 min, but remained unchanged in type 1 diabetic patients. Blood glucose response was more pronounced in diabetic children than in short normal children. These results indicate that circulating growth hormone-releasing hormone does not play a dominant role in the regulation of insulin and somatostatin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01748167
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  • 2
    Electronic Resource
    Electronic Resource
    Abnormalities of carbohydrate metabolism in spontaneously hypertensive rats (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 924-927 
    Details
    ISSN: 1432-1440
    Keywords: Hypertension ; Insulin ; Glucagon ; Skeletal muscle ; Glycogen ; Glucose ; Glycogen synthetase ; Glycogen phosphorylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was performed to investigate as to whether peripheral insulin resistance exists in spontaneously hypertensive rats (SHR). After a 12 h fasting period, SHR had significantly higher serum glucose and higher plasma glucagon values in comparison to normotensive control rats (WKY). There was a tendency for higher serum insulin concentrations as well, but this difference did not reach significance. After oral glucose loading or glucose/insulin administration, serum glucose and insulin levels were also higher in SHR compared to WKY rats. Muscle glycogen and glucose concentrations were identical in fasted SHR and WKY rats. With an oral glucose load or glucose/insulin treatment there was a significant increase in muscle glycogen, whereas glucose values declined in skeletal muscle. Both total (a+b-form) phosphorylase activity as well as the active a-form of the enzyme were similar in skeletal muscle of SHR and WKY rats. Glucose/insulin administration or oral glucose loading induced a considerable reduction of both a+b-form and a-form activities. The decrease in muscle phosphorylase activities was almost identical in both groups of animals. There was also a comparable activity of muscle glycogen synthetase activity in all groups of rats. Despite subtile changes of glucose, glucagon and to a lesser degree insulin levels which would be suggestive of insulin resistance, the data obtained from skeletal muscle argue against peripheral insulin resistance in spontaneously hypertensive rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01728956
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  • 3
    Electronic Resource
    Electronic Resource
    A morphological analysis endocrine tumour genesis in pancreas and anterior pituitary of AVP/SV40 transgenic mice (1988)
    Springer
    Virchows Archiv 412 (1988), S. 255-266 
    Details
    ISSN: 1432-2307
    Keywords: AVP/SV40 transgenic mice ; Immunocytochemistry ; Insulin ; Pancreatic polypeptide ; Large T-antigen ; Heterochromatin ; Dysplasia ; Neoplasia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insertion into the mouse genome of the hybrid oncogene made up of bovine vasopressin gene derived 5′ upstream sequences and the coding sequences of SV40 large T-antigen promoted tumours in anterior pituitary and endocrine pancreas of mice bearing this transgene. In order to investigate the morphology of the steps in the neoplastic process, we used light and electron microscopy to study these organs in 42 animals belonging to the 3rd, 4th and 5th generations, subdivided into 4 age groups from 20 days to 100 days of life. Antibodies to large T-antigen were used to identify sites of expression of the hybrid oncogene, thus monitoring the steps in neoplastic transformation. Large T-antigen immunoreactivity was identified in dysplastic lesions of younger animals and in both dysplastic lesions and tumours of older mice. Insulin (100% of cases) and pancreatic polypeptide (25% of cases) immunoreactivities were revealed in pancreatic lesions but no hormonal immunoreactivity was detected in the pituitary lesions. The ultrastructural study confirmed that the majority cell population of the pancreatic neoplasms was B-type and that the anterior pituitary tumours were poorly granulated. The subcellular localization of large T-antigen immunoreactivity was investigated by the immunogold method and was confined to the heterochromatin of tumour cell nuclei. These findings provide evidence for the dysplasia-neoplasia sequence in the genesis of endocrine tumours of pituitary and pancreas of transgenic mice. The vasopressin-SV40 large T-antigen transgenic mice may therefore be an useful model for the study of endocrine cell oncogenesis,
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00737150
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  • 4
    Electronic Resource
    Electronic Resource
    Enhancement of carbon tetrachloride-induced liver injury by glucagon and insulin treatment (1988)
    Springer
    Research in experimental medicine 188 (1988), S. 27-33 
    Details
    ISSN: 1433-8580
    Keywords: Carbon tetrachloride ; Insulin ; Glucagon ; Cytochrome P450
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats given a dose of carbon tetrachloride (CCl4) immediately received injections of glucagon and insulin every 4h. They frequently died after 4h and showed a significantly higher mortality between 8h and 28h as compared to the control rats where such deaths occurred 16h later. At 8h, the derangements of SGPT values and prothrombin time were significantly greater in the hormone-treated rats than in the control rats. In these CCl4-intoxicated rats, hepatic reduced glutathione content at 4h was significantly reduced after hormone treatment. The treatment significantly enhanced CCl4 metabolism, conversion of14CCl4 into14CO2 in vitro, by microsomes isolated from the liver, whereas it did not affect the microsomal cytochrome P450 content. These results suggest that glucagon and insulin treatment increased CCl4 hepatotoxicity in rats through activating the cytochrome P450-dependent mono-oxygenase system. This would merit consideration for the clinical application of this treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01852091
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  • 5
    Electronic Resource
    Electronic Resource
    Transient coappearance of glucagon and insulin in the progenitor cells of the rat pancreatic islets (1988)
    Springer
    Anatomy and embryology 178 (1988), S. 489-497 
    Details
    ISSN: 1432-0568
    Keywords: Pancreatic islet ; Insulin ; Glucagon ; Ontogeny ; Immunohistochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ontogenetic appearances of glucagon, insulin and tyrosine hydroxylase (TH) were immunohistochemically investigated on developing pancreatic islets of rats. Glucagon immunoreactivity appeared first in some epithelial cells (g-cells) of the dorsal anlage of the pancreas on day 11.5 of gestation. On day 12.5, g-cells increased in number manufacturing the primitive islets, in which some cells appeared to be immunoreactive for insulin (i-cells) and about 40% of g-cells indicated also a slight immunoreactivity for insulin (g/i-cells). Afterwards, all the islet cells, especially g-cells, increased in number, and almost half of g-cells were g/i-cells. After day 16.5 of gestation, numerical increase of the cells with insulin immunoreactivity exceeded that of the cells with glucagon immunoreactivity, and about one fifth of g-cells were g/i-cells. After 20.5 days, however, no g/i cells were found. On day 16.5 of gestation, the immunoreactivity for TH appeared in occasional cells of the islets, but the cells did not show immunoreactivity for glucagon or insulin. It is concluded that the progenitor cells of the pancreatic islets appear to synthesize both glucagon and insulin by day 20.5 of gestation, but differentiate giving rise to mature A and B cells of adult isoets afterward.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305036
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  • 6
    Electronic Resource
    Electronic Resource
    The pattern of basal and stimulated insulin responses to intravenous glucose in first degree relatives of Type 1 (insulin-dependent) diabetic children and unrelated adults aged 5 to 50 years (1988)
    Springer
    Diabetologia 31 (1988), S. 430-434 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; glucose ; age ; children ; puberty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The pattern of insulin secretion was studied in 107 normal individuals aged 5 to 50 years. Intravenous glucose tolerance tests were performed on 64 islet-cell antibody negative siblings of diabetic children and on 43 normal adults. Puberty was staged using Tanner's criteria and subjects were grouped as follows: I — stage 1 (n=22), II — stages 2 and 3 (n=18), III — stages 4 and 5 (n=20), IV — adults 〉17 years (n=47). Basal and stimulated (incremental 0–10 and 10–60 min areas) insulin responses rose throughout puberty (Groups I–III), declined following puberty until the third decade (Groups III and IV) and then appeared constant thereafter. Insulin levels in the 17.6–22.5 year group were lower than in the 12.6–15 year group (p〈0.01). Fasting insulin to glucose ratios and incremental 0–60 min insulin to glucose area ratios produced a similar age-related pattern indicating that changes in insulin levels were independent of glucose concentrations. Gender did not affect these changes and multiple regression analysis showed that HLA haplotype sharing did not influence insulin responses in siblings of diabetic patients. Age and pubertal status must be carefully considered when interpreting intravenous glucose tolerance tests from patients suspected of having early abnormalities of carbohydrate metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271587
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  • 7
    Electronic Resource
    Electronic Resource
    In vitro insulin action on erythrocyte glucose metabolism in normal and diabetic rats (1988)
    Springer
    Diabetologia 31 (1988), S. 51-53 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; erythrocyte ; diabetes ; glucose metabolism ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Alloxan-induced diabetes in rats significantly impaired the capacity of the erythrocytes to metabolise glucose in vitro to either lactic acid or CO2. Both these metabolic activities were initially insensitive to insulin in normal as well as in diabetic animals; but became responsive when these cells were subjected to insulin and glucose ‘starvation’ for 1 h through incubation in their absence. This action of insulin in starved cells showed concentration dependence and required preincubation with the hormone prior to addition of glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279133
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  • 8
    Electronic Resource
    Electronic Resource
    Glucoregulatory function of glucagon in hypo-, eu- and hyperthyroid miniature pigs (1988)
    Springer
    Diabetologia 31 (1988), S. 368-374 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; glucagon ; thyroid hormones ; glucose turnover ; glucose production ; glucose utilisation ; glucoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The glucoregulatory function of glucagon was investigated in hypo-, eu- and hyperthyroid miniature pigs. Infusion glucagon, (3 ng x kg body weight−1 · min−1) transiently increased blood glucose (p〈0.01) and hepatic glucose production (p〈0.01) in euthyroidism, but was without effect in hyperthyroidism. Infusing glucagon plus somatostatin (2 ng x kg body weight−1 · min−1 and 0.2 μg x kg body weight−1 · min−1) transiently increased blood glucose (Δ 3.0 to 4.3 mmol/l) and hepatic glucose production (Δ 3.3 to 7.7 umol x kg body weight−1 · min−1) in all thyroid states, the effect was less pronounced in hyperthyroid pigs. By contrast, hypoglucagonaemia (74 to 107 pg/ml) at basal insulin (28 to 35 μU/ml) provoked hypoglycaemia (1.4 to 2.2 mmol/l) and a fall in glucose production (Δ 4.7 to 8.3 umol x kg body weight−1 · min−1), which was independent of the thyroid state; the effect was most pronounced in hyperthyroidism (p〈0.01). Hepatic glycogen content, arterial gluconeogenic precursor concentrations as well as the glycaemic response (Δ 0.60 mmol/l) to alanine infusion (23 umol x kg body weight−1 · min−1) were all unaffected by hyperthyroidism. We conclude that moderate experimental hyperthyroidism reduces glucagon action due to reduced glycogen mobilisation. This may in part result from increased insulin sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341505
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  • 9
    Electronic Resource
    Electronic Resource
    Ontogenic development of peptide hormones in the mammalian fetal pancreas (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 1-9 
    Details
    ISSN: 1420-9071
    Keywords: Insulin ; glucagon ; pancreatic polypeptide ; somatostatin ; fetal pancreas ; ontogeny ; immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ontogeny of insulin, glucagon, PP and somatostatin in the mammalian fetal pancreas has been examined in recent years largely by immunocytochemistry and in some instances by radioimmunoassay. Complete ontogenic data are available only for the rat, human pig and sheep. Figure 3 compares the time of appearance of the endocrine cell-types within the fetal pancreas when the periods of gestation of the four species are converted to a uniform scale. The striking ontogenic difference in the rat probably reflects the immaturity of the rodent fetus at birth compared with the human, pig and sheep. In the fetal pancreas, differences in cell number of glucagon and PP cells in the dorsal and ventral lobes become apparent from an early gestational period. Factors responsible for the functional and structural maturation of the fetal pancreatic endocrine cells and the processes involved in pancreatic organogenesis are poorly understood. Studies in these areas would have clinical implications since it may be possible in the future to employ agents for selective replication of fetal β-cells for transplantation in patients with Type I diabetes, bearing in mind that such cells must have the capacity to respond to normal stimuli and repressors when transplanted. The presence of the other islet cell-types may be obligatory for these appropriate responses. This would require a more complete knowledge of those factors which produce the normal selectivity of the four hormonal cell-types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960221
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  • 10
    Electronic Resource
    Electronic Resource
    The packing of acetylcholine into quanta at the frog neuromuscular junction is inhibited by increases in intracellular sodium (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 258-263 
    Details
    ISSN: 1432-2013
    Keywords: Acetylcholine ; Quanta ; Na+−K+ exchange pump ; Ouabain ; Adrenaline ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pretreatment with hypertonic solutions, insulin, or adrenaline increases the size of quanta at the frog neuromuscular junction, as determined by measurements of miniature end plate potentials or currents (Van der Kloot and Van der Kloot 1985, 1986). The increase in quantal size apparently is due to an increase in acetylcholine (ACh) content of individual quanta. These treatments, therefore, can be used to study the packaging of ACh. Previously, I reported that increases are blocked by an inhibitor of active ACh uptake into vesicles (Van der Kloot 1986b, 1987b). The present study shows that the increases in quantal size were antagonized by inhibiting the Na+−K+ exchange pump with 100 μM ouabain, 10 μM dihydroouabain, or K+-free solutions. The increases in quantal size were also antagonized by 10 μM monensin, a Na+ ionophore, or by 5 μM aconitine, which opens Na+ channels at normal resting potentials. Apparently a rise in intracellular [Na+] inhibits the addition of ACh to quanta. The mechanism by which a rise in intracellular Na+ inhibits ACh packing is unknown, but apparently it is not due to inhibition of choline reuptake into the terminals. Also consistent with the above hypothesis is that the increase in quantal size following depolarization for 2 h in elevated [K+]out was substantially enhanced when tetrodotoxin (TTX) was present, suggesting that in the absence of TTX there is a rise in [Na+]in that antagonizes the incorporation of additional ACh into the quanta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582506
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  • 11
    Electronic Resource
    Electronic Resource
    Insulin receptors along the rat nephron: [125I] Insulin binding in microdissected glomeruli and tubules (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 604-612 
    Details
    ISSN: 1432-2013
    Keywords: Nephron microdissection ; Glomeruli ; Tubules ; [125I] Insulin binding ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Binding of [125I] Tyr A14 human insulin ([125I] insulin) was measured at 4°C in glomeruli and pieces of tubule microdissected from collagenase-treated rat kidneys. For glomeruli and all segments tested, total and non specific binding increased linearly with glomeruli number or tubular length. When determined with 4.0 nM labelled hormone, the distribution of specific binding sites (expressed as 10−18 mol [125I] insulin bound per glomerulus or mm tubule length) was as follows: glomerulus, 2.5±0.3; proximal convoluted tubule (PCT), 12.6±0.6; pars recta (PR), 4.0±2.3; thin descending limb (TDL), 0.6±0.2; thin ascending limb (TAL), 0.6±0.2; medullary thick ascending limb (MAL), 0.8±0.1; cortical ascending limb (CAL), 2.1±0.1; distal convoluted tubule (DCT), 5.6±1.1; cortical collecting tubule (CCT), 3.2±0.3 and outer medullary collecting tubule (MCT), 2.3±0.1. Specific [125I] insulin binding to glomeruli and tubule segments was time- and dose-dependent, saturable, reversible after elimination of free labelled ligand, and inhibited by unlabelled human insulin. When analysed in Scatchard and Hill coordinates, the binding data revealed a negative cooperation in the interaction processes between [125I] insulin and glomerular and tubular binding sites, with apparent dissociation constants and Hill coefficients of the following values: glomerulus, 0.6 nM and 0.60; PCT, 10.0 nM and 0.55; MAL, 4.3 nM and 0.80; CAL, 2.0 nM and 0.74; CCT, 7.6 nM and 0.80 and MCT, 1.0 nM and 0.57 respectively. The stereospecificity of nephron binding sites was assessed in competitive experiments showing that unlabelled bovine and procine insulins were as efficient as human insulin for displacing [125I] insulin, whereas A and B chains of insulin and unrelated peptide hormones were almost inactive. These results indicate that the detected [125I] insulin binding sites may correspond to physiological insulin receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583761
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  • 12
    Electronic Resource
    Electronic Resource
    Electron microscope localisation of insulin-like immunoreactivity of conventionally processed human insulinomas (1988)
    Springer
    Virchows Archiv 412 (1988), S. 443-450 
    Details
    ISSN: 1432-2307
    Keywords: Insulin ; Insulinomas ; Ultrastructure ; Immunogold technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Localisation of insulin-like immunoreactivity has been studied using the immunogold staining procedure on thin sections of 6 human insulinomas, conventionally processed for electron microscopy. The labelling was restricted to the secretory granules. Depending on their morphology, these either resembled B-cell granules of human adult pancreas or belonged to the atypical (non-diagnostic) group. Within the former group, those with a crystalloid core or an amorphous dense or moderately dense core were strongly immunoreactive, whereas others, filled with a pale material, were poorly labelled. Most granules of this type were stored together within the heavily granulated cells of 3 insulinomas, presenting the classical features of clinical and biological behaviour and a typical light microscopic staining pattern. In contrast, the non-diagnostic granules, characterized by their smaller size, a very dense core and a thin halo, were mainly found within the poorly granulated cells making up the other tumours, and showed a very uneven labelling. Strongly labelled granules were found in one insulinoma that also belonged to the classical type; these were stored together with a few diagnostic granules within the same cells. Only poorly labelled atypical granules were present in two cases revealing a number of unusual features; these included moderate elevation of insulinaemia, uncertain tumour histology, as well as weak immunostaining for insulin/proinsulin and variable argyrophilia of the tumour in paraffin sections. These findings suggest that human insulinomas differ not only in storage capacity but also in their degree of granule maturation. This may involve some deficiency of either the prohormone conversion or the subsequent processing of the cleavage products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750578
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  • 13
    Electronic Resource
    Electronic Resource
    Lysosomes and pancreatic islet function (1988)
    Springer
    Cell & tissue research 252 (1988), S. 9-15 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Insulin ; Immunocytochemistry ; Lysosomes ; Crinophagy ; Mouse (NMRI)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies of pancreatic islets have suggested that crinophagy provides a possible mechanism for intracellular degradation of insulin in the insulin-producing B-cells. In the present study, a quantitative estimation of crinophagy in mouse pancreatic islets was attempted by morphometric analysis of lysosomes containing immunoreactive insulin. Isolated islets were incubated in tissue culture for one week in 3.3, 5.5 or 28 mmol/l glucose. The lysosomes of the pancreatic B-cells were identified by morphological and enzyme-cytochemical criteria and divided into three subpopulations comprising primary lysosomes and insulin-positive or insulin-negative secondary lysosomes. Both the volume and numerical density of the primary lysosomes increased with increasing glucose concentration. The proportion of insulin-containing secondary lysosomes was highest at 5.5 and lowest at 3.3 mmol/l glucose. Insulin-negative secondary lysosomes predominated at 3.3 mmol/l glucose. Studies of the dose-response relationships of glucose-stimulated insulin biosynthesis and insulin secretion of the pancreatic islets showed that biosynthesis had an apparent Km-value for glucose of 7.0 mmol/l, whereas it was 14.5 mmol/l for secretion. The pronounced crinophagic activity at 5.5 mmol/l glucose may thus be explained by the difference in glucose sensitivity between insulin biosynthesis and secretion resulting in an intracellular accumulation of insulin-containing secretory granules. The predominance of insulin-negative secondary lysosomes at 3.3 mmol/l glucose may reflect an increased autophagy, whereas the predominance of primary lysosomes at 28 mmol/l glucose may reflect a generally low activity of intracellular degradative processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213820
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  • 14
    Electronic Resource
    Electronic Resource
    TRH-like immunoreactivity in endocrine cells and neurons in the gastro-intestinal tract of the rat and guinea pig (1988)
    Springer
    Cell & tissue research 253 (1988), S. 347-356 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Stomach ; Intestine ; Immunohistochemistry ; Thyrotropin-releasing hormone (TRH) ; Somatostatin ; Avian pancreatic polypeptide ; Insulin ; Gastrin ; Rat ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By use of the indirect immunofluorescence technique, the cellular localization of thyrotropin-releasing hormone (TRH) was studied in the gastrointestinal tract of rats and guinea pigs of different ages. TRH-like immunoreactivity (LI) was observed in many pancreatic islet cells of young rats and guinea pigs but only in single cells of 6-month-old rats. In aged guinea pigs, a reduction in the number of TRH-positive cells was evident; however, numerous strongly fluorescent cells were still present. In the guinea pig, TRH-LI was in addition observed in gastrin cells in the stomach. TRH-positive nerve fibers occurred in the myenteric plexus of the oesophagus, stomach and intestine of the rat, and in the muscle layers of the guinea pig. These results suggest a functional role of TRH both as hormone and neuroactive compound in various portions and sites of the gastro-intestinal tract of the rat and guinea pig
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222291
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  • 15
    Electronic Resource
    Electronic Resource
    Lipoprotein lipase activity in skeletal muscle and adipose tissue of marathon runners after simple and complex carbohydrate-rich diets (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 75-80 
    Details
    ISSN: 1439-6327
    Keywords: Energy metabolism ; Carbohydrate-rich diet ; Lipoprotein lipase ; Free fatty acids ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A comparison of the influence of simple and complex carbohydrate (CHO) consumption on adipose tissue- and skeletal muscle-lipoprotein lipase activity (AT-LPLA, SM-LPLA) was examined. Twenty male marathon runners were divided into two equal dietary groups: simple-CHO and complex-CHO. Half of the subjects in each group consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days. Immediately following this dietary period, the subjects consumed a CHO-rich diet (70% E intake) predominant in simple-CHO or in complex-CHO for an additional 3 days. Thereafter, all subjects returned to a normal mixed diet. Skeletal muscle biopsies, adipose tissue aspirations, and venous blood samples were obtained prior to dietary manipulation (PRE), upon completion of the 6 day diet (POST I), and 2 weeks after returning to a normal diet (POST II). The samples were analysed for AT-LPLA, SM-LPLA, serum insulin, and free fatty acids (FFA), and blood glucose, and lactate. SM-LPLA fell 71% from PRE values of 0.39±0.30 μ mol · g−1 · h−1 to POST I values of 0.11 ±0.09 μ mol · g−1 · h−1 (means±SD) (p〈0.05), after a complex-CHO diet. However, the simple-CHO diet did not alter SM-LPLA. AT-LPLA similarly decreased (p〈0.05) after the complex-CHO diet, and no significant decrease was noted after the simple-CHO diet. Serum FFA decreased significantly (p〈0.05) after a simple-CHO diet (0.82±0.13 to 0.65±0.10 mmol l−1) but were unchanged after a complex-CHO diet. Blood glucose and lactate, and serum insulin were not altered following a CHO-rich diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691242
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  • 16
    Electronic Resource
    Electronic Resource
    Metabolic effects of glucose, medium chain triglyceride and long chain triglyceride feeding before prolonged exercise in rats (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 126-131 
    Details
    ISSN: 1439-6327
    Keywords: Glucose and fat feeding ; Glycogen sparing ; Ketone bodies ; Insulin ; Lipolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to test the hypothesis that oral ingestion of lipids could increase endurance by slowing the rate of glycogen depletion. Trained rats were killed after a 2 h run on a rodent treadmill, following an intragastric infusion of water, glucose, medium chain triglycerides (MCT) or long chain triglycerides (LCT). Glucose and triglycerides were administered in equicaloric concentrations (50 kJ). The results show that oral ingestion of lipids (MCT or LCT) did not reduce glycogen depletion in liver, heart or skeletal muscle after exercise whereas the fat diet increased muscle and heart glycogen stores in resting conditions. In contrast, glucose feeding induced a significant sparing effect on endogenous carbohydrate utilization and reduced physical exercise lipolysis. These data indicated, firstly, that enhanced lipid availability induced by a single lipid meal before exercise was not able to modify the glycogen depletion occuring after exercise and, secondly, that the glucose/fatty acid cycle was not effective in these conditions. The comparison between lipids indicated that the effect on glycogen use of MCT did not differ from that of LCT, and did not seem to be of any particular importance during physical exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691251
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  • 17
    Electronic Resource
    Electronic Resource
    Comparison of penetration-enhancing ability of laurocapram, N-methyl-2-pyrrolidone and dodecyl-L-pyroglutamate (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 189-192 
    Details
    ISSN: 1573-739X
    Keywords: Absorption, transdermal ; Brilliant Blue ; Dodecyl-l-pyroglutamate ; Insulin ; Laurocapram ; N-Methyl-2-pyrrolidone ; Permeability, enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The study reports on penetration enhancers used to improve drug absorption through the skin. All experiments were carried out in permeation cellsin vitro. Insulin (2.5 mg/ml) and Brilliant Blue (50.0 mg/ml) served as model drugs. They were formulated into a 40% solution of propylene glycol with increasing concentrations ofN-methyl-2-pyrrolidone (NMP) (0.0 to 20.0%), dodecylazacycloheptan-2-one (laurocapram) and a new compound dodecyl-l-pyroglutamate (DLP; 0.0 to 0.5%). The maximum amount of insulin permeated within 24 h was almost 200 μU/ml in the case of 0.1% laurocapram, while in the case of 0.1% DLP it was approximately half of that. The optimum concentration of NMP was 12.0%. Experiments performed with Brilliant Blue showed no significant difference among formulations containing either 6.0, 12.0 or 20.0% of NMP. When NMP was omitted, flux, permeability as well as the maximum concentration estimated after 26 h reached 50% of the values obtained with NMP. The lag time was twice as long in this case in comparison with the formulations containing NMP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01956869
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  • 18
    Electronic Resource
    Electronic Resource
    Adsorption of human and porcine insulins to intravenous administration sets (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 213-216 
    Details
    ISSN: 1573-739X
    Keywords: Adsorption ; Equipment and supplies ; Infusions, parenteral ; Insulin ; Polyethylenes ; Polyvinylchloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A comparison between human and porcine insulins with regard to their adsorption to administration sets was performed. A125I-mono(A14)-iodinated insulin was used to follow the adsorption phenomenon over time and the adsorption was quantified with radioimmunoassays of unlabelled insulin. The obtained data were similar for both methods. No relevant difference in adsorption was found between human and porcine insulin. Both insulins showed a significantly more pronounced initial drop in delivered insulin when polyethylene tubing was used. After 3 h a steady state was reached, resulting in the administration of a more predictable dose. Particularly in the initial phase an important reduction in the amount of both insulins actually delivered to the patient was observed when compared to the expected amount as calculated from the concentration present in the container and the infusion rate. Therefore, the mainstay in treatment of a patient with ketoacidosis remains frequent serum glucose measurement and making appropriate infusion rate adjustments on that basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01956873
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  • 19
    Electronic Resource
    Electronic Resource
    Abstracts of Dutch doctoral theses (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 93-95 
    Details
    ISSN: 1573-739X
    Keywords: Anthracyclines ; Chemistry ; Drug stability ; Mitomycins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01962686
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  • 20
    Electronic Resource
    Electronic Resource
    Etoposide and teniposide (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 101-116 
    Details
    ISSN: 1573-739X
    Keywords: Chemistry ; Chromatography ; Etoposide ; Immunoassay ; Metabolism ; Podophyllotoxin ; Pharmacokinetics ; Teniposide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Etoposide (VP 16-213) and teniposide (VM 26) are semisynthetic epipodophyllotoxin derivatives active against a variety of tumours. The clinical efficacy has led to an increasing interest in these compounds. This review presents information on the mechanism of action, biochemical pharmacology, bioanalysis, metabolism and pharmacokinetics of etoposide and teniposide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01959294
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  • 21
    Electronic Resource
    Electronic Resource
    Insulin effect on GABA uptake in astroglial primary cultures (1988)
    Springer
    Neurochemical research 13 (1988), S. 1119-1124 
    Details
    ISSN: 1573-6903
    Keywords: Insulin ; astroglia ; cultures ; GABA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Astroglial cultures from newborn mouse cerebral cortex contain [125I]insulin binding sites. Binding was specific reversible, time dependent and reached equilibrium after 45 min. Insulin analogues compete for this [125I]Insulin binding. Incubation of cerebral cortex astroglial cultures with insulin induced a time-and dose-dependent inhibition of the [3H]GABA high affinity uptake. A decrease in theV max rather than, an effect on theK m was observed. This effect was dose-dependent and effective at 10−10 M. Autoradiographic observations on the cell monolayer showed the presence of two groups of cells: one which strongly takes up [3H]GABA and consist in smaller GFAP positive process-bearing cells and another group of much flatter and larger GFAP positive cells which uptake was lower. The smaller stellate cells were apparently the most sensitive to insulin effect. These results: 1) confirm the presence of insulin binding sites on astroglial primary cultures, 2) show an effect of insulin of [3H]GABA high affinity uptake of these cells; this effect being optimal on a stellate-like population of astrocytes, and 3) indicate, that insulin may interfere in neuromodulation through astroglial signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00971628
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  • 22
    Electronic Resource
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    Insulin: Its binding to specific receptors and its stimulation of DNA synthesis and 2′,3′-cyclic nucleotide phosphohydrolase activity in cerebral cells cultured from embryonic mouse brain (1988)
    Springer
    Neurochemical research 13 (1988), S. 429-433 
    Details
    ISSN: 1573-6903
    Keywords: Insulin ; receptors ; brain ; cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The presence and specificity of insulin receptors was investigated in cultured cells obtained from 15–16 days old embryonic mouse cerebra. Developmental studies suggested that the maximum insulin binding occurred at about 11 days in vitro (DIV). Scatchard analysis of binding data revealed two types of binding sites. One type of receptor was the high affinity type (K d=7.77×10−9 M; number of receptor sites,B max=350 fmol/mg protein) while the other type was of low affinity type (K d=5.75×10−8 M;B max=1150 fmol/mg protein). The specificity of receptors for insulin was also confirmed by showing that [125I]insulin was displaced by non-radioactive insulin but not by glucagon or growth hormone. Insulin displayed a clear dose-dependent stimulation of thymidine incorporation. It also stimulated the activity of the enzyme 2′,3′-cyclic nucleotide phosphohydrolase (CNPase), which is specifically associated with myelin produced from oligodendroglia. Thus insulin has a positive influence on the proliferation and differentiation of brain cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01268877
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  • 23
    Electronic Resource
    Electronic Resource
    Effects of insulin on rat brain noradrenaline (1988)
    Springer
    Neurochemical research 13 (1988), S. 887-892 
    Details
    ISSN: 1573-6903
    Keywords: Insulin ; streptozotocin ; diabetes ; noradrenaline ; dopamine ; p-tyrosine ; hypothalamus ; olfactory tubercles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A single intracardial injection of streptozotocin produced a significant increase in rat hypothalamic noradrenaline while no changes were observed in the olfactory tubercles. The parenteral administration of a single dose of insulin decreased rat hypothalamic noradrenaline; the effect had a rapid onset and lasted for at least six hours. Similar noradrenaline reductions were observed in the olfactory tubercles but in this tissue the depletion started later and recovered earlier. In addition, in olfactory tubercles after insulin injection, tyrosine level and dopamine metabolism were increased. The results show that the increases in hypothalamic NA observed in streptozotocin diabetic rats are counteracted by insulin administration and possibly the consequence of changes in noradrenaline turnover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00970758
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  • 24
    Electronic Resource
    Electronic Resource
    A contribution to the UV degradation of polyurethanesPaper presented at the 18th Colloquium of Danubian Countries for “Natural and artificial ageing of plastics” in Villach June 24-26, 1987. (Austria) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 247-263 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of the nature of the polyols used in polyurethane (PUR) synthesis on the structural transformations after ageing by UV irradiation has been studied. The investigations were performed on PUR prepared from polyester and polyether diol oligomers.The characterization of the samples before and after ageing in view of the structural changes, which influence the course of the photooxidative degradation and photocrosslinking as well as in view of changes of mechanical properties has been done. Comparative investigations were performed by spectroscopic and viscometric measurements.The results show pronounced heterogeneity of the degradative reactions, including the existence of crosslinking processes and producing thus very inhomogeneous polymeric material. The course and the intensity of photooxidative degradation of PUR differ together with changes of mechanical properties depending whether polyester or polyether polyol have been used. The processes of photooxidative degradation is less expressed in polyesterurethane then in polyurethane based on polyether, under the same conditions of experiments. Different structures of polyester diols caused the various ageing behaviour of PUR too.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580114
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  • 25
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    Beurteilung von hals-verbindungenVortrag anlä-sslich des 18. Donäulandergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich), vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 283-300 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: QUALIFICATION OF HALS COMPOUNDSA complex method of examination has been developed suitable for the qualification of light stabilizers; by this method, according to experience, the efficacy of HALS compounds can be extensively and expediently characterized.Several light stabilizers of the HALS-type were examined and qualified, used alone or together with a UV-absorber.It has been found that, when selecting the appropriate structure for a given polymer, the weatherability of polyolefine foils is effectively increase to six-eightfold; the increase is even tenfold when the stabilizer is combined with a benzophenone-type compound.As a utilization of these experiences, a contract with the industry, led to the production of an LDPE based agricultural foil with a life-time of several years.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580116
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  • 26
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    Electronic Resource
    Simulation des natürlichen hagelschlags an transparenten kunststoffplattenVortrag anläßlich des 18. Donäulandergesprächs über “Nattürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 301-311 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Natural hail impact tests are scarcely available because hailstorms are limited to a small area and cannot be predicted regarding time, place and intensity. Therefore we relied on laboratory tests simulating natural hailstones by polyamide balls (5-50 mm dia.) whose final velocity could be varied according to meteorological data. So the influence of diameter (weight) and velocity of the artificial hailstones could be taken into consideration independently.The energy of damage or equivalent natural hailstone diameter were determined for 16 mm double skin sheet from PMMA as 0.2 J (14 mm dia.) for star shaped cracks and 2 J (26 mm dia.) for holes. These values do not significantly decrease after 10 years weathering. 10 mm double skin sheets from PC show an extremly high energy of damage of abt. 10 J (38 mm dia.) which decreases to a medium level of 2 J (26 mm dia.) after several years weathering. This decrease is remarkably reduced by weather resistant protective coating.As hailstorms consist to more than 80% of hailstones below 10 mm dia. (0.04 J) the mentioned sheet materials are quite hail resistant also after long weathering periods, but they cannot withstand an extreme hail catastrophe as in Munich July 12, 1984.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580117
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  • 27
    Electronic Resource
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    Specimen temperature as a constant marginal condition and as a variable test parameter during accelerated weatheringVortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24.-26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 313-320 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the specimen temperature on many ageing processes is well known. Two aspects is dealt with: -Measurements of the specimen temperature on several positions of a specimen in commercial weathering devices at different exposure conditions. Technical measures to achieve to uniform ageing at all positions of a planar and homogeneous specimen. Examples from practical use.-Changing specimen temperatures (+60°C to -20°C) during the course of accelerated weathering, i.e. a combination of conventional accelerated weathering with a temperature cycle test.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580118
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  • 28
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    Some special aspects of thermal ageing of isotactic polypropylene (measuring method: Isothermal long-term DTA)Vortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24.-26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 321-334 
    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: An Folien (Dicke 100 pm) aus isotaktischem Polypropylen mit verschiedenen Antioxidansgehalten (0,0% bis 0,1%) wird die thermooxidative Alterunq mit der isothermen Langzeit-Differential-Thermo-Analyse (ILDTA) bis zu Temperaturen weit unter dem Kristallitschmelzbereich verfolqt und die Messwerte mit Ergebnissen aus dem Zeitstand-Zugversuch korreliert. Dabei zeigt sich, daß aus Messunqen mit der ILDTA bereits vor Einsetzen der autokatalytischen Zersetzunq sreaktion Ruckschlüsse auf die thermische Vorqeschichte der Proben und Aussagen auf das rnit einem Abfall der mechanischen Eigenschaften verbundene Ende der thermo-oxidativen Stabilität des Polymeren getroffen werden können.Weiters bietet die ILDTA die Moglichkeit, durch den direkten Zusamenhang zwischen Oxidationszeit und Antioxidansögehalt die örtliche Stabilisatorverteilung in Platten und in Folien zu bestimmen und damit Diffusionsvorqange zu verfolgen.
    Notes: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580119
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  • 29
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    Coupling particle size distribution technique. A new ultracentrifuge technique for determination of the particle size distribution of extremely broad distributed dispersionsDedicated to Prof. Dr. H.-J. Cantow on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 35-52 
    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 Größenverteilungsfunktion von Dispersionen mit extrem breiter Verteilung (Durchmesserbereich 20 〈 D 〈 2000 nm) kann in der analytischen Ultrazentrifuge (AUC) nicht durch eine Standardmethode, z. B. durch Messung der Trübung τ bei einer einzigen Konzentration, bestimmt werden, weil sich die spezifische Trübung τ/c von sehr kleinen und sehr großen Teilchen zu stark unterscheidet. Um dieses Problem zu lösen, haben wir eine neue AUC-Technik, die sogenannte Coupling-PSD-Technik entwickelt. Dabei werden zwei unterschiedliche Konzentrationen derselben Dispersion gleichzeitig in einem einzigen AUC-Lauf vermessen und zwei korrespondierende Lichtintensitiit-Zeit-Kurven aufgezeichnet. Bei einer niedrigen Standardkonzentration cs werden hauptsachlich die größeren Teilchen erfaßt während bei einer 5 bis 30 mal heheren Konzentration ch vor allem die kleineren Teilchen registriert werden. Die beiden I(t)-Kurven werden mathematisch verkniipft und unter Verwendung des Stokeschen Gesetzes und der Streutheorie von Mie für homogene isotrope Kugeln in die gesuchte breite Verteilungsfunktion umgerechnet. Wir benutzen eine mit einem 8-Zellen-Rotor und einem Multiplexer ausgestattete AUC. Da sehr groBe und sehr kleine Teilchen gleichzeitig in einem einzigen Zentrifugenlauf bestimmt werden, kennen wir nicht mehr wie zuvor eine konstante Rotorgeschwindigkeit N anwenden, sondern miissen diese mit Hilfe eines Geschwindigkeitsprogramms N(t) innerhalb einer Stunde von 0 auf 40000 U/min erhehen.
    Notes: The particle size distribution (PSD) of extremely broad distributed dispersions (diameter range 20 〈 D 〈 2000 nm) is not possible to be measured by analytical ultracentrifuge (AUC) using the standard technique, i.e. measuring turbidity τ at a single concentration c, because the specific turbidity τ/c varies too much between very small and very large particles. To solve this problem we have developed a new AUC technique, the so-called Coupling-PSD-Technique. Here two different concentrations of the same dispersion are measured simultaneously by one single AUC run with two corresponding curves of light intensity I vs. time t being registered. At a low standard concentration cs, mainly the larger particles are detected, while at a concentration ch 5 to 30 times higher mainly the smaller particles are registered. Both I(t)-curves are coupled mathematically and transformed into the requested broad distribution curve employing Stokes' law and Mie's light scattering theory for homogeneous isotropic spheres.We use an AUC together with an 8-cells-rotor and a multiplexer. Because very large and very small particles are to be measured simultaneously in one single run, we can no more apply a constant rotor speed N as before, but by means of a time program N(t) we always have to increase the rotor speed from 0 to 40000 rpm within one hour.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051620103
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    Graft copolymerization of methyl methacrylate on poly(vinyl chloride) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 135-148 
    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 chemische Modifizierung von Polyvinylchlorid (PVC) durch ein Amin verleiht dem Polymeren höhere Reaktivität gegenüber der Pfropfcopolymerisation mit einem Vinylmonomeren. Die Pfropfcopolymerisation von Methylmethacrylat auf mit n-Butylamin modifiziertes PVC wurde thermisch mit Benzoylperoxid (Bz2O2) als Initiator oder photoaktiviert mit Benzophenon (BP) als Photosensibilisator gestartet. Das aus bestimmten Experimenten erhaltene rohe Polymerprodukt wurde durch fraktionierte Fällung in die verschiedenen Bestandteile wie Polymethylmethacrylat (PMMA, Homopolymeres), PVC-g-PMMA (Pfropfcopolymeres) und unverändertes (aminiertes) PVC aufgespalten. Die getrennten Fraktionen wurden mit Hilfe der IR-Spektroskopie und der Thermogravimetrie charakterisiert. Der Mechanismus der Pfropfcopolymerisation von den beiden verschiedenen Systemen wurde erörtert. In beiden Fällen wurden Pfropfausbeuten um 30 - 70%* und Pfropfcopolymerzusammensetzungen, PMMA/PVC (w/w) zwischen 2 und 3 erhalten.
    Notes: Chemical modification of poly(vinyl chloride), PVC, by an amine renders the polymer more reactive towards graft copolymerization with a vinyl monomer. The graft copolymerization of methyl methacrylate (MMA) on PVC modified by treatment with n-butylamine (n-BA) was started thermally at 30° using benzoyl peroxide (Bz2O2) as initiator and under photoactivation at 40° using benzophenone (BP) as photo sensitizer. The gross polymer products from selected experiments were fractionally separated into the constituent polymeric entities viz., poly(methyl methacrylate), PMMA (homopolymer), PVC-g-PMMA (graft copolymer), and unreacted (aminated) PVC following a method of fractional precipitation. The separated fractions were characterized by IR spectroscopy and thermogravimetry. The mechanisms of graft copolymerization for the two different systems have been discussed. In each case, grafting efficiencies of the order of 30-70% and graft copolymers having compositions given as PMMA/PVC (w/w) equal to 2-3 were readily obtained.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051620109
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    Surface sulphonated highly crosslinked styrene-divinylbenzene copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 193-201 
    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 oberflächensulfonierter, makroporöser Styrol-Divinylbenzol-Copolymerer mit unterschiedlichen Gehalten an SO3H-Gruppen wurden hergestellt. Sowohl von diesen Copolymeren als auch vom nichtsulfonierten Copolymeren wurden Porenstruktur, Oberflächenhydrophilie und -polarität sowie das Sorptionsverhalten gegenüber einigen in Blut vorkommenden Substanzen bestimmt. Der Sorptionsgrad wird umso kleiner, je größer die Oberflächenpolarität ist. Die teilsulfonierten Polymeren könnten eine Anwendung in der Hämoperfusion finden.
    Notes: A series of surface sulphonated macroporous styrene-divinylbenzene (S-DVB) copolymers containing various amounts of  - SO3H groups was obtained. Porous structure, surface hydrophilicity and polarity, and sorption properties of these copolymers as well as those of starting S-DVB resin towards some substances which are present in blood were determined. The sorption degree becomes the smaller the higher is the surface polarity. The partially sulphonated copolymers may find an application in hemoperfusion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051620113
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    Studies on the enhancement of separation characteristics of sulfonated poly(phenylene oxide)/polysulfone thin film composite membranes for reverse osmosis applications. I. Effect of chemical treatment (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 1-13 
    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 chemischen Behandlung von dünnen Filmen einer Composit-Membran aus sulfoniertem Polyphenylenoxid wurde untersucht. Über den Einfluß der Konzentration von wáßrigen Lösungen von Formaldehyd, Schwefelsäure, Salzsäure, Phosporsäure, Natriumhydroxid sowie der Behandlungsdauer auf die Trenncharakteristik der inversen Osmose der Composit-Membranen mit einer Ionenaus-tauschkapazität von 2,14 und 2,50 meq/g in verschiedenen Kombinationen wird ausführlich berichtet. Die Ergebnisse zeigen, daß unter den besten chemischen Behandlungsbedingungen eine Erhöhung der Trenncharakteristik der inversen Osmose der sulfonierten Polyphenylenoxid/Polysulfon-Composit-Membran erreicht wird.
    Notes: The effect of chemical treatment on the reverse osmosis (RO) separation characteristics of sulfonated poly(phenylene oxide) (SPPO) thin film composite membranes was investigated. The effects of the concentrations of aqueous solutions of formaldehyde, sulfuric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, and treatment time on the RO separation characteristics of the composite membranes with ion exchange capacity (IEC) of 2.14 and 2.50 meq/g in various combinations are reported in detail. The results indicate some enhancement in RO separation characteristics of the SPPO/polysulfone (PS) composite membrane under the best conditions of the chemical treatment.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630101
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  • 33
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    Studies on the enhancement of separation characteristics of sulfonated poly(phenylene oxide)/polysulfone thin film composite membranes for reverse osmosis applications. II. Effects of nitromethane and the chemical treatment combined with gamma-ray irradiationPart I cf. lit.3. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 15-21 
    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: Bei der Herstellung dünner Filme von sulfonierten Polyphenylenoxid/Polysulfon (SPPO/PS)-Composit-Membranen wurde untersucht, daß ein Zusatz von Nitromethan zu einer Lösung von sulfoniertem Polyphenylenoxidnatrium erhöhte Wirkung auf die Trenncharakteristik der inversen Osmose besitzt. Der Einfluß von gamma-Strahlung auf dünne Filme der Composit-Membran unter nassen und trockenen Bedingungen wurde ebenfalls untersucht. Um die maximal mögliche Verbesserung zu erreichen, wurden die Composit-Membranen einer kombinierten chemischen und Gammastrahlen-Behandlung unter nassen und trockenen Bedingungen unterworfen.Die experimentellen Ergebnisse dieser kombinierten Behandlung zeigen, dalß die SPPO/PS Composit-Membran dabei abgebaut wird.
    Notes: The enhancement effect of the addition of nitromethane into the coating solution of sulfonated sodium poly(phenylene oxide) (SPPONa) polymer for the synthesis of sulfonated poly(phenylene oxide)/polysulfone (SPPO/PS) thin film composite membranes on reverse osmosis (RO) separation characteristic was studied. The effect of gamma-ray irradiation on the SPPO/PS thin film composite membranes was also evaluated when the membrane samples were in the wet and dry conditions. The composite membranes were also subjected to a chemical treatment combined with gamma-ray irradiation in both wet and dry conditions in the hope of obtaining the maximum possible enhancement under each treatment. However, the experimental data of this combined treatment indicated the possibility of some degradation of the SPPO/PS composite membranes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630102
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    Electronic Resource
    Effect of blending techniques on the curing of elastomer blends (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 37-45 
    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: Mischungen aus Poly(styrol-co-butadien)/Polybutadien, Naturkautschuk/Poly-(ethylen-co-propylen-co-dien und Naturkautschuk/Poly(butadien-co-acrylnitril)) wurden nach drei unterschiedlichen Verfahren compoundiert und Härtungsverhalten sowie Zugfestigkeit und Bruchdehnung der Vulkanisate wurden verglichen.
    Notes: Compounding of styrene-butadiene copolymer/polybutadiene, natural rubber/ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer blends was done in three different ways and their curing behaviour and the tensile properties of the vulcanizates are compared.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630104
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    Modification of starch by graft copolymerisation with methyl methacrylatePresented at 12th National Conference of the Chemical Society of Nigeria, Calabar, Nigeria, Sept. 23-25, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 93-99 
    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: Methylmethacrylat (MMA) wurde mit Hilfe von Cerammoniumnitrat als Initiator auf Stärke gepfropft. Die Pfropfcopolymeren wurden durch selektive Lösungsextraktion in einem Soxhlet-Extraktor isoliert. Der Einfluß von Reaktionszeit, Initiatorkonzentration, Temperatur sowie der Monomer- und Särekonzentration auf die Pfropfausbeute wurde untersucht. Eine erste Studie der Kinetik dieser Pfropfcopolymerisationsreaktion zeigt, daß sie dem üblichen kinetischen Verhalten einer Radikalpolymerisation folgt.
    Notes: Methyl methacrylate (MMA) was grafted onto starch using ceric ammonium nitrate as initiator. The graft copolymers were isolated by selective solvent extraction in a Soxhlet apparatus. The effects of reaction time, initiator concentration, temperature, monomer, and acid concentrations on the graft yields were investigated. A preliminary kinetic study of the graft copolymerisation reactions shows that they follow the conventional kinetic behaviour of free radical polymerisation.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051630108
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  • 36
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    Adsorption of phenols on carbonaceous adsorbents produced from phenol-formaldehyde-resin mixed with olive stones (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 47-61 
    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: Durch Verwendung von Phenol-Formaldehyd-Harz mit gepreßten Olivenkenen im Gewichtsverháltnis 20/80 wurden kleine zylindrische Formkörper durch Härtung hergestellt. Diese wurden pyrolysiert und einige Proben mit Wasserdampf aktiviert. Für diese Formkörper und für zwei kommerzielle Aktivkohlen für Laboratoriumsbzw. Industrie-Anwendungen wurden folgende Eigenschaften bestimmt: die spezifische Oberfláche, die Struktur, die Adsorptionseigenschaften sowie die Adsorptionskapazität. Die Ergebnisse zeigen, daß die hergestellten kohlenstoffhaltigen Materialien durch Aktivierung höhere Werte für die untersuchten Eigenschaften ergeben als die nur pyrolysierten Proben und die zwei kommerziellen Aktivkohlen. Es wurde festgestellt, daß die Adsorption des 4-Nitrophenols für alle untersuchten kohlenstoffhaltigen Materialien gemäß der Freundlich-Gleichung stattfindet. Die Raster-Elektronenmikroskopie zeigt, daß die hergestellten kohlenstoffhaltigen Materialien andere Porenarten aufweisen als die kommerziellen Aktivkohlen. Die experimentellen Ergebnisse werden durch die molekularen Dimensionen der zur Adsorption verwendeten Substanzen und den Polarisationseffekt der Substituenten am Benzolring erklärt.
    Notes: Mixtures of phenol-formaldehyde-resin and pressed olive stones in a weight ratio of 20/80 were cured as small cylinders and then pyrolyzed. Some samples were also activated by steam. For these specimens and for two commercial activated carbons of laboratory or industrial uses the specific surface area, the structure, the adsorption properties, and the adsorption capacity were determined. The results indicate that the carbonaceous material produced by activation has greater values for the examined properties in comparison to the only pyrolyzed and the two commercial activated carbons, respectively. It was found that the Freundlich-equation is valid for the adsorption of 4-nitrophenol on all carbonaceous materials examined. The produced carbonaceous materials have different kinds of pores than the commercial activated carbons. The experimental results are explained with regard to the molecular dimensions of the adsorptive substances and the polarization effect of the substituents of the benzene ring.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630105
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    Nonlinear programming methods to determine surface free energy components of polymers using harmonic mean approximation (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 101-114 
    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: Durch Anwendung der nichtlinearen Programmiermethode basierend auf der mittleren harmonischen Näherung wurden aus den Kontaktwinkeldaten die freie Dispersions- und polare, freie Oberflächenenergie, γSVd und γSVp, sowie die kritische, freie Oberflächenenergie, γc, von Polymeren bestimmt. Die Komponenten der freien Oberflächenergie der zu untersuchenden Flüssigkeiten, γLVd und γLVp, die die Bedingungen für den maximalen Wechselwirkungsparameter, Φ, wiedergeben, wurden ebenfalls mit Hilfe dieser Methode bestimmt.
    Notes: The dispersion and polar surface free energy components, γSVd and γSVp, and the critical surface free energy, γc, of polymers were determined from contact angle data by the application of a nonlinear programming method using harmonic mean approximation.The surface free energy components of the probe liquids, γLVd and γLVp, which reflect the conditions of the maximized interaction parameter, Φ, were also simultaneously determined by this method.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630109
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  • 38
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    Gemeinsame kondensation von bisphenol A, melamin und formaldehyd (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 169-193 
    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 condensation reaction of bisphenol A, melamine, and formaldehyde was investigated by gel permeation chromatography, 13C-NMR-spectroscopy, IR-spectroscopy and elemental analysis. Because of the high reaction rates the condensation could be investigated only in the range of pH 6-10. At pH 6 and 7 the reaction of melamine with formaldehyde is dominating.With increasing pH-value the condensation of bisphenol A with formaldehyde is observed preferably. At pH 10 the condensation results in high molecular products. Cocondensation of melamine and bisphenol A through methylene bridges does not take place. But as a separation of the bisphenol A-formaldehyde condensates from the other condensation products was not possible, the three components may be connected through methylene-ether groups and/or intermolecular hydrogen bridges.
    Notes: Die gemeinsame Kondensation von Bisphenol A, Melamin und Formaldehyd wurde mit Hilfe der Gelpermeationschromatographie, der 13C-NMR-Spektroskopie, IR-Spektroskopie und Elementaranalyse untersucht. Wegen der hohen Kondensationsgeschwindigkeit verläuft die Reaktion in Gegenwart der drei Komponenten nur im Bereich von pH 6-10 kontrollierbar. Bei pH 6 und 7 überwigt die Kondensation zwischen Melamin und Formaldehyd. Mit steigendem pH-Wert tritt die Reaktion von Bisphenol A mit Formaldehyd in den Vordergrund und führt bei pH 10 zu hochmolekularen Kondensationsprodukten.Auf direkte Cokondensation hinweisende Methylenverknüpfungen zwischen der phenolischen Komponente und Melamin konnten nicht nachgewiesen werden. Die Kondensationsprodukte des Melamins bzw. des Bisphenol A mit Formaldehyd lassen sich aber nicht mehr vollständig aus den Reaktionsgemischen der Vorkondensation abtrennen, was dafür spricht, daß die Komponenten über Methylenetherbrücken und/oder intermolekularen Wasserstoffbrücken miteinander verknüpft sind.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051630115
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    Preparation of cyclodextrin membrane-modified electrodes as sensor materials (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 205-207 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cyclodextrin membrane-modified electrodes as sensor materials have been prepared by dipping platinum electrodes in the water suspensions of an oriented cyclodextrin polymer, followed by drying the polymer layers on the electrodes. The polymer is obtained by the solid-liquid reaction between the crystal of cyclodextrin inclusion complex and hexamethylene diisocyanate in anisole. The thickness (2 - 80 μm) of the cyclodextrin membrane is satisfactorily controlled by changing the concentration of the water suspension of the polymer. The cyclodextrin membranemodified electrodes show a significant response to p-nitrophenolate in water which is highly in contrast with no measurable response to o- and m-nitrophenolates.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630118
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    Antioxidants and stabilizers, 107Part 106 cf. Polym. Degr. Stabil. 17 (1987) 287.. Reaction of N-phenyl-1,4-benzoquinoneimine with the 1-cyano-1-methylethyl-radical (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 91-104 
    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: Im Zusammenhang mit dem Studium des Wirkungsmechanismus von industriell hergestellten Antidegradantien vom Typus der N-Phenyl-N′-sek-alkyl-1,Cphenylendiamine wurde die Reaktion von N-Phenyl-1,4-benzochinonimin (I) und 4-Hydroxydiphenylamin (II) mit dem Kohlenstoff-Radikal 1-Cyano-l-methylethyl (R·) studiert. Das Gemisch von I und II reagiert mit R· sehr leicht unter Bildung der Verbindungen III, VI und VIII. I allein reagiert wesentlich langsamer, und das Reaktionsgemisch enthält mehrere Produkte. Neben der Verbindung III wurden auch die Verbindungen IV und VII identifiziert. II allein reagiert bei denselben Bedingungen nicht. Die Verbindung IV bildet die zwei isomeren Strukturen syn und anti. Die Verbindung VIII ist ziemlich unbeständig; aus ihren Umwandlungsprodukten wurde XI isoliert. Bei der Reduktion von IV entsteht die Verbindung V, die ähnlich wie VIII unbeständig ist.
    Notes: The reaction of N-phenyl-1,4-benzoquinoneimine (I)Decoding of abbreviations see p. 103/104. and 4-hydroxydiphenylamine (II) with the carbon centred 1-cyano-1-methylethyl radical (R·) was studied in connection with an investigation of the action mechanism of industrial antidegradants, such as N-phenyl-N′-sec-alkyl-1,4-phenylenediamines. The mixture of I and II reacts very readily with R·, giving rise to III, VI, and VIII. I alone reacts much slowlier, and the reaction mixture contains more products. IV and VII were identified along with III. Under the conditions used, II alone does not react at all. IV exists in two isomeric forms, syn and anti. VIII is very labile; XI was isolated from its transformation products. Reduction of IV gives V, which is labile, similarly to VIII.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051560109
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    Ozoninduzierter Abbau von Polyoxymethylen (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 123-137 
    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: Samples of polyoxymethylene (unstabilized and stabilized with the antiozonants N-isopropyl-N′-phenyl-p-phenylenediamin (IPPD) and bis-(1,2,3,6-tetrahydrobenzaldehyd)pentaerithritylacetal (Vulkazon AFS)) were ozonized under mechanical load in a special climate chamber. Surface damages were determined by IR-spectroscopy and scanning electron microscopy. During the ozonolysis a damaged layer is formed, the thickness of which increases with increasing time of ozonization. During this damaging reaction acetal groups are attacked and oligomers are formed.
    Notes: Proben von unstabilisiertem und mit den Antiozonantien N-Isopropyl-N′-phenyl-p-phenylendiamin (IPPD) und Bis-(1,2,3,6-tetrahydrobenzaldehyd)-pentaerithrityl-acetal (Vulkazon AFS) stabilisiertem Polyoxymethylen wurden unter mechanischer Belastung in einer Klimakammer ozonisiert. Die Schädigungen auf der Oberfläche wurden IR-spektroskopisch und rasterelektronenmikroskopisch untersucht. Während der Ozonisierung von POM bildet sich eine geschädigte Schicht, deren Dicke mit zunehmender Ozonisierungszeit wächst. Hierbei wird das Polymere an den Acetalbindungen angegriffen, wodurch Ketten gespalten werden und Oligomere entstehen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051560111
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    On the structure of macroreticular styrene-divinylbenzene copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 105-121 
    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: Mit Hilfe verschiedener Methoden wurde der Einfluß der Entfernung unterschiedlicher porenbildender Verdünner aus porösen Styrol-Ethylstyrol-Acrylnitril-Divinylbenzol-Copolymeren auf die Netzwerkstruktur untersucht. Der günstigste Weg, den ursprünglichen strukturellen Bau des porösen Netzwerkes zu bewahren, welches in Gegenwart von solvatisierenden Verdünnern erhalten wurde, ist das Entfernen des inerten Mediums mit Methanol. Wenn die Wasserdampfmethode angewendet wird, fin det der sog. Kollapseffekt statt, und die aus solchen Harzen hergestellten Anionenaustauscher adsorbieren weniger Farbstoff im Vergleich zu jenen, die aus Perlen hergestellt worden sind, die mit Methanol behandelt wurden; Grund hierfür ist die durch den Kollaps veränderte Porengröße. Es wurde ebenfalls festgestellt, daß die in Anwesenheit von solvatisierenden Verdünnern (Mischungen aus Quellungs- und Fällmitteln) hergestellten Copolymeren in Methanol sehr gut quellen, obwohl dieses ein Fällungsmittel für Polystyrol ist.
    Notes: The influence of the removal of various diluents, pore forming agents from the porous styrene-ethylstyrene-acrylonitrile-divinylbenzene copolymers on the structure of the matrix was investigated by several methods. The most advantageous pathway to preserve the initial structural edifice of the porous networks performed in the presence of solvating diluents consisted in the removal of the inert media with methanol as it was noticed from the experimental data. If the steam treatment is applied, the collapse effect takes place and the anion exchangers prepared from such matrices exchange/adsorb less dye stuff by comparison with ones formed from beads treated with methanol, because the pore size was changed. It was also noticed that the porous copolymers performed in the presence of the solvating diluents (mixtures of solvatings and precipitants) swell very well in methanol though it is a precipitating medium for the polystyrenic macromolecular chains.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051560110
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    Heat stability of styrene-zinc acrylate copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), 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: An Styrol-Zinkacrylat-Copolymeren wurde die Abhängigkeit der Glasübergangstemperatur von der Aufheizgeschwindigkeit und der Zusammensetzung mit Hilfe der Differential-Scanning-Calorimetrie untersucht. Die Thermogravimetrie wurde benutzt, um die Pyrolyse dieser Copolymeren an Luft bei drei verschiedenen Aufheizge-schwindigkeiten zu untersuchen. Die thermische Zersetzung von Ionomeren ist ein 3-Stufen-Prozeß. Die Reaktionsordnung und Aktivierungsenergie wurde für jede Stufe der Zersetzung bestimmt unter Verwendung eines Computerprogramms, das auf den Methoden von Kissinger, Freeman-Carrol und Ozawa basiert. Es zeigte sich, daß die thermische Stabilität durch die ionischen Gruppen abnimmt.
    Notes: The dependence of glass temperature on the heating rate and the composition for styrene-zinc acrylate copolymers has been investigated by differential scanning calorimetry. Thermogravimetry was used in order to examine these copolymers undergoing pyrolysis in an atmosphere of air at three different heating rates. Thermal decomposition of ionomers is a three-stage process. The orders and activation energies have been determined for each stage of decomposition using the computer programs based on the methods of Kissinger, Freeman-Carrol, and Ozawa. It was found that the heat stability is lowered by the ionic groups.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051560112
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    Free radical grafting of some hydrophilic monomers onto unsaturated segmented polyurethanes  -  a kinetic study (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 151-162 
    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 Pfropfung der hydrophilen Monomeren N-Vinylpyrrolidon, 2-Hydroxyethyl-methacrylat und Acrylamid auf ungesättigte segmentierte Polyurethane in N,N-Dimethylformamid mit 2,2′-Azobisisobutyronitril als Initiator wurde untersucht. Die Pfropfcopolymeren wurden von den Homopolymeren durch selektive Extraktion in Soxhlet-Apparaturen abgetrennt. Die kinetische Untersuchung der Pfropfcopolymerisation zeigte, daß die Reaktionen dem gewöhnlichen kinetischen Verhalten radikalischer Polymerisationen folgen. Die Abhängigkeiten der Pfropfungsgeschwindigkeit von der Initiator- und N-Vinylpyrrolidonkonzentration waren von 0,5 bzw. 1,0 Ordnung. Für 2-Hydroxyethylmethacrylat wurden sie zu jeweils 0,5 und 2,0 gefunden. Die Gesamtaktivierungsenergie der Pfropfcopolymerisation des 2-Hydroxyethylmethacrylats und des N-Vinylpyrrolidons betragen jeweilig 21,81 und 16,28 kJ/mol.
    Notes: Grafting of unsaturated segmented polyurethanes with some hydrophilic monomers such as N-vinyl pyrrolidone, 2-hydroxyethylmethacrylate and acrylamide in N,N-dimethylformamide have been studied using 2,2′-azobisisobutyronitrile (AIBN) as initiator. Graft copolymers were isolated from homopolymers by selected solvent extraction using a Soxhlet apparatus. A kinetic study of graft copolymerization reactions showed that the reactions follow the conventional kinetic behaviour of free radical polymerization. The dependencies of the grafting rate on initiator and N-vinyl pyrrolidone concentrations were of 0.5 and 1.00 order, respectively. However, for the 2-hydroxyethylmethacrylate, the dependencies of the grafting rate on initiator and monomer concentrations were found to be of 0.5 and 2.00 order, respectively. The overall activation energy for the graft copolymerization of the 2-hydroxyethylmethacrylate and N-vinyl pyrrolidone were 21.81 kJ/mol and 16.28 kJ/mol, respectively.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051560113
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    Highly dispersed Ni catalysts on carbon from thermal decomposition of cellulose-hydrous nickel gel membrane (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 179-185 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultra fine particles were impregnated by using a finely porous cellulose gel membrane. The impregnated gel membrane is a green transparent one and looks like a solid solution. Highly dispersed Ni catalysts on carbon were obtained from thermal decomposition of these gel membranes. The particle size is in the range of several nm to a few ten nm. They show interesting catalytic properties for hydrogenation of olefins such as cyclooctadiene.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051560115
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    Ageing of polyethylene filled with a mineral fillerPaper presented at the 18th Colloquium of Danubian Countries for “Natural and artificial ageing of plastics” in Villach (Austria) June 24-26, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 351-362 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermo-oxidation resistance and weatherability of LDPE and HDPE compositions, containing up to 45 wt.% calcium carbonate, are investigated. The thermo-oxidation resistance is investigated by dynamic DTA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behaviours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051580121
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    Influence of production parameters on ageing processes of thermoplasticsVortrag anläßlich des 18. Donauländergespächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 335-349 
    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: An Proben aus Polypropylen, die bei sehr unterschiedlichen Einstellungen von Spritzgußmaschinen und Extrudern hergestellt wurden, stellten sich deutliche Abhängigkeiten des Alterungsverhaltens von den thermischen und mechanischen Produktionsparametern ein, die nicht durch unterschiedliche Schmelzetemperaturen bedingt sind. Insbesondere kann ausgesagt werden, daß bei Spritzguß eine hähere Scherbelastung und damit stärkere Orientierungen -eine stärkere Veränderung der Eigenspannungen hervorrufen-einen früheren Glanzabfall und-eine geringere Initialzeit bis zur Rißbildung bewirken.Bei Extrusion fiihrt eine geringere Abkühlgeschwindigkeit und damit ein gröberes Gefüge zu -einer stärkeren Veränderung der Eigenspannungen-einem friiheren und ausgeprägteren Glanzverlust-sowie zu einem früheren Abfall der Reißdehnungen.Unbekannt ist, -ob diese Wirkungen auch bei anderen Thermoplasten als PP auftreten-ob sie auch bei stabilisierten Systemen in relativ gleichem Umfange auftreten-und ob es sich lohnt, die beobachteten Effekte ggf. durch ge zielte Maschineneinstellungen auszunutzen.Auf jeden Fall sollten auf diesem Gebiet weitere Arbeiten durchge-führt werden.
    Notes: Specimens of unmodified polypropylene have been manufactured using extreme adjustings of injection moulding machines and extruders. After artificial weathering, distinct relations of ageing processes to thermal and mechanical production parameters were found, which are not influenced by different melting temperatures. It can be started in particular, that during injection moulding a larger shear stress (resulting in more distinct orientation) results in -a greater change in residual stresses-an earlier gloss reduction-a shorter initial period before cracking.During extrusion a lower cooling rate (resulting in a coarser structure) leads to -a greater change in residual stresses-an earlier and more distinct gloss reduction-an earlier loss of ultimate strain.It remains unknown, whether -these relationships will be similar with other thermoplastic materials than PP-these relationships appear to the same relative extend with stabilized systems-it may be advantageous, to use the observed effects by adjusting the injection moulding and extrusion machines in a special way.It seems to be significant to do more research work in this field.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051580120
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  • 48
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    Electronic Resource
    Solvolytic degradation of aliphatic polyesteroligomers: Poly(tetramethylene adipate) diol (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 1-15 
    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(tetramethylenadipat)diol mit einer Molmasse von 2000 wurde bei Temperaturen von 60 und 80°C in Gegenwart von Wasser bzw. 1,4-Butandiol sowie den gebräuchlichsten PUR-Katalysatoren (Dabco und Dibutylzinndilaurat) gelagert und die Solvolyse untersucht. Die Geschwindigkeit der Solvolyse nimmt mit steigender Temperatur deutlich zu. Die Alkoholyse wird durch Dibutylzinndilaurat weitaus stärker katalysiert als durch 1,4-Diazabicyclo[2.2.2]oktan. Die Hydrolyse verläuft langsamer, da vermutlich die Katalysatoren bei diesem Prozeß desaktiviert werden. Die mechanischen Eigenschaften von Polyurethanen, die mit den partiell abgebauten Diolen hergestellt wurden, korrelieren gut mit der Abnahme der Molmasse.
    Notes: Poly(tetramethylene adipate)diol having a molar mass of 2000 was stored at temperatures of 60 and 80°C in the presence of water or 1,4-butanediol and a common PUR-catalyst like 1,4-diazabicyclo [2.2.2]octane (DABCO) or dibutyltindilaurate (DBTL) and the solvolysis was investigated. The rate of solvolysis is low at 60°C except for DBTL and shows a drastic increase at 80°C. In the alcoholysis reaction DBTL is a much more active catalyst than DABCO. The rate of hydrolysis is slower probably because the catalysts are deactivated by the acidic products formed in this process. The mechanical properties of polyurethanes made from the degraded polyols are in good correlation with the decrease in molar mass.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600101
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  • 49
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    Electronic Resource
    Carbon fibre reinforced bismaleimide composites, I (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 17-28 
    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 der Zugabe von Bis(allylphenyl) Typ (TM 120)-Monomeren auf die Eigenschaften von unidirektional mit Carbonfasern verstärkten 4,4′-Bismaleimidodiphenylmethan (BM) - 2,4-Tolylendiamin (A) (1:0,3 Molverhältnis) (BM-A)-Verbundkörpern wird vorgestellt. Das Aushärteverhalten sowie das thermische Verhalten in Luft wurde mit Hilfe der Differentialkalorimetrie (DSC) und der Thermogravimetrie (TGA) untersucht. Die thermische Stabilität nimmt mit ansteigenden Konzentrationen von TM 120 deutlich zu. Demgegenüber steht ein Anstieg der Biegefesigkeit, der interlaminaren Scherfestigkeit sowie der Schlagzähigkeit mit zunehmender Monomerkonzentration. Optimale mechanische Eigenschaften wurden bei etwa 20 Tle./100 Tle. TM 120 erreicht.
    Notes: The paper deals with the effect of addition of bis(allylphenyl) type (TM 120) monomer on the properties of unidirectionally carbon fibre reinforced 4,4′ bismaleimidodi-phenyl methane (BM) - 2,4-tolylene diamine (A) (1:0.3 molar ratio) (BM-A) composites. The curing and thermal behaviour of the blends was investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in air atmosphere. A marginal decrease in thermal stability was observed with increasing concentration of TM 120. Flexural, interlaminar, and impact strength of the laminates increased in the presence of this monomer. Optimum mechanical properties were observed at ∼ 20 phr of TM 120.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600102
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  • 50
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    Structure and aging in the welded bonds of PP- homopolymer with PP- copolymer (PP-R)Vortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 363-378 
    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: In dieser Arbeit wurden Veränderungen des verschweisßten Rohr- und Fittingmaterials (isotaktisches Polypropylen Homo- bzw. Copolymer PP-R grau pigmentiert) wührend der für die Praxis relevanten Innendruckversuche untersucht.Bei der technischen Verschweißung von Polyolefinen entstehen charakteristische Gefüigezonen im Schweißnahtbereich, welche vom Fßgematerial und den Fngebedingungen beeinflußt werden. In der vorliegenden Untersuchung wurden sowohl die Materialcbergange im Fiigebereich (mit den Methoden - schichtenweise Differentialkalorimetrie, Polarisations- bzw. Elektronenmikroskopie sowie Fluoreszenzspektroskopie mit extrem hoher Ortsauflösung) als auch die Eigenspannungen hinsichtlich ihrer Verlnderung bei Langzeitpriifung im Innendruckzeitstandversuch bei 95°C bis zu einer Prüfzeit von 18.100h untersucht.Die Abbauvorgänge der Makromoleküle bei der Langzeitprüfung der 364 untersuchten Schweißmuster werden in einer gesonderten Arbeit behandelt (1).Durch die Innendruckversuche bei 950 C findet eine Nachkristallisation und eine Gefügevergrijberung sowohl in der Schweißnaht als auch im Gefüge der Schweißpartner statt. Dabei werden die beim Schweißvorgang eingebrachten Orientierungen und Eigenspannungen unter dem Einfluß von Wärme beim Innendruckversuch weitgehend abgebaut. Durch die unter Druckeinwirkung einsetzenden Flieävorgange jedoch werden neue Eigenspannungen eingebracht.Es konnte gezeigt werden, daß bei guter Verschweißung von PP mit PPCO ein kontinuierlicher Übergang (Mischungsbereich) vom Homopolymeren zum Copolymeren auftritt, der auch beim Langzeiteinsatz im Innendruckversuch erhalten bleibt.
    Notes: The present study deals with changes of welded material of pipes and fittings (isotactic polypropylene homo and copolymer PP-R grey pigmented) during the standardized internal pressure tests, which are commonly used for these products.Technical welding of polyolefines causes characteristic structures, which depend on the natural of the welded material and the welding conditions.In this investigation both the transition of material in the welding seam and the changes of internal stresses during internal pressure tests at 95°C until 18.100h test time were examined. The methods we used were Differential calorimetry of think layers, Polarization- and Electron microscopy, Fluorescence spectroscopy with extreme high local resolution.The effects of decomposition of the macromolecules in the welded samples during the internal pressure tests will be described in a separate paper (1).The internal pressure tests at 95O C cause a recrystallization and an increase of the particle size in the structure of the welding seam and in the structure of the welded parts themselves. Under the above described testing conditions the orientations and internal stresses initiated by the welding procedure will relaxe influenced by heat. However the creep effects that occur in the material when exposed to pressure introduce new internal stresses. It could be shown that in perfectly welded parts a continuous transition from PP to PPCO occurs, which did not change after long time application of internal pressure tests.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051580122
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    Coordination polymers, 1. Magnetic, spectral, and thermal properties of coordination polymers derived from terephthalaldehyde bis(S-benzyldithiocarbazate) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 67-81 
    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: Es wurden neue Coordinationspolymere mit Schiffschen Basen aus Terephthalal dehyd und S-Benzyldithiocarbazol als Liganden in DMF-Lösung hergestellt. Die erhaltenen Coordinationspolymeren wurden durch Elementaranalyse, magnetische Suszeptibilität, elektronische und IR-Spektroskopie charakterisiert. Die durch Thermogravimetrie bestimmte thermische Stabilität der Coordinationspolymeren nahm in der folgenden Reihenfolge ab: \documentclass{article}\pagestyle{empty}\begin{document}${\rm Zn} \simeq {\rm Fe} 〉 {\rm Co} 〉 {\rm Ni} 〉 {\rm Min} \simeq {\rm Cu}$\end{document} Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymere haben eine Oktaederstruktur mit der Koordinationszahl6, während bei den Cu(II)- und Zn(II)-Coordinationspolymeren eine 4-fach koordinierte quadratisch-planare bzw. eine tetraedrische Struktur gefunden wurde. Ligandenfeld- und nephelawetische Parameter wurden aus den Spektren errechnet. Dam wurde die Ligandenfeldtheorie spin-erlaubter Übergänge angewandt, die sich als konsistent mit einer 6-fach koordinierten Struktur für Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymere erwies. Die Elementaranalysen ergaben bei allen Coordinationspolymeren ein Ligand: Metall-Verhältnis von 1 : 1 und deuteten bei den Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymeren auf am Zentralatom assoziierte Wassermoleküle hin.
    Notes: New Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) coordination polymers of Schiff base ligand derived from terephthalaldehyde and S-benzyldithiocarbazate have been synthesized in DMF media. The coordination polymers have been characterized by their elemental analysis, magnetic susceptibility, and by electronic and infrared spectral measurements.The thermal stability of each polymer was found out by thermogravimetric analysis. The thermal stability of coordination polymers obtained from thermograms has the following order: \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Zn} \simeq {\rm Fe} 〉 {\rm Co} 〉 {\rm Ni} 〉 {\rm Min} \simeq {\rm Cu}$\end{document} Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers are of a six-coordinated octahedral structure while Cu(II) and Zn(II) coordination polymers are found to be four-coordinated square planar and tetrahedral structure, respectively. The ligand-field and nephelauxetic parameters have been determined from the spectra, using ligand-field theory of spin-allowed transitions which are found consistent with six-coordinate structure for Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers. Elemental analyses indicates a ligand: metal ratio of 1 : 1 in all the coordination polymers and the association of water molecules with central metal atom in case of Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051600105
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  • 52
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    Studies on the electrodeposition of polyimides (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 91-106 
    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: Emulsionen von aromatischen Polyamidsären (PMPE and PBPPM) in DMF und Methanol wurden benutzt, um gleichmäßige Filme auf Leiteroberflächen durch Elektrophorese abzuscheiden. Die Ausbeute und Qualität der abgeschiedenen Filme hängen von der Art der Polyamidsäre, dem Lösemittel, dem Fällungsmittel, dem oberflächenaktiven Mittel, dem pH-Wert und dem Polymergehalt ab. Die Bedingungen zum Erreichen der höchsten Abscheidungsausbeuten wurden bestimmt.
    Notes: The emulsions of aromatic polyamic acids (PMPE and PBPPM) in DMF and methanol were used to coat uniform films on conductor surfaces by electrodeposition. The deposition yield and quality of the deposited films are dependent on sort of polyamic acid, solvent (DMF), precipitant (MeOH), surfactant (TEA), pH value and solid content. To get maximum deposition yields from PMPE and PBPPM, the best conditions of electrodeposition were required as follows: pH value 5.7 and 5.58, MeOH/DMF weight ratio 3.0 and 2.8, solid content 3.5 and 2.4 wt.-%. Deposition yield was found to obey Faraday's law of electrolysis, and the higher the equivalent weight of the polyamic acid, the higher the coulombic yield.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600107
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    Electronic Resource
    Model of double associates for sorption of binary gas mixtures on polymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 107-115 
    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 einfaches Modell von Doppelassoziaten wurde verwendet, um die Doppelschichtsorption von binären Gasgemischen an flexiblen linearen Polymerketten zu beschreiben. Die Isothermengleichung nach diesem Modell ist ein einfaches Produkt der isothermen Gleichung, die die Doppelschichtadsorption von binären Gasgemischen an einer homogenen festen Oberfläche beschreibt und einer Funktion, die die spezifischen Merkmale der Sorption an Polymeren widerspiegelt.
    Notes: A simple model of double associates is used to represent bilayer sorption of binary gas mixtures on a flexible linear chain of a polymer. The isotherm equation derived in terms of this model is a simple product of the isotherm equation describing bilayer adsorption of binary gas mixtures on a homogeneous solid surface and a function reflecting specific features of sorption on polymers.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051600108
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  • 54
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    Einfluß der polymerisationsbedingungen auf die morphologie von schwefel-styrol-polymerisaten (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 131-140 
    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 a polymer system sulfur-styrene containing 10 wt.-% styrene the morphologie depending on the polymerization temperature and time is described. Besides the characteristical orthorhombic phase a monoclinic and a pseudoorthorhombic phase were detected. Moreover amorphous material exists, depending on the polymerisation parameters.
    Notes: Für ein Polymersystem Schwefel-Styrol mit 10% Styrol wird die Abhängigkeit der Morphologie von der Polymerisationstemperatur und -zeit beschrieben. Neben der charakteristischen orthorhombischen Phase wurden röntgenographisch eine monokline und eine pseudoorthorhombische Phase nachgewiesen. Außerdem liegt, abhängig von den Polymerisationsparametern, ein amorpher Anteil vor.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600110
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  • 55
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    Electronic Resource
    Molecular weight distribution of living polymers in a semi-batch reactor (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 117-129 
    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: Für eine anionische Polymerisation mit langsamer Start- und schneller Wachstumsreaktion wurde ein analytischer Ausdruck entwickelt, der es erlaubt, mittlere Molekulargewichte und Molekulargewichtsverteilungen von Polymeren vorauszuberechnen, die in einem halbkontinuierlichen Polymerisationsverfahren bei Zulauf einer verunreinigten Monomerlösung zu einer vorgelegten Initiatolösung entstehen. Die Gültig keit des Modells wurde an der Polymerisation von Isopren mit n-Butyllithium in n-Heptan überprüft. Die beobachteten Unterschiede zwischen theoretischen und experimentellen Werten werden auf die Änderungen in den Geschwindigkeitskonstanten von Start- und Wachstumsreaktion zurückgeführt, die dadurch hervorgerufen werden, daß sich die Polarität der Lösung durch die Anreicherung mit polaren Verbindungen ändert. Weiterhin wird gezeigt, daß bimodale Molekulargewichtsverteilungen entstehen, wenn sich an die halbkontinuierliche Verfahrensweise eine diskontinuierliche zur Erhöhung des Monomerumsatzes anschließt.
    Notes: For anionic polymerization with slow initiation and rapid propagation step analytical expressions are presented to calculate average molecular weights and molecular weight distributions for a semi-batch process, in which a monomer solution contaminated by impurities is fed to an initiator solution in the reactor. The validity of the model was checked for the case of the polymerization of isoprene by n-butyllithium in n-heptane. The differences observed between theoretical and experimental values are explained by the changes in the rate constants of the initiation and the propagation step caused by the change in the polarity of the reaction solution by the continuously fed impurities. Furthermore it is shown that polymers with bimodal molecular weight distributions are formed if the semi-batch procedure is followed by a batch one to increase the monomer conversion.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051600109
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  • 56
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    Electronic Resource
    Thermosetting mechanism of polyethersulfone (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 141-154 
    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 Wärmehärtungsmechanismus von zu Anstrichen verwendeten Polyethersulfonen wurde unter Verwendung von FTIR/PAS und ESCA untersucht. Als Ergebnis wurde bestätigt, daß der Luftsauerstoff Einfluß auf den Wärmehärtungsmechanismus hat. Das heißt, die Härtung des Polyethersulfonfilms beginnt an der Oberfläche und verläuft entsprechend Reaktion (4) weiter.
    Notes: Thermosetting mechanism of paint-use polyethersulfones was studied by utilizing FTIR/PAS and ESCA. As a result, it was confirmed that the oxygen in the air has an effect on the thermosetting mechanism. That is, the polyethersulfone film were baked from the surface, and proceeded according to reaction (4).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600111
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  • 57
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    Synthesis and characterization of resins from 4-ethylphenol and cinnamaldehyde (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 155-162 
    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: Es wurde der Mechanismus der Reaktion von 4-Ethylphenol mit Zimtaldehyd mittels HET 2DJ 13C-NMR Spektroskopie, 1H-NMR Spektroskopie und GPC untersucht. In der ersten Stufe findet die Addition des 4-Ethylphenols an die Carbonylgruppe und an die Doppelbindung des Zimtaldehyds statt. In der zweiten Stufe reagiert die —CH(OH)-Gruppe mit 4-Ethylphenol und bildet verzweigte Produkte in rötlich gefärbten Harzen mit einem Durchschnittsmolekulargewicht on 600. Die Reaktion verläuft bei Temperaturen über 100°C in stark saurem Medium.
    Notes: The mechanisms of the reaction between 4-ethylphenol and cinnamaldehyde were studied by means of HET 2DJ 13C-NMR spectroscopy, 1H-NMR spectroscopy and GPC. In the first step of the reaction the addition of 4-ethylphenol to carbonyl group and to double bond of cinnamaldehyde takes place. In the second step of the reaction the —CH(OH)-group reacts with 4-ethylphenol to form branched products of red coloured resins with an average molecular weight of 600. The reaction takes place at temperatures above 100°C in strong acid medium.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600112
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    Studies on electrical and paramagnetic properties of poly(phenylene sulphide) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 163-173 
    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 elektrischen und paramagnetischen Eigenschaften des durch eine direkte Methode aus Benzol und Schwefel synthetisierten Poly(phenylensulfid)s wurden untersucht. Die Geichstromdunkelleitfähigkeit dieses Polymeren im nativen Zustand ist 10-10 S/m. Sie nimmt während des Dotierens mit Jod um 8 Größenordnungen zu. Es wurde für undotierte Proben n-Typ- und für die mit Jod dotierten Proben p-Typ-Leitfähigketi beobachtet. Anhand der ESR-Messungen wurden die Zahl der paramagnetischen Zentren und der g-Faktor bestimmt, die entsprechend gleich 0.80 · 1017 Spins/g und 2.0037 für das undotierte Polymere bei Raumtemperatur betragen. Änderungen der Spinkonzentration sowohl für die mit Jod dotierten als auch für die im Temperaturbereich von 513 - 903 K getemperten Proben werden dargestellt. Es wird versucht, die Form der ESR-Linien auf eine quantitative Weise zu diskutieren.
    Notes: Electrical and paramagnetic properties of poly(phenylene sulphide) synthesized by a direct method from benzene and sulphur were investigated. In darkness dc conductivity of the polymer in its pristine state is of the order 10-10 S/m. Upon doping with iodine it increases by 8 orders of magnitude. For undoped samples the n-type conductivity and for those doped with iodine the p-type conductivity was observed. On the basis of ESR experiments the number of spins and g-value were determined, which for undoped polymer at room temperature are equal to 0.80 · 1017 spins/g and 2.0037, respectively. Next, the changes in spin concentration both for the iodine doped samples and these annealed within the temperature range 513 - 903 K were described. An attempt to discuss the ESR lineshape in a quantitative way was also made.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600113
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  • 59
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    Synthesis and study of the chelating properties of 3-carboxy-4-hydroxyacetophenone-formaldehyde resins (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 175-186 
    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: 3-Carboxy-4-hydroxyacetophenon (CHAP) wurde in verschiedenen Mengenverhältnissen mit Formaldehyd unter Verwendung von Alkali als Katalysator polykondensiert. Die erhaltenen Polykondensate (CHAP-F) wurden durch Elementaranalyse, IR-Spektroskopie, Bestimmung des Zahlenmittels der Molmasse (M̄n), Thermogravimetrie und Bestimmung der Grenzviskosität charakterisiert. Es wurden polymere Metallchelate mit Cu2+ -, Fe3+ -, Co2+ -, Ni2+ - und UO2+2 -Ionen hergestellt und charakterisiert. Mit Hilfe der Batch-Austauschmethode wurden Ionenaustauschereigenschaften eines CHAP-F Harzes gegen Fe3+ - Cu2+ - und Ni2+ -Ionen bestimmt.
    Notes: 3-Carboxy-4-hydroxyacetophenone (CHAP) was polycondensed with various proportions of formaldehyde using alcoholic alkali as catalyst. The resin samples, designated as CHAP-F, have been characterized by elemental analyses and IR spectroscopy, by estimation of their number average molecular weights (M̄n), by measurement of intrinsic viscosity, and by TGA. Polymeric metal chelates of one CHAP-F sample with Cu2+, Fe3+, Co2+, Ni2+, and UO22+ ions have been prepared and characterized.Ion-exchanging properties of one CHAP-F resin sample for Fe3+, Cu2+, and Ni2+ metal ions are studied by the application of the batch-equilibration method.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600114
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    Nucleophilic addition to phenylisocyanates: A theoretical study (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 187-192 
    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 Reaktionsenthalpien für die Addition von Hydroxidanion an substituierte Phenylisocyanate wurden mit MNDO berechnet. Die erhaltenen Werte stimmen sehr gut mit den Reaktionsgeschwindigkeiten der Addition von 2-Ethylhexanol an Phenylisocyanate überein. Dies ermöglicht eine Abschätzung der Reaktionsgeschwindigkeiten für nucleophile Additionen innerhalb vernünftiger Grenzen, ohne daß experimentelle Arbeiten durchgeführt werden müssen.
    Notes: The enthalpies for the addition of hydroxide anion to substituted phenylisocyanates have been calculated with MNDO. The results obtained correlate well with the rates of addition of 2-ethylhexanol to phenylisocyanates. This allows us to estimate the rates for nucleophilic addition within reasonable limits without the need for experiments.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051600115
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    Mitteilungen (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), 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.1988.051600118
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  • 62
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    Modification of epoxy resins with acrylic rubbers containing a pendant epoxy group (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 63-76 
    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: Durch Copolymerisation von Butylacrylat (BA) mit Vinylbenzylglycidylether (VBGE) wurden neue Acrylkautschuke mit Epoxyseitengruppen hergestellt. Um die Zähigkeit eines gehärteten Epoxidharzes (Bisphenol A/Diglycidylether/p,p′-Diaminodiphenylsulfon) zu erhöhen, wurde dieses mit den erhaltenen Acrylkautschuken modifiziert. Eine Zugabe von 20 Gew.-% eines Copolymeren mit 74% BA und 26% VBGE-Einheiten führte zu einer 30proz. Zunahme der Bruchzähigkeit (KIC) des gehärteten Harzes bei einer minimalen Einbuße an Festigkeit und Steifigkeit. Die modifizierten Harze wiesen eine Zwei-Phasen-Morphologie auf, bei der Kautschukteilchen mit einer mittleren Größe von 2 μm in eine Epoxymatrix eingebettet sind. Das Copolymere ohne Epoxyseitengruppen, das aus BA und Vinylbenzylmethoxyethylether hergestellt wurde, war als Modifier unwirksam, was darauf hindeutet, daß die seitenstándigen Epoxidgruppen zu einer guten Zwischenphasenadhäsion zwischen Kautschukteilchen und Matrix, und damit zu erhöhter Zähigkeit führen. Kautschuke, die 55 oder 86% BA-Einheiten enthielten, waren ebenfalls ungenügende Modifier. Zugabe des ersteren ergab Harze mit einer homogenen Phasenstruktur, während die Zugabe des letzteren zu einer Phasentrennung zwischen Kautschuk und Epoxidharz führte.
    Notes: New acrylic rubbers with a pendant epoxy group were prepared by copolymerization of butyl acrylate (BA) with vinylbenzyl glycidyl ether (VBGE). The modification of an epoxy system (bisphenol-A diglycidyl ether/p,p′-diaminodiphenyl sulfone) with the acrylic rubbers was carried out in order to increase the toughness of the cured epoxy resin. The addition of 20 wt.-% of the copolymer containing 74% of BA and 26% of VBGE units resulted in a 30% increase in the fracture toughness (KIC) of the cured resin at minimal expenses of strength and modulus of the resin. The modified epoxy resin had two-phase morphology in which the rubber particles with average diameter of 2 μm are dispersed in the epoxy matrix. The copolymer without the pendant epoxy group, prepared from BA and vinylbenzyl methoxyethyl ether, was ineffective as a modifier, indicating that the reaction of the pendant epoxide with the epoxy matrix resulted in good interfacial adhesion between the rubber particles and the matrix, and in the increased toughness. The epoxide-containing copolymers with 55 or 86% of BA units were also insufficient modifiers. The addition of the former yielded cured resins with homogeneous structure, whereas that of the latter resulted in macroscopic phase separation between the rubber and the epoxy resin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1988.051630106
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    Polyurethane ionomers: Effects of emulsification on properties of toluene diisocyanate based polyether polyurethane cationomers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 77-91 
    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: Lösungen von Polyether/Polyurethan-Kationomeren, die auf Toluoldiisocyanaten basieren, wurden hergestellt und durch Zugabe von Wasser emulgiert. Die Eigenschaften von aus diesen Lösungen und Emulsionen gegossenen Filmen werden mit Hilfe der Infrarot-Spektroskopie, dynamisch-mechanischer Messungen, der Differentialkalorimetrie, der Weitwinkel-Röntgendiffraktometrie und von Zug-Dehnungsmessungen untersucht. Der Einbau eines asymmetrischen, kettenverlängernden Bausteins, wie N-Methyldiethanolamin, führt zu einem Polyurethan (PU), das, ßhnlich wie das mit symmetrischem, kettenverlängerndem 1,4-Butandiol aufgebaute Polyurethan, eine meßbare Ordnung innerhalb der Hartsegmente aufweist. Nach der Quarternisierung mit Glykolsaure haben die PU-Kationomeren erhöhte Werte für Reißdehnung, Zugmodul und -festigkeit. Dies kann auf die Coulomb-Wechselwirkung zwischen benachbarten Hartsegmenten zurückgefiihrt werden. Das Emulgieren der PU-Ionomer-Lösung führt zu einer verstärkten Mischung der Weich-und Hartsegmente, wodurch die ursprünglichen Hartsegmentbereiche mit asymmetrischen 2,4-Urethanisomeren eine höhere Konzentration an 2,6-Isomeren enthalten. Die Hartsegmentbereiche erreichen dadurch höhere Ordnung. Diese erhähte Ordnung und Phasenmischung führt zu einer Verbesserung der mechanischen Eigenschaften. Die Veränderung der Leitfähigkeit und Viskosität wahrend dem Emulgieren zeigt, daß das Wasser zuerst auf der Oberfäche des Mikroionengitters der Hartsegmente adsorbiert wird und dann in die ungeordneten und geordneten Hartsegmentbereiche eindringt.
    Notes: Toluene diisocyanate based polyether polyurethane cationomer solutions are prepared and then emulsified by adding water. Properties of films cast from the solutions and emulsions are studied using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, wide-angle X-ray diffraction, and tensileelongation testing. It is found that the use of the asymmetric chain extender, N-methyl-diethanolamine, also leads to a polyurethane (PU) with detectable order in the hard domains as in the PU with symmetric chain extender such as 1,4-butandiol. After quaternization with glycolic acid, the PU cationomers have increased elongation and tensile strength and modulus. These can be attributed to the proper Coulomb interaction between two neighboring hard segments. The emulsification of the PU ionomer solution results in an increased mixing between the soft segments and the hard segments with asymmetric 2,4-urethane isomers originally located in the hard domains, and therefore make the hard domains containing a higher concentration of symmetric 2,6-isomer. The hard domains then become more ordered. Such increased order and phase mixing leads to an increase of the three tensile properties. During the emulsification conductivity and viscosity variations show that water is firstly adsorbed on the surface of the hard segment microionic lattices and then enters into the disordered and ordered hard domains successively.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1988.051630107
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    Conformational studies of nucleic acids. V. Sequence specificities in the conformational energetics of oligonucleotides: The homo-tetramers (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 59-77 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational energetics of the tetranucleoside triphosphates d(ApApApA), d(GpGpGpG), d(CpCpCpC), d(TpTpTpT), ApApApA, GpGpGpG, CpCpCpC, and UpUpUpU are thoroughly examined using a classical potential energy function. The sugar modeling method and multiple correlation functions derived in previous papers of this series are utilized in these examinations. The data are analyzed and compared in terms of the energy profiles for rotation about the conformation-determining torsion angles in the tetramers. Overall, the predictions are in reasonable qualitative agreement with the existing experimental data. It is found that the base type does not greatly affect the locations of the important minima in these profiles, but rather exerts a large influence on the relative depths of the minima and the barriers to conversion between them. Conformational sequence dependence is manifest to a greater extent by the DNA tetramers than the RNA tetramers. Of the DNA tetramers, d(CpCpCpC) appears, from the results presented herein, to have the greatest potential for polymorphism. This and other findings are analyzed in terms of the preferences of particular DNA sequences for either the A-, B-, or Z-conformation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270105
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    A simplified analysis of scatchard plots for systems with two interacting binding sites (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 79-86 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple graphical method for calculating stoichiometric and site binding constants for systems with two initially equivalent interacting sites is derived from a modified Scatchard equation. The binding constants can be calculated from Scatchard plots (r/[A] as a function of r) using the values of r/[A] (r is the molar ratio of bound ligands to total protein and [A] is the equilibrium concentration of free ligand) when r = 0 and r = 1 (half-saturation). The applicability of the method to the adsorption of bilirubin by peptide pendants immobilized on a polyacrylamide support is demonstrated.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270106
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    Application of the augmented theory of α-helix-to-random-coil transitions of two-chain, coiled coils to extant data on synthetic, tropomyosin-analog peptides (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 87-96 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The statistical mechanical theory for the helix-to-random-coil transition in two-chain coiled coils is applied to extant data for two synthetic coiled-coil polypeptides. These peptides have the primary structure K(LEALEGK)n, in which n = 4, 5. This repeating heptet sequence mimics the pattern of hydrophobic, acidic, and basic residues characteristic of the 284-residue tropomyosin molecule, the prototypical coiled-coil protein. Theoretical calculations for single chains show that such model peptides cannot be directly compared to proteins like tropomyosin because of differences in chain length (29 and 36 residues vs 284) and in intrachain interactions, the latter caused by the differences in amino acid composition and seqeunce between protein and model. Application of the theory to extant data on the two synthetic peptides provides a semiquantitative fit and results in an assessment of the interhelix interaction in the model peptides. The value obtained, ∼ 2000 cal · (mol of turn pairs)-1, is four to five times larger than has been obtained for tropomyosin. This probably is a result of greater regularity in the structure of the synthetics and of the exclusive presence of leucine in the hydrophobic interface. The theory employed here insists that this powerful interhelix interaction in the synthetic is the principal reason that such short chains can be so highly helical at moderate and low temperatures. Theory predicts, indeed, that a tropomyosin-length chain with a sequence homologous to these synthetics would be completely thermally stable in the entire temperature range accessible in aqueous solutions. Theory also predicts a much more pronounced effect of concentration on the 29- and 36-residue synthetic polymers than is predicted or observed in the case of tropomyosin, and it also predicts a pronounced stabilizing effect of pH-reduction on the thermal curves. On the last two points, sufficient data are not yet available with which to test the theory.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270107
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    The source of energy for bacteriophage dna packaging: An osmotic pump explains the data (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 165-169 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270113
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    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270201
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    The combined use of NMR, distance geometry, and restrained molecular dynamics for the conformational study of a cyclic somatostatin analogue (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 323-338 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A cyclic peptide analogue of somatostatin, including the o-aminomethylphenylacetic acid spacer, was studied by the combined use of two-dimensional nmr spectroscopy, distance geometry, and restrained molecular dynamics. Analysis of distances determined from nuclear Overhauser effect (NOE) buildup rates revealed that these were inconsistent with a unique backbone conformation near the spacer. Assuming that the conformational heterogeneity is localized to the spacer, the NOE distances measured for the remaining part of the molecule were used to generate a large number of structures with the distance geometry algorithm, which were then refined by restrained energy minimization. Four classes of structures emerged, which together account for all observed NOEs. A representative structure of each class was further refined with the restrained molecular dynamics technique, and shown to be stable on a 20-ps time scale. The flexibility of the spacer was examined by simulating interconversions induced by an appropriate restraining potential. As a result, the explanation for the lack of somatostatin activity of the analogue studied was reconsidered.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270211
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    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270301
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    Optical activity of saccharides - the vacuum-uv origin of sodium-D rotation (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 415-421 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A semiempirical theory of saccharide optical activity indicates that the dominant source of NaD rotation is a vacuum-uv CD band near 150 nm, a band observed experimentally in polysaccharide film CD spectra. The model is a modification of polarizability theory in which high-energy electronic excitations are coupled by degenerate perturbation theory, giving rise to “molecular excitons.” The existence of an excitation mode well separated in energy from even higher energy modes arises from the local symmetry of tetrahedral carbon atoms in a puckered ring structure. Calculated NaD rotations correlate well with experimental values.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270305
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    Prediction of protein helix content from an autocorrelation analysis of sequence hydrophobicities (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 451-477 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is demonstrated that protein α-helix content can be predicted from an autocorrelation analysis of the protein hydrophobicity sequence. The Fourier transform of the autocorrelation function yields the spectral densities or weights of the various frequencies contributing to the autocorrelation function. Using sequence and secondary structure data from more than 160 proteins and domains, a linear relationship was found between spectral density at periodicity 3.7 and protein α-helix content (r = 0.83). This relation permits prediction of the helix content (x) of proteins of known sequence to within ± 15%, i.e., as (x ± 15)%. Predictions based on the autocorrelation procedure are compared with values obtained by other methods.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270308
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    Induced CD provides evidence for helical solution conformation in cellulosic chains (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 479-491 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evidence for a helical contribution to the conformation of methylcellulose in dilute solution is given by CD measurements. Congo red binds to methylcellulose in dilute aqueous solution and becomes optically active. The shape of the induced CD spectra is as predicted by exciton coupling for a helical arrangement of chromophores. The magnitude of the induced CD changes reversibly with temperature, decreasing upon heating. The dimer analogue of the polymer, prepared by acid methanolysis, does not show this effect. These observations suggest that the induced optical activity reflects the conformational dissymmetry of the polymer. Analogous experiments with the cellulose oligomers (cellotriose through cellohexaose) show that five anhydroglucose units are necessary before asymmetry is induced upon dye binding.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270309
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    Polarized raman scattering from oriented single microcrystals of d(A5T5)2 and d(pTpT) (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 493-507 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polarized Raman spectra have been obtained from single microcrystals of the duplex of the decamer d(A5T5)2 using a Raman microscope. This is the first report of Raman spectra from a crystal of a deoxyoligomer that contains only long, nonalternating sequences of adenine and thymine. Sequences containing d(A)n and d(T)n are of interest in view of recent suggestions that they induce bends in DNA and that they might exist in a nonstandard B-conformation. Polarized Raman spectra of a crystal of d(pTpT) have also been obtained. Both crystals display Raman bands whose intensities are very sensitive to the orientation of the crystal with respect to the direction of polarization of the incident laser beam. These spectra indicate that the helical axes of the oligonucleotides are parallel to the long axes of the crystals and that the d(A5T5)2 is not appreciably bent in the crystal. The Raman spectrum from the d(pTpT) crystal indicates that all of the furanose ring puckers are in a C2′-endo configuration since only the C2′-endo marker band at 835 ± 5 cm-1 is present. Crystals of d(A5T5)2 show measurable Raman intensities in both the 838- and 816-cm-1 bands. This indicates the presence of both the C2′-endo and C3′-endo, or possibly other non-C2′-endo, furanose conformations. The 816-cm-1 band is weak so that only a small fraction of the residues are estimated to be in the non-C2′-endo conformation. In both the d(pTpT) and d(A5T5)2 crystals the intensity of the bands due to vibrations of the backbone show only a small dependence on orientation of the crystals. This result is explained by the low symmetry of the puckered sugar rings. It is concluded that Raman spectra obtained from oligonucleotide crystals in which the orientation of the crystal axes to the laser polarization is not carefully controlled may contain intensity artifacts that are due to polarization effects.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270310
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    A critical review of the nucleosidic vibration modes appearing in the 800-500-cm-1 spectral region, based on new harmonic dynamics calculations (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 605-616 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the basis of a harmonic dynamics calculation, it is shown that in the 800-500-cm-1 spectral region of DNA vibrational spectra, the characteristic Raman peaks and ir bands do not arise from the same nucleosidic motions. The Raman spectra involve mainly the ring-breathing modes of nucleic bases while the ir spectra reveal essentially their out-of-plane vibrations. Moreover, the calculated results show the splitting of the guanine- and adenine-residue breathing modes upon their coupling with the sugar-pucker motions. This fact is in agreement with the poly[d(G-C)] and poly[d(A-T)] Raman spectra.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270405
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    A type II β-turn in a flexible peptide: Proton assignment and conformational analysis of the α-factor from saccharomyces cerevisiae in solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 431-449 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-dimensional 1H-nmr spectra of the α-mating factor [in dimethyl sulfoxide-d6 (DMSO) and in water] and several dodecapeptide analogues (in DMSO) were obtained. Homonuclear correlated spectroscopy resulted in the complete and unequivocal assignment of all backbone and side-chain resonances of the peptides. The solution conformation of the pheromones was probed using two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY) and rotating frame nuclear Overhauer effect spectroscopy (ROESY). The 2D NOE results, and results of complementary one-dimensional experiments, suggest that a type II β-turn is assumed by the central portion of active pheromones in both DMSO and water. Inactive analogues of the α-factor do not exhibit this structural feature. Except for this one β-turn, the nmr parameters for α-factor are indicative of a conformationally flexible molecule in both solvents. This conclusion is in contrast to that of other researchers who have proposed a highly structured conformation of α-factor in aqueous solution.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270307
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    Quantitative analysis of the three regimes of DNA electrophoresis in agarose gels (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 509-524 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extensive series of experiments has been performed to study the mobility of DNA fragments ranging in size from 2.0 to 48.5 kilobose pairs. By varying the agarose concentration in the gels and the electric field strength, three DNA electrophoresis regimes were clearly identified: the Ogston regime (small DNA fragments in large pores of agarose), the reptation regime without DNA chain stretching (small pores of agarose and weak electric fields), and the reptation regime with DNA chain stretching (small pores of agarose, strong electric fields, and large DNA fragments). Here we report on the experimental identification of these regimes and on the conditions governing the transition between each of them. The onset of reptation and of stretching of DNA chains in gel electrophoresis are described quantitatively for the first time, and a phase diagram for the dynamics of DNA during electrophoresis is presented.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270311
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    Conformations and mitochondrial uncoupling activity of synthetic emerimicin fragments (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 683-701 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several amino terminal fragments of the emerimicins (Ac-Phe1-Aib2-Aib3-Aib4-Val5-Gly6-Leu7-Aib8-Aib9-Hyp10-Gln11-D-Iva12-Hyp13-Ala/Aib14-Phol15) ranging in length from five to ten residues have been synthesized. Nuclear magnetic resonance studies have been carried out on the 1-5, 6-10, 1-6, 1-7, 1-8, 1-9, and 1-10 fragments. The number of solvent-shielded NH groups in CDCl3 solutions for 1-5, 1-6, 1-7, 1-8, 1-9, and 1-10 indicate that 310-helical structures are favored in this solvent. In (CD3)2SO, an additional NH group, assigned to Aib(3) NH is solvent exposed in the fragments longer than six residues, suggesting partial unfolding of the N-terminal β-turn or transition to an α-helical conformation. The data for fragment 6-10 are consistent with a conformation having a single Leu-Aib β-turn. Infrared studies suggest an increase in the number of intramolecular hydrogen bonds with increasing peptide chain length. Appreciable mitochondrial uncoupling activity is observed for peptides with a chain length of at least seven residues. The order of efficiencies of the fragments is 1-7 〈 1-8 ∼ 1-10 〈 1-9, with the decapeptide exhibiting anomalously low uncoupling activity.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270411
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    Molecular and crystal structures of three monothiated analogues of the terminally blocked ala-aib-ala sequence of peptaibol antibiotics (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 747-761 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular and crystal structures of three monothiated analogues of the blocked L-Ala-Aib-L-Ala sequence of peptaibol antibiotics, t-Boc-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, and Ac-ψ(CSNH)-L-Ala-Aib-L-Ala-OMe, determined by x-ray diffraction analyses, are reported. In all cases the peptide chain is folded with ϕ,ψ angles close to or slightly distorted from those expected for a type II β-bend conformation. However, the 4 → 1 H-bond distance falls within the accepted limits only for Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe. The structures are compared with those already published for their two oxygenated analogues.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270504
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  • 80
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    Collapse of a polypeptide chain as a result of the intramolecular formation of antiparallel β-sheets (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 805-819 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The folded nature of an intramolecular antiparallel β-sheet suggests that the introduction of this structure into a statistical coil might be accompanied by a contraction of the chain. The magnitude of the contraction, and the conditions that produce the maximum contraction, have been assessed by the combination of generator matrices with an earlier formulation for the configuration partition function. The results show that the mean square dimensions do indeed pass through a minimum upon the transition from a statistical coil to an antiparallel β-sheet. The depth of the minimum is relatively insensitive to the values of δ and τ, provided the assignments are within the physically sensible range. (The borders of the ordered region are assumed to be of higher energy than the interior.) In contrast with the depth of the minimum, the β-sheet content that produces the minimum is quite sensitive to plausible variation in δ and τ. A much greater collapse of the chain can be produced by antiparallel β-sheet formation than that found in the course of the helix-coil transition. The collapse may cause the volume pervaded by the chain to come within an order of magnitude of the volume characteristic of the globular state.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270508
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  • 81
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    The crystal and molecular structure of the anticancer drug actinomycin D - some explanations for its unusual properties (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 843-864 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of the antitumor antibiotic actinomycin D has been determined by the methods of x-ray crystallography. There are three independent molecules in the asymmetric unit. Two of the molecules form a hydrogen-bonded dimer. The peptides within all three molecules have very similar conformations. The greatest conformational variability in the drug molecules occurs in the torsion angles of the bonds connecting the phenoxazone ring to the peptide rings. The results of this analysis has allowed us to explain the unusual physical properties of ActD as well as to provide an explanation for the thermodynamics of its interactions with DNA.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270511
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  • 82
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    Sedimentation coefficients of DNA topoisomers: The helical wormlike chain (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 675-682 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sedimentation coefficient sN of the DNA topoisomer with the linking number N is evaluated as a function of N and chain length on the basis of a (circular) twisted wormlike chain, i.e., a special case of the helical wormlike chain. Evaluation is carried out by an application of the Oseen-Burgers procedure of hydrodynamics to the cylinder model with the preaveraged Oseen tensor. The necessary mean reciprocal distance between two contour points is obtained by a Monte Carlo method. It is shown that sN increases as |ΔN| is increased from 0 in the range of small |ΔN|, where ΔN = N - N, with N the number of helix turns in the linear DNA chain in the undeformed state. It is found that there is semiquantitative agreement between the Monte Carlo values and the experimental data obtained by Wang for sN.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270410
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  • 83
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    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270501
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  • 84
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    A 2H-nmr study of the DNA hydration water in solid li-DNA assemblies (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 717-732 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-resolution 2H-nmr is employed to monitor the D2O in hydrated solids of Li-DNA prepared from solution by three different methods: lyophilization, slow evaporation of the water, and wet spinning in alcohol. From the spectral shapes and spin-spin relaxation measurements, the DNA in the lyophilized samples is found to be locally ordered with a domain size of ∼ 0.4 μm. Much longer range macrosopic ordering is found in samples prepared by slow evaporation of the water. Here the DNA spontaneously assembles into a structure that is probably cholesteric, in which the pitch axis is perpendicular to the plane on which the DNA dried. The wet-spinning method produces macroscopically, uniaxially oriented DNA molecules with a maximum helix axis disorder of 12°. To aid in the comparison between calculated and experimental line shapes, a two-dimensional technique is employed to separate the contributions to the line width arising from DNA static disorder, magnetic inhomogeneities, and spin-spin relaxation.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270502
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  • 85
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    Mechanism of fibrin coagulation based on selective, cation-driven, protofibril association (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 763-774 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cation sensitivity of linear and lateral assembly processes of thrombin- and reptilase-activated fibrinogen was examined. Analytic ultracentrifugation shows that the linear assembly of fibrin oligomers (protofibrils) is neither cation dependent nor sensitive to chelating agents. Protofibrils generated with thrombin-hirudin gelate with either 1-2 mM Ca(II) or 15-100 μM Zn(II). By contrast, protofibril B, generated with reptilase-diisopropylfluorophosphonate, gelates only with Ca(II) but is insensitive to Zn(II). These results indicate that the release of fibrinopeptides A and B (FPA and FPB) expose two types of lateral binding sites that are sensitive to Ca(II) and Zn(II) respectively. Transmission electron (TEM) micrographs of negatively stained gels indicate that the linear packing of the monomers within the fibrin- and cation-induced protofibrin fibers is essentially identical. Scanning electron (SEM) micrographs show that the Ca(II)-induced protofibrin B gel is similar to fibrin. In all, it seems that branching and gelation derive from two types of cation-sensitive, lateral associative processes. Based on these findings, a new paradigm for fibrin coagulation is proposed.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270505
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  • 86
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    Distance distributions in native and random-coil troponin I from frequency-domain measurements of fluorescence energy transfer (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 821-830 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We used time-dependent fluorescence energy transfer to determine the distribution of donor-to-acceptor distances in native and denatured troponin I(TnI). The single tryptophan residue (Trp 158) of TnI served as the donor (D), and the acceptor (A) was a labeled cysteine residue (Cys 133). The time-dependent intensity decays of the donor were measured by the frequency-domain method from 10 to 320 MHz. The frequency response of the donor emission, in the absence and presence of acceptor, was used to recover the distribution of D to A distances, using an algorithm that accounts for the intrinsic multiexponential decay of the donor. In the native state the D-A distribution is characterized by an average distance of 23 Å and a half-width of 12 Å. Denaturation results in a modest increase in the average distance to 27 Å, and a dramatic increase in half-width to 47 Å. We believe the ability to recover distance distributions will have numerous applications in the characterization of biological macromolecules.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270509
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  • 87
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    The association behavior of β-lactamases in polyethylene glycol solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 865-881 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The β-lactamases (EC 3.5.2.6) from Bacillus licheniformis 749/C, Enterobacter cloacae P99, and TEM plasmid RP4 are studied in 10-14% (w/v) polyethyleneglycol (PEG) 8000 solutions at pH 6.5 by x-ray scattering and in 18% PEG by equilibrium sedimentation. Although all three enzymes crystallize with twofold crystal symmetry from PEG 8000, it is not possible in this study to prove that dimerization occurs; however, both techniques give evidence for association above 1% (w/v) protein concentration. For the B. lichen., P99, and TEM enzymes, a dimerization of at most 0, 5, and 10% (v/v), respectively, account for the variation of radii of gyration Rg with concentration, after accounting for the effects of nonideality. Apparent Rg were 3-5% smaller in PEG solution than in PEG-free solution. Enhanced ordering of the molecules in PEG solution or the presence of a PEG-depleted hydration shell around the enzymes can account for the observation of reduced Rg values. Accordingly, values of the partial specific volume (defined at constant chemical potential of PEG) indicate considerable PEG exclusion and are consistent with the ability of high Mr PEGs to induce crystallization of these enzymes.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270512
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  • 88
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    Conformation of the second disulfide loop in human transforming growth factor-α studied by two-dimensional nmr spectroscopy (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 923-937 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of the conformation of a cyclic heptadecapeptide derived from the second loop of human transforming growth factor-α, [Ala21]-hTGF-α-(16-32), is described. Two-dimensional homonuclear Hartmann-Hahn and rotating-frame cross-relaxation spectroscopy in H2O were used to obtain the complete proton resonance assignments and the necessary distance constraints between nonbonded hydrogen atoms to derive a conformation without involving any energy minimization. The result is an ellipsoidal-shaped structure with a turn at Gly19 and a bend formed by residues 26-29, Gln-Glu-Asp-Lys. Comparison is made with the second loop of human epidermal growth factor and the results are discussed in terms of receptor binding and biological activity.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270604
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  • 89
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    Study of the bisintercalation of the antitumor drug ditercalinium by 31P-nmr (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 957-968 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bisintercalation of ditercalinium, a potent antitumoral 7H-pyriodo[4,3-c]carbazole rigid dimer, into the self-complementary tetranucleotides d(CpGpCpG)2, d(m5CpGpm5CpG) and the self-complementary hexanucleotide d(CpGpApTpCpG)2 was investigated by 162-MHz 31P-nmr. The slow exchange, on the nmr time scale, observed between the free and complexed nucleotides allows identification of the phosphorus signals in the complexes through two-dimensional chemical exchange spectroscopy. Differences in 31P chemical shifts upon intercalation are discussed in relation to the complex geometry and nature of the drug.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270606
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  • 90
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    Small angle neutron and x-ray scattering studies of concentrated protein solutions II. Cytochrome C (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1065-1083 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) techniques were used to study two series of concentrated protein solutions containing horse heart cytochrome C (a spherical protein molecule with hydrated diameter σH = 32.6 Å and pI = 10.2) at pD = 2.9 and 11.9, respectively. The concentration of the protein ranges from 1.2 to 24 g/dL. A titration experiment was made to determine the protein charge (Zt) for each sample. Since the form factor of the protein was already determined from a previous experiment [C. F. Wu and S. H. Chen (1987) J. Chem. Phys. 87, 6199-6205] at pD = 6.8, the present series of experiments was used to test the effect of protein charge on the interparticle structure factor. It is demonstrated that the absolute values of both SANS and SAXS cross sections can be calculated with a theory (called the generalized one-component macroion theory) of the interparticle structure factor, which contains a single unknown parameter, the effective protein charge Zp. Comparison of Zt and Zp thus obtained shows that when the bare surface charge density of the protein calculated by using Zt exceeds about 3 μC/cm2, Zp becomes much smaller than Zt. This is interpreted as a charge renormalization phenomenon similar to that known to occur for highly charged polystyrene latex particles in aqueous solution [S. Alexander, P. M. Chaikin, P. Grant, G. J. Morales, and P. Pincus (1984) J. Chem. Phys. 80, 5776-5781].
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270703
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  • 91
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    Effects of pH and temperature on cardioactive polypeptides from sea anemones: A 1H-nmr study (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1143-1157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of pH and temperature on the 300-MHz 1H-nmr spectra of three cardioactive polypeptides from sea anemones, anthopleurin-A from Anthopleura xanthogrammica (AP-A) and Anemonia sulcata toxins I and II (ATX I and II), are described. AP-A and ATX II exhibit major spectral heterogeneity. Evidence from the pH and temperature studies and from high performance liquid chromatography indicates that this heterogeneity is conformational rather than chemical in origin. By contrast, purified isotoxins of ATX I show no evidence of conformational heterogeneity. The pKa values of most of the ionizable groups in these polypeptides are not strongly perturbed by interactions in the tertiary structure, with the exception of one of the Asp carboxylates, which has a pKa of ≲ 2 in AP-A and ATX II and 3.0 in ATX I. Protonation of this carboxylate, suggested to be Asp-9, leads to a conformational change in all three molecules. All three polypeptides are thermally stable, showing some conformational changes but not major unfolding at elevated temperatures.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270708
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  • 92
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    Terbium(III) induced Z to A transition in poly(dG-m5dC) (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1183-1186 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270711
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  • 93
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    Evidence for similar function of transmembrane segments in receptor and membrane-anchored proteins (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1171-1182 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transmembrane (TM) regions of receptor proteins should have unique structural and/or chemical characteristics if these regions contain residues functional in TM signal transduction. However, in a survey of the membrane-occurring residues in 37 integral membrane proteins, we found that amino acid compositions of TM regions of receptor proteins (n = 11) could not be distinguished statistically from corresponding regions of membrane-anchored proteins (e.g., recognition molecules) with a functional external domain attached to a single hydrophobic membrane-spanning anchor segment (n = 16). TM regions in both categories of proteins differed from the compositions of TM regions in membrane-transport proteins (n = 10). The analysis implies that TM regions in receptor proteins may function mainly to anchor (and position) receptors in their cellular membranes, and therefore residues in receptors that participate in signal transduction need not be restricted to these regions. In addition to mechanisms involving receptor aggregation, ligand-activated conformational perturbation of a receptor external aqueous domain, resulting in membrane penetration of hydrophobic segment(s) of this domain to produce intramembranous contact with its cytoplasmic domain, is hypothesized as a further possible mode of signal transduction.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360270710
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  • 94
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    Molecular dynamics of structural transitions and intercalation in DNA (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1239-1248 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The large-scale flexibility of DNA and the intercalation of actinomycin D have been studied by computer simulation using molecular dynamics. The stretching and unwinding of B and Z forms of DNA and intercalation in B-DNA were examined through molecular dynamics simulations, and the energetics of transitions were calculated by the conformational energy minimization method. The principal results of this research are as follows: (1) A dynamic conformational pathway is presented for longitudinal stretching and unwinding of the double helix to open an intercalation site. (2) Large-scale transitions are possible in both B and Z forms of DNA through a conformationally allowed kinetic pathway. (3) The stretching and untwisting of a 5′(CG)3′ step is energetically more favorable than for a GC step in B-DNA. (4) The formation of an adjacent second cavity in B-DNA requires larger energy than the formation of the first cavity, affirming the neighbor-exclusion principle of intercalation. (5) Docking an intercalated actinomycin D in the stretched structure is shown to be geometrically and energetically feasible.
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    URL: http://dx.doi.org/10.1002/bip.360270805
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  • 95
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    Microcalorimetric studies of solvent-induced conformational change of sodium and cesium salts of poly(L-glutamic acid) in aqueous media (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1267-1281 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic solvent-induced coil → helix conformational change of poly(sodium) L-glutamate (NaPLG) and poly(cesium L-glutamate) (CsPLG) in solution in aqueous mixed solvents have been studied at 25°C. Heats of dilution of NaPLG in the water-dioxane pair have been measured as a function of polymer concentration and solvent composition. The results indicate that the overall chain conformation in the disordered form is not too different from that in the α-helical form. Heat capacity measurements by flow microcalorimetry have also been done. The apparent monomolar heat capacity at constant pressure of the polymer, Cp, φ, decreases with dilution similarly to other strong polyelectrolytes in aqueous media. In the water-dioxane pair, Cp, φ increases with the dioxane content due to partial desolvation of ionic species resulting from increasing ionic association. In the case of the water-2-chloroethanol (CE) pair, the transition takes place at low CE content and results show a fast decrease in Cp, φ when the α-helical conformation predominates. It is believed carboxylate groups and CE molecules associate themselves into a complex formation responsible for the transition. The size of the cation plays a significant role in the thermodynamic properties of these polyelectrolytes in solution since sodium ions are more strongly bound to the chain than cesium ions.
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    URL: http://dx.doi.org/10.1002/bip.360270807
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  • 96
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    Excluded-volume effect on the bidimensional conformation of DNA molecules adsorbed to protein films (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1329-1331 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270811
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  • 97
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    Helix-coil dynamics of a Z-helix hairpin (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1319-1327 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transition of a Z-helix hairpin formed from d(C-G)5T4(C-G)5 has been characterized by equilibrium melting and temperature jump experiments in 5M NaClO4 and 10 mM Na2HPO4, pH 7.0. The melting curve can be represented by a simple all-or-none transition with a midpoint at 81.6 ± 0.4°C and an enthalpy change of 287 ± 15 kJ/mole. The temperature jump relaxation can be described by single exponentials at a reasonable accuracy. Amplitudes measured as a function of temperature provide equilibrium parameters consistent with those derived from equilibrium melting curves. The rate constants of Z-helix formation are found in the range from 1800 s-1 at 70°C to 800 s-1 at 90°C and are associated with an activation enthalpy of -(50 ± 10) kJ/mole, whereas the rate constants of helix dissociation are found in the range from 200 s-1 at 70°C to 4500 s-1 at 90°C with an activation enthalpy +235 kJ/mole. These parameters are consistent with a requirement of 3-4 base pairs for helix nucleation. Apparently nucleation occurs in the Z-helix conformation, because a separate slow step corresponding to a B to Z transition has not been observed. In summary, the dynamics of the Z-helix-coil transition is very similar to that of previously investigated right-handed double helices.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270810
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  • 98
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    Crystal structure and molecular conformation of N-boc-L-pro-dehydro-leu-OCH3 (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1595-1606 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The peptide N-Boc-L-Pro-dehydro-Leu-OCH3 was synthesized by coupling dehydroleucine methyl ester with Boc-Pro-OH. It was crystallized from its solution in a methanol-water mixture at 4°C and the crystals belong to the orthorhombic space group P212121 with a = 10.239(1) Å, b = 19.276(4) Å, c = 20.319(3) Å, V = 4010(1) Å3, and Z = 8. The structure was solved by direct methods using MULTAN 80. The structure was refined to an R value of 0.095 for 1871 observed reflections. There are two crystallographically independent molecules in the unit cell. The molecular dimensions of the two molecules are very similar. The backbone conformation angles of these molecules are as follows: θ1 = -176(1)°, ω0 = -2(2)°, φ1 = -72(1)°, ψ1 = 141(1)°, ω1 = 169(1)°, φ2 = -98(1)°, ψ2 = -179(1)°, θT = 179(1)°, θ11 = 174(1)°, ω10 = -3cm-1, φ11 = -64(1)°, ψ11 = 148(1)°, ω11 = 167(1)°, φ12 = -67(1)°, ψ12 = 175(1)°, and θ1T = 172(1)°, respectively. Other torsion angles such as θ′2 = 86(1)°, χ2 = -5(2)°, ′12 = 131(1)°, and χ12 = -16(2)° are interesting to define the backbone conformation together with the dehydro-Leu side chain as a conformation similar to that of the β-bend type II. The central amide bond of Pro-dehydro-Leu segment is deviated from the planarity. The Boc group adopts a trans-cis conformation. The side-chain torsion angles χ1, χ2, χ3, χ4, and χ0 for Pro-residue in the two molecules are 11(2)°, -11(2)°, 6(2)°, 2(1)°, -9(1)° and -18(1)°, 31(1)°, -31(1)°, 21(1)°, and -1(1)° respectively. The side chain of the Pro residue of molecule A is in the flattened Cγ-endo conformation while the pyrrolidine ring in miolecule B adopts the well-known Cγ-exo conformation. The side-chain torsion angles χ, χ2,1, and χ2,2 in the leucyl residues of molecules A and B are -5(2)°, -111(2)°, 126(2)° and -16(2)°, -110(2)°, and 133(2)°, respectively. The molecular packing is stabilized by intermolecular hydrogen bonds and van der Waals interactions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360271005
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  • 99
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    Formation and stability of helical poly (N∊, N∊, N∊-trimethyl-L-lysine) in sodium perchlorate solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1627-1640 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(trimethyl-L-lysine), [Lys(Me3)]n, is converted from random coil to α-helix at about 1/30 of the NaClO4 concentration required by poly(L-lysine), (Lys)n. NaClO4 generates turbidity in [Lys(Me)3]n at concentrations above that required for helix formation, and decreases turbidity above lM NaClO4. The turbidity runs parallel to enhanced, and then decreased, fluorescence of a dansyl label. Helix formation per se does not induce enhanced fluorescence. Increasing NaClO4 concentration increases Tm linearly with log[NaClO4] for both (Lys)n and [Lys(Me3)]n until the denaturing effect of high NaClO4 sets in. Increasing NaClO4 also increases the breadth of the transition. Heating helical [Lys(Me3)]n or (Lys)n does not produce a CD spectrum resembling that of “random-coil” (Lys)n, except for [Lys(Me3)]n at relatively low NaClO4 concentration.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360271008
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  • 100
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    Conformational behavior of α,α-dialkylated peptides: Ab initio and empirical results for cyclopropylglycine (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1673-1685 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preferred conformations of model cyclopropylglycine peptides have been investigated by means of ab initio and empirical methods. Empirical computations performed with fixed bond lengths and valence angles using two well-known force fields show that only values of φ in the ranges ±70° ± 20° are sterically allowed, and that the C7-conformation corresponds to the absolute energy minimum irrespective of the terminal groups used. Also, ab initio computations give similar results, but suggest greater stabilities for bridge and, especially, extended structures. These discrepancies can be removed, adding to the empirical force field a twofold torsional potential on ψ and using softer steric repulsive potentials. Complete geometry optimization using both ab initio and empirical methods does not affect the relative stabilities of folded conformations, but leads to a further significant stabilization of the fully extended structure via large modifications of some valence angles.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360271011
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