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  • Insulin
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  • 1985-1989  (353)
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  • 1
    Digitale Medien
    Digitale Medien
    Plasma growth hormone-releasing hormone levels in type 1 (insulin-dependent) diabetic children following a mixed meal (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 257-260 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Growth hormone-Releasing hormone ; Somatostatin ; Insulin ; Type 1 diabetic patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Following a mixed meal, plasma hormone responses were measured in four type 1 diabetic children and in eight short normal children. Between 60 and 150 min after ingestion of the mixed meal there was a significant increase in circulating growth hormone-releasing hormone values both in diabetic and in normal children. Mean plasma GHRH peak values were not different between diabetic patients (27.0±3.9 ng/l) and controls (24.6±4.9 ng/l). No time relationship to spontaneous growth hormone peaks was observed. Whereas normal children showed a characteristic biphasic plasma somatostatin response, somatostatin plasma levels in diabetic children did not change. In normal children plasma insulin values increased between 30 and 150 min, but remained unchanged in type 1 diabetic patients. Blood glucose response was more pronounced in diabetic children than in short normal children. These results indicate that circulating growth hormone-releasing hormone does not play a dominant role in the regulation of insulin and somatostatin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01748167
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  • 2
    Digitale Medien
    Digitale Medien
    Abnormalities of carbohydrate metabolism in spontaneously hypertensive rats (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 924-927 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Hypertension ; Insulin ; Glucagon ; Skeletal muscle ; Glycogen ; Glucose ; Glycogen synthetase ; Glycogen phosphorylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The present study was performed to investigate as to whether peripheral insulin resistance exists in spontaneously hypertensive rats (SHR). After a 12 h fasting period, SHR had significantly higher serum glucose and higher plasma glucagon values in comparison to normotensive control rats (WKY). There was a tendency for higher serum insulin concentrations as well, but this difference did not reach significance. After oral glucose loading or glucose/insulin administration, serum glucose and insulin levels were also higher in SHR compared to WKY rats. Muscle glycogen and glucose concentrations were identical in fasted SHR and WKY rats. With an oral glucose load or glucose/insulin treatment there was a significant increase in muscle glycogen, whereas glucose values declined in skeletal muscle. Both total (a+b-form) phosphorylase activity as well as the active a-form of the enzyme were similar in skeletal muscle of SHR and WKY rats. Glucose/insulin administration or oral glucose loading induced a considerable reduction of both a+b-form and a-form activities. The decrease in muscle phosphorylase activities was almost identical in both groups of animals. There was also a comparable activity of muscle glycogen synthetase activity in all groups of rats. Despite subtile changes of glucose, glucagon and to a lesser degree insulin levels which would be suggestive of insulin resistance, the data obtained from skeletal muscle argue against peripheral insulin resistance in spontaneously hypertensive rats.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01728956
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  • 3
    Digitale Medien
    Digitale Medien
    A morphological analysis endocrine tumour genesis in pancreas and anterior pituitary of AVP/SV40 transgenic mice (1988)
    Springer
    Virchows Archiv 412 (1988), S. 255-266 
    Details
    ISSN: 1432-2307
    Schlagwort(e): AVP/SV40 transgenic mice ; Immunocytochemistry ; Insulin ; Pancreatic polypeptide ; Large T-antigen ; Heterochromatin ; Dysplasia ; Neoplasia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Insertion into the mouse genome of the hybrid oncogene made up of bovine vasopressin gene derived 5′ upstream sequences and the coding sequences of SV40 large T-antigen promoted tumours in anterior pituitary and endocrine pancreas of mice bearing this transgene. In order to investigate the morphology of the steps in the neoplastic process, we used light and electron microscopy to study these organs in 42 animals belonging to the 3rd, 4th and 5th generations, subdivided into 4 age groups from 20 days to 100 days of life. Antibodies to large T-antigen were used to identify sites of expression of the hybrid oncogene, thus monitoring the steps in neoplastic transformation. Large T-antigen immunoreactivity was identified in dysplastic lesions of younger animals and in both dysplastic lesions and tumours of older mice. Insulin (100% of cases) and pancreatic polypeptide (25% of cases) immunoreactivities were revealed in pancreatic lesions but no hormonal immunoreactivity was detected in the pituitary lesions. The ultrastructural study confirmed that the majority cell population of the pancreatic neoplasms was B-type and that the anterior pituitary tumours were poorly granulated. The subcellular localization of large T-antigen immunoreactivity was investigated by the immunogold method and was confined to the heterochromatin of tumour cell nuclei. These findings provide evidence for the dysplasia-neoplasia sequence in the genesis of endocrine tumours of pituitary and pancreas of transgenic mice. The vasopressin-SV40 large T-antigen transgenic mice may therefore be an useful model for the study of endocrine cell oncogenesis,
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00737150
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  • 4
    Digitale Medien
    Digitale Medien
    Enhancement of carbon tetrachloride-induced liver injury by glucagon and insulin treatment (1988)
    Springer
    Research in experimental medicine 188 (1988), S. 27-33 
    Details
    ISSN: 1433-8580
    Schlagwort(e): Carbon tetrachloride ; Insulin ; Glucagon ; Cytochrome P450
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Rats given a dose of carbon tetrachloride (CCl4) immediately received injections of glucagon and insulin every 4h. They frequently died after 4h and showed a significantly higher mortality between 8h and 28h as compared to the control rats where such deaths occurred 16h later. At 8h, the derangements of SGPT values and prothrombin time were significantly greater in the hormone-treated rats than in the control rats. In these CCl4-intoxicated rats, hepatic reduced glutathione content at 4h was significantly reduced after hormone treatment. The treatment significantly enhanced CCl4 metabolism, conversion of14CCl4 into14CO2 in vitro, by microsomes isolated from the liver, whereas it did not affect the microsomal cytochrome P450 content. These results suggest that glucagon and insulin treatment increased CCl4 hepatotoxicity in rats through activating the cytochrome P450-dependent mono-oxygenase system. This would merit consideration for the clinical application of this treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01852091
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  • 5
    Digitale Medien
    Digitale Medien
    Transient coappearance of glucagon and insulin in the progenitor cells of the rat pancreatic islets (1988)
    Springer
    Anatomy and embryology 178 (1988), S. 489-497 
    Details
    ISSN: 1432-0568
    Schlagwort(e): Pancreatic islet ; Insulin ; Glucagon ; Ontogeny ; Immunohistochemistry ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ontogenetic appearances of glucagon, insulin and tyrosine hydroxylase (TH) were immunohistochemically investigated on developing pancreatic islets of rats. Glucagon immunoreactivity appeared first in some epithelial cells (g-cells) of the dorsal anlage of the pancreas on day 11.5 of gestation. On day 12.5, g-cells increased in number manufacturing the primitive islets, in which some cells appeared to be immunoreactive for insulin (i-cells) and about 40% of g-cells indicated also a slight immunoreactivity for insulin (g/i-cells). Afterwards, all the islet cells, especially g-cells, increased in number, and almost half of g-cells were g/i-cells. After day 16.5 of gestation, numerical increase of the cells with insulin immunoreactivity exceeded that of the cells with glucagon immunoreactivity, and about one fifth of g-cells were g/i-cells. After 20.5 days, however, no g/i cells were found. On day 16.5 of gestation, the immunoreactivity for TH appeared in occasional cells of the islets, but the cells did not show immunoreactivity for glucagon or insulin. It is concluded that the progenitor cells of the pancreatic islets appear to synthesize both glucagon and insulin by day 20.5 of gestation, but differentiate giving rise to mature A and B cells of adult isoets afterward.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305036
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  • 6
    Digitale Medien
    Digitale Medien
    The pattern of basal and stimulated insulin responses to intravenous glucose in first degree relatives of Type 1 (insulin-dependent) diabetic children and unrelated adults aged 5 to 50 years (1988)
    Springer
    Diabetologia 31 (1988), S. 430-434 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; glucose ; age ; children ; puberty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The pattern of insulin secretion was studied in 107 normal individuals aged 5 to 50 years. Intravenous glucose tolerance tests were performed on 64 islet-cell antibody negative siblings of diabetic children and on 43 normal adults. Puberty was staged using Tanner's criteria and subjects were grouped as follows: I — stage 1 (n=22), II — stages 2 and 3 (n=18), III — stages 4 and 5 (n=20), IV — adults 〉17 years (n=47). Basal and stimulated (incremental 0–10 and 10–60 min areas) insulin responses rose throughout puberty (Groups I–III), declined following puberty until the third decade (Groups III and IV) and then appeared constant thereafter. Insulin levels in the 17.6–22.5 year group were lower than in the 12.6–15 year group (p〈0.01). Fasting insulin to glucose ratios and incremental 0–60 min insulin to glucose area ratios produced a similar age-related pattern indicating that changes in insulin levels were independent of glucose concentrations. Gender did not affect these changes and multiple regression analysis showed that HLA haplotype sharing did not influence insulin responses in siblings of diabetic patients. Age and pubertal status must be carefully considered when interpreting intravenous glucose tolerance tests from patients suspected of having early abnormalities of carbohydrate metabolism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00271587
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  • 7
    Digitale Medien
    Digitale Medien
    In vitro insulin action on erythrocyte glucose metabolism in normal and diabetic rats (1988)
    Springer
    Diabetologia 31 (1988), S. 51-53 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; erythrocyte ; diabetes ; glucose metabolism ; rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Alloxan-induced diabetes in rats significantly impaired the capacity of the erythrocytes to metabolise glucose in vitro to either lactic acid or CO2. Both these metabolic activities were initially insensitive to insulin in normal as well as in diabetic animals; but became responsive when these cells were subjected to insulin and glucose ‘starvation’ for 1 h through incubation in their absence. This action of insulin in starved cells showed concentration dependence and required preincubation with the hormone prior to addition of glucose.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279133
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  • 8
    Digitale Medien
    Digitale Medien
    Glucoregulatory function of glucagon in hypo-, eu- and hyperthyroid miniature pigs (1988)
    Springer
    Diabetologia 31 (1988), S. 368-374 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; glucagon ; thyroid hormones ; glucose turnover ; glucose production ; glucose utilisation ; glucoregulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The glucoregulatory function of glucagon was investigated in hypo-, eu- and hyperthyroid miniature pigs. Infusion glucagon, (3 ng x kg body weight−1 · min−1) transiently increased blood glucose (p〈0.01) and hepatic glucose production (p〈0.01) in euthyroidism, but was without effect in hyperthyroidism. Infusing glucagon plus somatostatin (2 ng x kg body weight−1 · min−1 and 0.2 μg x kg body weight−1 · min−1) transiently increased blood glucose (Δ 3.0 to 4.3 mmol/l) and hepatic glucose production (Δ 3.3 to 7.7 umol x kg body weight−1 · min−1) in all thyroid states, the effect was less pronounced in hyperthyroid pigs. By contrast, hypoglucagonaemia (74 to 107 pg/ml) at basal insulin (28 to 35 μU/ml) provoked hypoglycaemia (1.4 to 2.2 mmol/l) and a fall in glucose production (Δ 4.7 to 8.3 umol x kg body weight−1 · min−1), which was independent of the thyroid state; the effect was most pronounced in hyperthyroidism (p〈0.01). Hepatic glycogen content, arterial gluconeogenic precursor concentrations as well as the glycaemic response (Δ 0.60 mmol/l) to alanine infusion (23 umol x kg body weight−1 · min−1) were all unaffected by hyperthyroidism. We conclude that moderate experimental hyperthyroidism reduces glucagon action due to reduced glycogen mobilisation. This may in part result from increased insulin sensitivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02341505
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  • 9
    Digitale Medien
    Digitale Medien
    Ontogenic development of peptide hormones in the mammalian fetal pancreas (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 1-9 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Insulin ; glucagon ; pancreatic polypeptide ; somatostatin ; fetal pancreas ; ontogeny ; immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ontogeny of insulin, glucagon, PP and somatostatin in the mammalian fetal pancreas has been examined in recent years largely by immunocytochemistry and in some instances by radioimmunoassay. Complete ontogenic data are available only for the rat, human pig and sheep. Figure 3 compares the time of appearance of the endocrine cell-types within the fetal pancreas when the periods of gestation of the four species are converted to a uniform scale. The striking ontogenic difference in the rat probably reflects the immaturity of the rodent fetus at birth compared with the human, pig and sheep. In the fetal pancreas, differences in cell number of glucagon and PP cells in the dorsal and ventral lobes become apparent from an early gestational period. Factors responsible for the functional and structural maturation of the fetal pancreatic endocrine cells and the processes involved in pancreatic organogenesis are poorly understood. Studies in these areas would have clinical implications since it may be possible in the future to employ agents for selective replication of fetal β-cells for transplantation in patients with Type I diabetes, bearing in mind that such cells must have the capacity to respond to normal stimuli and repressors when transplanted. The presence of the other islet cell-types may be obligatory for these appropriate responses. This would require a more complete knowledge of those factors which produce the normal selectivity of the four hormonal cell-types.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01960221
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  • 10
    Digitale Medien
    Digitale Medien
    The packing of acetylcholine into quanta at the frog neuromuscular junction is inhibited by increases in intracellular sodium (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 258-263 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Acetylcholine ; Quanta ; Na+−K+ exchange pump ; Ouabain ; Adrenaline ; Insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Pretreatment with hypertonic solutions, insulin, or adrenaline increases the size of quanta at the frog neuromuscular junction, as determined by measurements of miniature end plate potentials or currents (Van der Kloot and Van der Kloot 1985, 1986). The increase in quantal size apparently is due to an increase in acetylcholine (ACh) content of individual quanta. These treatments, therefore, can be used to study the packaging of ACh. Previously, I reported that increases are blocked by an inhibitor of active ACh uptake into vesicles (Van der Kloot 1986b, 1987b). The present study shows that the increases in quantal size were antagonized by inhibiting the Na+−K+ exchange pump with 100 μM ouabain, 10 μM dihydroouabain, or K+-free solutions. The increases in quantal size were also antagonized by 10 μM monensin, a Na+ ionophore, or by 5 μM aconitine, which opens Na+ channels at normal resting potentials. Apparently a rise in intracellular [Na+] inhibits the addition of ACh to quanta. The mechanism by which a rise in intracellular Na+ inhibits ACh packing is unknown, but apparently it is not due to inhibition of choline reuptake into the terminals. Also consistent with the above hypothesis is that the increase in quantal size following depolarization for 2 h in elevated [K+]out was substantially enhanced when tetrodotoxin (TTX) was present, suggesting that in the absence of TTX there is a rise in [Na+]in that antagonizes the incorporation of additional ACh into the quanta.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00582506
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  • 11
    Digitale Medien
    Digitale Medien
    Insulin receptors along the rat nephron: [125I] Insulin binding in microdissected glomeruli and tubules (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 604-612 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Nephron microdissection ; Glomeruli ; Tubules ; [125I] Insulin binding ; Insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Binding of [125I] Tyr A14 human insulin ([125I] insulin) was measured at 4°C in glomeruli and pieces of tubule microdissected from collagenase-treated rat kidneys. For glomeruli and all segments tested, total and non specific binding increased linearly with glomeruli number or tubular length. When determined with 4.0 nM labelled hormone, the distribution of specific binding sites (expressed as 10−18 mol [125I] insulin bound per glomerulus or mm tubule length) was as follows: glomerulus, 2.5±0.3; proximal convoluted tubule (PCT), 12.6±0.6; pars recta (PR), 4.0±2.3; thin descending limb (TDL), 0.6±0.2; thin ascending limb (TAL), 0.6±0.2; medullary thick ascending limb (MAL), 0.8±0.1; cortical ascending limb (CAL), 2.1±0.1; distal convoluted tubule (DCT), 5.6±1.1; cortical collecting tubule (CCT), 3.2±0.3 and outer medullary collecting tubule (MCT), 2.3±0.1. Specific [125I] insulin binding to glomeruli and tubule segments was time- and dose-dependent, saturable, reversible after elimination of free labelled ligand, and inhibited by unlabelled human insulin. When analysed in Scatchard and Hill coordinates, the binding data revealed a negative cooperation in the interaction processes between [125I] insulin and glomerular and tubular binding sites, with apparent dissociation constants and Hill coefficients of the following values: glomerulus, 0.6 nM and 0.60; PCT, 10.0 nM and 0.55; MAL, 4.3 nM and 0.80; CAL, 2.0 nM and 0.74; CCT, 7.6 nM and 0.80 and MCT, 1.0 nM and 0.57 respectively. The stereospecificity of nephron binding sites was assessed in competitive experiments showing that unlabelled bovine and procine insulins were as efficient as human insulin for displacing [125I] insulin, whereas A and B chains of insulin and unrelated peptide hormones were almost inactive. These results indicate that the detected [125I] insulin binding sites may correspond to physiological insulin receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00583761
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  • 12
    Digitale Medien
    Digitale Medien
    Electron microscope localisation of insulin-like immunoreactivity of conventionally processed human insulinomas (1988)
    Springer
    Virchows Archiv 412 (1988), S. 443-450 
    Details
    ISSN: 1432-2307
    Schlagwort(e): Insulin ; Insulinomas ; Ultrastructure ; Immunogold technique
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Localisation of insulin-like immunoreactivity has been studied using the immunogold staining procedure on thin sections of 6 human insulinomas, conventionally processed for electron microscopy. The labelling was restricted to the secretory granules. Depending on their morphology, these either resembled B-cell granules of human adult pancreas or belonged to the atypical (non-diagnostic) group. Within the former group, those with a crystalloid core or an amorphous dense or moderately dense core were strongly immunoreactive, whereas others, filled with a pale material, were poorly labelled. Most granules of this type were stored together within the heavily granulated cells of 3 insulinomas, presenting the classical features of clinical and biological behaviour and a typical light microscopic staining pattern. In contrast, the non-diagnostic granules, characterized by their smaller size, a very dense core and a thin halo, were mainly found within the poorly granulated cells making up the other tumours, and showed a very uneven labelling. Strongly labelled granules were found in one insulinoma that also belonged to the classical type; these were stored together with a few diagnostic granules within the same cells. Only poorly labelled atypical granules were present in two cases revealing a number of unusual features; these included moderate elevation of insulinaemia, uncertain tumour histology, as well as weak immunostaining for insulin/proinsulin and variable argyrophilia of the tumour in paraffin sections. These findings suggest that human insulinomas differ not only in storage capacity but also in their degree of granule maturation. This may involve some deficiency of either the prohormone conversion or the subsequent processing of the cleavage products.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00750578
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  • 13
    Digitale Medien
    Digitale Medien
    Lysosomes and pancreatic islet function (1988)
    Springer
    Cell & tissue research 252 (1988), S. 9-15 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pancreas, endocrine ; Insulin ; Immunocytochemistry ; Lysosomes ; Crinophagy ; Mouse (NMRI)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Ultrastructural studies of pancreatic islets have suggested that crinophagy provides a possible mechanism for intracellular degradation of insulin in the insulin-producing B-cells. In the present study, a quantitative estimation of crinophagy in mouse pancreatic islets was attempted by morphometric analysis of lysosomes containing immunoreactive insulin. Isolated islets were incubated in tissue culture for one week in 3.3, 5.5 or 28 mmol/l glucose. The lysosomes of the pancreatic B-cells were identified by morphological and enzyme-cytochemical criteria and divided into three subpopulations comprising primary lysosomes and insulin-positive or insulin-negative secondary lysosomes. Both the volume and numerical density of the primary lysosomes increased with increasing glucose concentration. The proportion of insulin-containing secondary lysosomes was highest at 5.5 and lowest at 3.3 mmol/l glucose. Insulin-negative secondary lysosomes predominated at 3.3 mmol/l glucose. Studies of the dose-response relationships of glucose-stimulated insulin biosynthesis and insulin secretion of the pancreatic islets showed that biosynthesis had an apparent Km-value for glucose of 7.0 mmol/l, whereas it was 14.5 mmol/l for secretion. The pronounced crinophagic activity at 5.5 mmol/l glucose may thus be explained by the difference in glucose sensitivity between insulin biosynthesis and secretion resulting in an intracellular accumulation of insulin-containing secretory granules. The predominance of insulin-negative secondary lysosomes at 3.3 mmol/l glucose may reflect an increased autophagy, whereas the predominance of primary lysosomes at 28 mmol/l glucose may reflect a generally low activity of intracellular degradative processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00213820
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  • 14
    Digitale Medien
    Digitale Medien
    TRH-like immunoreactivity in endocrine cells and neurons in the gastro-intestinal tract of the rat and guinea pig (1988)
    Springer
    Cell & tissue research 253 (1988), S. 347-356 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pancreas, endocrine ; Stomach ; Intestine ; Immunohistochemistry ; Thyrotropin-releasing hormone (TRH) ; Somatostatin ; Avian pancreatic polypeptide ; Insulin ; Gastrin ; Rat ; Guinea pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary By use of the indirect immunofluorescence technique, the cellular localization of thyrotropin-releasing hormone (TRH) was studied in the gastrointestinal tract of rats and guinea pigs of different ages. TRH-like immunoreactivity (LI) was observed in many pancreatic islet cells of young rats and guinea pigs but only in single cells of 6-month-old rats. In aged guinea pigs, a reduction in the number of TRH-positive cells was evident; however, numerous strongly fluorescent cells were still present. In the guinea pig, TRH-LI was in addition observed in gastrin cells in the stomach. TRH-positive nerve fibers occurred in the myenteric plexus of the oesophagus, stomach and intestine of the rat, and in the muscle layers of the guinea pig. These results suggest a functional role of TRH both as hormone and neuroactive compound in various portions and sites of the gastro-intestinal tract of the rat and guinea pig
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00222291
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  • 15
    Digitale Medien
    Digitale Medien
    Lipoprotein lipase activity in skeletal muscle and adipose tissue of marathon runners after simple and complex carbohydrate-rich diets (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 75-80 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Energy metabolism ; Carbohydrate-rich diet ; Lipoprotein lipase ; Free fatty acids ; Insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A comparison of the influence of simple and complex carbohydrate (CHO) consumption on adipose tissue- and skeletal muscle-lipoprotein lipase activity (AT-LPLA, SM-LPLA) was examined. Twenty male marathon runners were divided into two equal dietary groups: simple-CHO and complex-CHO. Half of the subjects in each group consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days. Immediately following this dietary period, the subjects consumed a CHO-rich diet (70% E intake) predominant in simple-CHO or in complex-CHO for an additional 3 days. Thereafter, all subjects returned to a normal mixed diet. Skeletal muscle biopsies, adipose tissue aspirations, and venous blood samples were obtained prior to dietary manipulation (PRE), upon completion of the 6 day diet (POST I), and 2 weeks after returning to a normal diet (POST II). The samples were analysed for AT-LPLA, SM-LPLA, serum insulin, and free fatty acids (FFA), and blood glucose, and lactate. SM-LPLA fell 71% from PRE values of 0.39±0.30 μ mol · g−1 · h−1 to POST I values of 0.11 ±0.09 μ mol · g−1 · h−1 (means±SD) (p〈0.05), after a complex-CHO diet. However, the simple-CHO diet did not alter SM-LPLA. AT-LPLA similarly decreased (p〈0.05) after the complex-CHO diet, and no significant decrease was noted after the simple-CHO diet. Serum FFA decreased significantly (p〈0.05) after a simple-CHO diet (0.82±0.13 to 0.65±0.10 mmol l−1) but were unchanged after a complex-CHO diet. Blood glucose and lactate, and serum insulin were not altered following a CHO-rich diet.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00691242
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  • 16
    Digitale Medien
    Digitale Medien
    Metabolic effects of glucose, medium chain triglyceride and long chain triglyceride feeding before prolonged exercise in rats (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 126-131 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Glucose and fat feeding ; Glycogen sparing ; Ketone bodies ; Insulin ; Lipolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The purpose of this study was to test the hypothesis that oral ingestion of lipids could increase endurance by slowing the rate of glycogen depletion. Trained rats were killed after a 2 h run on a rodent treadmill, following an intragastric infusion of water, glucose, medium chain triglycerides (MCT) or long chain triglycerides (LCT). Glucose and triglycerides were administered in equicaloric concentrations (50 kJ). The results show that oral ingestion of lipids (MCT or LCT) did not reduce glycogen depletion in liver, heart or skeletal muscle after exercise whereas the fat diet increased muscle and heart glycogen stores in resting conditions. In contrast, glucose feeding induced a significant sparing effect on endogenous carbohydrate utilization and reduced physical exercise lipolysis. These data indicated, firstly, that enhanced lipid availability induced by a single lipid meal before exercise was not able to modify the glycogen depletion occuring after exercise and, secondly, that the glucose/fatty acid cycle was not effective in these conditions. The comparison between lipids indicated that the effect on glycogen use of MCT did not differ from that of LCT, and did not seem to be of any particular importance during physical exercise.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00691251
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  • 17
    Digitale Medien
    Digitale Medien
    Comparison of penetration-enhancing ability of laurocapram, N-methyl-2-pyrrolidone and dodecyl-L-pyroglutamate (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 189-192 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Absorption, transdermal ; Brilliant Blue ; Dodecyl-l-pyroglutamate ; Insulin ; Laurocapram ; N-Methyl-2-pyrrolidone ; Permeability, enhancement
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The study reports on penetration enhancers used to improve drug absorption through the skin. All experiments were carried out in permeation cellsin vitro. Insulin (2.5 mg/ml) and Brilliant Blue (50.0 mg/ml) served as model drugs. They were formulated into a 40% solution of propylene glycol with increasing concentrations ofN-methyl-2-pyrrolidone (NMP) (0.0 to 20.0%), dodecylazacycloheptan-2-one (laurocapram) and a new compound dodecyl-l-pyroglutamate (DLP; 0.0 to 0.5%). The maximum amount of insulin permeated within 24 h was almost 200 μU/ml in the case of 0.1% laurocapram, while in the case of 0.1% DLP it was approximately half of that. The optimum concentration of NMP was 12.0%. Experiments performed with Brilliant Blue showed no significant difference among formulations containing either 6.0, 12.0 or 20.0% of NMP. When NMP was omitted, flux, permeability as well as the maximum concentration estimated after 26 h reached 50% of the values obtained with NMP. The lag time was twice as long in this case in comparison with the formulations containing NMP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01956869
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  • 18
    Digitale Medien
    Digitale Medien
    Adsorption of human and porcine insulins to intravenous administration sets (1988)
    Springer
    Pharmacy world & science 10 (1988), S. 213-216 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Adsorption ; Equipment and supplies ; Infusions, parenteral ; Insulin ; Polyethylenes ; Polyvinylchloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A comparison between human and porcine insulins with regard to their adsorption to administration sets was performed. A125I-mono(A14)-iodinated insulin was used to follow the adsorption phenomenon over time and the adsorption was quantified with radioimmunoassays of unlabelled insulin. The obtained data were similar for both methods. No relevant difference in adsorption was found between human and porcine insulin. Both insulins showed a significantly more pronounced initial drop in delivered insulin when polyethylene tubing was used. After 3 h a steady state was reached, resulting in the administration of a more predictable dose. Particularly in the initial phase an important reduction in the amount of both insulins actually delivered to the patient was observed when compared to the expected amount as calculated from the concentration present in the container and the infusion rate. Therefore, the mainstay in treatment of a patient with ketoacidosis remains frequent serum glucose measurement and making appropriate infusion rate adjustments on that basis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01956873
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  • 19
    Digitale Medien
    Digitale Medien
    Insulin effect on GABA uptake in astroglial primary cultures (1988)
    Springer
    Neurochemical research 13 (1988), S. 1119-1124 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Insulin ; astroglia ; cultures ; GABA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Astroglial cultures from newborn mouse cerebral cortex contain [125I]insulin binding sites. Binding was specific reversible, time dependent and reached equilibrium after 45 min. Insulin analogues compete for this [125I]Insulin binding. Incubation of cerebral cortex astroglial cultures with insulin induced a time-and dose-dependent inhibition of the [3H]GABA high affinity uptake. A decrease in theV max rather than, an effect on theK m was observed. This effect was dose-dependent and effective at 10−10 M. Autoradiographic observations on the cell monolayer showed the presence of two groups of cells: one which strongly takes up [3H]GABA and consist in smaller GFAP positive process-bearing cells and another group of much flatter and larger GFAP positive cells which uptake was lower. The smaller stellate cells were apparently the most sensitive to insulin effect. These results: 1) confirm the presence of insulin binding sites on astroglial primary cultures, 2) show an effect of insulin of [3H]GABA high affinity uptake of these cells; this effect being optimal on a stellate-like population of astrocytes, and 3) indicate, that insulin may interfere in neuromodulation through astroglial signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00971628
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  • 20
    Digitale Medien
    Digitale Medien
    Insulin: Its binding to specific receptors and its stimulation of DNA synthesis and 2′,3′-cyclic nucleotide phosphohydrolase activity in cerebral cells cultured from embryonic mouse brain (1988)
    Springer
    Neurochemical research 13 (1988), S. 429-433 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Insulin ; receptors ; brain ; cultures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The presence and specificity of insulin receptors was investigated in cultured cells obtained from 15–16 days old embryonic mouse cerebra. Developmental studies suggested that the maximum insulin binding occurred at about 11 days in vitro (DIV). Scatchard analysis of binding data revealed two types of binding sites. One type of receptor was the high affinity type (K d=7.77×10−9 M; number of receptor sites,B max=350 fmol/mg protein) while the other type was of low affinity type (K d=5.75×10−8 M;B max=1150 fmol/mg protein). The specificity of receptors for insulin was also confirmed by showing that [125I]insulin was displaced by non-radioactive insulin but not by glucagon or growth hormone. Insulin displayed a clear dose-dependent stimulation of thymidine incorporation. It also stimulated the activity of the enzyme 2′,3′-cyclic nucleotide phosphohydrolase (CNPase), which is specifically associated with myelin produced from oligodendroglia. Thus insulin has a positive influence on the proliferation and differentiation of brain cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01268877
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  • 21
    Digitale Medien
    Digitale Medien
    Effects of insulin on rat brain noradrenaline (1988)
    Springer
    Neurochemical research 13 (1988), S. 887-892 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Insulin ; streptozotocin ; diabetes ; noradrenaline ; dopamine ; p-tyrosine ; hypothalamus ; olfactory tubercles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A single intracardial injection of streptozotocin produced a significant increase in rat hypothalamic noradrenaline while no changes were observed in the olfactory tubercles. The parenteral administration of a single dose of insulin decreased rat hypothalamic noradrenaline; the effect had a rapid onset and lasted for at least six hours. Similar noradrenaline reductions were observed in the olfactory tubercles but in this tissue the depletion started later and recovered earlier. In addition, in olfactory tubercles after insulin injection, tyrosine level and dopamine metabolism were increased. The results show that the increases in hypothalamic NA observed in streptozotocin diabetic rats are counteracted by insulin administration and possibly the consequence of changes in noradrenaline turnover.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00970758
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  • 22
    Digitale Medien
    Digitale Medien
    Erratum (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 585-585 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330614
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  • 23
    Digitale Medien
    Digitale Medien
    Theoretical studies on conformational preferences of model modified nucleic acid base N6-(N-alanylcarbonyl) adenineNCL Communication No. 4069. (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 37-46 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational preferences of model modified nucleic acid base N6-(N-alanylcarbonyl) adenine, ac6Ade, have been investigated using the quantum chemical PCILO (perturbative configuration interaction using localized orbitals) method. The multidimensional conformational space has been searched using selected grid points formed by combining the various torsion angles that take favored values derived from energy variation with respect to each torsion angle individually.The preferred molecular structure is stabilized by an intramolecular hydrogen bond from N(11)H of the amino acid to N(1) of the adenine. The observed crystal structure conformations for the naturally occurring, anticodon adjacent, threonyl analogs, tc6Ade, correspond to the predicted most stable conformation for the model modified base ac6Ade. Three stable, low energy conformations differing in the orientations of the carboxyl group and the amino acid side chain are predicted within 1 kcal/mol of the most stable structure. The possible bifurcated hydrogen bonding of N(11)H with N(1) and either of the carboxyl oxygens is of minor significance.The indicated orientational flexibility for the carboxyl group and the amino acid side chain may enable convenient probing of the molecular environment, in the vicinity of the anticodon in tRNA, by the amino acid substituent, with only modest changes in energy stabilization.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340106
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  • 24
    Digitale Medien
    Digitale Medien
    Erratum (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 89-90 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340111
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  • 25
    Digitale Medien
    Digitale Medien
    A regular periodic table of the elements and its quantum mechanical requirement (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 107-119 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By using the n + (1/2)l filling rule of the atomic Aufbau principle, where n is the principal quantum number and l is the azimuthal quantum number, a new periodic table is presented, its periods having, in order, 8, 18, 18, 32, 42, 50, … elements. The mentioned rule is proposed instead of the n + l rule (or Madelung's rule) which constitutes the quantum mechanical basis of the current periodic table and predicts periods having, in order, 2, 8, 8, 18, 18, 32, 32, 50, … elements. The new periodic table is called “regular” because its groups are formed according to a single rule (namely, the first elements of each period are placed in the same order as the elements of the preceding period), in contrast with the current periodic table, where no simple rule can be applied for the same purpose. The most characteristic feature of the regular periodic table is the fact that its groups are also related in a periodic manner.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340204
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  • 26
    Digitale Medien
    Digitale Medien
    Control over theoretical descriptions of atoms and molecules. An information theoretic approach to the automatic classification and systematic improvement of approximate wave functions (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 185-190 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A rigorous approach to the study of the quality of theoretical descriptions of atoms and molecules is proposed. Theoretical descriptions, i.e., collections of atomic or molecular properties obtained via quantum chemical methods, are associated with information quantities defined with respect to reference theoretical or experimental data. In this way the comparison of two theoretical descriptions is reduced to the comparison of the respective information quantities. An increase in information is interpreted as improvement of the theoretical description. The aforementioned approach should be useful in problems related to classifications and systematic improvements of approximate wave functions and consequently for comparing the performance of quantum chemical methods in calculations of atomic and molecular properties. This approach should also constitute a powerful tool for the construction of suitable basis sets for use in calculations of atomic and molecular properties.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340209
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  • 27
    Digitale Medien
    Digitale Medien
    Spin and charge densities from Hiller-Sucher-Feinberg identities. Test calculations for He, B, C, N, O, and F atoms and H2O, N2, and CH3 molecules (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 195-197 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340212
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  • 28
    Digitale Medien
    Digitale Medien
    Fifth-order constant denominator perturbation therory within a localized bond model: Contributions from single and double excitations (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 497-527 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A Fifth-order constant denominator perturbation treatment of all single and double excitations occuring in the third-order perturbation wave function is presented for the perturbation configuration interaction using localized orbitals (PCILO) method. Contributions from triple and quadruple excitations which decay back to singles and doubles at third order are automatically included in this theory. This method is computationally very fast, with an execution speed proportional to N3, Where N is the number of orbitals present. A [2,1] Padé approximate involving only singles and doubles contributions through to fifth order is shown to be remarkably accurate.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330604
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  • 29
    Digitale Medien
    Digitale Medien
    Hall transformation of exp( - r): Correction of the results (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 563-566 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Owing to an error in his determination of the repulsion integral and the kinetic energy. Hall's results [1] for the ground state of atomic two-electron systems are wrong. Here these results have been corrected. For Z ≤ 5, the results have been obtained by determining the pertinent integrals numerically: but for Z ≥ 5, these can be found sufficiently accurately from Z expansions.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330608
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  • 30
    Digitale Medien
    Digitale Medien
    Ab-initio calculation of resonance states of H2O (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 567-576 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In a dissociation attachment experiment of water, three peaks were observed at 7,9, and 12 eV. The origin of the third peak has been believed to be 2B2. However, the calculated energy of this state is 0.6 eV higher than the experimental value. This discrepancy is quite large compared with the case of the lower two peaks. In this study we propose new candidates for resonant states responsible for the third peak. The configurations considered are (3a1)-1(3pa1)2, (3a1)-1(3pb1)2, (3a1)-1(3pb2)2, (3a1)-1(3pa1)1(3pb1)1, (3a1)-1(3pb2)1(3pa1)1, and (3a1)-1(3pb2)1(3pb1)1 which have the parent state (3a1)-1(3pa1)1, (3a1)-1(3pb1)1, or (3a1)-1(3pb2)1. The energy levels arising from these configurations are calculated by a method of configuration interaction. A Few resonance states, which could be responsible for the third peak, are found. New decay process of these states are proposed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330609
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  • 31
    Digitale Medien
    Digitale Medien
    The sequential product of geminals and the ground states of some atoms (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 9-14 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By means of the SPG function which is associated with an extreme point of the set of N-representable second-order reduced density matrices, an attempt is made to perform the calculations of the ground states of some atoms with four electrons such as Be. The results show that the SPG function is as suitable as the well-known AGP function for approximating the ground states of atoms and molecules.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340103
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  • 32
    Digitale Medien
    Digitale Medien
    A sequential product of geminals and its applications (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 15-23 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper, an SPG function, which is associated with an extreme point of the set of N-representable second-order reduced density matrices, is used to perform the calculation of the ground state energy of LiH with the variation of internuclear separation. The result of our calculation essentially is in accordance with that of AGP function.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340104
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  • 33
    Digitale Medien
    Digitale Medien
    The concept of the topological atom within the MO-LCAO approach. II. On the nature of the nephelauxetic effect (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 1-8 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new MO-LCAO description of the nephelauxetic effect is proposed based on the concept of the topological atom and on the method of reduced density matrices. This approach allows one to overcome some conceptual difficulties of ligand-field theory and to derive effective parameters of d-d electron repulsion of a bound transition-metal in a proper way. The two ligand-field mechanisms of the nephelauxetic effect - the central field covalency and the symmetry-restricted covalency - are clarified and generalized. In addition, a new factor, important for the nephelauxetic effect is found: its size-dependence on the region of the topological atom.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340102
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  • 34
    Digitale Medien
    Digitale Medien
    A Crystal Orbital approach for two- and three-dimensional solids on the basis of CNDO/INDO Hamiltonians. Basis equations (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 47-71 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A Hartree-Fock (HF) self-consistent field (SCF) crystal orbital (CO) formalism for two- and three-dimensional (2D/3D) solids on the basis of semiempirical CNDO/INDO (complete neglect of differential overlap; intermediate neglect of differential overlap) Hamiltonians is presented. The employed SCF variants allow for the treatment of atomic species up to bromine under the inclusion of the first (i.e., 3d) transition metal series. Band structure investigations of 2D and 3D materials containing more than 30 atoms per unit cell are feasible by the present SCF HF CO formalism. The theoretical background of the computational scheme is given in this contribution. Special emphasis is placed on physically reliable truncation criteria for the lattice sums, the adaptation of the crystal symmetry in k space, as well as the suitable choice of domains in Brillouin zone (BZ) integrations required in the determination of charge-density matrices. The capability and limitations of the semiempirical SCF HF CO approach is demonstrated for some simpler solids by comparing the present computational results with those of ab initio CO schemes as well as conventional numerical methods in soid-state theory. The employed model solids are graphite and BN (2D and 3D networks for both solids) as well as diamond, silicon, germanium, and TiS2.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340107
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  • 35
    Digitale Medien
    Digitale Medien
    Long distance electron transfer (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 1-22 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quantum mechanical models to treat long distance electron transfer are being developed. The model is based on the theory of R.A. Marcus. Our contribution is in the calculation of the electron coupling factor k. Estimations of the latter number, as well as the bond and solvent relaxation energies, λi and λo, respectively, are necessary to be able to calculate the rate constant for a reaction of the conductivity in an electric field. k may be approximately calculated from orbital energy differences at avoided crossings between orbitals localized in different parts of the system. A novel spectroscopic NDO method is suggested in which one may include any atom of the periodic table. Another problem discussed is the inclusion of electronic relaxation effects of the solvent or protein in the calculation. Applications are made to systems where metal ions are connected by organic bridges of different kinds such as dipyridine with coplanar and perpendicular pyridyl groups. As expected the electronic factor depends strongly on the conformation of the bridge. A strong conformational dependence is also obtained for a saturated bridge of the type NH2 · (CH2)n · NH2. In another study we use an α helix as a bridge between two metal ions. If one glycine in this α-helix is substituted by phenylalanine the electronic factor increases by factors of 1.5-10. It is suggested, however, that larger enhancement factors are possible if an aromatic group is positioned in a favorable way. The CNDO/S method is used to study the charge separation process in a bichromophoric molecule and in the reaction center (RC) of Rhodopseudomonas viridis. In those cases where the electronic coupling is large enough for the charge transfer states to be seen in the spectrum, the calculated results agree well with the experimental ones, but suggest a novel assignment. The CNDO/S results verify that electron transfer is possible through saturated spacers. In the special pair of RC the S1 state is calculated at approximately the correct position. Like the ground state, it has a delocalized character.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340704
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  • 36
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    Digitale Medien
    Electrostatic interactions and conformation of some thromboxane antagonists (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 67-84 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A class of thromboxane antagonists exists where the prostaglandin side chain containing the C16 hydroxyl moiety is replaced by a phenyl ring, and the bridged six-membered pyranose moiety by cyclohexane, pyranose and dioxane ring systems. Analysis of antagonist potency data in terms of a binding constant model previously used for membrane bound receptor-drug interactions shows that the major patterns of antagonist potency are governed as much by axial/equatorial conformer preference of the phenyl moiety and its orientation as by electrostatic effects of the aliphatic ring oxygen atoms. The conformational restriction of the two substituted side chains of the σ-bonded 6-membered ring is shown to be a primary requirement for binding to thromboxane receptors, and a quantitative separation of electrostatic and conformational components in the potency data is attempted.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340708
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  • 37
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    Digitale Medien
    An ab initio molecular orbital study of hydrogen bonding and ion-molecule association in model systems for DNA bases (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 119-135 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio calculations have been performed to investigate hydrogen bonding and ion-molecule association in complexes of H2O with the neutral, protonated, and Li+ complexes of N-formylformaldehyde and N-formylformamidine. In the complexes with the neutral bases, H2O assumes an in-plane bridging position in the amide and amidine regions. The most stable complex is the bridging N-formylformamidine-H2O complex in the amidine region, which has an MP2/6-31 + G(d,p) binding energy of -9 kcal/mol. Hydrogen bonded complexes of H2O with the oxygen-protonated bases have open structures with the protonated bases as proton donors, and binding energies ranging from -16 to -24 kcal/mol. Nitrogen protonation of N-formylformamidine leads to an equilibrium chelated hydrogen bonded structure with a stabilization energy of -21 kcal/mol. When Li+ associates with these bases at a carbonyl oxygen, hydrogen-bonded bridging structures with H2O reappear, and wobble complexes exist in the amide and amidine regions of N-formylformaldehyde and N-formylformamidine. These complexes have binding energies of -13 to -14 kcal/mol. However, the most stable comples has H2O directly bonded to Li+, with an MP2 binding energy of -30 kcal/mol. No hydrogen bonded structures of H2O with N-formylformamidine exist in the amide region when Li+ associates with this base at the C=N group. Hydrogen bond energies computed at the single-determinant Hartree-Fock level with the 6-31G(d) basis set approximate correlated MP2/6-31 + G(d, p) energies to within 1 kcal/mol for all of the neutral and charged complexes. However, when H2O is bonded to Li+, HF6-31G(d) association energies overestimate MP2/6-31 + G(d, p) energies by 3 kcal/mol.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340712
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  • 38
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    Digitale Medien
    Dependence of MO shapes on a continuous measure of delocalization (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 1-13 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Whereas localization of orbitals has long been a tool for a semiclassical interpretation of chemical properties, it is in fact electron delocalization that is a fundamental property of quantum mechanical molecules. A mathematically well-defined measure is suggested for the degree of delocalization of molecular orbitals. It is shown that an orbital set of maximum delocalization exists for which the degree of delocalization depends on the charge distribution of the molecule. Hartree-Fock canonical orbitals are definitely more localized than the most uniformaly distributed MO's giving an equivalent description of the molecule. The changes in the geometrical shape of molecular orbitals are studied passing (quasi-) continuously from the strongly localized description towards the most delocalized picture. In the case of charge-inhomogeneities even the most delocalized orbitals remain rather compact. The degree of maximum delocalization may be correlated with chemical properties such as reactivity. The shape distortion of MO's under the perturbing effect of other ions and small molecules is investigated in several examples.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340804
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  • 39
    Digitale Medien
    Digitale Medien
    Density and density matrix from optimized linearly independent product basis functions for Be (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 43-49 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The density matrix was computed from the density using basis orbitals which form linearly independent products (LIP). Calculations were performed on the Be atom using LIP bases containing several of the natural spin orbitals from an accurate nonrelativistic 650-term configuration interaction (CI) wavefunction. Calculations were also performed using a basis set of 6 s-type orbitals optimized so that the lowest eigenvalue, d1, of the overlap matrix of products is maximized and the energy of a small CI wavefunction is minimized. The value of d1 in the optimized basis is 1 × 10-7. The density and the potential energy obtained from the 650-term CI wavefunction were accurately reproduced by the density matrix expressed in the optimized LIP basis, but the kinetic energy was somewhat less accurate.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340809
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  • 40
    Digitale Medien
    Digitale Medien
    Geometry optimization using local-density functional methods: Numerical aspects (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 77-84 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The need to perform a numerical integration of the exchange-correlation functional because of its non-analyticity severely complicates the accurate application of local-density functional methods to molecules and clusters. The optimal choice of grid points for this integration and the estimation of the error made by the choice are subtle considerations. In particular, because the position and/or weighting of each grid point must change when the nuclear positions change, these errors are most noticeable when different geometries are compared. We have determined a method of grid point selection and weighting that reduces these errors. We have also determined a simple method of estimating the extent of the error made in the particular density of points used for the grid. These results are illustrated for a selection of small molecules.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340813
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  • 41
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    Digitale Medien
    Topological electronic rules for polycyclic hydrocarbons - quantum chemical deductions directly from structural formulas (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 143-147 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: All bicyclo[p.q.0] conjugated hydrocarbons are found to fall into ten homolog classes each characterized by the numbers of nonbonding, bonding, and antibonding molecular-orbitals of its first prototype and by the prototype itself. The energy level patterns are obtained by the new “structural covariance” pictorial rules directly from structural formulas. The HOMO-LUMO types, aromaticity or three types of nonaromatic behavior, and reactivities towards nucleophiles or electrophiles thereby also result.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340818
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  • 42
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    Digitale Medien
    Calculation of harmonic frequencies and harmonic force fields by the hartree-fock-slater method (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 173-181 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Results are presented from Hartree-Fock-Slater (HFS) calculations on harmonic frequencies and force constants of H2O, H2S, NH3, PH3, CH4, SiH4, and C2H4. Both frequencies and force constants were calculated by a numerical (finite difference) differentiation of analytical energy gradients. It is shown by a comparison with experimental data and results from ab initio Hartree-Fock (HF) calculations that the HFS-method provides harmonic frequencies and force constants in at least as good agreement with experiment as the HF-scheme.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340821
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  • 43
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    Digitale Medien
    A progress report on the status of the COLUMBUS MRCI program system (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 149-165 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The COLUMBUS program system is a collection of Fortran programs for performing general multireference single- and double-excitation configuration interaction (MRSDCI) wave function optimization based on the graphical unitary group approach. The program system also includes integral generation, SCF and MCSCF orbital optimization, integral transformation, and wave function analysis programs. The original program system was written in 1980 to 1981. Since that time, it has evolved into one of the most popular MRSDCI program systems used in the computational chemistry community. The discussion of this evolution will include the exploitation of efficient matrix-matrix and matrix-vector product computational kernels, the use of generally contracted symmetry-adapted orbital basis sets, general Hamiltonian diagonalization procedures, energy-based internal walk selection, flexible DRT specification, improved coupling-coefficient evaluation methods, coupled-pair functional and multireference CPF capabilities, and density matrix construction. The numerous versions of the program system that are maintained at different sites and on different computers are now in the process of being merged. The source code for this combined version will be made available to the computational chemistry community. The source code for a specific computer may be generated from the source code for another computer by a single pass through a simple filter utility that is included with the program system. The directly supported computers will initially include various models of VAX, Cray, FPS, IBM, CDC, and ETA machines with the addition of other machines shortly thereafter. The ongoing developments of the COLUMBUS system that are discussed include a new method for computing analytic energy gradients for MRSDCI wave functions. This effective-density-matrix based method avoids the “coupled perturbed MCSCF” solutions for each coordinate direction, avoids the transformation of any derivative-integral quantities from the AO to the MO basis, avoids the transformation of the coupling coefficients from the MO to the AO basis, allows a subset of the MCSCF doubly occupied orbitals to be frozen in the CI wave function, and allows the MRSDCI wave function to be generated from general reference CSFs that are not necessarily related to the MCSCF expansion CSFs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340819
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  • 44
    Digitale Medien
    Digitale Medien
    Theoretical study of the geometry of Mn5 (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 231-236 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The geometry of Mn5 in rare gas matrices has been proposed to be a planar pentagon with 25 unpaired electrons. Simple unrestricted Hartree-Fock (UHF) calculations have been carried out using a basis of STO-6G for 1s, 2s, and 2p orbitals with STO-4G for 3s, 3p, 3d, 4s, and 4p in the HONDO5 program. The structure is optimized at the UHF level using the analytic gradient formalism for a planar pentagon. Binding energies and spinmixing are given for the optimized structure.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340827
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  • 45
    Digitale Medien
    Digitale Medien
    Molecular hardness and softness parameters and their use in chemistry (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 349-366 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The semiempirical Atoms-in-a-Molecule (AIM) hardness matrix, η, is defined, using the usual finite difference formula, ηii = Ii - Ai, for the diagonal AIM hardness and the Ohno formula, ηij = 1/(a2 + R2ij)1/2, for the off-diagonal AIM hardness. The Ohno formula is shown to exhibit the correct asymptotic behavior and satisfies the relevant stability criterion. The normal displacements in the AIM electron populations are examined for pyrrole and N-methyl pyrrole, and their relation to the polarization channels is briefly discussed. The new AIM hardness matrix is also tested by comparing the predicted global hardnesses with the corresponding experimental finite difference data for selected diatomics and triatomics. Finally implications of the hardness combination rules are examined and the corresponding softness combination rules are used to calculate the regional and global softnesses of selected molecules. We examine how the regional softnesses reflect known trends in selectivity of protonation of five membered heterocycles, and comment on the signs of the AIM fukui function and the Hard-Soft-Acids-and-Bases principle.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340840
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  • 46
    Digitale Medien
    Digitale Medien
    Modified breit-pauli hamiltonian suitable for variational calculations (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 425-430 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A Breit-Pauli type Hamiltonian with an effective positive term in substitution of the Darwin term is proposed for variational calculations. The Hamiltonian is bounded from below and does not exhibit variational collapse. Calculations on one electron atoms for the ground state, 2pl/2 and 2p3/2 states are presented. The results essentially coincide with those obtained from first order perturbation theory.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340845
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  • 47
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    Digitale Medien
    Titanium in large silicon clusters (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 297-308 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The application of molecular ab initio methods to investigate the electronic structure of localized impurities in semiconductors requires the study of the convergence of the results with increasing cluster size. Here we compare results for interstitial Ti in silicon, obtained with clusters of increasing size: TiSi10H16, TiSi30H40, and TiSi66H64. These clusters contain one, two, or three shells of silicon atoms, respectively, centered around Ti at a Td interstitial site. The hydrogen atoms serve as saturators of the dangling bonds. The Si core electrons are replaced by an effective potential. The calculations are based on open shell RHF theory and limited CI extensions. The charge distribution in the central part of the three clusters is very similar. In the clusters the partially occupied orbitals are much more delocalized than the 3d orbitals in the free ions. The total impurity-induced electronic charge, however, is quite localized, due to the compensating response of the Si closed shell density. Ionization of the impurity also causes a compensating response of the Si closed shells: only about 10% of the density difference is in the impurity region and the major part is behind the outermost shell of Si atoms. Transition metal associated (3d-like) excitation energies are not very dependent on the cluster size, and the relative ordering of the lowest lying states remains unchanged. Impurity associated ionization energies decrease considerably due to the extra relaxation offered by the additional shells of Si atoms. Our results indicate that a reliable description of interstitial transition metals in silicon can be provided by calculations on reasonably small clusters: Si30H40 is sufficiently large.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340834
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  • 48
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    Digitale Medien
    Theoretical kinetic and thermodynamic study on the disilene-silylsilylene isomerization (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 343-347 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The titled isomerization has been studied at the HF/3-21G level. The changes in thermodynamic functions, equilibrium constant K(T), conversion efficiency C(T), and the rate constant k(T) for the isomerization have been calculated using our energies of the reactant (R), transition state (TS), and product (P), their harmonic vibrational frequencies, and the classical and corrected barrier (by vibrational zero-point energies). In the range of temperature, 300-1200K, ΔH 〈 0, ΔS 〉 0 and ΔG 〈 0; i.e., it is exothermic, increasing in the entropy, and spontaneous reaction. ΔS≠ 〈 0, log A is about 12.0 ±0.15 (s-1), but the k(T) is from 2.627 × 10(-33) to 6.933 × 10(8) (5-1); i.e., it passes through a tight TS, the A factor changes little, but the rate constant varies rapidly with the temperature. These results agree with the fact that the isomerization occurs readily at high temperature. Furthermore, Newman's mechanism, 2SiH2 → (H2SiSiH2)* → (HSiSiH3)* → Si2H2 + H2, is supported. Similarly, the isomerization, HDSiSiH2 → HSiSiDH2, is also studied.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340839
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  • 49
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    Digitale Medien
    Iteration of the many-particle schrödinger equation in momentum space (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 437-444 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A generalization of the Fourier convolution theorem is used to iterate the many-particle Schrödinger equation in momentum space. The method is applied using hyperspherical coordinates, with many-dimensional hydrogenlike wave functions as the starting point for iteration. The problem of angular integration is converted into a problem of differentiation by means of the theory of harmonic polynomials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340847
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  • 50
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    Digitale Medien
    Relativistic CASSCF/CI calculations: Applications to transition metal dihydrides (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 465-476 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A complete active space MCSCF (multi-configuration self-consistent field) scheme (CASSCF) using relativistic effective potentials followed by configuration interaction and relativistic CI calculations provides a very good description of the electronic states and potential energy surfaces of transition metal dihydrides. Such calculations are of considerable value not only in our understanding of the transition metal-hydrogen bonding but also in the prediction of the barrier to insert the metal atom into the H2 bond. All-electron CASSCF/CI calculations are carried out on twelve electronic states of CoH2. Comparable RECP-CASSCF/CI calculations are also carried out to show that the RECP-CASSCF/CI calculations provide an accurate method for the investigation of transition metal compounds. The general method of RECP-CASSCF/CI calculations for molecules containing heavy atoms is described. The calculations on CoH2 are compared with similar calculations on ScH2, YH2, PtH2, and PdH2. A critical comparison of all these transition metal hydrides reveals that in general the low-spin excited metal atom inserts into H2 spontaneously while the high spin ground state atom has to surmount a large barrier.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340850
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  • 51
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    Digitale Medien
    The nonabelian two-dimensional algebra and the franck-condon integral (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 503-505 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two mapping operators are used to relate the eigenstates of two distorted and displaced oscillators. It is found that these operators satisfy a nonabelian two-dimensional algebra. We exemplify the method by calculating the Franck-Condon integral for the case of two harmonic oscillator wells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340855
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  • 52
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    Digitale Medien
    Use of quantum mechanical models in studies of reaction mechanisms (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 557-566 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The problems involved in determining the mechanisms of reactions by quantum mechanical calculations are discussed. Various precautions must be taken if the results of any calculation are to be chemically meaningful. Ab initio studies of reactions must also be carried out at a high level, using large basis sets and allowing for electron correlation. Such calculations are usually restricted to the simplest example of a reaction, which is often untypical. More information can usually be obtained at far less cost through AM1 calculations for a number of examples of a reaction for which experimental data are available. These points are illustrated by recent studies of the Cope rearrangement.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340860
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  • 53
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    Digitale Medien
    Symbolic computation in quantum mechanics. Several simple examples (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 537-548 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The aim of this article is to illustrate the use of symbolic computation in solving some problems in quantum theory. Emphasis will be given to the possibility of manipulating expressions symbolically and to the interface of numerical and algebraic languages. The illustrate the use of the scientific computation language Maple as a research tool, we present our work on lower energy bounds for anharmonic oscillators and on the spherical Zeeman effect. Another example consists in the perturbation calculations of the N-dimensional hydrogen atom, keeping the quantum labels in general form. Further, we describe the interface of Maple, Fortran, and the typesetting language, Troff. The basic feature is illustrated on the application of the inner projection technique and of the method of intermediate Hamiltonians on the benzene molecule as well as on the geminal approach to the butadiene molecule; the main calculations were first done in Maple and then transferred into Fortran's notation so that Fortran subroutines could be used. Finally, the results either in Maple or in Fortran can be transferred to a Troff file.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340858
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  • 54
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    Simple models for describing the fragmentation behavior of multiply charged cations (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 567-573 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The potential energy curve describing the fragmentation of a diatomic dication AB2+ is considered as arising from an avoided crossing between an attractive diabatic curve (correlating with A2+ + B) and a repulsive diabatic curve (correlating with A+ + B+). The simplest avoided-crossing (AC) model neglects diabatic coupling and polarization and leads to useful predictions of the transition structure bond length (rTS) and the kinetic energy released (T) in fragmentations of dicationic systems in which the difference (Δ1) between the ionization energies of A+ and B is small. When Δ1 is not small, it is necessary to include diabatic coupling and polarization in the treatment. The resultant ACDCP (avoided crossing with diabatic coupling and polarization) model provides very satisfactory estimates of rTS and T for both small and large Δ1. Its implementation requires only atomic ionization energy and polarizability data and comes at virtually no computational cost. Both the AC and ACDCP models are readily generalized to fragmentations of more highly charged cations.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340861
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  • 55
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    Spatial correlation of electrons in metals (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 655-664 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of electron-electron repulsions is assessed, primarily in the expanded fluid alkali metals, by confronting experimental data on these systems with the predictions of theory. This is usefully divided into two types of approach: (i)full inclusion of the long-range Coulomb interaction e2/rij between electrons i and j, but perturbative treatment of electron-ion interaction and(ii)the simplified on-site interaction described by the Hubbard U.The main conclusion is that both electron-ion and electron-electron correlations are of major importance in the expanded fluid alkali metals, and especially in Cs. The momentum distribution of the conduction electrons is changed in a very important quantitative way from the predictions of the jellium model at the same density by the electron-ion interaction. This leads to a metal-insulator transition at a much higher electron density than the jellium prediction. The relevance of this conclusion to crystalline alkalis is finally referred to.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340867
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  • 56
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    Electrostatic potential maps of flavone acetic acids: A new class of antitumor drugs (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 697-705 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Complete geometry optimizations have been carried out with the AM1 method on flavone acetic acid and several of its derivatives. Molecular electrostatic potential maps have been used to predict new com.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340870
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  • 57
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    Digitale Medien
    Erratum (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 741-741 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340876
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  • 58
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    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340101
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  • 59
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    Digitale Medien
    A spin-free form of valence bond theory (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 25-36 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Classical valence bond theory is recast in a spin-free form which provides a practicable route to ab initio calculations of molecular electronic structure. The approach is simple and direct and requires only efficient algorithms for the generation and processing of permutations and the handling of Rumer diagrams: it makes modest demands on computing power and pilot calculations have indeed been performed entirely within the fast memory of a personal computer, which should be sufficient for dealing with systems possessing up to 10 electrons outside a closed shell. Simple applications confirm the conclusion of Cooper et al. [1] that, by using strongly overlapping orbitals, a small number of classical (nonpolar) structures can give results close to those obtained in a “full CI” calculation.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340105
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  • 60
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    The role of hydrophobicity in the Ames test. The correlation of the mutagenicity of nitropolycyclic hydrocarbons with partition coefficients and molecular orbital indices (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 91-101 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A set of 20 nitropolycyclic aromatic hydrocarbons, whose mutagenicity has been determined in the Ames test, has been studied using octanol-water partition coefficients (P) as a measure of relative hydrophobicity and molecular orbital energies to account for variation in their electronic characteristics. A good structure-activity relationship was found using log P and ∊LUMO. The latter were taken from the results of ab initio calculations performed by Maynard, Pedersen, Posner, and McKinney [7] and were also calculated by the MNDO method. The dependence of mutagenicity on hydrophobicity was found to be similar to that observed for triazenes [2]. ∊LUMO values calculated by MNDO and STO-3G were found to be strongly correlated, and the role of hydrophobicity in correlating mutagenicity was not significantly affected by the molecular orbital model employed.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340202
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  • 61
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    Molecular conformations and molecular shape: A discrete characterization of continua of van der Waals surfaces (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 517-526 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A characterization of molecular model surfaces is proposed. It is based on a graph associated with the van der Waals surface, defined by the detailed information on the interpenetration of van der Waals spheres of the constituent atoms. This “van der Waals graph” describes the three-dimensional body of the molecule, and it does not coincide in general with the less informative bond graph obtainable from the molecular skeleton.The description in terms of the graph reveals clearly the changes in molecular shape induced by conformational rearrangements. The nuclear configurations can be classified by the graph associated with the molecular surface, and the graph-theoretical analysis provides a rigorous partitioning of the configurational space based on shape properties.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340605
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  • 62
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    Digitale Medien
    The use of symmetry in reciprocal space integrations. Asymmetric units and weighting factors for numerical integration procedures in any crystal symmetry (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 571-594 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A systematic collection of spatial domains for reciprocal space integrations is derived for all possible crystal symmetries. This set can be used as a simpler alternative to the conventional Brillouin zones. The analysis is restricted to integrations where the function in the integrand satisfies inversion symmetry in k space. In this case only 24 different spatial domains have to be defined in order to allow for k space integrations in the 230 different crystal symmetries. A graphic representation of the asymmetric unit for each of the 24 integration domains is given. Special positions and the associated weighting factors required for numerical integrations in theoretical solid-state approaches are tabulated.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340609
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  • 63
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    Digitale Medien
    Thermodynamic calculations on biological molecules (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 221-234 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Application of free-energy simulation methods to the calculation of thermodynamic properties for biologically relevant processes will be presented. Attention will be given to the usefulness of thermodynamic methods to explore the accuracy of empirical energy functions. Calculations of aqueous hydration and binding thermodynamics for drug molecules (trimethoprim and other related compounds) to biological targets (the enzyme dihydrofolate reductase) will be presented. In these applications we will discuss differences in “binding modes” for different drugs and the ability of thermodynamic methods to predict these changes. Finally, comments will be made regarding the free energy derivative methods and coordinate-coupled free energy calculations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340720
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  • 64
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    Digitale Medien
    A rational selection of graph-theoretical indices in the QSAR (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 267-285 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper we have addressed an important problem: how to develop a strategy for identification of the topological indices which are most important in establishing a model for structure-activity analysis. In particular we consider a rational selection of graph theoretical (topological) indices in QSAR. The approach is illustrated by the study of the toxicity of ethers on mice. The indices examined include the connectivity indices based on adjacency matrix, the conceptually related graph distance indices, and an information theoretic index based on partitioning of electrons in various domains. We have outlined the similarities and differences and discuss advantages and limitations among different approaches. Our emphasis is on the problem how to select in a rational way appropriate graph-theoretical descriptors and how to introduce higher “corrections” in order to improve derived correlation.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340724
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  • 65
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    Digitale Medien
    Vibrational frequencies and assignments for some isotopomers of urcail using a scaled ab initio force field (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 1-17 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vibrational frequencies and IR band intensities for 18 isotopomers of uracil, including deuterated 15N and 18O species, have been calculated using the scaled ab initio force field of Ref. 1. The results obtained are compared with available experimental data, and a number of refinements in former assignments are proposed. The good agreement between the calculated and experimental frequencies confirms the reliability of the scaled quantum mechanical-force field.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330102
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  • 66
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    The complexes of phenyl acetylene with HF, H2O, and NH3: An ab initio study (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 69-76 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Phenyl acetylene complexes with HF, H2O, and NH3 are investigated with ab initio molecular orbital calculations using the 6-31G Gaussian basis set. HF is found to form a π complex, whereas H2O and NH3 form σ complexes. Observations of experimental spectroscopic shifts are rationalized.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330202
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  • 67
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    Announcement (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 169-169 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330208
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  • 68
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    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330301
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  • 69
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    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330401
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  • 70
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    Self-consistent reaction field calculations on the proton transfer in ammonia-formic acid systems as a model for hydrogen bonding in amino acids in solution (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 41-52 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction field (RF) model of solvent effects, implemented within the SCF-CNDO/2 scheme of calculation, has been applied to analyze the proton transfer in the NH3…HCOOH system in the presence of several polarizable media. The aim of such a study was to characterize the tatutomeric equilibrium between the neutral and zwiterionic forms of H-bonded amino acids in aprotic solvents. Qualitative results concerning the energetics of this equilbrium show the stabilization of two different H-bonded complexes, corresponding to two separate minima in the free energy surface. These well known double minima potentials are found to be dependent on both the intermolecular N—O distance and the strength of the reaction field. The behavior of this model is qualitatively consistent with experimental observations of nitrogen-substituted amino acids in solution: both show, for low values of the dielectric constant, tautomeric equilibria where the H-bonded complexes appear to be more stable than the corresponding monomeric forms. The charge transfer process associated with the proton migration along the H-bond is also discussed. It is found that the amount of charge transferred increases with the N—O distance and with the RF strength, In order to test the general approach and compare it with previous work, calculations on the real monomeric systems glycine, β-alanine, and γ-amino butyric acid was also performed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330105
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  • 71
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    Digitale Medien
    Analytical potential from ab initio calculations for the Fe+-H2O and Feo-H2O systems (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 77-85 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Analytical intermolecular potentials for the Fe+-H2O and Feo-H2O systems have been determined from ab initio calculations. Interaction energies for a lot of points along the two potential energy surfaces were calculated using Huzinga's MINI-2 basis set. The results obtained were fitted to an analytical function containing 11 adjustable parameters that we have already used with success for the Fe2+-H2O system. The goodness of the generated intermolecular potentials is discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330203
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  • 72
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    Inclusion of relativistic effects into ZDO methods. II. Solavation of metal complexes (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 159-167 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quasirelativistic CNDO/1 method has been in investigating the geometry, electronic structure, and redox stability of metal complexes. The systems of [Co(NH3)6]q and [MCl4]q, M being Ni, Pd, and Pt, have been studied. A modified Germer model of solvation has been implemented into the method. This yields reliable results on the redox stability of complexes in aqueous solutions. The calculated excitation energies resemble the electronic spectra of [MCl4]2- complexes.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330207
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  • 73
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    Digitale Medien
    The energy of the homogeneous electron gas to second order (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 173-175 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The energy of an infinite, homogeneous electron gas is examined by second order perturbation theory using a Hartee-Fock rather than a noninteracting particle unperturbed state. The second order energy still diverges for small promotions k, albert than as ln|ln k| rather than as In k.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330302
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  • 74
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    Digitale Medien
    Quantum phenomena in small semiconductor structures and devicesInvited lectures presented at the Kandy Symposium on Condensed Matter Physics, Kandy, Sri Lanka, April 20-25, 1987. (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 217-245 
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    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ability to artificially structure new semiconductor materials on an atomic scale, using advanced crystal growth methods such as molecular beam epitaxy and metal organic chemical vapor deposition, has led recently to the observation of new physical phenomena as well as the creation of entirely new classes of devices based on band gap and wave function engineering. In these lectures an elementary introduction is given to the quantum aspects of these new structures.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330306
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  • 75
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    Digitale Medien
    Variational energy derivatives and perturbation theory (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 271-277 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this note we discuss the variational forms of the energy derivatives and the method of obtaining them. We show that perturbation theory can be formulated in terms of stationary energy derivatives and that this formulation extends the idea of the Hylleraas functional to infinite order and excited states.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330403
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  • 76
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    Digitale Medien
    Dimensionality dependence of total energy of closed shells in a bare Coulomb field for large atomic number (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 301-304 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: For Z particles moving independently in an unscreened Coulomb potential energy -Ze2/r, it is known that the total energy E = -(3/2)1/3Z7/3 in nonrelativistic theory as Z→∞. The generalization of this result to d dimensions in the same asymptotice limit is obtained as \documentclass{article}\pagestyle{empty}\begin{document}$$E(Z,d) = - \frac{{2\left({\frac{{d!}}{4}} \right)^{1 - (2/d)} }}{{(d - 1)!(d - 2)}}Z^{3 - (2/d)},$$\end{document} which includes the known result above for the three-dimensional case.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330405
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  • 77
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    Digitale Medien
    Announcement (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 369-369 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330410
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  • 78
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    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330501
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  • 79
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    Digitale Medien
    An examination of perturbation-variational theory and scaling at fifth order (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 373-394 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We examine various perturbation-variational approximations for molecular electronic energy when the fifth-order perturbational energies are available. Such theories require very little additional computation once the sequence of perturbation energies are known yet supply a bound even when the peturbation sequence is poorly convergent. We choose for computational examples results obtained very rapidly from a zeroth order wave function consisting of doubly occupied localized bonds and examine polarization within these bonds, delocalization, and bond breaking. In general, we find that the fifth-order energy itself, and especially the [2, 1] Padé approximant on this sequence, are especially accurate in estimating the total energy and more accurate than any variational scheme when the zeroth order localized wave function is a good description of the electronic structure. The variational results, however, are nearly as accurate, and a [1, 0] Padé on the sequence of variational results is remarkably robust, even in those cases where the perturbation sequence is poorly defined.We also examine several scaling techniques, or partitionings of the Hamiltonian. Although these scaling techniques do accelerate convergence of the perturbation sequence, none that we examine give better results, than the [2, 1] padé, which is independent of any scaling.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330502
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  • 80
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560330601
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  • 81
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    Digitale Medien
    Extrapolation of the total energy of polymers to the bulk limit using generalized padé approximants (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 225-229 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Generalized Padé approximants are used to extrapolate the total energy of polymers described by alternant Hamiltonians to the bulk limit. The method provides an upper bound to the energy. The origin of (quasi) periodic oscillations of the energy per unit cell as the function of the number of unit cells is enlightened through analysis of the moments of the Hamiltonian.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340305
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  • 82
    Digitale Medien
    Digitale Medien
    Intershell nl4f electron correlation effects (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 279-288 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The pair correlation energies for some nl4f pairs of the ground state of the Yb atom are calculated for the first time. The partial wave (PW) increments to the second-order pair energies are generated using numerical first-order radial pair functions obtained as the solution of two-dimensional differential equations. The analysis of the PWs contributions shows the dominant role of the df, fg, and gh PWs for the 4d4f pair, of the pf and dg PWs for the 4p4f and 5p4f pairs, and of the sf and pg PWs for the 4s4f, 5s4f, and 6s4f pairs. A discussion of the similarities and differences of the structure of the correlation energy found in this paper with those calculated earlier for smaller atoms is given.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340309
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  • 83
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    Digitale Medien
    Method of local-scaling transformations and density functional theory in quantum chemistry. III. The energy density functional: Spin-restricted approach (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 307-307 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340313
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  • 84
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340401
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  • 85
    Digitale Medien
    Digitale Medien
    Particle-hole symmetry and complementary quantum systems (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 333-359 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is well known that positive and negative ions derived from the same alternant hydrocarbon have almost indistinguishable electron spectra. Effective charges, bond orders, and many other properties also correlate between the two systems. These «alternancy» properties are due to the particle-hole symmetry, and they can be generalized far beyond alternant hydrocarbons. In general, with each quantum system one can associate a «complementary» system. The eigenstates of the complementary system are related to the eigenstates of the original system in the same way as the anionic eigenstates of an alternant hydrocarbon are related to the cationic eigenstates of this hydrocarbon. In particular, the (N + k)-electron spectrum of the complementary system is the same, up to the uniform shift, as the (N - k)-electron spectrum of the original system; the effective charges in the complementary system are opposite to the corresponding effetive charges in the original system; bond orders in the two systems between vertices of the same and of the opposite parity are, respectively, opposite and the same, etc. Each particle-hole symmetry operator associates with the original system one such complementary system. There is hence a large number of the systems complementary to the same original system. In the PPP model and in various generalizations of this model, systems complementary to conjugated hydrocarbons are Möbius-type alterations of original hydrocarbons. In the case of conjugated heterocompounds, there is a formal replacement of all heteroatoms with some other heteroatoms, with or without an additional Möbius-type change. Such complementary systems may correspond to entirely different molecules, and they also may describe some transition states of these molecules.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340404
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  • 86
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340501
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  • 87
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    Digitale Medien
    Modified all-valence INDO/spd method for ground and excited state properties of isolated molecules and molecular complexes (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 423-435 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new semiempirical all-valence method, GRINDOL (Ghost and Rydberg INDO), based on the INDO approximation, is described. Linderberg-Seamans relation (extended to the d and Rydberg orbitals) for the resonance integrals and a new semitheoretical expression for the core-core repulsion term and energy correction including basis-set superposition error (intermolecular as well as intramolecular) has been applied. The proposed method enables calculation of ground and excited state properties. The ground state results (including intermolecular interactions) as well as the spectral properties are in reasonable agreement with relevant experimental (or ab initio) studies for isolated molecules, molecular complexes, and transition metal compounds. The method contains only one adjustable parameter, all two-center integrals and terms are only basis-set dependent. The one-center integrals are evaluated from the respective atomic terms.
    Zusätzliches Material: 11 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340504
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  • 88
    Digitale Medien
    Digitale Medien
    Optical activity of small peptide chains with right-handed α-helix structure (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 471-481 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The optical activity of oligopeptides in the conformation of the right-handed α-helix was calculated by the direct semiempirical quantum chemical CNDO/OPTIC method. The oligomers of glycine and alanine from dimer up to pentamer were considered. The comparison with results obtained using the model of interacting groups (MIG) based on the perturbation approach was carried out. The calculational results show that the circular dichroism (CD) of oligopeptide α-helices is essentially different from the CD of the peptide polymers in the same conformation. The comparison between results obtained by the CNDO/OPTIC method and by the MIG leads to doubts about the reliability of the use of the MIG to calculate rotatory strengths of nπ* transitions of oligopeptides in α-helix conformation.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340508
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  • 89
    Digitale Medien
    Digitale Medien
    Structure of consistent ground state: Re - derivation of RPA vacuum and inclusion of higher RPA effects (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 489-503 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Here is presented a method to determine the consistent ground state (CGS) which satisfies the so-called killer condition for the excitation operator. This method may be called an extended application of the procedure employed by Weiner and Goscinski in deriving the random phase approximation (RPA) vacuum.The RPA vacuum is derived by solving the recurrence formula of the configuration coefficients of a multiconfigurational state vector. The role of boson approximation to the primitive p-h excitation operator is also investigated and by using the present formalism the cluster-expansion-type CGS is derived as the RPA vacuum under the boson approximation.Inclusion of the effects of a higher RPA in the CGS leads to the simultaneous equations of the configuration coefficients of the CGS. In including the effect of the second RPA, only the symmetry-broken CGS can exist. When the third RPA effect is involved instead of the second RPA, there can be a symmetry-adapted CGS, in which the picture of electron pairs acquired in the standard RPA vacuum is modified. Thus the exact CGS vectors are analytically obtained in the case of simple model systems of two or four electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340602
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  • 90
    Digitale Medien
    Digitale Medien
    Theoretical investigation of the Na+ + H2 system. III. Trajectory calculations of vibrationally inelastic collision processes (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 559-569 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: On the basis of an analytical potential energy surface for the electronic ground state of the Na+ + H2 system reported recently, extensive trajectory calculations have been performed to study the collision dynamics of vibrationally inelastic processes at total energies up to ∼3 eV. Special attention is given to the relative efficiacy of translational and rotational energy, respectively, in promoting vibrational energy transfer. Vibrational transitions are found to be substantially enhanced by initial molecular rotation. Furthermore, the applicability of simple models is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340608
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  • 91
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    Digitale Medien
    Eigenlevel calculations for screened coulomb potential systems via an integration-free algorithm: Space pruning technique (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 231-245 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this work, an algebraic method is developed to determine the eigenlevels of radially screened Coulomb potential systems. The method is mainly based on the concept of space pruning. The basis functions are combined in a way such that the resulting approximate eigenfunction and its several images under certain positive integer powers of the system's Hamiltonian (H) remain in the domain of H. Certain structural parameters are introduced into the basis functions to imitate some known behaviors of the true eigenfunctions of the system.The main purpose of this work is not to reproduce the results for screened Coulomb potential systems but to develop a method which does not necessitate integration at any stage and can later be adapted to atomic and molecular systems as easily as possible.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340306
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  • 92
    Digitale Medien
    Digitale Medien
    Core/valence partition and relativistic effects in effective potentials for transition metals (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 267-277 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two different versions, relativistic and nonrelativistic, of the “shape-consistent” effective potential (EP) formalism are analyzed in ab initio calculations for transition metals. The influence of alternative core/valence partitions on the reliability of the procedure is discussed. The accuracy of EP results for transition metals is shown to depend on adequate choices of the valence subspace and proper inclusion of relativistic effects.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340308
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  • 93
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    Digitale Medien
    On characterization of three-dimensional structuresOn the occasion of 70th birthday and retirement this paper is dedicated to Professor R. S. Hansen, Director of Ames Laboratory, who, without reservations, has generously supported research on chemical graph theory over the past dozen years. (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 201-208 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular descriptors currently used in structure-property-activity studies are based on molecular graphs rather than on a structure as a three-dimensional object. Here we suggest a way to amend graph-theoretic invariants with additional geometric information, thereby providing new molecular descriptors for possible use in quantitative structure-activity correlations. In the approach we assume molecular structures embedded on a regular grid. As an illustration we consider first chains of different length embedded on graphite-like lattice. Subsequently, we consider all possible conformations of hexatriene. Although the cases considered here relate to graphite-like lattice, the approach is general and applies to embedings of molecules on three-dimensional lattices, or, in general, to molecules of arbitrary spatial conformations.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340718
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  • 94
    Digitale Medien
    Digitale Medien
    Shape description of conformationally flexible molecules: Application to two-dimensional conformational problems (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 33-54 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nuclear configuration and molecular shape are two different concepts. The former refers to the geometry of the nuclear framework, whereas the shape of a molecule is better represented by a molecular envelope surface enclosing the nuclei. Nevertheless, there exist relationships between the molecular shape and the conformational arrangements of the nuclei. For certain changes in the nuclear geometry, the shape of a molecular surface does not change significantly, whereas for some others it may undergo essential topological changes. The characterization and interrelations of these changes provide a rigorous classification of reaction paths and conformational rearrangements for flexible molecules in terms of shape features. In this article we use a recently introduced topological tool to study molecular shape and molecular conformations: the “shape groups” (symmetry-independent homology groups) of a molecule. Van der Waals surfaces are considered as illustrative examples of molecular surfaces. We study the changes in the shape of van der Waals surfaces of hydroquinone, resorcinol, and catechol for a number of two-dimensional conformational problems, where the nonrigid conformational paths have been calculated at the STO-3G ab initio Hartree-Fock level.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340706
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  • 95
    Digitale Medien
    Digitale Medien
    Conformational basis of the receptor-binding potency of normal and mutant insulin molecules with relevance to the pathophysiology of noninsulin dependent diabetes mellitus (NIDDM) (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 95-101 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Residues 23-26 (Gly-, Phe-, Phe-, Tyr) of the B-chain of insulin constitute a critical area of the receptor-binding region of the molecule. Three chemically distinct mutant insulins have recently been identified in patients with NIDDM, each involving substitution of either B24 of B25 phenylalanine. Two of the mutations have been unambiguously characterized: a B25 phenylalanine-to-leucine substitution [B25(Phe → Leu)], and the other, a B24 phenylalanine-to-serine [B24 (Phe → Ser)]. We have calculated the preferred conformations of normal and mutant insulins using a global optimization method developed by us earlier. The mutant insulins exhibit significant alterations in conformation and in the average distances between amino acid side-chains as compared to normal insulin. Therefore, the decreased binding affinity of mutant insulin could be either due to an alteration in the nature of the substituted residue (hydrophilic in place of hydrophobic) or to the alteration in one or more critical side-chain distances in the case of a hydrophobic to hydrophobic substitution.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340710
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  • 96
    Digitale Medien
    Digitale Medien
    3- and 5-Isoxazolol zwitterions: A model of interaction with the GABA-A receptor relating to agonism and antagonism (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 149-165 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Using molecular orbital methods, we propose various models of interactions between GABA or analogs (TACA, muscimol, isomuscimol) and an hypothetical receptor molecular fragment, a methylguanidinium ion. The respective geometries of the GABA-, TACA-, muscimol-, and isomuscimol-methylguanidinium ion complexes are optimized using the semi-empirical MNDO method. Stabilization energies of the complexes obtained by substraction of the heats of formation of the optimized complexes from those of the optimized isolated molecules differentiate the behavior of the anionic heads between the agonist and antagonist compounds. Affinity and stabilization are confirmed by computing ab initio STO-3G ionization potentials and interaction energies taking into account counterpoise corrections. Results show a decrease of the interaction energy from GABA and TACA (-54.9 and -49.4 kcal/mol) to isomuscimol (-35.6 kcal/mol), via muscimol (-46.0 kcal/mol). The low interaction energy of the 5-isoxazolols as isomuscimol compared to the 3-isoxazolols, as muscimol, may explain their antagonist character.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340714
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  • 97
    Digitale Medien
    Digitale Medien
    The chain build-up procedure in computing the structures of biologically active polypeptides and proteins (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 209-220 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chain-buildup method is presented for sampling the low energy conformations of polypeptides and enzyme-substrate complexes. This method circumvents the multiple minimum problem. It is shown that the method can compute structures in agreement with experiment.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340719
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  • 98
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    Digitale Medien
    List of Participants (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. vii 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340703
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  • 99
    Digitale Medien
    Digitale Medien
    Energy-Conformational studies of β-endorphins: Identification of plausible folded conformers (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 55-66 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: β-Endorphins are 31 amino acid endogenous opioid peptides with high receptor affinity and antinociceptive activity. Because of their importance as neurohormones and the significant experimental effort that has been made to understand their structure activity profiles, we have begun to develop procedures that could be useful first to identify low-energy conformers of β-endorphins and ultimately their bioactive form. In the initial studies reported here, we have identified plausible initial structures of the full peptide by calculating and comparing the conformational preference of all possible extended tetrapeptide fragments of β-endorphin starting from each of the first 28 residues. Comparisons of fragment energies suggested two types of compact folded β-endorphin conformers were plausible: a helix-turn-helix and an antiparallel β-sheet conformer. These structures, as well as an extended α-helical and β-strand conformer, were assembled and total geometry optimization performed using the empirical-energy-based program AMBER. The results yield an α-helical structure as the lowest energy form consistent with recently reported NMR studies of β-endorphin. The two more compact folded structures obtained, however, are reasonable starting conformations for further planned molecular dynamics simulation studies and could yield competing low-energy structures as candidates for the bioactive form of these peptides.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340707
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  • 100
    Digitale Medien
    Digitale Medien
    Continuum electrostatics and hydration phenomena (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 103-118 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A formalism for a computational treatment of the polarization of a solvent and polar solutes immersed in it is presented. The solvent is modeled as a continuum dielectric. Polarization effects are represented by a polarization charge density at the dielectric boundaries and by induced dipoles at the polarizable atoms. Applications of this formalism with nonpolarizable atoms have led to excellent agreement between the calculated and experimental hydration enthalpies of a variety of polar molecules. A problem of the choice of the charge distribution of the solute is addressed in calculations of the solution dipole moment and hydration enthalpy of polarizable molecule of water in solution. Experimental values of these properties were well reproduced in calculations starting with point charges fitted to the vacuum dipole moment of the water molecule. Tests calculations for spherical models and for a 13-residue peptide show good convergence of the computational method. It is shown in calculations on simplified models that a change in the exposure of a charged side chain can lead to large changes in the potential inside protein measured at a fixed distance from the charge and at the same depth from the protein surface. Calculations performed for the C-peptide of the ribonuclease suggest that the differential screening of partial charges can reverse the sign of the vacuum potential of the helix dipole.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560340711
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