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  • 1995-1999  (690)
  • 1990-1994  (1,980)
  • 1975-1979
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  • Computational Chemistry and Molecular Modeling  (836)
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  • 1995-1999  (690)
  • 1990-1994  (1,980)
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  • 1
    Electronic Resource
    Electronic Resource
    Maternally inherited diabetes and deafness: a new diabetes subtype (1996)
    Springer
    Diabetologia 39 (1996), S. 375-382 
    Details
    ISSN: 1432-0428
    Keywords: Genetics ; maternally inherited diabetes and deafness ; NIDDM ; IDDM ; mitochondria ; MELAS syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Diabetes mellitus is a common disease with many forms of clinical expression. In addition, the development of diabetic complications is not only dependent on glycaemic control but also on individual factors which may be related to genetic heterogeneity. At present, multiple genetic factors are being recognized as contributing to the development of diabetes or possibly modulating its clinical expression. The purpose of this review is to give an overview of our current knowledge on a subtype of diabetes which is apparently caused by a single mutation in the mitochondrial DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400668
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  • 2
    Electronic Resource
    Electronic Resource
    Do animal models have a place in the genetic analysis of quantitative human behavioural traits? (1996)
    Springer
    Journal of molecular medicine 74 (1996), S. 515-521 
    Details
    ISSN: 1432-1440
    Keywords: Key words Emotionality ; Behaviour ; Genetics ; Animal models ; QTL analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It seems that the genetic basis of common psychiatric diseases such as schizophrenia and manic-depressive psychosis is amenable to the genetic mapping strategies that have been successful in other complex disorders such as diabetes. The next challenge is the genetic dissection of quantitative behavioural traits such as mood, personality and intelligence. Quantitative traits pose new problems for gene cloning experiments. We argue that one way forward is by using animal models. One of the features of quantitative traits is that the DNA sequence variants which are responsible for them are unlikely to be immediately recognizable. In contrast to many qualitative traits where a discrete phenotypic difference is often the consequence of an inactivating mutation, the allelic variation responsible for quantitative traits probably has a more subtle basis. This distinction means that strategies to clone the genetic basis of quantitative behavioural traits will have to rely on functional assays of alleles thought to be important in determining the phenotype. We suggest that an efficient strategy for detecting sequences that give rise to quantitative behavioural traits can be devised in the mouse. The importance and utility of the mouse for quantitative trait analysis make it worthwhile to investigate mouse models of human behaviour; these advantages outweigh the difficulties that arise in attempts to validate the animal models. As an example we review the evidence that validates rodent emotionality as an animal model for susceptibility to human anxiety. We show that there is good evidence that rodent emotionality is a central nervous system state with a genetic basis, and that there are neuropharmacological and neuroanatomical parallels with human anxiety. Furthermore, our own work has shown that the genetic basis of the trait is relatively simple, and that the task of characterizing it at a molecular level is feasible. We expect that future experiments will show us how genetic variation gives rise to quantitative behavioural traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050054
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  • 3
    Electronic Resource
    Electronic Resource
    Do animal models have a place in the genetic analysis of quantitative human behavioural traits? (1996)
    Springer
    Journal of molecular medicine 74 (1996), S. 515-521 
    Details
    ISSN: 1432-1440
    Keywords: Emotionality ; Behaviour ; Genetics ; Animal models ; QTL analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It seems that the genetic basis of common psychiatric diseases such as schizophrenia and manic-depressive psychosis is amenable to the genetic mapping strategies that have been successful in other complex disorders such as diabetes. The next challenge is the genetic dissection of quantitative behavioural traits such as mood, personality and intelligence. Quantitative traits pose new problems for gene cloning experiments. We argue that one way forward is by using animal models. One of the features of quantitative traits is that the DNA sequence variants which are responsible for them are unlikely to be immediately recognizable. In contrast to many qualitative traits where a discrete phenotypic difference is often the consequence of an inactivating mutation, the allelic variation responsible for quantitative traits probably has a more subtle basis. This distinction means that strategies to clone the genetic basis of quantitative behavioural traits will have to rely on functional assays of alleles thought to be important in determining the phenotype. We suggest that an efficient strategy for detecting sequences that give rise to quantitative behavioural traits can be devised in the mouse. The importance and utility of the mouse for quantitative trait analysis make it worthwhile to investigate mouse models of human behaviour; these advantages outweigh the difficulties that arise in attempts to validate the animal models. As an example we review the evidence that validates rodent emotionality as an animal model for susceptibility to human anxiety. We show that there is good evidence that rodent emotionality is a central nervous system state with a genetic basis, and that there are neuropharmacological and neuroanatomical parallels with human anxiety. Furthermore, our own work has shown that the genetic basis of the trait is relatively simple, and that the task of characterizing it at a molecular level is feasible. We expect that future experiments will show us how genetic variation gives rise to quantitative behavioural traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204977
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  • 4
    Electronic Resource
    Electronic Resource
    Familial Mediterranean fever in Arab children: The high prevalence and gene frequency (1996)
    Springer
    European journal of pediatrics 155 (1996), S. 540-544 
    Details
    ISSN: 1432-1076
    Keywords: Amyloidosis ; Arab children ; Familial Mediterranean fever ; Genetics ; Recurrent abdominal pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Over a period of 3 years, 192 children with familial Mediterranean fever were prospectively studied. Of these, 106 (55%) were girls and 86 (45%) were boys. The prevalence was 1∶2600 children with a gene frequency of 1∶50. The age at onset ranged between 4 months and 16 years. Of these patients 24% started their illness below the age of 2 years and 88% were symptomatic before the age of 10 years: 82% had recurrent abdominal pain, 43% had pleurisy, 37% had arthritis, 15% had cutaneous manifestations, 12% had splenomegaly and 4% had hepatomegaly. The presenting symptoms were abdominal pain in 51%, unilateral chest pain in 23% and arthritis in 26%. The family history was positive in 62%. Of 12 affected families 19 members had/have renal failure and amyloidosis was confirmed in 7 patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01957901
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  • 5
    Electronic Resource
    Electronic Resource
    Familial Mediterranean fever in Arab children: the high prevalence and gene frequency (1996)
    Springer
    European journal of pediatrics 155 (1996), S. 540-544 
    Details
    ISSN: 1432-1076
    Keywords: Key words Amyloidosis ; Arab ; children ; Familial Mediterranean ; fever ; Genetics ; Recurrent ; abdominal pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Over a period of 3 years, 192 children with familial Mediterranean fever were prospectively studied. Of these, 106 (55%) were girls and 86 (45%) were boys. The prevalence was 1 : 2600 children with a gene frequency of 1 : 50. The age at onset ranged between 4 months and 16 years. Of these patients 24% started their illness below the age of 2 years and 88% were symptomatic before the age of 10 years; 82% had recurrent abdominal pain, 43% had pleurisy, 37% had arthritis, 15% had cutaneous manifestations, 12% had splenomegaly and 4% had hepatomegaly. The presenting symptoms were abdominal pain in 51%, unilateral chest pain in 23% and arthritis in 26%. The family history was positive in 62%. Of 12 affected families 19 members had/have renal failure and amyloidosis was confirmed in 7 patients. Conclusion Our data show a high prevalence of familial Mediterranean fever and a high gene frequency in Arab children similar to that reported in Jews and Armenians.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01957901
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  • 6
    Electronic Resource
    Electronic Resource
    Eye tracking dysfunction in families with multiple cases of schizophrenia (1996)
    Springer
    European archives of psychiatry and clinical neuroscience 246 (1996), S. 175-181 
    Details
    ISSN: 1433-8491
    Keywords: Schizophrenia ; Genetics ; Liability ; Vulnerability ; Eye-tracking dysfunction ; Eye movements ; Smooth-pursuit eye movements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is increasing evidence that the genetic predisposition for schizophrenia in families affects more individuals than those fulfilling the criteria for schizophrenia. This finding is supposed to be one of the major problems in molecular genetic schizophrenia research, especially when linkage studies are employed. Eye-tracking dysfunction (ETD), which is conceived as a possible phenotypic marker for genetic liability to schizophrenia, may offer considerable advantages. However, there is only little information from families with multiple occurrence of schizophrenia. It is still unclear whether in these families ETD aggregates with diagnoses from the schizophrenia spectrum. This first report from an ongoing study presents the results of 48 individuals from 6 multiplex families. Smooth-pursuit eye movements were recorded by infrared reflectometry and assessed by quantitative measurement techniques. Along with the high degree of psychiatric morbidity in these families, in 56.3% of the individuals ETD was assessed. Reduced mean pursuit gain was present in 39.6%. The distribution of eye-tracking dysfunction resembles the distribution of schizophrenia-related psychiatry morbidity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02188950
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  • 7
    Electronic Resource
    Electronic Resource
    Early-onset dementias: clinical, neuropathological and genetic characteristics (1996)
    Springer
    Acta neuropathologica 91 (1996), S. 451-465 
    Details
    ISSN: 1432-0533
    Keywords: Key words Alzheimer’s disease ; Clinicopathological ; correlations ; Early-onset dementia ; Genetics ; Pick’s ; disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050452
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  • 8
    Electronic Resource
    Electronic Resource
    The clinical and genetic correlates of MRI findings in myotonic dystrophy (1996)
    Springer
    Neuroradiology 38 (1996), S. 629-635 
    Details
    ISSN: 1432-1920
    Keywords: Key words Myotonic dystrophy ; Magnetic resonance imaging ; Brain ; Muscles ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amplification of an unstable CTG trinucleotide repeat sequence in a protein kinase gene on chromosome 19 has recently been recognised as the molecular basis of myotonic dystrophy (DM), a multisystem disorder with a wide spectrum of muscular and extramuscular manifestations. The CTG expansion of 40 patients was assessed by direct genotype analysis of the white blood cell DNA and correlated with MRI of the brain and muscles, and with functional clinical data. Cerebral pathology on MRI consisted of diffuse atrophy (68 %), subcortical white matter lesions (65 %), wide Virchow-Robin spaces (38 %) and thickening of the skull (35 %). Cerebral atrophy and extent of white matter disease correlated significantly with mental retardation, duration of disease and CTG fragment amplification. MRI of the muscular system showed fatty degeneration of different degrees in neighbouring muscles causing a mosaic pattern of the thigh in 38 % and the calf in 44 %. Muscular changes on MRI were strongly correlated with muscular impairment but less strongly with CTG expansion. Changes on MRI reflect the stage of development of tissue pathology in DM, modified by defect of the DM gene. Pathology on MRI is strongly correlated with functional deficits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050322
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  • 9
    Electronic Resource
    Electronic Resource
    Geographic variation in seed dormancy among populations of Echinochloa crus-galli (1996)
    Springer
    Oecologia 108 (1996), S. 419-423 
    Details
    ISSN: 1432-1939
    Keywords: Barnyard grass ; Seed dormancy ; Geographic variation ; Genetics ; Ecophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1991–1993, we investigated the incidence of seed dormancy in 25 local populations of barnyard grass, Echinochloa crus-galli (L.) P.Beauv., in the western Czech Republic. The percentage of germination after 4 months afterripening of dry seeds at 25°C varied between 0.0 and 83.6%. Although there were significant annual differences in the percentage of germination at some localities, typical proportions of dormant seeds persisted over 3 years at field sites where the seed bank was not disturbed. One-way ANOVA (using data from 14 cultivated or abandoned fields) revealed that 73.0% of variance in seed dormancy incidence could be attributed to the effect of locality (P〈0.001). Incidence of dormancy was not correlated with mother plant stature (dry above-ground biomass, number of tillers, maximal stem height) nor seed mass. There was a significant correlation (r 2=0.403, P〈0.005) between dormancy incidence at natural localities in 1991 and in F1 offspring sown at experimental grounds at Praha-Ruzyně in 1992. The results indicate that heredity is important in maintaining local variation in seed dormancy, probably favoured by the self-pollinating reproduction of barnyard grass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333716
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  • 10
    Electronic Resource
    Electronic Resource
    Inbred mouse strains vary in oral self-selection of nicotine (1996)
    Springer
    Psychopharmacology 124 (1996), S. 332-339 
    Details
    ISSN: 1432-2072
    Keywords: Nicotine ; Genetics ; Self-administration ; Reinforcement ; Seizures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Inbred mouse strains differ in sensitivity to a first dose of nicotine and in the development of tolerance to nicotine. The experiments reported here used six inbred mouse strains (A, BUB, C3H, C57BL/6, DBA/2, ST/b) that differ in sensitivity to an acute challenge dose of nicotine to determine whether differences in oral self-selection of nicotine exist. Animals were presented with solutions containing nicotine or vehicle (water or 0.2% saccharin) and their daily intake of the two fluids was measured for 4 days starting with a 10 µg/ml nicotine solution. This was followed by sequential 4-day testing with 20, 35, 50, 65, 80, 100, 125, 160, and 200 µg/ml nicotine solutions. The strains differed dramatically in their self-selection of nicotine and in maximal daily dose (mg/kg); the rank order of the strains was C57BL/6〉DBA〉BUB〉A≥C3H≥ST/b for both the tap water and 0.2% saccharin choice experiments. Correlations between nicotine consumption and sensitivity to nicotine, as measured by a battery of behavioral and physiological responses, were also calculated. Strain differences in nicotine intake were highly correlated with senstivity to nicotine-induced seizures. As senstivity to nicotine-in-duced seizures increases, oral self-selection of nicotine decreases. This finding may suggest that this toxic action of nicotine serves to limit intake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247438
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  • 11
    Electronic Resource
    Electronic Resource
    The genetics of proximal femur geometry, distribution of bone mass and bone mineral density (1996)
    Springer
    Osteoporosis international 6 (1996), S. 178-182 
    Details
    ISSN: 1433-2965
    Keywords: Bone density ; Femor geometry ; Genetics ; Twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To estimate genetic effects on femoral neck geometry and the distribution of bone mineral within the proximal femur a cross-sectional twin analysis was carried out at a university hospital that compared correlations in these traits in pairs of mono- and dizygo-tic female twins. Monozygotic (MZ, n=51 pairs, age 49.1±9.3 years) and dizygotic (DZ, n=26 pairs, age 45.7±11.3 years) twins were randomly selected from a larger sample of twins previously studied. Measurements of bone mineral density (BMD), femoral neck angles and length, cross-sectional area and moment of interia, the center of mass of the narrowest cross-section of the femoral neck, and BMDs of regions within the femoral neck were made. A summary index of the resistance of the femoral neck to forces experienced in a fall with impact on the greater trochanter (Fall Index, FI) was calculated. MZ pair intraclass correlations (rMZ) were significantly (p〈0.05) different from zero for all bone mass and femoral geometry variables (0.35〈rMZ〈0.82). DZ pair correlations (rDZ) were lower thanrMZ for all variables (0.04〈rDZ〈0.52) except femoral neck length (rDZ=0.38, rMZ=0.36). After adjustment for BMD of the femoral neck,rMZ was significantly greater thanrDZ, yielding high heritability estimates for regional BMDs (0.72〈H 2〈0.78), the center of mass of the femoral neck (H 2=0.70, −0.04 to 1.43 95% CI) and the resistance of the femoral neck to forces experienced in a fall (FI,H 2=0.94, 0.06 to 1.85 95% CI), but not for femoral neck length. Adjustments for age did not alter these findings. It is concluded that there are significant familial influences on the distribution of femoral bone mass and on the calculated structural strength of the proximal femur, but not on femoral neck length. If the assumptions of the twin model are correct, this is evidence for genetic factors influencing these traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623944
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  • 12
    Electronic Resource
    Electronic Resource
    Die Genetik der Migräne (1996)
    Springer
    Der Nervenarzt 67 (1996), S. 837-845 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Migräne ; Genetik ; Familiäre Hemiplegische Migräne ; Linkageanalyse ; Zwillingsstudien ; Assoziationsstudien ; Key words Migraine ; Familial Hemiplegic Migraine ; Genetics ; Linkage analysis ; Twin studies ; Association studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Several historical reports focusing on the heredity of migraine, as well as recent studies on its epidemiology and molecular biology, have revealed evidence for a decisive role of genetic factors in the aetiopathogenesis of familial migraine. Indeed, family studies, segregation analyses and twin studies have shown that genetic factors play an important role in disposition towards migraine but could not explain the entire aetiopathogenesis. The influence of extragenetic factors, however, remains mostly unknown. Recent linkage analyses have provided evidence for genetic heterogeneity. A locus for Familial Hemiplegic Migraine (FHM), the only known type of migraine that follows autosomal-dominant transmission, has been linked to chromosome 19p13 but genetic heterogeneity has also been shown, i. e. different types of migraine could be excluded from this locus. Further investigations should concentrate on identifying the FHM gene on chromosome 19p13, on linkage analyses with markers for different susceptibility genes, and on genomic analyses of highly informative pedigrees. This would lead to further clues to the pathogenesis underlying migraine and, thus, to therapeutic developments.
    Notes: Zusammenfassung Nachdem bereits in historischen Beschreibungen eine genetische Verursachung der Migräne vermutet worden war, haben epidemiologische und molekularbiologische Forschungen in den letzten Jahren differenzierte Ergebnisse über genetische Faktoren in der Ätiopathogenese der familiären Migräne geliefert. Aufgrund von Familien- und Segregationsanalysen und von Zwillingsstudien wird dargestellt, daß genetische Faktoren mit größter Wahrscheinlichkeit eine Rolle in der Pathogenese der typischen Migräne spielen. Inwieweit extragenetische Faktoren auf die Ätiopathogenese der Migräne Einfluß nehmen, ist weitgehend offen. Linkageanalysen haben in jüngster Zeit gezeigt, daß möglicherweise mehrere verschiedene Gene für diese Erkrankung verantwortlich sind. Für die Familiäre Hemiplegische Migräne (FHM), der einzigen Migräneform, für die ein autosomal-dominanter Erbgang nachgewiesen ist, konnte ein Genlocus auf Chromosom 19p13 gefunden werden, gleichzeitig wurde aber auch genetische Heterogenität nachgewiesen. Verschiedene andere Formen der Migräne zeigten keine Linkage zu diesem Locus. Weitere Forschungen sollten neben der Identifizierung des FHM-Gens auch Linkageanalysen für Kandidatengene und Genomanalysen an großen informativen Familien zum Ziel haben. Letztlich werden die Ergebnisse genaueren Einblick in die Pathophysiologie der Migräne liefern und damit therapeutisch relevant sein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050061
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  • 13
    Electronic Resource
    Electronic Resource
    The genetics of adult-plant blackleg (Leptosphaeria maculans) resistance from Brassica juncea in B. napus (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 382-387 
    Details
    ISSN: 1432-2242
    Keywords: Genetics ; Blacking resistance ; Brassica napus ; Brassica juncea ; Leptosphaeria maculans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic control of adult-plant blackleg (Leptosphaeria maculans) resistance in a Brassica napus line (579NO48-109-DG-1589), designated “R13” possessing Brassica juncea-like resistance (JR), was elucidated by the analysis of segregation ratios in F2 and F3 populations from a cross between “R13” and the highly blackleg-susceptible B. napus cultivar “Tower”. The F2 segregration ratios were bimodal, demonstrating that blackleg resistance in “R13” was controlled by major genes. Analysis of the segregation ratios for 13 F3 families indicated that blackleg resistance in these families was controlled by three nuclear genes, which exhibited a complex interaction. Randomly sampled plants of F3 progeny all had the normal diploid somatic chromosome number for B. napus. The similarities between the action of the three genes found in this study with those controlling blackleg resistance in B. juncea is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223683
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  • 14
    Electronic Resource
    Electronic Resource
    Genetics of virulence in Leptosphaeria maculans (Desm.) Ces. et De Not., the cause of blackleg in rapeseed (Brassica napus L.) (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 301-306 
    Details
    ISSN: 1432-2242
    Keywords: Leptosphaeria maculans ; Brassica napus ; Blackleg ; Genetics ; Virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic basis of virulence of 24 isolates of L. maculans collected from various sites throughout south-eastern and south-western Australia were studied using five clone-lines of B. napus. The experimental design allowed the estimation of the environmental and genetic components of variance using a standard analysis of variance. Virulence of these isolates (as measured by the percentage of stem girdling, %G) on the clonelines NCII and Tap was found to be most likely controlled by a small number of genes; the broad-sense heritabilities were 79.7% and 67.5% for virulence on NCII and Tap, respectively. The significance of these results in relation to the potential of L. maculans in adapting to new resistant B. napus cultivars is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223169
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  • 15
    Electronic Resource
    Electronic Resource
    Inheritance of resistance to potato viruses Y and A in progeny obtained from potato cultivars containing gene Ry:evidence for a new gene for extreme resistance to PVA (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 710-716 
    Details
    ISSN: 1432-2242
    Keywords: Extreme virus resistance ; Potyviruses ; Genetics ; Genes Ry and Ra ; New gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extreme resistance in cultivated potato (Solanum tuberosum) to potato viruses Y and A (PVY and PVA) conditioned by the presence of Ry genes introduced from Solanum stoloniferum was described by Cockerham (1970). Cockerham detailed a number of genes which controlled a variety of reactions, including extreme resistance to both viruses (i.e. little or no visible reaction of plants and no viral replication following graft and manual inoculation) controlled by gene Ry sto. In the present study, cvs ‘Pirola’ and ‘Barbara’, which contain a Ry gene, were found to have extreme resistance to PVY isolates from the ordinary (PVY°), veinal necrosis (PVYN) and potato tuber necrotic ringspot (PVYNTN) subgroups, and PVA. The inheritance of this phenotype was examined in seedling progenies obtained by crossing ‘Barbara’ and ‘Pirola’ with susceptible cultivars. Segregation data for resistance to PVY and PVA in a progeny involving cv ‘Pirola’ best fitted a genetical model of one gene controlling extreme resistance to both PVY and PVA, although the possibility that there are two genes, each controlling resistance to one virus but closely linked, cannot be excluded. Segregation data from progenies involving cv ‘Barbara’ best fitted a genetical model in which there are two independent genes, one controlling extreme resistance to PVA and PVY and a second gene controlling extreme resistance to PVA but not to PVY. This previously unrecognised gene conferring extreme resistance to PVA only, should be given the notation Ra in keeping with nomenclature used for other resistance genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224066
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  • 16
    Electronic Resource
    Electronic Resource
    Variability and genetics of tolerance for aluminum toxicity in rice (Oryza sativa L.) (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 738-744 
    Details
    ISSN: 1432-2242
    Keywords: Aluminum toxicity ; Diallel analysis ; Genetics ; Rice ; Variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was undertaken to investigate the variability among lowland rice cultivars and the mode of gene action of aluminum (Al) toxicity tolerance in rice. Pregerminated seeds were grown in a nutrient solution containing 30 ppm Al and in normal nutrient solution, and relative root length (RRL) was determined at the 14-day-old stage to characterize genotypes for tolerance. Sixty-two traditional rice cultivars grown on lowland acid sulfate soil areas of Asia and West Africa were tested. Tolerant varieties ‘Azucena’, ‘IRAT104’, and ‘Moroberekan’, moderately sensitive ‘IR29’ and ‘IR43’, and sensitive ‘IR45’ and ‘IR1552’ were used to investigate the genetics of tolerance by diallel analysis. Of the 62 cultivars tested, only 3 were found to be sensitive to A l toxicity. Among the tolerant cultivars identified, 11 (‘Siyam Kuning’, ‘Gudabang Putih’, ‘Siyam’, ‘Lemo’, ‘Khao Daeng’, ‘Siyamhalus’, ‘Bjm-12’, ‘Ketan’, ‘Seribu Gantang’, ‘Bayer Raden Rati’, and ‘Padi Kanji’) were found to possess higher levels of tolerance than the improved tolerant upland cultivar ‘IRAT104’. Diallel analysis revealed that high RRL is governed by both additive and dominance effects with a preponderance of additive effects. The trait exhibited partial dominance, and one group of genes was detected. Heritability was high, and environmenal effects were low. Findings suggest that when breeding for A1 toxicity tolerance, selection can be made in early generations. The pedigree method of breeding would be suitable. Combining ability analysis revealed the importance of both general combining ability (GCA) and specific combining ability (SCA) in the genetics of A1 toxicity tolerance in rice. GCA was more prevalent than SCA. Tolerant parens ‘Azucena’, ‘IRAT104’, and ‘Moroberekan’ were the best general combiners. The presence of reciprocal effects among crosses suggested the proper choice of parents in hybridization programs. Results indicated that ‘Azucena’, ‘IRAT 104’, and ‘Moroberekan’ should be used as the female in crosses for A1 toxicity tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224070
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  • 17
    Electronic Resource
    Electronic Resource
    Comparative mapping in F2:3 and F6:7 generations of quantitative trait loci for grain yield and yield components in maize (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    Details
    ISSN: 1432-2242
    Keywords: Key words  Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination ; Abbreviations  RFLPs Restriction fragment length polymorphisms ; QTL quantitative trait loci ; RIs recombinant inbreds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2:3 and F6:7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6:7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2:3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2:3 seem to be dissected into multiple, linked QTL in the F6:7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6:7 generation for all traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050198
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  • 18
    Electronic Resource
    Electronic Resource
    Diallel analysis for aluminium tolerance in tropical soybeans [Glycine max (L.) Merrill] (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 267-272 
    Details
    ISSN: 1432-2242
    Keywords: Cerrado ; Savannah ; Acid soils ; Hydroponics ; Nutrient ; Variety ; Genetics ; Inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The soybean is a major crop in the agricultural systems of the Brazilian Cerrados (Savannahs), whose soils are acidic, devoid of nutrients and need to be amended before they are cultivated. However, below the ploughed layer there is a scarcity of nutrients and toxic aluminium (Al). These limit root growth, subsequently causing nutritional imbalance and drought stress. Our aim in the investigation described here was to identify genetic differences in the aluminium tolerance of soybeans by a 9 × 9 diallel cross among contrasting varieties grown in high-Al areas and in hydroponics. Combining ability analysis indicated predominantly additive gene effects, and the additive-dominance model explained most of the genetic differences in this germ plasm for mineral element absorption and root growth under aluminium stress. The relationship between the two factors suggest that conjugation hydroponics and field evaluations in breeding programmes would further improve soybeans with respect to yield stability under tropical cultivation conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223384
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  • 19
    Electronic Resource
    Electronic Resource
    Comparative mapping in F2∶3 and F6∶7 generations of quantitative trait loci for grain yield and yield components in maize (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2∶3 and F6∶7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6∶7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2∶3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2∶3 seem to be dissected into multiple, linked QTL in the F6∶7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6∶7 generation for all traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221893
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  • 20
    Electronic Resource
    Electronic Resource
    The genetics of blackleg [Leptosphaeria maculans (Desm.) Ces, et De Not.] resistance in rapeseed (Brassica napus L.) (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 932-940 
    Details
    ISSN: 1432-2242
    Keywords: Genetics ; Adult-plant ; Blackleg resistance ; Brassica napus ; Leptosphaeria maculans ; Australian cultivar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetic control of adult-plant blackleg [Leptosphaeria maculans (Desm.) Ces. et De Not.] resistance in rapeseed (Brassica napus L.) was studied in the F2 and first-backcross populations of the cross “Maluka” (blackleg-resistant) x “Niklas” (highly susceptible). A L. maculans isolate possessing high levels of host specificity (MB2) was used in all inoculations. Resistance/susceptibility was evaluated using three separate measures of crown-canker size, i.e. the percentage of crown girdled (%G), external lesion length (E) and internal lesion area (%II). Disease severity scores for the F2 and first-backcross populations based on E and %II gave discontinuous distributions, indicating major-gene control for these measures of resistance; but those for %G were continuous, indicating quantitative genetic control for this measure. Chi-square tests performed on the (poorly-defined) resistance classes, based on E, in the F2 and first-backcross populations indicated the likelihood for resistance being governed by a single, incompletely dominant major gene. Although the distributions of the F2 and first-backcross populations, based on%II, were clearly discontinuous, the observed segregation ratios for resistance and susceptibility did not fit any of the numerous Mendelian ratios which were considered. Differences in inheritance of resistance according to the assessment method and blackleg isolate used, were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224096
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  • 21
    Electronic Resource
    Electronic Resource
    Pathophysiology of non-insulin-dependent diabetes and the search for candidate genes: dangerous liaisons? (1996)
    Springer
    Acta diabetologica 33 (1996), S. 257-262 
    Details
    ISSN: 1432-5233
    Keywords: Key words NIDDM ; Candidate genes ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571560
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  • 22
    Electronic Resource
    Electronic Resource
    Pathophysiology of non-insulin-dependent diabetes and the search for candidate genes: dangerous liaisons? (1996)
    Springer
    Acta diabetologica 33 (1996), S. 257-262 
    Details
    ISSN: 1432-5233
    Keywords: NIDDM ; Candidate genes ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571560
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  • 23
    Electronic Resource
    Electronic Resource
    Evaluation of the BCL-2 gene locus as a susceptibility locus linked to the clinical expression of systemic lupus erythematosus (SLE) (1996)
    Springer
    Rheumatology international 16 (1996), S. 121-124 
    Details
    ISSN: 1437-160X
    Keywords: SLE ; Apoptosis ; bcl-2 gene ; Susceptibility ; Linkage ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by the production of a large number of autoantibodies. It has been postulated that this may be the result of prolonged longevity of auto-reactive B cells due to defective regulation of programmed cell death (apoptosis). The proto-oncogenebcl-2 is involved in the control of apoptosis in immunocompetent cells, and its over-expression is noted in T and B cells from SLE patients. This study examined the genetic linkage between thebcl-2 gene locus and SLE susceptibility using the affected sib-pair method in SLE families. Seventeen caucasian multiplex families were evaluated. A polymorphic microsatellite marker closely linked to thebcl-2 gene on 18g21.3 was used to determine thebcl-2 genotype. We demonstrated that haplotype sharing among the affected sibling pairs was not statistically different from random (P〉0.5). This suggests that thebcl-2 gene locus does not confer a genetic susceptibility to SLE expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01409984
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  • 24
    Electronic Resource
    Electronic Resource
    Differential genetic etiology of reading disability as a function of mathematics performance (1996)
    Springer
    Reading and writing 8 (1996), S. 295-306 
    Details
    ISSN: 1573-0905
    Keywords: Differential diagnosis ; Etiology ; Genetics ; Mathematics performance ; Reading disability ; Twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Education
    Notes: Abstract In order to assess the etiology of reading disability as a function of mathematics performance, data from 168 monozygotic (MZ) and 127 same-sex dizygotic (DZ) twin pairs in which at least one member of each pair was reading-disabled were subjected to quantitative genetic analyses. MZ and DZ concordance rates for reading disability were computed for different levels of mathematics performance, and reading performance data were fitted to an extension of the basic multiple regression model for the analysis of selected twin data. Results of these analyses suggest that genetic factors may be especially salient as a cause of reading disability in children with borderline deficits in mathematics performance: thus, mathematics performance may be a valid dimension for diagnosing subtypes of reading disability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395110
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  • 25
    Electronic Resource
    Electronic Resource
    Differential risk for developmental reading disorders in the offspring of compensated versus noncompensated parents (1996)
    Springer
    Reading and writing 8 (1996), S. 407-417 
    Details
    ISSN: 1573-0905
    Keywords: Compensation ; Dyslexia ; Environment ; Familial aggregation ; Genetics ; Risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Education
    Notes: Abstract When one or both parents have a history of developmental reading disorder (RD) in childhood, the risk to their offspring for developing reading problems is substantially increased. However, risk research has usually assumed a stability of reading problems across the lifespan (i.e., if a parent was affected in childhood, he or she remains affected in adulthood). Yet, some individuals with RD in childhood compensate for the disorder as they grow older. Both an environmental and genetic hypothesis would predict that the risk for RD in offspring will vary as a function of parental compensation. This study examined whether risk to offspring was dependent on the parents' successful or unsuccessful compensation for their childhood reading problems. Two large family data sets were analyzed (N=907). Diagnoses with either an age discrepant or IQ discrepant criteria essentially showed that having at least one still affected parent (i.e., RD both as a child and as an adult) put the offspring at a higher risk for RD than having at least one compensated parent (i.e., RD as a child but not as an adult). The lowest risk to an offspring occurred when both parents were never affected (i.e., not RD as a child or as an adult). The implications of these findings are discussed with regard to counseling and early diagnosis of reading problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404002
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  • 26
    Electronic Resource
    Electronic Resource
    Detection of oncogene mutation from neoplastic colonic cells exfoliated in feces (1996)
    Springer
    Diseases of the colon & rectum 39 (1996), S. 1238-1244 
    Details
    ISSN: 1530-0358
    Keywords: Colorectal neoplasms ; Genetics ; K-ras ; Gene mutations ; Early diagnosis ; Polymerase chain reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Best chances of a cure from colorectal cancer are obtained before metastatic spread. Lack of specific tests allowing early diagnosis of the tumor accounts for investigation of gene alterations involved in carcinogenesis by a noninvasive method. In the present study, K-ras codons 12 and 13 mutations were studied in neoplastic cells shed from the bowel into the stool and those contained in the tumor and normal mucosa. Moreover, healthy patients and a few others with precancerous conditions were examined. METHODS: Stool, tumor, and mucosa samples were taken from 25 patients with colorectal adenocarcinoma. Stool and mucosa samples were obtained from 11 healthy patients, and stool, pathologic bowel tissue, and normal mucosa samples were obtained from 3 patients with adenoma (1) or ulcerative colitis (2). Polymerase chain reaction amplification and restriction enzyme analysis were performed. RESULTS: K-ras codon 12 mutations were detected in both tumor and stool samples of 10 cancer patients, and no gene alterations were observed in 14 patients. In one patient with a tumor, a mutation was shown in only the tumor tissue. The agreement rate in tumor and stool analysis was 96 percent. A normal pattern of K-ras codons 12 and 13 was observed in the bowel mucosa. All stool and mucosa samples from healthy patients were not altered in K-ras.Agreement was registered between samples taken from patients with preneoplastic lesions. CONCLUSIONS: These preliminary findings show a high rate of accuracy in the investigation of K-ras alterations in the colorectal cells shed into the feces, suggesting that such an approach could be used to study other gene alterations and, prospectively, to identify early colorectal cancers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02055116
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  • 27
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of an internal emission standard and applications to fluorescence studies of photosystem II (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 167-171 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Fluorescence measurements of photosynthetic organisms and isolated proteins at ambient and low temperature have played an important role in understanding their function. When comparing fluorescence measurements at cryogenic temperatures, the differences in the scattering properties of frozen samples make it difficult to compare the fluorescence intensity of these samples. An internal emission standard can be used to scale the fluorescence intensity, compensating for these differences. We report the synthesis, purification and characterization of a luminescent terbium chelate complex for use as an internal emission standard for the study of photosystem II fluorescence at cryogenic temperatures. The ligand consists of a diethylenetriaminepentaacetic acid derivative where pyrimidine rings sensitize the terbium luminescence, overcoming the inherently low absorption of terbium. The chelated lanthanide remains in solution in the aqueous phase and does not interfere with photosystem II function. By scaling to the terbium emission, the fluorescence intensity of different samples can be readily compared. This chelate complex could also be used as an internal emission standard for studies of other proteins. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 28
    Electronic Resource
    Electronic Resource
    Two-photon-induced fluorescence of cholestane (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 219-224 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Cholestane is a fully saturated alkane with a structure analogous to cholesterol. We observed fluorescence emission from cholestane with a maximum near 235 nm when excited with picosecond laser pulses at 298 nm. The emission intensity of cholestane was found to depend on the square of the laser power, indicating the biphotonic process of two-photon excitation. The lifetime of cholestane in cyclopentane was found to be near 1.4 ns. Cholestane was found to be efficiently collisionally quenched by methanol and oxygen, as seen from decreased lifetime in the presence of these quenchers. These results suggest that cholestane or its analogs can be used as intrinsic probes in biologic systems. Two-photon excitation avoids the use of vacuum ultraviolet wavelength (130-170 nm), which requires special optics and exclusion of oxygen, and is generally incompatible with biologic samples. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 29
    Electronic Resource
    Electronic Resource
    Chemical bonding in the hydrogen molecule (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 421-431 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical bond in the hydrogen molecule is examined using the electron density and the generalized overlap amplitudes. Logarithmic derivatives of the electron density provide a clear picture of its behavior in the bonding region as well as in the outer region. The GOA expansion of the density is used to examine the dependence of the rate of decay of the density on the GOA ionization potentials. The increase in the electron density at the nuclei and in the bonding region coincides with the higher ionization potential of H2 over the H atom. The density in the bonding region along the internuclear axis does not decay exponentially, but its shape is very nearly an inverted Gaussian. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    Theoretical characterization of the ground state of the alkaline-earth monocarbides: Ordering of the two lower-lying states of the BeC, MgC, and CaC molecules (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 433-438 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two lower-lying electronic states (3Σ- and 5Σ-) of the BeC, MgC, and CaC molecules were investigated using restricted Hartree-Fock (RHF), generalized valence bond (GVB), and configuration interaction (CI) calculations to establish the relative ordering of those states as a function of the size of the alkaline-earth element. It is shown that as a result of the competition between bonding effects, which predominate for the 3Σ- states, and exchange effects, which stabilize the 5Σ- states, the ordering of these states can be reversed as we move from the Be to the Ca atom. For both the BeC and MgC molecules, the ground state was found to be a triplet X3Σ- state, but for the CaC molecule, the high-spin X5Σ- becomes more stable. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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  • 31
    Electronic Resource
    Electronic Resource
    Nodal structure of the electronic Wigner function of many-electron atoms and moleculesDedicated to Professor R. McWeeny in recognition of his outstanding contributions to quantum chemistry. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 439-452 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the example of several atomic and small molecular systems, the regular behavior of nodal patterns in the electronic one-particle reduced Wigner function is demonstrated. An expression found earlier relates the nodal pattern solely to the dot-product of the position and the momentum vector, if both arguments are large. An argument analogous to the “bond-oscillatory principle” for momentum densities links the nuclear framework in a molecule to an additional oscillatory term in momenta parallel to bonds. It is shown that these are visible in the Wigner function in terms of characteristic nodes. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 32
    Electronic Resource
    Electronic Resource
    Interatomic potential for the X1Σ+g state of Be2 (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 453-466 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extended geminal model has been applied to determine the interatomic potential for the X1Σ+g state Be2. By adopting a [11s, 9p, 6d, 4f, 2g] contracted Gaussian-type basis, the following potential minimum parameters are obtained: Re = 4.67 a.u. (4.63 a.u.) and De = 3.70 mH (3.82 ± 0.05 mH), experimental values in parentheses. A calculation with a nuclei-centered [9s, 7p, 4d, 2f, 1g] GTO basis plus two sets of bond-type function, each set comprising diffuse (2s, 2p, 2d, 2f, 1g) GTOs, yielded -3.79 mH as the value of the potential at R = 4.63 a.u. On the basis of an error analysis the best theoretical estimate of the binding energy is determined to be 3.83 ± 0.08 mH. The calculated value for the fundamental vibrational frequency is v0→1 = 224.7 cm-1 (exp. = 224 ± 3 cm). © 1996 John Wiley & Sons, Inc.
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  • 33
    Electronic Resource
    Electronic Resource
    On the lowest electronic states of the C2F radical (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 467-473 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The adiabatic energy surfaces of the lowest three electronic states [2(2A′ and 2A′)] and 2Σ+[2A′] of the C2F radical were investigated by the Hartree-Fock multiconfiguration self-consistent field (HF - MCSCF) ab initio method using a large set of atomic natural orbitals (ANO) and an extended configuration space, and the results were shown to be in agreement with the predictions of valence theory for this radical. The electronic ground state was found to have a bent equilibrium structure, hence contradicting the Walsh rule which predicts for the isoelectronic molecules a 2 linear state. The three states were found to be nearly degenerate and the potential energy surfaces of the two lowest electronic states exhibit an avoided crossing at an energy ∼2000 cm-1 above the ground-state minimum, lower than the highest vibrational fundamental. The strong adiabatic interaction which is responsible for the ordering of the electronic states and their equilibrium geometry involves not only the bending coordinate as normally found for Renner-Teller pairs of states, but also the C - C stretching coordinate, due to the near degeneracy of the 2Σ+ and the 2 lowest electronic states at linear geometries. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 34
    Electronic Resource
    Electronic Resource
    Generalized oscillator strengths of polyatomic molecules. II. NH3 (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 475-486 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Generalized oscillator strengths for a number of singlet transitions of the NH3 molecule, evaluated according to the random-phase approximation approach, are presented and discussed so as to provide characterization of some portions of the Bethe surface of the molecule. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 35
    Electronic Resource
    Electronic Resource
    MCSCF calculation of the frequency-dependent hyperpolarizability of the lithium atomDedicated to Roy McWeeny. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 487-492 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The second electric dipole hyperpolarizability of the lithium atom is calculated using a series of multiconfiguration SCF wave functions with an increasing number of active space orbitals. In agreement with other recent calculations, we find a very large correlation correction to the hyperpolarizability. We analyze the frequency dependence of the dc Kerr hyperpolarizability γK(ο) = γ (- ο ο, 0, 0) and observe very significant dispersion effects. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 36
    Electronic Resource
    Electronic Resource
    A study of the molecular orbital localization into an extended Hartree - Fock approach: Application to the BeH2 ground state (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 493-504 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article, we present a study of the localization and properties of the molecular orbitals (MOs) of polyatomic systems by using a comprehensive version of the G1 model. In this version, the wave function is written as a DODS product of univocally determined spin orbitals (MOs), “projected” on the singlet ground state. A procedure for determining the MOs is given and applied to the BeH2 ground state. Equivalent split shell and localized MOs are found. The Be orbitals are seen to exhibit sp hybridization and the localized valence MOs are found to produce - 13.7 kcal/mol localization energy. Multistructural calculations are carried out and show that the present approach is able to describe localized and well-oriented bonds whenever the molecule under study presents only a single well-defined nonresonant chemical structure. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 37
    Electronic Resource
    Electronic Resource
    Potential energy surfaces of pseudoaromatic molecules: An MMVB and CASSCF study of pentalene (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 505-512 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The S0 and S1 potential energy surfaces of pentalene were studied using MMVB - a hybrid force-field/parametrized valence bond (VB) method designed to simulate CASSCF calculations for ground and covalent excited states. The results were calibrated against full CASSCF calculations. Four distinct critical points were optimized: on S0, a C2h minimum (with alternating single and double bonds) and a D2h transition structure; and on S1, a D2h minimum and an adjacent S1/S0 conical intersection. A VB exchange density matrix (which is independent of the choice of the spin-coupled basis) was used to rationalize the S0 and S1 surface topologies. Craig defined pseudoaromatic molecules to be those with nontotally symmetric electronic ground states. For pentalene, this is true for both CASSCF and MMVB calculations: the CASSCF S0 transition structure is an open-shell B1x singlet, and the VB ground state is dominated by a spin-coupling which transforms as B1g. A C2v minimum and a D2h transition structure were located on the CASSCF S2 potential energy surface. This state cannot be represented by MMVB because of the importance of ionic configurations. The characters of the S1 S2 states of pentalene are shown to be reverse of the S1 and S2 states of benzene. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 38
    Electronic Resource
    Electronic Resource
    Bond length alternation in cyclic polyenes. VII. Valence bond theory approachThis paper is dedicated to Professor Roy McWeeny with affection and admiration on the occasion of his 70th birthday. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 513-527 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of bond length alternation in linear extended φ-electron systems with conjugated double bonds is examined using the valence bond theory applied to a simple model of cyclic polyenes CNHN with N = 4v and N = 4v + 2 sites as described by the Pariser-Parr-Pople Hamiltonian. Overlap enhanced atomic orbitals are employed in order to achieve the optimal treatment with only two Kekulé structures. The predicted bond length alternation and its magnitude are in good agreement with earlier molecular orbital based calculations and with experiment. Special attention is given to the discussion of the origin of bond length alternation in long polyenic chains and to the role of the resonance energy leading to stabilization of undistorted, symmetric structures for small aromatic (N = 4v + 2) cycles. © 1996 John Wiley & Sons, Inc.
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    Calculation of 13C shielding of the isotopomers CH3Cl, CH2DCl, CHD2Cl, and CD3Cl (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 529-534 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C shielding of the isotopomers CH3Cl, CH2 DCl, CHD2Cl, and CD3Cl has been calculated for a range of temperatures from an self-consistent field (SCF) shielding surface computed by Buckingham and Olegario. It is found that each successive deuterium substitution increases the shielding by about 0.19 ppm and that a very slight nonadditivity occurs. The principal factor which governs the nuclear motion correction for each isotopomer is the stretching of the bonds with both first- and second-order terms being significant. Angle bending contributions are very small at first order but quite substantial at second order. Not only should the 13C-isotope shifts in this experimentally uninvestigated series be easily measured but the temperature dependence of the shielding in any one isotopomer should be observable provided that careful measurements are made. The 13C-shielding difference between CH3 35Cl and CH3 37Cl has also been calculated and is found to agree well with experiment. © 1996 John Wiley & Sons, Inc.
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    Exchange - correlation potential and excited-state density functional theory (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 535-543 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exchange-correlation potential associated with excited-state density functional theory is studied numerically using accurate electron densities for ground and excited states of He, Be, Ne, Mg, and Ar. The long-range and short-range behaviors of this potential are discussed. First-excitation energies are estimated using various prescriptions. © 1996 John Wiley & Sons, Inc.
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  • 41
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    Modern valence-bond description of the electronic structure of benzocyclobutadiene (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 545-552 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ground state of benzocyclobutadiene, a bicyclic molecule with 8π electrons containing a benzene and a cyclobutadiene ring, is studied by means of modern valence bond (VB) theory in its spin-coupled (SC) form and the complete-active-space self-consistent field (CAS SCF) approach. The CAS SCF wave function is used to optimize the geometry, and SC theory - to obtain a well-correlated and easy to visualize and understand model of the active space hosting the π electrons. It is shown that the π system of the ground state of benzocyclobutadiene can be described with sufficient accuracy as a combination of the π systems of a distorted benzene ring and an isolated double bond. Each of the eight SC orbitals is found to be well-localized about one carbon atom only, with small distortions toward its nearest neighbors. The analysis of the optimal active-space spin-coupling pattern within the SC wave function for benzocyclobutadiene shows unambiguously that this molecule inherits neither the aromatic nor the antiaromatic character of its cyclic components, and it is most appropriate to regard it as nonaromatic. © 1996 John Wiley & Sons, Inc.
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    Momentum-space electron densities - localized orbitals in hydrocarbons, boranes, and transition metal complexes (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 579-592 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Position and momentum space plots are presented for localized molecular orbitals in hydrocarbons, boranes, a carborane, and two octahedral transition metal complexes. The p-space representation proves to be valuable for visualizing such orbitals since it highlights the differences in their character from one molecule to another. Factors influencing the form of the orbitals in p space, including the oscillatory behavior caused by contributions to an orbital from more than one center, are examined in detail. © 1996 John Wiley & Sons, Inc.
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    Roy McWeeny (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1-2 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600102
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    Applications of the group-function theory to the field of materials science (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 617-634 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The group-function theory, as proposed by McWeeny for the study of weak intermolecular interactions and developed by Huzinaga in the context of valence-electron methods, is shown to be applicable to the ab initio study of tunable solid-state laser materials made of defective ionic crystals. The applicability of the theory relies on the existence of local electronic states (to which the demonstrated/potential laser activity is ascribed), which are essentially localized in a small cluster of atoms including the defect and whose electron correlation interactions with the surrounding crystal components are negligible. According to the group-function formalism, it is possible (a) to neglect electron correlation effects beyond the defect cluster and (b) to define a quantum mechanical embedding potential which embodies the rest of the so-called host effects. Computationally, the theory becomes applicable as the embedding potential is approximated through ab initio model potentials (AIMP). The results of AIMP embedded-cluster calculations demonstrate that it is possible to calculate the local structure and spectroscopy of the active defect at an ab initio level, the attainable accuracy being comparable to the usual one in molecular ab initio studies in the gas phase. Also, in this article, we present a systematic study of the local distortions produced upon doping divalent first-series transition-metal ions in rock-salt oxides, MO:Me2+ (M=Mg, Ca, Sr; Me=Sc-Zn) and Tl+ in KMgF3 and KF hosts. This study leads to the calculation of the local structures of the defects in these materials, which have not been measured. The results suggest that the use of the mismatch of the empirical ionic radii of the impurity and the substituted ion in order to predict local distortions in doped ionic crystals is not significant when it is smaller than 0.1 Å, and when it is larger, it should be weighted by a reduction factor depending on the host. For the first-series divalent transition-metal ion impurities, this factor is shown to be 0.15 for SrO, 0.25 for CaO, and around 0.50 for MgO. © 1996 John Wiley & Sons, Inc.
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    Accurate lower and upper bounds of the energy spectrum for the asymmetrical two-well potentials (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 641-648 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trigonometric basis sets are used in a Rayleigh-Ritz variational method for computing two-sided eigenvalue bounds of the Schrödinger equation in one dimension. The method is based on truncating the infinite interval and solving an eigenvalue problem which obeys the von Neumann and the Dirichlet boundary conditions, respectively. Highly accurate numerical results are presented for the asymmetrical two-well oscillators. © 1996 John Wiley & Sons, Inc.
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    On the evaluation of overlap integrals with the same screening parameters of Slater-type orbitals using binomial coefficients (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 637-640 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general formula has been established for the overlap integrals with the same screening parameters of Slater-type orbitals in terms of bionomial coefficients. The final results are especially useful for the calculation of these integrals for large quantum numbers, which occur in the multicenter integrals. © 1996 John Wiley & Sons, Inc.
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    Study of methanetriol decomposition mechanisms (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 649-655 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using ab initio HF/6-31G** and MP2/6-31G** calculations alternative reactions HC(OH)3 → HCO2H + H2O and HC(OH)3 + H2O → HCO2H + 2H2O are investigated and the results are compared with relevant PM3, HF/3-21G, and HF/6-31G data. Reactant and product complexes as well as transition states are located on corresponding potential energy surfaces. © 1996 John Wiley & Sons, Inc.
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    Importance of angular and radial electron correlations in first born (e, 2e) spectroscopies of heliumlike targets (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 657-665 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ground-state electronic structure of heliumlike systems can be described by several simple wave functions expressed in terms of the three distances between particles (one nucleus and two electrons). The dependence of (e, 2e) ionization cross sections on the description of radial and angular correlations between target electrons is analyzed. The cases of plane wave and Coulomb wave representations of ejected electron trajectories are examined together with the feasibility of analytic calculations. The relative sensitivity of (e, 2e) cross sections to the description of correlations between K-shell electrons is also investigated as a function of nuclear charge. Existing experimental data on helium are used to support a comparison with calculated (e, 2e) cross sections. © 1996 John Wiley & Sons, Inc.
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    Absorption maxima study of chromophores of indigoid dyes (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 681-687 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular structure of 21 chromophores of indigoid dyes were studied by an ab initio MP2/6-31 + G*/ /HF/6-31 + G* method. Bond lengths and bond angles were affected by π-electron conjugation. The difference between molecular structures of chromophores and indigoid dyes indicated that benzene rings and five-membered rings in indigoid dyes are structurally important. Absorption maxima of chromophores were successfully calculated by the CI-singles-MP2/6-31 + G* theory. Like indigoid dyes, absorption maxima of the chromophores are affected by the positions of the donor and acceptor groups on the trimethine group. Bathochromic shifts of the absorption maxima were observed with the best donor group of (SINGLE BOND)NH among (SINGLE BOND)NH, (SINGLE BOND)O, and (SINGLE BOND)S groups. Appropriate substitution of longer-chain polymethines brought about chromophoric systems having hypsochromic shifts. From these calculations, the absorption maxima of some indigoid dyes could be explained by their chromophores qualitatively. © 1996 John Wiley & Sons, Inc.
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    Ensemble-representable densities for atoms and molecules. II. Application to CoCl4 2- (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 667-680 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the previous article we introduced a method to obtain an ensemble density describing a molecule in a crystal from diffraction experiment structure factors. Here the method is applied to the CoCl42- molecular ion in a Cs3CoCl5 crystal for which accurate magnetic structure factors are known. First, the approximations involved in the interpretation of polarized neutron experiment are reviewed with special emphasis on the collinearity approximation which has been avoided in this work. Second, the derivation of magnetic structure factors corresponding to theoretical ensemble densities is explained (the spin and the exact orbital contributions have been included). Third, the fitting procedure is presented and results at different levels of approximation are discussed. The main conclusions are: (1) A density built by using several molecular wave functions can give a very good agreement with the experimental data. (2) The ensemble representability constraint is necessary to retrieve physical information from the optimized parameters. (3) Taking into account the proper paramagnetic contribution to the magnetization improves significantly the agreement between theory and experiment. (4) Neglecting the diamagnetic contribution and the fact that the magnetization may be locally noncollinear to the applied external field is fully justified for the system under study. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600201
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    Near-dissipationless coherent excitations in biosystemsPresented at the 1995 Sanibel Symposium. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 689-697 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We consider the question of long-range propagation of informational signals in biosystems. This is done for the case of a modeled biosystem of the type considered by H. Fröhlich and A. S. Davydov but under general nonequilibrium thermodynamic conditions. For that purpose we resort to the so-called informational statistical thermodynamics. It is shown that Fröhlich's effect may follow in this system. It consists in the emergence of a self-organized dissipative homogeneous and stationary structure (in Prigogine's sense), resembling a nonequilibrium Bose-Einstein condensation in the low-lying-in-frequency modes of polar vibrations. It follows once a critical level of pumping of metabolic energy is achieved. Furthermore, it is shown that signals in this system propagate in the form of Davydov solitons, which are strongly thermally damped in near equilibrium at physiological conditions. However, the situation drastically changes in nonequilibrium conditions, leading to Fröhlich's condensation, when the lifetime of a Davydov-like soliton is enormously enhanced, allowing for very long range propagation of signals. © 1996 John Wiley & Sons, Inc.
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    Dynamics during spectroscopic transitions - basic concepts, E. Lippert and J. D. Macomber, Editors, Springer-Verlag, Berlin, Heidelberg, 1995, 580 pp., 214 figures, 7 tables. Hardcover ISBN 3-540-58703-9 (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 709-709 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600202
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  • 54
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    An optimized approach to compute hybridization displacement charge and a study of its effects on electrostatic potentials of some biologically important molecules (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 699-708 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrostatic potential maps of certain biologically important molecules (guanine, adenine, cytosine, thymine, and two conformers of glycine) were studied employing a “hybridization displacement charge (HDC)” correction to Löwdin charge distributions and using the conventional Mulliken charge distributions of the molecules. In these calculations, the magnitude of each of the point charges was distributed in 3-dimension in a spherically symmetric manner. The method of computing HDC using MNDO wave functions was optimized by introducing two adjustable parameters. It has been clearly demonstrated that HDC-corrected Löwdin charge distributions of the molecules mentioned above are able to reproduce most of the important features of their ab initio MEP maps, while the conventional Mulliken charge distributions fail in many respects. Thus, HDC-corrected Löwdin charge distributions are shown to be quite reliable for the study of molecular electrostatic properties, particularly for molecules with more than one competing electrophilic site. © 1996 John Wiley & Sons, Inc.
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    Statistical mechanics and therniodynamics, Claude Garrod, Oxford University Press, New York, 1995, 622 pp, one 3.25 in. diskette. Hardcover, ISBN 0-19-508523-X (IBM software), ISBN 0-19-509775-0 (Macintosh software) (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 711-711 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600203
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    Secular polynomials for chemical graphs of alkanes in terms of atoms and bonds and their spectral properties (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 743-752 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Secular polynomials (SPs) have been constructed and studied for the adjacency matrices A(GaCh) and A(GbCh) corresponding to chemical graphs of alkanes in terms of atoms (GaCh) and in terms of bonds (GbCh). The three second-class Chebyshev polynomials Up(Q), Up - 1(Q), and Up - 2(Q), with respect to the variable Q proportional to the SP of an isolated CH2-like subgraph, have been shown to appear within both SPs P[A(GaCh)] and P[A(GbCh)] and to play the role of algebraic analogues of a (CH2)p-like subgraph. Common noncanonical algebraic expressions for both SPs reflecting the regular internal structure of alkanes have been constructed on this basis. Spectral properties of both graphs GaCh and GbCh have been shown to be determined by those of Up(Q), e.g., the band limits of spectra proved to be related to the orthogonality interval Q = [-1;1] for polynomials Up(Q). Since the adjacency matrices (AMs) A(GbCh), but not A(GaCh), are proportional to definite model Hamiltonian matrices, the obtained results serve to interpret the one-electron spectra of alkanes in terms of peculiarities of usual chemical structure. © 1996 John Wiley & Sons, Inc.
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    The calculation of NMR shielding tensors based on density functional theory and the frozen-core approximation (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 753-766 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the frozen-core approximation to the calculation of the shielding tensor of nuclear magnetic resonance (NMR) spectroscopy is discussed and an implementation is presented. A complete formulation of the shielding calculation within the frozen-core approximation is given, both in general terms and for the special case of density functional theory (DFT) and “gauge including atomic orbitals” (GIAOs). The practical implementation is validated by a detailed discussion of the consequences of the approximation. The general conclusion is drawn that the frozen-core approximation is a useful tool for shielding calculations - if the valence space is increased to contain at least the ns, np, (n - 1)p, (n - 1)d (fourth period and higher) shells, where n is the number of the given period in the periodic table of elements. The new method is applied to 77Se shieldings and chemical shifts for a small number of compounds. The agreement between theory and experiment is good for relative shifts, whereas calculated absolute shieldings are generally too small by about 300-400 ppm. This difference is attributed to the relativistic contraction of the core density at the selenium atom that had been explicitly incorporated into the experimental absolute shielding scale. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600301
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  • 59
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    A comparison of Hartree - Fock, MP2, and DFT results for the HCN dimer and crystal (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 767-778 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of hydrogen-bond related quantities - geometries, interaction energies, dipole moments, dipole moment derivatives, and harmonic vibrational frequencies - were calculated at the Hartree - Fock, MP2, and different DFT levels for the HCN dimer and the periodic HCN crystal. The crystal calculations were performed with the Hartree - Fock program CRYSTAL92, which routinely allows an a posteriori electron-correlation correction of the Hartree - Fock obtained lattice energy using different correlation-only functionals. Here, we have gone beyond this procedure by also calculating the electron-correlation energy correction during the structure optimization, i.e., after each CRYSTAL92 Hartree - Fock energy evaluation, the a posteriori density functional scheme was applied. In a similar manner, we optimized the crystal structure at the MP2 level, i.e., for each Hartree - Fock CRYSTAL92 energy evaluation, an MP2 correction was performed by summing the MP2 pair contributions from all HCN molecules within a specified cutoff distance. The crystal cell parameters are best reproduced at the Hartree - Fock and the nongradient-corrected HF + LDA and HF + VWN levels. The BSSE-corrected MP2 method and the HF + P91, HF + LDA, and HF + VWN methods give lattice energies in close agreement with the ZPE-corrected experimental lattice energy. The (HCN)2 dimer properties are best reproduced at the MP2 level, at the gradient-corrected DFT levels, and with the B3LYP and BHHLYP methods. © 1996 John Wiley & Sons, Inc.
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    Quantum mechanical electronic structure calculations with chemical accuracy, edited by S. R. Langhofl, Kluwer Academic Publishers, Dordrecht, 1995, 447 pp., $208, ISBN 0-7923-3264-4 (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 791-791 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600303
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    Virtual orbitals (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 793-801 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the conventional concepts based on the use of the HOMO and LUMO are founded on very questionable assumptions. In particular, it is shown both theoretically and computationally that the LUMO of almost all neutral atoms and molecules is a continuum function with energy zero. The LUMO of any SCF calculation is an artifact of the basis-expansion method. A proposal is made for the identification of the pair donor and pair acceptor orbitals which play the true role of the HOMO and LUMO. © 1996 John Wiley & Sons, Inc.
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    Valence energy in variational Monte Carlo: CuH dissociation energy (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 803-808 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We show how to estimate the dissociation energy of CuH using the variational Monte Carlo method. The techniques involved are (i) an all-electron approach, (ii) a diffusion-only Metroplis algorithm which is well-suited for sampling the nodal regions properly, and (iii) a core-valence partitioning scheme such that the dissociation energy is estimated from the valence energies of CuH and Cu only. This approach avoids several of the approximations inherent in pseudopotential methods. Using relatively crude wave functions, we obtain an estimate of the dissociation energy and dipole moment with an accuracy on par with much more elaborate calculations in the literature. © 1996 John Wiley & Sons, Inc.
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    Basis sets for ab initio periodic Hartree - Fock studies of zeolite/adsorbate interactions: He, Ne, and Ar in silica sodalite (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 809-820 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Silica sodalite is an ideal model system to establish base-line computer requirements of ab initio periodic Hartree-Fock (PHF) calculations of zeolites. In this article, we investigate the effect of various basis sets on the structural and electronic properties of bulk silica sodalite. We also study the interaction of He, Ne, and Ar with the sodalite cage. Our work shows that basis-set superposition errors (BSSE) in calculations using STO-3G and 6-21G(*) basis sets are as large as the interaction energies, leading to poor confidence in the results. To cure this problem, we present high-quality basis sets for Si, O. He, Ne, and Ar, optimized for use with PHF methods, and demonstrate that the new basis set greatly reduces BSSE. The theoretical barriers for transfer of the rare gases between sodalite cages are 5.6, 13.2, and 62.1 kcal/mol for He, Ne, and Ar. © 1996 John Wiley & Sons, Inc.
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    Note on the generation of Gaussian bases for pseudopotential calculations (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 821-824 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a technique to generate Cartesian Gaussian bases for electronic configuration and cross-section calculations on molecules. The technique is specially useful for pseudopotential work, when the bases cannot be tabulated because they depend on the specific choice of the pseudopotential. © 1996 John Wiley & Sons, Inc.
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    Factorization of interaction graphs with n-fold symmetry: Some applications in PPP calculation and molecular vibrational analysis (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 825-832 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The G and F matrices in the molecular vibration problem, the secular matrix in Hückel calculation including some nonneighbor interactions, and the Fock matrices at any stage of iteration in the Pariser-Parr-Pople (PPP) calculations on cis- and trans-butadiene, benzene, and s-triaminobenzene systems have been shown to be factorizable by representing them graphically and then applying the generalized technique of splitting of graphs with n-fold symmetry. © 1996 John Wiley & Sons, Inc.
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    Symmetry reduction of the matrix elements of a two-particle operator (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 833-841 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Local coordinate systems are chosen for each quadruple of atoms relative to a four-center integral, in order to avoid linear combinations of orbitals when symmetry operations perform on an orbital. This choice can utilize the complete molecular symmetry to attain the optimal number of symmetry-unique integrals and to construct two-particle matrix elements by multiplying symmetry-unique integrals, called the “standard four-center integrals,” by the corresponding coefficients, called the “C coefficients.” A simple algorithm to use the complete molecular symmetry to reduce calculations of molecular matrix elements is outlined for general highly symmetric molecules. A tetrahedral molecule is analyzed. © 1996 John Wiley & Sons, Inc.
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    On the use of multipole expansion of the Coulomb potential in quantum chemistry (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 843-852 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some features of the multipole expansion of the Coulomb potential V for a system of point charges are studied. It is shown that multipole expansion is convergent both locally in L2(R3) and weakly on some classes of functions. One-particle Hamiltonians Hn = H0 + Vn, where H0 is the kinetic energy operator and Vn is the n-th partial sum of the multipole expansion of V, are discussed, and the convergence of their eigenvalues to those of H = H0 + V with increasing n is proved. It is also shown that the discrete spectrum eigenfunctions of Hn converge to those of H both in L2(R3) (together with their first and second derivatives) and uniformly on R3. © 1996 John Wiley & Sons, Inc.
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    The π, π* state in formaldehyde and thioformaldehyde (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1661-1671 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For formaldehyde, the C — O stretch potential of 1(π, π*) crosses all 1A1 Rydberg potentials, such as n, 3py, n, 3dyz, etc., thereby transferring the intensity of the unassigned 1(π, π*) ← X??? system to these Rydberg states. For thioformaldehyde, the situation is similar but a shift in the potentials allows for direct observation of 1(π, π*). In its 1(π, π*) state, H2CO is planar, having a low barrier of about 0.2 eV toward the nonplanar 1(σ, π*) state. For H2CS, the planar conformation of 1(π, π*) is a saddle point, with 1(π, π*) being the global minimum on the 21A′ surface. The triplet π, π* states of H2CO and H2CS are nonplanar, having inversion barriers of 0.1 and 0.05 eV, respectively. For both H2CO and H2CS, the π, π* configuration also crosses the ground-state configuration, which explains predissociation and radiationless transitions of some Rydberg states. © 1996 John Wiley & Sons, Inc.
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    Condensed-phase effects on the conformational equilibrium of ethylene glycol (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1651-1660 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Density functional calculations for ethylene glycol (CH2OHCH2OH) in the gas and in a dielectric medium are reported. The condensed-phase calculations are based on the self-consistent reaction field approach and the environment has the dielectric constant of liquid methanol. NPT Monte Carlo simulations of ethylene glycol (ETG) in liquid methanol are also reported. The simulations were carried out for three conformers of ETG (tGg′, gGg′, and tTt). Comparison between SCRF results for the conformational equilibrium in the gas and in the dielectric suggests that the tGg′ conformer is slightly stabilized relative to the gGg′ conformer in the solvent. However, the energy difference between them is less the 1.0 kJ/mol, which indicates that frequent interconversions between the tGg′ and gGg′ conformers are expected in the condensed phase. The all-trans conformer (tTt) is higher than the most stable conformer in the gas by 14 kJ/mol. Monte Carlo simulations predict that the tGg′ and gGg′ conformers have very similar energies in the solvent. However, the simulations also show, in agreement with experimental data, that the tTt conformer is stabilized in liquid methanol, relative to the gas phase. The microscopic mechanism leading to the stabilization of the tTt conformer in the liquid is related to the differential hydrogen-bonding formation between the ETG conformers and the methanol molecules. © 1996 John Wiley & Sons, Inc.
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    SCMEH-MO calculations on lanthanide systems. III. Ln(CO)6, Ln(OC)6 (Ln = Nd, Sm) (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1673-1677 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The SCMEH-MO method with average relativistic and spin-orbit effects has recently been applied to study the electronic structure and bonding in samarium pentamethylcyclopentadienyls. In this report the same approach has been utilized in studying the electronic structures of Nd and Sm hexacarbonyls. In contrast to the stable transition metal d-block carbonyls, these lanthanide carbonyls are found to be quite unstable. These findings are based on calculated electronic structures and bond energies. © 1996 John Wiley & Sons, Inc.
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    The electronic g-tensor of MgF: A comparison of ROHF and MRD—CI level results (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1679-1684 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Despite their importance in the characterization of molecular magnetism, electronic g-tensors have received rather little theoretical attention. In this work, however, the ground-state g-tensor of MgF is computed at both the ROHF and multireference CI levels. The calculations are expanded complete to second order in appropriate Breit-Pauli terms and the contributions of all important magnetically coupled excited states are accounted for. Both the CI- and ROHF-level Δg∥-values (-59 and -55 ppm, respectively) are in agreement with experiment (-319 ± 500 ppm) within the range of experimental uncertainty. For Δg⊥, however, the ROHF treatment yields a value (-659 ppm) in substantial disagreement with experiment (-1319 ± 500 ppm). Fortunately, this discrepancy is alleviated by CI level treatment (Δg⊥ = -1447 ppm). © 1996 John Wiley & Sons, Inc.
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    Wave-function splitting technique for calculating above-threshold ionization electron spectra (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1685-1689 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In intense laser fields, atoms and molecules can absorb many more photons than required for ionization. This phenomenon is called above-threshold ionization (ATI) and it shows up in kinetic energy spectra of ionized electrons. The presence of very high energy photoelectrons necessitates the use of extremely large grids in numerical simulations based on the full time-dependent Schrödinger equation. We show that by using a wave function splitting scheme one can circumvent the problem of large grids and thus obtain accurate multiphoton photoelectron spectra. This scheme will be very useful in studies of ATI spectra generated by molecules in intense laser fields. We illustrate this method for a one-dimensional model of the H atom in intense laser fields. © 1996 John Wiley & Sons, Inc.
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    Kernel projector matrices for leu1—zervamicin (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1691-1700 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By performing ab initio calculations on fragments of leu1(SINGLEBOND)zervamicin, it is demonstrated that accurate wave functions can be obtained for this large structure by combining the results from the fragments. Input information consists of atomic coordinates as obtained, for example, from a crystal structure determination. The fragments are composed of a kernel of atoms surrounded by a chosen neighborhood of atoms. The entire molecule is divided into individual kernels and their neighborhoods are added for the individual fragment calculations on the basis of the distances of other atoms from the atoms in a kernel. The hydrated leu1(SINGLEBOND)zervamicin is composed of 295 atoms which could be handled in full by Gaussian 94. The results of the fragment calculations were combined to provide an electron density distribution for the molecule. This distribution was compared with one that represents the distribution obtained from a calculation on the entire molecule at once. The clear implication of this study is that it is feasible to perform ab initio calculations on structures by the use of fragments. The time involved increases essentially linearly with complexity. © 1996 John Wiley & Sons, Inc.
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    Fission of metal clusters: A comparison of jellium model calculations and shell correction method calculations (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1701-1707 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We investigate the fission process Ag2+23 → Ag+12 + Ag+11 in order to compare total energies that calculated by the shell correction method and jellium models. A cavity potential and a Woods-Saxon-type potential are used as the shell potential for the shell correction method, with which the single-particle energy levels are calculated. Shell corrections are obtained by using the Balian-Bloch formula and by smoothing the discrete energy levels in the shell potentials. The jellium model calculations are performed in the framework of the local spin density functional approximation. The conventional jellium model and stabilized jellium model are used. Although the qualitative agreement between the shell correction method calculations and the stabilized jellium calculations is very good, an improvement of the liquid drop energy will be necessary for the satisfactory quantitative agreement. © 1996 John Wiley & Sons, Inc.
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    Combined effect of the screening of a donor ion and the conduction band nonparabolicity on the binding energy of a donor at the center of a spherical quantum dot (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1719-1722 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We carried out variational model calculations for the assessment of the combined effect of the nonparabolicity of the electron effective mass and the screening of the donor ion by the valence electrons of GaAs for a donor placed at the center of a spherical quantum dot. We considered finite confining potentials between the GaAs QD and the surrounding Ga1-xAlxAs matrix. We found that the combined effect becomes more pronounced as the radius of the quantum dot decreases. © 1996 John Wiley & Sons, Inc. Int J Quant Chem 60: 507-510, 1996
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    Differential photoionization cross section calculations for HI using the random-phase approximation with L2 basis functions (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 409-419 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoionization cross sections and asymmetry parameters of the three main valence ionization processes in HI, corresponding to the formation of, respectively, 6π, 11σ, and 10σ holes, were calculated in the random-phase approximation (RPA). Our particular computational procedure, based on solving the integral equation for the half on the shell K-matrix upon a grid of points supplied by an L2 basis set calculation, affords recovery of the electronic continuum degeneracy of the final states. This makes it possible to compute the differential ionization cross section at any energy up to the fourth ionization threshold, allowing for the interaction of the three channels considered. The total cross section obtained by applying the Stieltjes imaging procedure to the discrete spectrum yielded by the RPA is also reported. © 1996 John Wiley & Sons, Inc.
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    Increased-valence structures and hypervalent molecules (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 553-566 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hypervalent molecules may involve the use of increased-valence structures to provide valence bond descriptions of their electronic structure. For electron-rich molecules with four electrons distributed among three overlapping (nuclear-centered) atomic orbitals, the increased-valence structures are Y(BOND)A·B and Y·A -  - B. Each structure involves a fractional electron-pair bond and a one-electron bond. It is deduced that the Armstrong-Perkins-Stewart valence of the A atom is able to exceed unity in each of these structures when the three bonding electrons occupy nonorthogonal localized molecular orbitals. It is also shown that increased valence for the A atom does not occur when the four electrons occupy localized molecular orbitals to give the valence-bond structure Y - A - B with three overlapping atomic orbitals, and the same number of orbital variational parameters as occurs in the wave functions for either of the increased-valence structures. The results of ab initio valence bond calculations with minimal basis sets are reported for H-3l, CH-5, HF-2, F-3, CIF3, and FF3, and the resulting wave functions for resonance between six canonical Lewis structures are related to those for resonance between the two increased-valence structures. The use of the latter structures to indicate how electronic reorganization proceeds via one-electron delocalizations for SN2 reactions is redescribed, and an elementary argument is presented to deduce that this class of reactions cannot involve the delocalization of a pair of electrons in concert from the nucleophile. Increased-valence wave functions are used to deduce an expression for the avoided crossing for the transition state of the identity SN2 reaction. © 1996 John Wiley & Sons, Inc.
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    Structural aspects of a possible transannular interaction in silatranes and azasilatranes: An ab initio studyWe are very happy to dedicated this work to Professor Roy McWeeny, Pisa University. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 567-578 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complete geometry optimizations using ab initio SCF/3-21G* calculations were performed on silatrane and azasilatrane, on their fluoro derivatives, and on methylsilatrane. By comparison with optimized geometries obtained for a series of model systems, the predicted transannular internuclear distances were interpreted in terms of the combined effects of electronegative substituents on Si and the anomeric interaction in the silatranes. The predicted geometries indicate that there is a weak transannular interaction in silatrane and a more significant one in azasilatrane, the predicted equilibrium distances being 2.66 and 2.15 Å, respectively. © 1996 John Wiley & Sons, Inc.
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    Masthead (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996) 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600101
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    Stability and structure of rare-gas ionic clusters using density functional methods: A study of helium clustersThis is a contribution to a symposium on “The Quantum Theory and the Chemical Bond” published in honor of Professor Roy McWeeney. The authors wish to affectionately dedicate this work to a great scientist and a long-standing friend. (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 593-608 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several modelings of exchange and correlation forces which can be carried out using density functional theory (DFT) methods have been analyzed to study their efficiency and reliability when evaluating possible competing structures of helium ionic clusters of increasing size. This study examines Hen+systems with n from 1 to 7 and compares the present calculations with earlier evaluations that used more conventional, and more computationally intensive, methods with configuration interaction (CI) approaches. The present results indicate that it is indeed possible to strike a fruitful balance between reduction of computational times and quality of the ensuing structural information. © 1996 John Wiley & Sons, Inc.
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    Ring currents in aromatic hydrocarbons (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 609-616 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coupled Hartree-Fock theory is used to compute and map the current density induced in planar hydrocarbons by an external magnetic field. Results of useful accuracy can be obtained with modest (6-31G**) basis sets by employing a continuous gauge transformation. Maps are presented and discussed for benzene, naphthalene, anthracene, tetracene, pentacene, heptacene, and biphenylene. © 1996 John Wiley & Sons, Inc.
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    Ultrafast processes in chemistry and photobioiogy, M. A. El-Sayed, I. Tanaka, and Y. Molin, Eds., Chemistry for the 2 1 st Century series, International Union of Pure and Applied Chemistry, published for IUPAC by Blackwell Science Ltd., Cambridge, Great Britain, 1995 (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 713-713 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600204
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    Structural and mechanistic organic chemistry: A tribute to professor Norman L. Allinger (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 715-715 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600205
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    An alternative way of solving secular equations for the Hamiltonian matrices of regular quasi-one-dimensional systems (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 717-729 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An alternative approach to secular problems for Hamiltonian matrices H of regular quasi-one-dimensional systems is suggested. The essence of this approach consists of the inverted order of operations against that of the traditional solid-state theory, viz., taking into account the local structure of the system is followed by regarding the translational symmetry of the whole chain. The first step is performed by reducing the initial system of secular equations into an effective N × N-dimensional secular problem, wherein a single equation corresponds to each of N elementary fragments of the initial chain. An implicit form of the dispersion relation and the level density function follow directly from the reduced problem without passing into the delocalized description of the system. The resulting eigenfunctions of the matrix H prove to be expressed as the Bloch sums of N nonorthogonal eigenvalue-dependent local-structure-determined orbitals of algebraic form, each of them corresponding to a definite elementary fragment of the chain. © 1996 John Wiley & Sons, Inc.
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    New “localized orbitals” appropriate for post-Hartree - Fock calculations (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 731-742 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work, we propose a new orbital set based on density matrices of subsystems. Most of the resultant orbitals are localized in the subsystems and resemble the natural orbitals of the subsystems. Correlation between two electrons, each in a distant localized orbital, should be small and the corresponding configurations can be neglected in a calculation. Test calculations are performed on hexatriene and the usefulness of these orbitals is shown. © 1996 John Wiley & Sons, Inc.
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    Substituent effects on methane activation and elimination by high-valent Zr complexes (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 779-788 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational study of substituent effects on methane activation and elimination by high-valent zirconium complexes is reported. Substituent (Z) effects (in a structural, electronic, and enthalpic sense) are substantially less important for the imido (LnZr(DOUBLE BOND)NZ) and imidolike TS than the amido (LnM(SINGLE BOND)NHZ). For the microscopic reverse reaction, methane CH activation, it suggests that tailoring imido reactivity through electronic modification of nitrogen substituents will be difficult. Analysis of the earliest part of the reaction coordinate for methane elimination entails structural deformation of the Zr - amido to assume an appropriate geometry for elimination, which, in some cases, is directly reflected in substantially higher elimination barriers. Lower elimination barriers correlate with stronger agostic bonding, providing further support for the crucial importance of agostic bonding in facilitating alpha-elimination processes for high-valent transition-metal complexes. © 1996 John Wiley & Sons, Inc.
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    Frontiers of chemical dynamics, edited by E. Yurtsever, Kluwer Academic Publishers, 1995, 406 pp. Hardcover, $1 87.00, ISBN 0-7923-3664-X (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 789-789 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600302
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  • 88
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    Masthead (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600701
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  • 89
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    Comparisons of the theoretical calculation of nitrogen clusters by semiempirical MO method (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1709-1718 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various nitrogen clusters, Nx, are selected for the present theoretical study. The number of nitrogen atoms chosen in this work varies from x = 8 to x = 32. PM3, which is known as one of the best semiempirical methods, is selected for the self-consistent molecular orbital calculations. The geometrical optimization, vibrational frequencies, and thermochemical computations are all involved for various types of molecular nitrogen clusters. The results show that all Nx's belong to the category of stable high-energy compounds. Comparison of average bond energy and delocalization energy of all cases reveals that N20(Ih symmetry) is the most stable molecule among all the nitrogen clusters studied. In addition, our results show five-membered rings are the most favored in the structures of nitrogen clusters (Nx). © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 90
    Electronic Resource
    Electronic Resource
    1996 Sanibel Symposia. List of participants (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. ix 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600702
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  • 91
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    Introduction (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1213-1213 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600703
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  • 92
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    Electronic Resource
    The Chairman's introductory remark (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1215-1215 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560600704
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  • 93
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    Comparative ab initio SCF conformational study of 4-chloro-indole-3-acetic acid and indole-3-acetic acid phytohormones (auxins) (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1727-1733 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio conformational analysis of 4-chloroindole-3-acetic acid was performed at the RHF/6-311G * * level. The mirror symmetrical conformer (in which the indole ring is coplanar with the COOH group) is most stable; next in energy are the two conformers with the C - COOH fragment perpendicular to the indole ring with relative energies of 2.72 and 6.69 kJ/mol. H(SINGLEBOND)Cl hydrogen bonding results in only a minor stabilization. The results are combined with those obtained earlier for indole-3-acetic acid and recent biological data regarding auxin (growth hormone) activity. From this, assumptions concerning the biologically active conformation are drawn. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 94
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    Electronic Resource
    UV photoelectron and ab initio quantum mechanical characterization of nucleotides: The valence electronic structure of anionic 2′-deoxyadenosine-5′-phosphate (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1735-1743 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: He(I) ultraviolet (UV) photoelectron spectroscopy and ab initio, self-consistent field (SCF) calculations with the 6-31G basis set have been employed to characterize the valence electronic structures of anionic 2′-deoxyadenosine-5′-phosphate (5′-dAMP-). Theoretical ionization potentials (IPs) of 5'-dAMP-, of the neutral model compounds 9-methyladenine (9-MeA) and 3-hydroxytetrahydrofuran (3-OH-THF), and of the model anion CH3HPO4- have been obtained by applying Koopmans' theorem to ab initio SCF results. The ionization potentials predicted from the SCF calculations have been compared to He(I) photoelectron spectra of 9-MeA and 3-OH-THF. The SCF calculations predict a value (8.45 eV), for the highest occupied π orbital in 9-MeA which agrees well with the experimental vertical IP (8.39 eV). However, IPs for the highest occupied lone-pair orbitals in 3-OH-THF are predicted to be more than 1.52 eV higher than the experimental IPs. Results from recently reported [H. S. Kim and P. R. LeBreton, Proc. Natl. Sci. USA 91, 3725-3729 (1994), and N. S. Kim and P. R. LeBreton, J. Am. Chem. Soc., 118, 3694 (1996)] second-order Møller-Plesset perturbation (MP2) calculations and configuration interaction calculations using the configuration interaction singles (CIS) method indicate that configuration interaction effects strongly influence the energies of the first five ionization events arising from removal of electrons from the closed-shell model anion CH3HPO4-. Results from the 6-31G SCF calculations of 5′-dAMP-, 9-MeA, 3-OH-THF, and CH3HPO4- indicates that valence orbital electron distributions in the nucleotide and in the model compounds and anion are similar. The correspondence between the orbital structure of the nucleotide, and the model compounds and anion makes it possible, employing experimental photoelectron data and MP2/CIS computational results for the model compounds and anion, to individually correct IPs calculated for the nucleotide at the 6-31G SCF level. Here, this approach has provided values for the 13 lowest IPs of 5′-dAMP- and indicates that the first IPs of the base, sugar, and phosphate groups are 6.1, 7.8, and 5.5 eV, respectively. © 1996 John Wiley & Sons, Inc.
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  • 95
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    Ab initio modeling of the interaction between guanine—cytosine base pair and mustard alkylating agents (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1745-1764 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interaction between the guanine-cytosine base pair and the episulfonium form of sulfur mustard (HD+) or the aziridinium form of nitrogen mustard (HN2+) was studied using the ab initio LCAO-MO method at the HF/6-31G level. The alkylation mechanism on the guanine N7 was analyzed by using a supermolecular modeling. Our stereostructural results associated with the molecular electrostatic potentials and highest occupied/lowest unoccupied molecular orbital (HOMO(SINGLEBOND)LUMO) properties show that in vacuum the alkylation of the N7 of guanine by HD+ in the agressive episulfonium form is a direct process without a transition state and of which the pathway is determined. Our study shows that interaction of guanine with the aziridinium form of HN2+ necessitates a transition state for the N7 alkylation route. When the N7 guanine alkylation by HD+ or HN2+ is achieved, about half of a positive charge moves from the alkylator toward the guanine in both cases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
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  • 96
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    Electronic Resource
    A comparative AM1 and ab initio study of the intramolecular proton transfer in tautomeric organic compounds (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1765-1773 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton-transfer barriers along the intramolecular hydrogen bond in a series of substituted salicylaldehyde anils were calculated using the AM1 SCF semiempirical method. The reliability of this method for the calculation of proton-transfer barriers was analyzed by the comparison of AM1 barriers for a series of different tautomeric organic compounds with those calculated using ab initio SCF and second-order perturbation theory with extended basis sets. In general, the AM1 method systematically overestimates the barrier height. However, this error is approximately constant for given pairs of groups involved in the intramolecular proton transfer. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 97
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    Electronic Resource
    AM1-based model system for estimation of brain / blood concentration ratios (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1775-1787 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Estimation of brain uptake of solutes and drugs would be useful in designing novel therapeutic agents. Given the problems associated with fragment-based models, including the need for strict additivity, we used AM1-derived molecular parameters in attempting to generate an equation for predicting the log of the brain-to-blood concentration ratios (log B:B) for a collection of compounds. Sequential fitting of the data using 10 AM1-derived variables indicated that dipole generated the most predictive one-term equation, dipole and log P, the best two-parameter system, dipole, log P, and molecular weight produced the optimal three-term model, and dipole, log P, molecular weight, and HOMO energy resulted in the best four-parameter paradigm. These systems were statistically similar to those generated using general solvation equations, but with the use of fewer parameters. An expanded parameter set may generated models of even better predictability. © 1996 John Wiley & Sons, Inc.
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  • 98
    Electronic Resource
    Electronic Resource
    DNA double-helix-mediated long-range electron transfer (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1789-1795 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theoretical analysis based upon large-scale self-consistent Hartree-Fock calculations at a semiempirical quantum theory level (CNDO/S) is performed to investigate long-range electron transfer in a donor-DNA-acceptor molecule, where the donor and acceptor moieties are tethered to the DNA. The π-stacked base pairs are found to dominate the long-range electronic coupling. Despite the π-electron mediated coupling, the exponential distance decay constant of the electron transfer rate is ∼ 1.2-1.6 Å-1, values typical of electron transfer proteins. The calculated long-range electron transfer rate of the order of 106 s-1 for a metal-to-metal distance of 21 Å is found to be in agreement with kinetic measurements by Meade and Kayyem. Based on the current analysis, the π-electrons dominate the long-range electronic coupling interactions in DNA, but they do not lead to one-dimensional molecular wire-like properties. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    Quantitative measures of molecular similarity: Methods to analyze transition-state analogs for enzymatic reactions (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1797-1804 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A formalism is presented for quantifying the similarity between any two molecules. The chemical descriptor used for comparison is the molecular electrostatic potential at the van der Waals surface. Thus, both the spatial properties of a molecule and its chemical features are captured in this approach. For molecules that are geometrically alike, the most useful similarity measure stems from orienting the two species so that their physical surfaces are aligned as well as possible, without regard to chemical patterns. After this alignment is achieved, a single measure sensitive to the spatial distribution of the electrostatic potential is used to rank the electronic similarity. Molecular similarity measures are applied to the enzyme systems AMP deaminase and AMP nucleosidase in order to understand quantitatively why their respective transition-state inhibitors bind more tightly than do their substrates. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 100
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    Electronic Resource
    Enzymatic transition states and inhibitor design from principles of classical and quantum chemistry (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1805-1813 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure is described which leads to experimentally based models for the transition-state structures of enzyme-catalyzed reactions. Substrates for an enzymic reaction are synthesized with isotopically enriched atoms at every position in which bonding changes are anticipated at the enzyme-enforced transition state. Kinetic isotope effects are measured for each atomic substitution and corrected for diminution of the isotope effects from nonchemical steps of the enzymic mechanism. A truncated geometric model of the transition-state structure is fitted to the kinetic isotope effects using bond-energy bond-order vibrational analysis. Full molecularity is restored to the transition state while maintaining the geometry of the bonds which define the transition state. Electronic wave functions are calculated for the substrate and the transition-state molecules. The molecular electrostatic potential energies are defined for the van der Waal surfaces of substrate and transition state and displayed in numerical and color-coded constructs. The electronic differences between substrate and transition state reveal characteristics of the transition state which permits the extraordinary binding affinity of enzyme-transition state interactions. The information has been used to characterize several enzymatic transition states and to design powerfully inhibitory transition-state analogues. Enzymatic examples are provided for the reactions catalyzed by AMP deaminase, nucleoside hydrolase, purine nucleoside phosphorylase, and for several bacterial toxins. The results demonstrate that the combination of experimental, classical, and quantum chemistry approaches is capable of providing reliable transition-state structures and sufficient information to permit the design of transition-state inhibitors. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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