Library

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (3,177)
  • 2005-2009
  • 1990-1994  (2,451)
  • 1970-1974  (445)
  • 1965-1969  (281)
  • 1950-1954
  • 1890-1899
  • Computational Chemistry and Molecular Modeling  (3,019)
  • Insulin
Material
  • Electronic Resource  (3,177)
Years
Year
  • 1
    ISSN: 1534-4681
    Keywords: Insulin ; TPN ; Protein kinetics ; Amino acids ; Nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Cancer cachexia is a significant cause of postoperative morbidity and mortality in patients with tumors of the upper gastrointestinal tract. Standard parenteral nutrition (TPN) has failed to alter this. The anabolic effect of insulin has been well documented, and its positive effect on protein economy in cancer patients has been recently demonstrated. This study examines the effect of high-dose insulin and parenteral nutrition on protein kinetics in postoperative cancer patients. Methods: Eleven patients underwent surgery for pancreatic, esophageal, or gastric carcinoma. Postoperatively, patients received standard TPN for 4 days (1 g/kg/day amino acids, 1,000 kcal/day dextrose, 100 g/day lipid), and hyperinsulinemic parenteral nutrition for 4 days (same as standard TPN plus 1.44 U/kg/day regular human insulin) in a crossover design. All patients received both treatments, and the order of treatment was determined randomly. Euglycemia was maintained during insulin infusion via a variable 30% dextrose infusion. Patients underwent protein metabolic studies after each treatment period and rates of whole body and skeletal muscle protein synthesis, breakdown, and net balance were determined by radioisotopic tracer methods using14C-leucine and3H-phenylalanine. Results: Compared with standard TPN (STD), hyperinsulinemic TPN (INS) resulted in a significant increase in skeletal muscle protein synthesis (INS: 52.04±10.22 versus STD: 26.06±6.71 nmol phe/100 g/min, p〈0.05) and net balance of protein (INS: 7.75±4.61 versus STD: −15.10±6.44 nmol phe/100 g/min, p〈0.01), but no difference in skeletal muscle protein breakdown (INS: 44.29±11.54 versus STD: 41.17±5.89 nmol phe/100 g/min). Whole-body net balance of protein also significantly increased with insulin-based TPN, compared with standard TPN (INS: 0.04±0.05 versus STD: −0.08±0.07 µmol leu/kg/min, p〈0.05), but no difference in whole-body protein synthesis (INS: 2.52±0.15 versus STD: 2.49±0.15 µmol leu/kg/min) or whole-body protein breakdown (INS: 2.48±0.16 versus STD: 2.58±0.19 µmol leu/kg/min) was observed. Patients received significantly more calories during the hyperinsulinemic TPN period than during the standard TPN period. There was no difference in total, essential, or branched-chain amino acids, and no difference in serum free fatty acids, triglycerides, or cholesterol was observed between the two treatment periods. Conclusion: High-dose insulin in conjunction with hypercaloric parenteral nutrition causes improved skeletal muscle protein synthesis, skeletal muscle protein net balance, and whole-body protein net balance compared with standard TPN in postoperative cancer patients.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1440
    Keywords: Myotonic dystrophy ; Growth hormone ; Growth hormone releasing hormone ; Insulin ; C-Peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Growth hormone (GH) levels were measured in 12 patients with myotonic dystrophy (MD; 7 men and 5 women, aged 21–49 years) and 14 volunteers after administration of 100 μg GH-releasing hormone (GHRH; 1–29). A 75-g oral glucose tolerance test was carried out to determine glucose, insulin, plasma C-peptide, and urinary C-peptide. The GH level in six MD patients responded normally to GHRH (group I), with a peak of 17.1 ± 1.46 μg/l, compared withcontrols (27.8 ± 19.6 μg/l, NS), and that in the other six patients responded subnormally, with a peak of 3.15 ± 1.46 μg/l, lower than in controls and in group I patients (P 〈 0.001). In group I the insulin response to the glucose tolerance test showed hyperinsulinism and was lower than that in group II patients; stimulated C-peptide was also higher in group II than in group I and in controls; urinary C-peptide levels were parallel to those in previous data. In all MD patients there were a negative correlation between absolute values of GH response to GHRH and insulin response to glucose tolerance test (r = - 0.79, P 〈 0.001). Our data suggest that the failure in GH release and peripheral insulin action is due to a generalized defect in cellular membrane function in MD patients.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1437-9813
    Keywords: Nesidioblastosis ; Insulin ; Radioimmunoassay ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present two cases of nesidioblastosis, a common cause of persistent hypoglycemia in infancy that, if inadequately treated, can lead to mental retardation. Tissue insulin data obtained from both radioimmunoassay and immunohistochemistry are presented. In each case, the insulin content correlated well with the quantity of insulinpositive cells in each portion of the pancreas. However, the insulin content varied from case to case and from portion to portion of the same pancreas. Thus, discrepancies in clinical results in nesidioblastosis may be due to variability of insulin content in the resected pancreas.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 425 (1994), S. 305-313 
    ISSN: 1432-2307
    Keywords: Rat ; Pancreatic beta cells ; Immunocytochemistry ; Ultrastructure ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract When studied morphologically in semi-thin sections in the rat in vivo, pancreatic beta cells displayed heterogeneous immunoreactivities for insulin and amylin, depending on the islet size and the intra-islet position of the beta cells. In larger islets, cortical beta cells (beta cells with contacts with all islet cell types and with the exocrine parenchyma) which are located in the periphery were more densely immunostained for insulin and amylin than medullary beta cells (beta cells with contacts only with other beta cells) which are located in the centre of the islet. Ultrastructurally, these findings were accompanied by differences in the number of secretory granules and mitochondria. Beta cells in small islets and at extra-islet sites exhibited a dense immunoreactivity. After administration of glibenclamide, immunoreactivities for insulin and amylin were diminished in a time-dependent manner, decreasing first in medullary and thereafter in cortical beta cells of larger islets. Ultrastructurally, the beta cells exhibited the typical signs of stimulation. A minority of beta cells in small islets and all beta cells in extra-islet locations remained unchanged. Thus pancreatic beta cells under basal and stimulatory conditions in vivo exhibit heterogeneity in hormone content and in ultrastructural features. These differences may represent the basis for a functional heterogeneity of the insulin secretory response of the individual beta cell both in vivo and in vitro in states of normal and impaired insulin secretion. As heterogeneity was observed only among beta cells in islets, while single beta cells surrounded by acinar cells exhibited no changes in insulin immunoreactivity, interactions between beta cells as well as between beta cells and other endocrine cells may be critical for expression of heterogeneity within the beta cell population.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-0428
    Keywords: Insulin ; islet amyloid polypeptide ; pancreas ; secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To determine whether chronic overproduction of islet amyloid polypeptide alters beta-cell function, we studied a line of transgenic mice which overexpress islet amyloid polypeptide in their beta-cells. At 3 months of age, these transgenic mice had greater pancreatic content of both islet amyloid polypeptide and insulin. Further, basal and glucose-stimulated secretion of both islet amyloid polypeptide and insulin were also elevated in the perfused pancreas of the transgenic animals. These findings demonstrate that chronic overproduction and secretion of islet amyloid polypeptide are associated with increased insulin storage and enhanced secretion of insulin in vitro. This increase in insulin storage and secretion may be due to a direct effect of islet amyloid polypeptide on the beta-cell or a betacell adaptation to islet amyloid polypeptide-induced insulin resistance.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-0428
    Keywords: Insulin ; metformin ; 3-0-methylglucose transport ; non-insulin-dependent diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Metformin has been demonstrated to lower blood glucose in vivo by a mechanism which increases peripheral glucose uptake. Furthermore, the therapeutic concentration of metformin has been estimated to be in the order of 0.01 mmol/l. We investigated the effect of metformin on insulin-stimulated 3-0-methylglucose transport in isolated skeletal muscle obtained from seven patients with non-insulin-dependent diabetes mellitus (NIDDM) and from eight healthy subjects. Whole body insulin-mediated glucose utilization was decreased by 45% (p〈0.05) in the diabetic subjects when studied at 8 mmol/l glucose, compared to the healthy subjects studied at 5 mmol/l glucose. Metformin, at concentrations of 0.1 and 0.01 mmol/l, had no effect on basal or insulin-stimulated (100 ΜU/ml) glucose transport in muscle strips from either of the groups. However, the two control subjects and three patients with NIDDM which displayed a low rate of insulin-mediated glucose utilization (〈20 Μmol·kg−1·min−1), as well as in vitro insulin resistance, demonstrated increased insulin-stimulated glucose transport in the presence of metformin at 0.1 mmol/l (p〈0.05). In conclusion, the concentration of metformin resulting in a potentiating effect on insulin-stimulated glucose transport in insulin-resistant human skeletal muscle is 10-fold higher than the therapeutic concentrations administered to patients with NIDDM. Thus, it is conceivable that the hypoglycaemic effect of metformin in vivo may be due to an accumulation of the drug in the extracellular space of skeletal muscle, or to an effect of the drug distal to the glucose transport step.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-0428
    Keywords: Insulin ; C-peptide ; fructosamine ; triglyceride ; birthweight ; fatty acid ; non-insulin-dependent diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Many ethnic groups at high risk of non-insulin-dependent diabetes mellitus are hyperinsulinaemic by early adult life. This study assessed whether such hyperinsulinaemia is present at birth. Cross sectional comparisons of maternal biochemistry, umbilical cord biochemistry and neonatal anthropometry were made between one ‘low risk’ and three ‘high risk’ ethnic groups, without diabetes in pregnancy in Auckland, New Zealand. The study comprised 123 European, Polynesian (Maori and Pacific Islands) and Indian normal pregnancies. Indian mothers were the smallest, with the highest insulin and non-esterified fatty acid concentrations. Polynesian mothers were the most obese with a higher fructosamine concentration. From these pregnancies, Indian neonates were smaller, slimmer, with the highest cord triglyceride (0.6 mmol/l vs 0.4 mmol/l, p〈0.01), and lowest cord insulin concentrations (7.1 mU/l vs 8.6 mU/l (European), 9.2 mU/l (Polynesian), p〈0.05). Polynesian babies had a high cord insulin: C-peptide ratio (52.5 mU/nmol vs 44.4 mU/ nmol (European), 44.1 mU/nmol (Indian), p=0.05). Although reduced intrauterine growth may contribute to the excess of diabetes and heart disease in Indians, it cannot explain the excess of diabetes in Polynesians. Exposure to minor relative maternal hyperglycaemia in the mother and abnormal neonatal insulin handling (as demonstrated by the higher insulin: C-peptide ratio) may be of long-term significance in Polynesians.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 55 (1994), S. 363-367 
    ISSN: 1432-0827
    Keywords: Skeletal unloading ; Bone formation ; Insulin ; Insulin-like growth factor-I ; Rat femur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The alteration of bone metabolism in the femur of rats with skeletal unloading for 4 days was investigated. Skeletal unloading was designed using the model of hindlimb hang in rats. Skeletal unloading caused a significant decrease in femoral weight, calcium, and phosphorus contents in the metaphysis but not diaphysis. Also, the unloading induced a significant decrease of zinc content, alkaline phosphatase activity, and deoxyribonucleic acid (DNA) content in the femoral diaphysis and metaphysis. When the femoraldiaphyseal and metaphyseal tissues from normal and skeletal-unloading rats were cultured in the presence of insulin (10-9 and 10-8 M) for 24 hours in vitro, the hormonal effect to increase alkaline phosphatase activity and DNA content in the diaphysis, but not metaphysis, was lost in the bone tissues from unloading rats. However, the culture with insulin-like growth factor-I (IGF-I; 10-8 and 10-7 M) produced a significant increase of alkaline phosphatase activity and DNA content in both the diaphyseal and metaphyseal tissues from normal and unloading rats. These results demonstrate that skeletal unloading causes an impairment of insulin effect, but not IGF-I effect, on bone metabolism in femoral tissues.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 8 (1994), S. 309-312 
    ISSN: 1432-198X
    Keywords: Glucose ; Insulin ; Growth ; Chronic renal failure ; Uremia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied glucose metabolism using the hyperglycemic technique in a cross-section of 23 children (15 pubertal, 8 prepubertal) with stable chronic renal failure as a possible cause of their poor growth. Linear growth was expressed as growth velocity standard deviation score (GVSDS). GVSDS correlated with glucose disposal rate but not with insulin sensitivity index in the pubertal (r=0.87,P〈0.001) and prepubertal (r=0.86,P〈0.02) children with chronic renal failure. Thirteen children were followed longitudinally during medical suppression of hyperparathyroidism with dietary phosphate restriction and high-dose phosphate binders. Following significant suppression of serum parathyroid hormone (PTH) levels back to the normal range (932±240 ng/l to 199±50 ng/l), GVSDS, glucose disposal rate and insulin secretion all increased significantly (P〈0.01), with no change in insulin sensitivity index and renal function. The changes in GVSDS correlated with the changes in glucose disposal rate (r=0.86,P〈0.02) and with the changes in insulin secretion (r=0.80,P〈0.01). However, the changes in GVSDS did not correlate with the changes in PTH. The hypothesis that insulin may be more important than PTH in the pathogenesis of growth failure in chronic renal disease deserves further investigation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-0738
    Keywords: Key words Cell proliferation ; Pancreas ; 5-Bromo-2′-deoxyuridine (BrdU) ; Immunohistochemistry ; Hormones ; Insulin ; Glucagon ; Somatostatin ; Phenobarbitone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A previous study demonstrated that administration of phenobarbitone to male AP Wistar rats for up to 7 days caused alterations in labelling indices (LIs) in several different tissues (including a reduction of the endocrine pancreas population LI) as determined by immunohistochemical visualisation of 5-bromo-2′-deoxyuridine (BrdU) incorporation into S-phase nuclei. The primary objective of this study was to determine whether treatment with phenobarbitone influenced the replicative states of specific cohorts of the islet (of Langerhans) cell population or generated a uniform depression of LI. Quantitation of the LIs of individual islet cell cohorts was achieved by utilisation of a dual immunohistochemical staining method for BrdU and islet hormones (insulin, glucagon and somatostatin) using a sequential peroxidase anti-peroxidase (PAP)/alkaline phosphatase anti-alkaline phosphatase (APAAP) method employing diaminobenzidine and New Fuchsin chromogens, respectively. We observed reductions, increases and no change in LIs of insulin-, glucagon- and somatostatin-positive cells, respectively. We conclude that the decreased LI of the insulin-positive cohort was not countered entirely by the LI increase in the glucagon-positive cohort due to the larger size of the former. Furthermore, the effects of phenobarbitone treatment are not manifested generally in the islet cell population but in the insulin- and glucagon-positive cohorts only. The causation of these effects is unknown but is likely to be due to enhanced carbohydrate and hormone metabolism. We believe that the visualisation and quantitation of replicating cells in specific hormone-positive cohorts of the islet cell population provide opportunities for understanding the influence of xenobiotics and disease processes on pancreatic function.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 153 (1994), S. 409-410 
    ISSN: 1432-1076
    Keywords: Key words     Children ; Diabetes ; Insulin ; Jet injection ; Pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract      The aim of this study was to investigate whether insulin application by jet injector is less painful than by needle. Pain was scored by 41 diabetic and seven healthy volunteers after injections with both methods. Injections by jet were no less painful than those by needle but produced several local side-effects.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 23 (1994), S. 177-187 
    ISSN: 1432-1017
    Keywords: Molecular dynamics simulation ; Insulin ; Crosslinked insulin ; Single chain insulin ; Active conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular dynamics simulations were carried out on an insulin crosslinked between the N-terminal A chain and the C-terminal B chain to form a so-called mini-proinsulin: N α -A1-N ε -B29-diaminosuberoyl insulin (DASI). To investigate the influence of crosslinking on the dynamics of the insulin moiety, the bridge was removed from a transient DASI structure and simulation was carried on independently with the then unlinked (ULKI) as well as with the crosslinked species. The effects of crystal packing and quaternary interactions were checked by simulating both types of monomers and dimers known from the hexamer structure. All simulations were compared to previous ones of native insulin. DASI shows general similarity to the native simulations in most parts of the structure. Deviations are visible in the segments to which the bridge is directly connected, i.e. their flexibility is reduced. Upon removal of the bridge the ULKI simulations reapproach those of native insulin. The influence of the bridge spreads over the whole molecule, but all of its main structural features remain intact. The simulations suggest that the displacement of the C-terminal B chain of native insulin, considered important for receptor interaction, is prevented by the bridge, which also partially shields some binding residues. This is in accordance with the poor biological potency of A1-B29-crosslinked insulins.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 1432-2013
    Keywords: Glucose oxidation ; Glucose infusion ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To determine the limits to oxidation of exogenous glucose by skeletal muscle, the effects of euglycaemia (plasma glucose 5 mM, ET) and hyperglycaemia (plasma glucose 10 mM, HT) on fuel substrate kinetics were evaluated in 12 trained subjects cycling at 70% of maximal oxygen uptake (VO2, max) for 2 h. During exercise, subjects ingested water labelled with traces of U-14C-glucose so that the rates of plasma glucose oxidation (R ox) could be determined from plasma 14C-glucose and expired 14CO2 radioactivities, and respiratory gas exchange. Simultaneously, 2-3H-glucose was infused at a constant rate to estimate rates of endogenous glucose turnover (R a), while unlabelled glucose (25% dextrose) was infused to maintain plasma glucose concentration at either 5 or 10 mM. During ET, endogenous liver glucose R a (total R a minus the rate of infusion) declined from 22.4±4.9 to 6.5±1.4 μmol/min per kg fat-free mass [FFM] (P〈0.05) and during HT it was completely suppressed. In contrast, R ox increased to 152±21 and 61±10 μmol/min per kg FFM at the end of HT and ET respectively (P〈0.05). HT (i. e., plasma glucose 10 mM) and hyperinsulinaemia (24.5±0.9 μU/ml) also increased total carbohydrate oxidation from 203±7 (ET) to 310±3 μmol/min per kg FFM (P〈0.0001) and suppressed fat oxidation from 51±3 (ET) to 18±2 μmol/min per kg FFM (P〈0.0001). As the rates of oxidation at more physiological euglycaemic concentrations of glucose were limited to 92±9 μmol/ min per kg FFM, and were similar to those reported when carbohydrate is ingested, the results of the current study suggest that the concentrations of glucose and insulin normally present during prolonged, intense exercise may limit the rate of muscle glucose uptake and oxidation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 1432-1912
    Keywords: Insulin ; Dimerized insulin derivatives ; Insulin receptor antagonists ; Glucose transport ; 3T3-L1 cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of 7 covalently dimerized insulin derivatives on glucose transport in differentiated 3T3-L1 cells were investigated. Symmetric cross-linkage at lysine B29 with a bridge of 2 (oxalyl), 8 (suberoyl) or 12 (dodecanedioyl) carbon atoms produced derivatives with essentially unaltered receptor binding affinity but largely reduced intrinsic activity. Regardless of the chain length, these derivatives inhibited the effect of submaximal insulin concentrations. Insulin derivatives cross-linked at phenylalanine 131 or asymmetrically at 131/1129 were full agonists of the insulin receptor. When lysine B29 was cross-linked with the inactive desoctapeptide(B23-B30)insulin at phenylalanine B1, the intrinsic activity of the resulting dimer was lower than that of insulin, but higher than that of the symmetric B29-dimers. It is concluded that linkage at the B29-lysines, and not at the B1-phenylalanine, leads to partial agonism of dimerized insulin derivatives, regardless of the length of the crosslinker.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 1432-5233
    Keywords: Insulin ; VMH ; Cardiovascular response ; VMH lesion ; Blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cardiovascular responses to insulin-induced hypoglycemia were studied in normal and ventral medial hypothalamic (VMH)-lesioned rats. The goal of this study was to investigate the role of the VMH in mediating the insulin-induced decreases in cardiovascular tone. Male Wistar rats were anesthetized with urethane/chloralose. Following the induction of anesthesia, the trachea, femoral artery, and femoral vein were cannulated. The femoral artery was attached to a pressure transducer for cardiovascular monitoring. The cardiovascular activity was recorded using a Modular Instruments Micro 5000 signal processing system. The mean arterial pressure and pulse pressures and heart rate were evaluated. In control studies, a stable plasma glucose and blood pressure were obtained with urethane/chloralose anesthesia for the duration of the experiments. Insulin (2.0 or 5.0 U/kg) significantly decreased the plasma glucose as well as the blood pressure. In VMH-lesioned rats, the lesions were accomplished by radiofrequency, and the cardiovascular response to insulin-induced hypoglycemia was investigated 1 or 6 weeks later. There was no difference in the cardiovascular response to insulin-induced hypoglycemia between the low or high insulin dose after 1 week in VMH-lesioned animals. The low dose after 6 weeks in VMH-lesioned animals did not produce a change in the mean arterial pressure response compared with controls. The pulse pressure was higher than in the sham-lesioned animals, and the plasma glucose response was greater. The high dose after 6 weeks in VMH-lesioned animals in contrast to sham-lesioned animals led to an increased cardiovascular response instead of a decrease. We propose that the decrease in cardiovascular activity in response to insulin-induced hypoglycemia in normal animals can be attributed to a direct or indirect effect on vascular dilation as well as possibly to an inhibition of sympathetic firing. However, it appears that insulin increases the vascular dilation as well as the parasympathetic tone after 1 week in the VMH-lesioned animals, similar to the findings in sham-lesioned animals. However, after 6 weeks, the insulin-induced decreased cardiovascular tone is minimal. Thus, we believe hat the VMH does not have a direct effect in modulating the insulin-induced decrease in cardiovascular tone, but its destruction appears to influence other regulatory centers.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 1439-6327
    Keywords: Catecholamines ; Insulin ; Growth hormone ; ACTH ; Erythropoietin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To establish whether or not hypoxia influences the training-induced adaptation of hormonal responses to exercise, 21 healthy, untrained subjects [26 (2) years, mean (SE)] were studied in three groups before and after 5 weeks' training (cycle ergometer, 45 min· day−1, 5 days· week−1). Group 1 trained at sea level at 70% maximal oxygen uptake ( $$\dot V$$ O2max), group 2 in a hypobaric chamber at a simulated altitude of 2500 m at 70% of altitude $$\dot V$$ O2max, and group 3 at a simulated altitude of 2500 m at the same absolute work rate as group 1. Arterial blood was sampled before, during and at the end of exhaustive cycling at sea level (85% of pretraining of $$\dot V$$ O2max). $$\dot V$$ O2 increased by 12 (2)% with no significant difference between groups, whereas endurance improved most in group 1 (P 〈 0.05). Training-induced changes in response to exercise of noradrenaline, adrenaline, growth hormone, β-endorphin, glucagon, and insulin were similar in the three groups. Concentrations of erythropoietin and 2,3-diphosphoglycerate at rest did not change over the training period. In conclusion, within 5 weeks of training, no further adaptation of hormonal exercise responses takes place if intensity is increased above 70% $$\dot V$$ O2max. Furthermore, hypoxia per se does not add to the training-induced hormonal responses to exercise.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 1573-6903
    Keywords: Insulin ; chick embryo ; retina ; development ; HPLC analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Retinas of chick embryos contain insulin (1) and further, are capable of synthesizing it, as demonstrated by incubating retinas at different ages (7th–18th day) with [3H]leucine. The synthesized radioactive insulin was isolated and assayed by means of a HPLC procedure. The synthesis of insulin was found to be highest in the youngest retinas studied (day 7), afterwards it declined with age except for an increment found at 14–15 day. Explants of chick embryo retinas, cultured in vitro, rapidly degraded insulin. Nevertheless, the content of immunoreactive insulin in retinal explants diminished slowly with the age of culture, so that, after 8 days of incubation, it was about 60% of the content found in the retinas at the beginning of incubation. This was proof that cultured explants are capable of efficiently synthesizing insulin. The synthesized [3H]insulin was released from explants into the medium. This was evident also after 6–8 days in culture.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 50 (1994), S. 317-332 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a systematic comparison of the correlation contribution at the level of the second-order polarization propagator approximation (SOPPA) and MP2 to the static dipole polarizability of (1) Be, BeH-, BH, CH+, MgH-, AIH, SiH+, and GeH+; (2) BH3, CH4, NH3, H2O, HF, BF, and F2; and (3) N2, CO, CN-, HCN, C2H2, and HCHO. Fairly extended basis sets were used in the calculations. We find that the agreement with experimental values is improved in SOPPA and MP.2 over the results at the SCF level. The signs and magnitudes of the correlation contribution in SOPPA are similar to those obtained in analytical derivative MP2 calculations. However, it is not possible to say, in general, which method gives the largest correlation contribution or the best agreement with experiment, nor is it possible to make a priori prediction of the sign of the correlation contribution. For the first group of molecules, which have a quasi-degenerate ground state, additional CCDPPA and CCSDPPA calculations were performed and compared with polarizabilities obtained as analytical/numerical derivatives of the CCD and CCSD energies. The CCSDPPA results were found to be in better agreement with other calculations than were the SOPPA results, demonstrating the necessity of using methods based on infinite-order perturbation theory for these systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 313-318 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio (TZV*, SBK*, and 3-21G* or 6-31G* basis sets) calculations were performed to predict the geometries and gas-phase proton affinities of Li2O, LiOH, LiNH2, Na2O, NaOH, NaNH2, K2O, KOH, and KNH2. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 285-291 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To accelerate the convergence of the HH expansion, we modified the HH-GLF method, a new simple hyperspherical harmonic method proposed recently by us, into the CFHH-GLF method. Applications of the CFHH-GLF method to the three-body systems He and e- e- e+ exhibit very fast convergence with number of HH basis sets. With only 36 HH and five GLF, we obtain the ground-state energy of -2.90371 au for He, compared with the exact value of -2.90372 au, and with only 36 HH and 10 GLF, we obtained the ground-state energy of -0.26188 au for e- e- e+, compared with the exact value of -0.26200 au. We formulate the CFHH-GLF method in this article. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 147-152 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An iso-energy cutoff scheme is introduced for the calculation of the potential of mean force between two ions in water. The cutoff criterion is based on the optimal interaction of the water dipole with the ion pair, for which analytical expressions are derived. Formulas are also derived to characterize the solvent reorganization contribution to the potential of mean force. Treatment of the contributions from waters outside the cutoff is also discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 267-280 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elongation method, a theoretical tool to synthesize the electronic states of polymers, is applied within the framework of the density functional approach and using a linear combination of Gaussian-type orbitals. In this treatment, the wave function of a cluster is localized and the interaction with an attacking monomer is self-consistently calculated according to the Kohn-Sham equation. The reliability and the applicability of our treatment are examined by the application to a random hydrogen molecule cluster, comparing the results with those obtained by the usual diagonalization method for the whole system. The results show that this treatment efficiently provides the electronic states of the end part of aperiodic polymers. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 301-308 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to the description of the formation of spherulites in a polymer solution is proposed. It is based on an analytical scheme that takes into account the mass conservation law as a fundamental evolution equation. Three physically interesting cases are considered, both which, on deterministic and stochastic levels, can reflect an asymptotic behavior characteristic for spherulites, namely, R(t) ∝ t, where R(t) is a radius of the spherulite measured at instant t. A few examples of systems similar to that under study are mentioned. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 309-319 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An elongation method, which had already been proposed to calculate the electronic structure of aperiodic polymer efficiently, was applied to atactic polypropylene, with the approximation level of the extended Hückel method. The atomic populations thus calculated were found to be dependent sensitively on the tacticity of the polymer. Next, this elongation method was applied to the π-electron stacking system composed of ethylene and butadiene, etc. Excellent agreement was found between the elongation method and the usual extended Hückel calculations. Thus, the elongation method can confidently be applied to π-electron molecular crystal systems. Finally, the local density of states of polyacetylene with both cis-transoid and trans-cisoid structures was calculated. We found that the site with large local density of state in the valence band of a polymer chain gives large electron transfer to the site with large local density of state in the conduction band of another polymer chain. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 395-412 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural and electronic properties of hydrogen-bonded infinite chains of hydrogen cyanide and formamide molecules have been investigated by the ab initio crystal orbital method using several, partly highly polarized, atomic basis sets of increasing size at the Hartree-Fock (HF) level and by including electron correlation effects in the second order of Møller-Plesset perturbation theory. The results obtained show that hydrogen bonding in molecular crystals of the type investigated is a highly cooperative phenomenon, both from the structural and energetic points of view. Comparison with clusters of up to four monomers demonstrate how various structural parameters converge toward their limiting values in the infinite system. The results obtained for infinite HCN chains show an excellent agreement with those observed for solid HCN, whereas the infinite formamide chain proves to be a reasonable model for the corresponding liquid phase. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 413-423 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The many-electron system in one and two dimensions are studied within the geminal approach. The analytical expressions for the wave functions and ground-state energies are obtained for a number of 1-D and 2-D systems: conjugated polymers, organic conductors, 2-D conductors with square lattices, and others. It is shown that electron excitations of a kink type can exist in 2-D systems with mixed valency. In this case, the correlation pairing of current carriers arises as a result of correlation effects leading to superconducting properties of the system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 425-435 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The multiparticle correlation expansion for the entropy of a classical monatomic liquid is presented. This entropy expresses the physical picture in which there is no free particle motion, but, rather, each atom moves within a cage formed by its neighbors. The liquid expansion, including only pair correlations, gives an excellent account of the experimental entropy of most liquid metals, of liquid argon, and of the hard-sphere liquid. The pair correlation entropy is well approximated by a universal function of temperature. Higher-order correlation entropy, due to n-particle irreducible correlations for n ≥ 3, is significant in only a few liquid metals, and its occurrence suggests the presence of n-body forces. When the liquid theory is applied to the study of melting, we discover the important classification of normal and anomalous melting, according to whether there is not or is a significant change in the electronic structure upon melting, and we discover the universal disordering entropy for melting of a monatomic crystal. Interesting directions for future research are extension to include orientational correlations of molecules, theoretical calculation of the entropy of water, application to the entropy of the amorphous state, and correlational entropy of compressed argon. We clarify the relation among different entropy expansions in the recent literature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 11-19 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Möbius transformations recently proposed for integrating functions with a sharp peak close to a single boundary of integration (H.H.H. Homeier and E.O. Steinborn, J. Comput. Phys. 87, 61, 1990) are used to extend Ruedenberg's algorithm for two-center exchange integrals to cases with very diffuse STOs. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 731-765 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first implementation of the intrinsic reaction coordinate (IRC) method within the density functional theory (DFT) framework is presented. The implementation has been applied to four different types of chemical reactions represented by the isomerization process, HCN = HNC (A); the SN2 process, H- + CH4 = CH4 + H- (B); the exchange process, H· + HX = HX + H· (X = F,Cl) (C); and the elimination process, C2H5Cl = C2H4 + HCl (D). The present study presents for each process optimized structures and calculated harmonic vibrational frequencies for the reactant(s), the transition state, and the product(s) along with the IRC path connecting the stationary points. The calculations were carried out within the local density approximation (LDA) as well as the LDA/NL scheme where the LDA energy expression is augmented by Perdew's and Becke's nonlocal (NL) corrections. The LDA and LDA/NL results are compared with each other as well as the best available ab initio calculations and experimental data. For reaction (D), ab initio calculations based on MP2 geometries and MP4SDTQ energies have been added due to the lack of accurate published post-HF calculations on this process. A detailed discussion is provided on the efficiency of the IRC algorithms, the relative accuracy of the DFT and ab initio schemes, as well as the reaction mechanisms of the four reactions. It is concluded that the LDA/NL scheme affords the same accuracy as does the MP4 method. The post-HF methods seem to overestimate activation energies, whereas the corresponding LDA/NL estimates are too low. The LDA activation energies are even lower than the LDA/NL counterparts. The incorporation of the IRC method into the DFT framework provides a promising and reliable tool for probing the chemical reaction path on the potential energy surfaces, even for large-size systems. IRC calculations by ab initio methods of an accuracy similar to the LDA/NL scheme, such as the MP4 scheme, are not feasible. © John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 809-816 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first discussion of the dynamics of Jahn-Teller systems in terms of the electronic density as the fundamental variable was given by W.J. Clinton in 1960, where the degenerate electronic configuration of a Jahn-Teller molecule was interpreted in terms of the infinite number of ways in which the charge distribution can be oriented for the same energy. The moving nuclear framework serves as the perturbation necessary to define the orientation of the charge density, with no activation energy required to put the charge cloud into motion. Recently, this notion of the electronic charge cloud in a Jahn-Teller molecule sweeping out the potential surface over which the nuclei move has found mathematical expression in our work in terms of a generalized electronic current density in nuclear-coordinate space [N. Sukumar and B.M. Deb, Int. J. Quantum Chem. 40, 501 (1991)]. The introduction of the electronic phase as a function of both electronic and nuclear coordinates, in addition to the electronic density, is a crucial component of this formulation. In the present work, the density-based treatment is extended to the nonadiabatic situation, with the Born couplings interpreted as nonadiabatic currents in parameter space. Abelian and non-Abelian gauge transformations of these currents are discussed. © John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 133-134 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 935-945 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Second-order density functional methods are used to introduce the electron correlation in Hartree-Fock (HF) ab initio electronic energy calculations of three-dimensional potential energy surfaces (PES). We analyze the behavior of these methods in PES calculations by applying them to the Li + FH reaction, which has been considered a prototype of the elementary atom-diatom reactions. This system has been studied also by the usual techniques, allowing a point-by-point (for a total of 317 grid points) comparison for the lowest 2A' adiabatic state. In particular, we compare the results obtained using the HF, Møller-Plesset (MP3 level), and configuration interaction (CISD and MRDCI levels) methods with the corresponding results obtained using the Colle-Salvetti (CS) and Moscardó-San Fabián (MSF) procedures using the HF results as the starting point. We found that the CS and MSF procedures support the prediction of a shallow well in the entrance channel that deepens slightly away from collinearity and disappears for a bond angle Θ 〈 74°. We also found that the constrained saddle-point positions remain essentially constant from Θ = 180°-90° and are clearly in the exit channel as for the MRDCI approach (corresponding to the best results). In conclusion, there is a good overall agreement, but there is a question in which this agreement is less pronounced: the heights of the saddle points including the transition state. In particular, the transition-state height is about 3 kcal/mol higher than the more accurate value obtained with the MRDCI approach. However, the second-order density functional methods have been capable of reducing the HF barrier from 18 to 9 kcal/mol (all of these values obtained by spline interpolation), the latter value being very similar to the CISD result. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 291-298 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the first time, we obtain practical density matrices approximately N-representable by correlated-determinant wave functions, which are functionals of the electron density and entirely defined by information obtainable from the X-ray coherent diffraction experiment. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 239-251 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical binding is modeled through interatomic charge transfer and accumulation of electron density at the bond center using the concepts of electronegativity and hardness parameters defined for the bond region. The generalized electronegativity and hardness parameters for the up- and down-spin electrons are also defined within the framework of spin-polarized density functional theory, leading to the formulation of covalent binding in molecules in terms of a two-way flow of unpaired electrons between the atoms. The associated energy changes corresponding to these descriptions are shown to provide quite accurate predictions of bond energies for simple heteronuclear diatomic molecules. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1247-1247 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1229-1243 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of the zinc ion in the active site of alcohol dehydrogenase has been studied by the ab initio Hartree-Fock method. Geometry optimizations were performed using analytical gradients and basis sets of double-zeta quality. Correlation effects were included at the MP2 level. The active site was modeled by Zn(HS)2XL(H2O)0-2, where X denotes ammonia or imidazole and L denotes water, methanol, ethanol, or the corresponding aldehydes or anions. It is shown that with uncharged L-ligands the four-coordinate complexes are about 20, 17, and 40kJ/mol more stable than are the corresponding three-, five-, and six-coordinate complexes, respectively. If the L-ligand is negatively charged, only the four-coordinate complexes are stable. These results suggest that the active-site zinc ion in alcohol dehydrogenase prefers a coordination number of four during the catalytic reaction, especially when the nonprotein ligand is negatively charged. Ligand exchange at the zinc ion is likely to proceed by an associative mechanism with intermittent formation of a five-coordinate complex. The results lend no support to mechanistic proposals attributing an important catalytic role to a negatively charged five-coordinate hydroxide or alkoxide ligand. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 495-509 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unrestricted Hartree-Fock, coupled-cluster calculations are reported for the ground state of NeH+ using atomic basis sets of increasing size and accuracy for both Ne and H. The goal is to determine the basis set and coupled-cluster level of calculation needed to obtain a NeH+ potential energy curve of known accuracy. Here, it is shown that calculations using a quintuple zeta basis at the coupled-cluster singles and doubles level with noniterative triples, CCSD(T), predict a Ne - H bond dissociation energy that is within about 0.01 eV of the exact Born-Oppenheimer molecular electronic structure result. Spectroscopic constants determined using the Simons-Parr-Finlan procedure are found to be in very good agreement with the experimental results. Calculations at the augmented quadruple zeta level for the two lowest triplet excited states of the NeH+ species are presented. Both of these states separate into ground-state Ne+ and H(1s). The resulting potential curves predict stable minima at the SCF, CCSD, and CCSD(T) levels with dissociation energies of about 0.07 eV. Spectroscopic constants from the potential curves and dissociation constants are reported. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 539-548 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 527-537 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have demonstrated molecular dynamics simulations using a combination of the classical molecular dynamics with density functional theory for argon clusters. Three different molecular dynamics schemes, which differ in their treatment of the potential energy and forces, have been carried out. The first uses a Lennard-Jones potential. In the second, the potential is computed using the Harris functional, and in the third, a combination of Lennard-Jones and Harris functional potentials is used. In addition to direct examination of the trajectories, the velocity autocorrelation function and its power spectrum have been computed to demonstrate the agreement between these three methods. The present studies show that a scheme that used a combination of model potentials and density functional theory provides a very useful tool for the dynamics simulation of systems that contain some fragments in which the analytical model potentials are not available. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 511-526 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Local spin density (LSD) methods were used to study the concerted 1,3-dipolar cycloadditions for fulminic acid plus acetylene, fulminic acid plus ethylene, and nitrone plus ethylene. Cartesian Gaussian double-zeta split-valence basis sets augmented with one set of polarization functions (DZVP) were used for the LSD calculations. The LSD calculations were performed with the LSD exchange functional (Dirac) and with the Vosko, Wilk, and Nusair correlation energy functional (VWN). Nonlocal spin-density corrections (NLSD) were estimated with the exchange functional of Becke and the correlation energy functional of Perdew (VWN + BP) and Becke, and the correlation energy functional of Lee, Yang, and Parr (B-LYP). Vibrational frequencies were computed at the VWN and B-LYP levels by numerical differentiation of the analytical first derivatives of the energy. Each of these reactions was examined using Hartree-Fock and Møller-Plesset perturbation theory for comparison. Geometry optimizations were carried out at the Hartree-Fock level with the 6-311G(d,p) basis set, and correlation energies were computed up to the MP4SDTQ/6-311G(d,p) level of theory. For the reactions of fulminic acid plus acetylene, fulminic acid plus ethylene, and nitrone plus ethylene, our best estimated density functional barrier heights are 7.8 ± 1.5, 8.9 ± 0.3, and 11.05 ± 1.9 kcal/mol, respectively. These results are in reasonable agreement with the correlated wave-function calculations and experimental estimates. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 549-557 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work, a way to approximate the correlation energy functional starting from a model correlation factor is shown. The problem is addressed by using formally exact properties of the second-order density matrix and actual values of correlation energies for atoms. An Ansatz for the correlation factor is proposed that allows one to derive some known and some new correlation energy density functionals. Results for atomic systems show the reliability of the approach. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 575-579 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis is presented of the results of earlier ab initio computational studies of cyclobutadiene, cyclooctatetraene, and 1,4-dihydropyrazine. The first and third of these are normally categorized as antiaromatic. All three molecules are polyenes, even when the last two are forced into planar conformations. There is no driving force for extensive π delocalization, even when it would appear to have been facilitated. Calculated isodesmic energies show a net destabilization only in the case of cyclobutadiene, which we attribute to strain and repulsion between the π electrons of the C=C double bonds. The other two molecules have negative isodesmic energies, indicative of net stabilizing effects. We conclude that the concept of antiaromaticity is useful for identifying molecules that resist the apparent opportunity for extensive © delocalization, but that it does not intrinsically imply net destabilization. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 559-573 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Use of orthogonalized Hartree product (OHP) orbitals as the reference orbitals in coupled-cluster (cc) calculations is presented. Since such orbitals are determined without exchange, they provide as “classical” a description as possible. The OHP orbitals were generated by implementing Harris's formulation of the original Hartree method. Some computational considerations of the formulation are discussed. A critical evaluation of the OHP method as an orbital localization scheme is presented. The OHP orbitals were used as the reference in CCD and CCSD calculations and compared with corresponding Hartree-Fock (HF) reference CC results. The average variation of localized Hartree product (LHP) reference CCSD energy from that of the HF reference is 0.83 kcal/mol, whereas for CCD, the average variation is 234 kcal/mol, indicating the importance of single-excitation effects in CC calculations with non-HF references. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 195-203 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of complete coupled-cluster singles, doubles, and triples (CCSDT) calculations have been performed with Hartree-Fock (HF) and Brueckner (B) orbitals. Calculations have been performed with a double-zeta plus polarization basis set on the H2O, SiH2, NH2, BeO, C2, CN+, and BN molecules. Calculations on H2O and SiH2 at equilibrium and stretched geometries show negligible difference between HF-and B-CCSDT energies. This is also true for NH2, except when the bonds have been stretched to twice their equilibrium values, at which point there is about a 2.5 milli-Hartree (mEh) difference. Calculations on the isoelectronic systems BeO, C2, CN+, and BN were performed at equilibrium geometries. Even though these systems have large T1 amplitudes, the difference between HF- and B-CCSDT energies is only about 1 mEh. For the CCSD method and the CCSD(T) method, which includes triple excitations in an approximate, noniterative manner, however, somewhat larger differences are observed between and HF-and B-CC results. Finally, some properties of BN were computed using HF- and B-CC methods. There are quite small differences between the HF- and B-CCSDT results, but significantly larger ones for the more approximate CCSD and CCSD(T) methods. For this difficult system, where the CCSD(T) approximation seems to be inadequate for HF orbitals, the use of Brueckner orbitals improves the agreement of CCSD(T) with CCSD(T) substantially for re and we, although the difference for μ is unaffected. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 181-194 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational study, using relativistic effective core potentials, is presented of transition metalmain group multiply bonded complexes, of interest in the context of catalysis and chemical vapor deposition of TM/MG materials. Model d0 transition metal complexes chosen are of the general form ClnME where M = Zr (n = 2), Ta (n = 3), and W (n = 4). Main group elements of interest are the tetrels (E = C, Si, Ge, Sn), pnictogens (E = N, P, As, Sb), and chalcogens (E = O, S, Se, Te). A comparison between calculated metric data and available experimental data for a wide range of TM = MG complexes will help in further assessing efficient computational approaches to TM complexes, particularly of the heavier MG elements, as a function of metal, ligand and level of theory. In the present work restricted Hartree Fock (RHF) and Møller-Plesset second order perturbation theory (MP2) wavefunctions were employed. In most cases there are small differences between RHF and MP2 calculated geometries, with both methods showing good agreement with experimental data, suggesting these approaches will be suitable for the study of larger, more experimentally relevant models. Changes in ZrE bond lengths for E = chalcogen (upon going from RHF to MP2) suggest a fundamentally different description between the Zr-oxo bond and heavier chalcogens, a result supported by recent experimental data for a series of Zr-chalcogenidos. To date no examples have been reported of arsinidene and stibinidene complexes. Computational results show similar behavior among the heavier pnictogen complexes, i.e., LnM = EH (E = P, As, Sb), suggesting that strategies used to synthesize phosphinidenes may be suitable in the search for the first LnM = AsR and LnM = SbR complexes. Additionally, calculations suggest that design of ligand sets which yield linearly coordinated phosphinidenes (and presumably As and Sb analogues) will lead to phosphinidenes with stronger metal-pnictogen bonds and increased thermodynamic stability versus nonlinearly coordinated examples. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 205-214 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relativistic pair correlation energies of Xe were computed by employing a recently developed relativistic coupled cluster theory based on the no-pair Dirac-Coulomb-Breit Hamiltonian. The matrix Dirac-Fock-Breit SCF and relativistic coupled cluster calculations were performed by means of expansion in basis sets of well-tempered Gaussian spinors. A detailed study of the pair correlation energies in Xe is performed, in order to investigate the effects of the low-frequency Breit interaction on the correlation energies of Xe. Nonadditivity of correlation and relativistic (particularly Breit) effects is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 215-226 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Topological properties of the charge density \documentclass{article}\pagestyle{empty}\begin{document}$ \rho (\vec r) $\end{document} of a series of diatomic molecules, as well as ethane, ethene, and acetylene are calculated at the Hartree-Fock level employing various basis sets, and by the AM1 method. The effect of the core orbitals on the bonding regions in these molecules is examined. The results help to evaluate the utility of AM1 wavefunctions for analyzing the topological properties of the charge density. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 343-344 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 397-405 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Slater-type orbitals (STOs) with a single-exponent by shell or by subshell have been constructed to reduce the number of integrals evaluated in the electronic calculations. The expansion of orbitals in these new basis sets has been carried out in detail for the ground state of the Ne atom. We have carried out a study of STO basis sets with a different size for this atom that could help to propose empirical rules for the selection of these basis sets for other atoms. The usefulness of STOs with single-exponent by shell and subshell and the splitting of s and p functions are discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 407-415 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An application of symplectic implicit Runge-Kutta (RK) integration schemes, the s-stage Gauss-Legendre Runge-Kutta (GLRK) methods of order 2s, for the numerical solution of molecular dynamics (MD) equation is described. The two-stage fourth-order GLRK method, the implicit midpoint rule, and the three-stage diagonally implicit RK method of order four are studied. The fixed-point iteraction was used for solving the resulting nonlinear system of equations. The algorithms were applied to a complex system of N particles interacting through a Lennard-Jones potential. The proposed symplectic methods for MD integration permit a wide range of time steps, are highly accurate and stable, and are thus suitable for the MD integration. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 425-437 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rapidly developing field of statistical theory of spectra of many-electron systems is briefly reviewed. In particular, new formal developments, their implementations in studying general properties of the model spaces, and links to the reduction problem are addressed. Applications in molecular and atomic spectroscopy are also discussed. © 1994 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 447-463 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The convergence properties of the expansions of (a) the function 1/r and (b) the function exp(-αr) in an even-tempered basis of Gaussians are studied analytically. The starting points are the Gaussian integral representations of 1/r and exp(-αr). One arrives at an expansion in a finite number of Gaussians in three steps: (1) a restriction of the integration domain, (2) a variable transformation, and (3) discretization of the integral. The cutoff error goes in both cases essentially as exp(-ah), and the discretization error, as exp(-b/h). The minimum overall error is reached for the β-parameter of an even-tempered basis β ∽ exp(c/√n), where n is the dimension of the basis, and the error itself decreases as ∊ ∽ exp(-d√n). Different optimum basis parameters are obtained depending on which quantity one wants to minimize, e.g., the error of the energy expectation value, the distance in Hilbert space, the variance of the energy, or the density at the nucleus. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 473-485 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantum Chemistry can today boast the fact that ordinary chemists - by means of personal computers and programs available - can study many theoretical properties of molecules by solving the Schrödinger equation and get an advance idea of how to properly arrange their experiments to find new features. For small molecules, they can use ab initio programs of the Hartree-Fock type, and for large molecules, they can use semiempirical programs available. To achieve higher accuracy and to include electron correlation properly, however, one has in the ab initio approach to use configurational interaction methods and giant computers, whereas in the semiempirical methods, the effect of correlating is often taken into account in the adjustable parameters forming the basis for this approach. In connection with the ab initio methods, it is further emphasized that the resolvent methods combined with the partitioning technique provide an excellent conceptual and mathematical framework for getting solutions of any accuracy desired, but that most of the programming of this approach remains to be done. Ordinary wave mechanics is valid at absolute zero of temperature, and - in order to include such important chemical concepts as temperature, entropy, free energy, etc. - one has to go over to general quantum theory and the Liouvillian formalism. One can stil start from the Coulombic Hamiltonian, but it becomes of importance to include the nuclear motion properly and preferably on the same level as that of the electronic motion. It is further emphasized that the irreversibility problem is not yet fully solved, that the theory of the interaction between matter and electromagnetic fields still needs some improvements, and that the question of the proper introduction of relativistic corrections in the quantum theoretical treatment of molecular systems involving heavier atoms still has a great deal to desire. © 1994 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 56
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A microscopic formulation of solution chemical reactions, taking reactants and medium structures into consideration, is presented on the basis of microscopic understandings obtained by recent quantum chemical methods (i.e., ab initio molecular orbital theory, etc.). Assuming thermal equilibrium of the medium bath, an effective internal Hamiltonian is derived, and, further, its derivative with respect to internal normal coordinates is proved explicitly to give the same force field as is provided by the free-energy surface or potential of mean force. The free-energy surface can be expressed in the composite normal coordinate system (CNCS) consisting of some normal coordinate systems of isolated reactants and surrounding solvent molecules (i.e., medium solvent molecules). In CNCS, in use of diagonal elements obtained in the Hessian matrix of the free-energy surface, effective normal-mode frequencies, which reflect the equilibrium solvent effect, are estimated. Furthermore, on the generalized Langevin equation (GLE) treatment, a closed expression of the time-dependent frictional coefficient is derived on a microscopic basis, reflecting the reactant and solvent structures. The nonequilibrium effect is estimated by an analytical expression similar to that in the Grote-Hynes theory. The rate constant is evaluated for a typical model system and it is shown that the equilibrium rate constants should be reduced by a factor 0.997. Finally, it is concluded that the present microscopic theory is reasonably applicable to the estimation of chemical reaction rate constants in solution. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 57
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of physical processes, such as autoionization, predissociation, ac- or dc-field-induced ionization, multiphoton dissociation, or chemical transformations, can be formulated as problems involving a nonstationary state satisfying a time-independent complex eigenvalue Schrödinger equation (CESE). The CESE gives rise to all the conceptual and practical difficulties associated with the polyelectronic structures of excited states, as well as novel ones due to the presence of external fields and to the physical significance of the continuous spectrum. In a series of articles from this institute, it has been shown how advanced electronic structure theory and methods suitable for excited states can be integrated in a practical way into selected elements of the rigorous theory of discrete states interacting with the continous spectrum in order to solve the CESE nonperturbatively and efficiently and compute properties such as positions and widths of inner hole or multiply excited states, multiphoton ionization rates, multichannel predissociation lifetimes, nonlinear static and frequency-dependent polarizabilities, and tunneling rates. The present article constitutes a review of the basic features of this theory and its computational methods. © 1994 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 51 (1994), S. 569-575 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for finding the chemical potential for an electronic system with density ρ = Σρi represented within the Kohn-Sham approximation is proposed. To find the chemical potential of the system under consideration, we propose to refer to the definition μ = δE/δρ and to apply the mathematical properties of functional derivatives. Particularly, in the case examined, the result μ = μ(r) ≠ const has been obtained, which may be explained in the framework of the calculus of variation. Taking the limit limr→∞ μ(r) as the best approximation to the proper equilibrium chemical potential of a free atom, one obtains μ = -I, where I denotes first ionization energy. A possibility of further applications of the proposed method in relation to crystalline systems is also discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 339-348 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydration energies of the proton, hydroxyl ion, and several inorganic ions were calculated using the multicavity self-consistent reaction field (MCa SCRF) method developed for the quantum-mechanical modeling of rotationally or flexible systems in dielectric media. The ionic complexes H3O+(H2O)4, OH-(H2O)4, NH4+(H2O)4, and Hal-(H2O)4, where Hal = F, Cl, or Br, have been studied. Each complex was divided between five spheres, corresponding to the central ion and four water molecules in their first coordination sphere, respectively. Each cavity was surrounded by a polarizable medium with the dielectric permittivity of water at room temperature (80). The ionic hydration energies of ions were divided into specific and nonspecific parts. After accounting for the cavity-formation energy using scaled particle theory, good agreement between the total calculated and experimental hydration energies was obtained for all ions studied. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 89-96 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We presnet a theoretical study of the effect of the conjugation length on the electronic properties and second-order molecular polarizabilities β in p-amino-p′-nitrodiphenylacetylene molecules where the number of triple bonds in the conjugated segment varies from 1 to 4. The β values are calculated via an intermediate neglect of differential overlap/single configuration interaction (INDO/SCI) sum-over-states (SOS) approach. We test the convergence of the SOS method and the validity of the two-state model to describe the β response. The results indicate that increasing the conjugation length results in a decrease of the charge transfer within the molecule. The two-state model is shown to break down as the conjugated segment extends to four triple bonds; this is due to the appearance of several low-lying nearly isoenergetic excited states that significantly contribute to the β response. The theoretical results are in excellent agreement with recent experimental data. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 62
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on the generalized relationship for calculating the nuclear spin-spin coupling constants and the correlation of the bond stretching frequencies with the coupling constants, a novel generalized reationship, which includes the contributions of not only the hybrid orbitals, but also the net atomic charges, is introduced for calculation of the bond stretching frequencies and employed to elucidate the C—H stretching frequencies in hydrocarbons and heterosubstituted hydrocarbons on the basis of the MBOHO calculation employing the CNDO/2 approximation. By use of the obtained concrete realtionships, one can get different νCH value for the C—H bonds existing in different chemical environments, which is coincident with chemical intuition. The calculated numerical results show that for hydrocarbons the contribution of the net atomic charges can be neglected, but it is necessary for heterosubstituted hydrocarbons to include the contribution of the net atomic charges to the C—H stretching frequencies. The calculated C—H stretching frequencies are in good ageement with the experimental data, which shows its reasonableness. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 135-146 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The so-called shake-up satellites accompanying C1s photoionization in C60 have been studied theoretically by means of INDO/CI. It is found that the lowest shake-up satellites in C60 correspond to global charge-transfer excitions that move charge from the opposite side of the fullerence cage to the core-hole region, whereas higher-energy satellites tend to move charge from regions nearer to the core hole. Analogies are drawn, with, on the one hand, smaller model molecules such as napthalene and acenaphtylene and, on the other hand, infinite systems such as graphite. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 165-175 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Hamiltonian model to describe molecular vibrations of triatomic molecules is proposed. The Hamiltonian is based on the use of the Kratzer potential variable for the stretching motions and a perturbed Poschl Teller potential for the bending one. The perturbation and variational treatments to compute the vibrational energies of this Hamiltonian can be developed using a zero-order system that includes part of the couplings between the stretching and bending motions. All the matrix elements involved in these calclations can be then evaluated in closed form. A numerical application to the HCN molecule is made. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 247-265 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron density theory is first employed to express the potential energy curve of the H2+ molecular ion in terms of bond midpoint properties. For heavy homonuclear diatomics, low-ordr density gradient theory is used, but now for the chemical potential, with a similar conclusion to that for H2+. Homonuclear clusters of alkali atoms are then treated in some detail. Finally the dissociation of doubly charged clusters is considered, by a study of supermolecular treated in some detail. Finally the dissociation of doubly charged clusters is considered, by a study of supermolecular ions (Na20+)2 and (K20+)2, again using a density gradient expansion in low order. The deviation between the barrier for fission and the Coulomb barrier is linear in the bond midpoint density over a substantial range of fragment separation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 211-225 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coupled-cluster (CC) methods at the level of CCSD, CCSD+T(CCSD), CCSD(T), CCSDT-1, and CCSDT-3 are applied to calculations of the dipole moment and polarizability of the CN molecule, ionization potentials and electron affinities of the oxygen and iron atoms and CN molecule, and the energy splitting of the 5D and 5F states of the iron atom. Both UHF and ROHF references are applied. Extended basis sets are used in some comparison of CC data to experiment. All calculated atomic and molecular properties are known as challenging problems, suitable for a careful analysis of the performance of sophisticated versions of the CC approach. Attention is paid to energy terms distinguishing CCSD(T) from CCSD+T(CCSD). We exploit results from various iterative and noniterative high-level CC methods in the assessment of error bars in calculations of atomic and molecular properties. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 481-500 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report some of our recent results from theoretical modeling of the interaction between metals and π-conjugated molecules. We apply the semiempirical Austin Model 1 method for the investigation of two fundamentally different systems: sodium interacting with diphenylpolyenes and aluminum interacting with poly (p-phenylenevinylene) and derivatives. In the former case, electronic-structure calculations are also performed using the nonempirical pseudopotential Valence Effective Hamiltonian (VEH) technique. For sodium interacting with diphenylpolyenes, we investigate the geometric and electronic structure modifications that are induced upon charge transfer in a series of diphenylpolyenes with an even number of carbons (from stilbene to α,ω-diphenyltetradecaheptaene, i.e., one to seven double bonds in the polyene part of the molecule). Densities of valence states generated from the VEH calculations are directly compared to experimental ultraviolet photoelectron spectroscopy valence band spectra; these are recorded during successive sodium exposure of the molecular solids. The charge-storage states in the series are discussed in terms of soliton-antisoliton-pairs and polaron-like states induced upon doping (reduction). Introducing aluminum atoms onto poly (p-phenylenevinylene) systems allows us to study the initial stages of interface formation. We find that aluminum atoms preferentially react with the vinylene linkages in both poly (p-phenylenevinylene) and poly (2,5-dimethoxy-p-phenylenevinylene). When carbonyl groups appear on the side of the chains, as in poly (2,5-dialdehyde-p-phenylenevinylene), new reactive sites are induced, leading to structures with stabilities comparable to those in the most stable configurations involving a single vinylene group. In all three systems investigated, the interaction with aluminum induces major modifications of the polymer chains with interruptions of the π-system caused by formation of sp3-like defects. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 553-563 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy surfaces of Mn+/SCN- and Mn+/OCN- (M = Li+ and Mg2+) ion pairs have been calculated at the Hartree-Fock and MP2 levels of theory. The electrostatic potential and the actual binding energies are compared. Besides linear ion pairs, nonlinear ones are also found and are in some cases the most stable ones. The electrostatic potential and the actual binding to cations are compared. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 541-551 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The minimum-energy structures and bonding properties of the hydrogenated lithium clusters, Li4H2 and Li7H, have been investigated by means of an ab initio Monte Carlo simulated annealing method. The minimum-energy structures of Li4H2 and Li7H are found to resemble those of the triangular planar (D3h) isomer of Li6 and Td isomer of Li8 clusters, respectively. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 329-337 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The full-optimized-APSG approach based on the MC SCF technique is developed and applied to study ground-state properties of one-dimensional correlated systems. The effects of electron-electron interactions and bond relaxation are considered for the conjugated diatomic polymer; charge distribution and bond relaxation are calculated for the N = 50 chain within a wide range of site energy and e-e integral modulation involving the case of alternancy symmetry for diatomic systems. With relation to the results obtained, the problem of the neutral-ionic transition in mixed-stack crystals is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 71
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The basic concepts of fractal geometry are reviewed and applied to quasi-two-dimensional zinc electrodeposits. Among the different structures developed during zinc electrodeposition, we have identified the open texture (obtained at large zinc sulfate concentration and small applied potential values) as a typical fractal self-similar structure. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 465-478 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Results of density functional calculations will be reported on a variety of hydrogen-bonded complexes, ranging from weak to strong hydrogen bonds. The charged bimolecular NH3—NH4+ complex and the dimers of water and methanol were investigated using a local approximation of the exchange-correlation potential and two different nonlocal potentials with gradient corrections. In the case of the water dimers, the dependence of the results on the extension of the atomic basis set has also been investigated. The equilibrium structures of all complexes have been determined. Dipole moments, hydrogen-bond lengths, and hydrogen-bonding energies, calculated with corrections for the basis-set superposition error using the counterpoise method, have been found to agree well with the corresponding experimental results. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 457-463 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although several authors proposed the existence of long-range correlations in DNA sequences [W. Li and K. Kaneko, Europhys. Lett. 17, 655 (1992); R.F. Voss, Phys. Rev. Lett. 68, 3805 (1992); C.-K. Peng et al., Nature 356, 168 (1992)], we claim that the real character of the correlations remains uncertain. To corroborate long-range correlations, one should prove that the correlation functions decay as an inverse power of the distance between the nucleotides in the DNA sequence. Instead of a direct calculation of the correlation functions, one can calculate either the Fourier transforms of the sequences or the characteristics of “DNA walk.” In our previous work we pointed out that the character of the results depends upon the way the DNA sequences are chosen. When looking for the correlations separately in introns and separately in exons, we found that the resulting correlations are short range. In this work, we discuss the numerical aspects of two computational approaches: the calculation of correlation function and the evaluation of “DNA walk” characteristics. We present the analytic results for the case of exponential correlations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 491-506 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantum chemical calculations for two different kinds of native proteins (pig insulin and hen egg white lysozyme) were done by the extended negative factor counting method in which the matrix elements have been calculated at the ab initio level with the help of a minimal basis and the simulation of the aqueous solution environment. The hopping conductivities were worked out by the formulas of the random walk theory of Lax and co-workers. The electronic density of states of these native proteins confirmed the conclusions obtained previously from aperiodic model peptides chains. The results show that the ac conductivity vs. frequency curve of these native proteins lies in the range of some typical good inorganic amorphous conductors and thus confirm that proteins, if doped, are amorphous conductors. The behavior of the ac conductivities of the proteins in different ranges of frequencies are discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 625-632 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We test an exchange-correlation functional with explicit dependence on kinetic-energy density as well as the density, its gradient, and its Laplacian, on the Gaussian-2 thermochemical data base. With a small degree of exact-exchange mixing, we find average errors with respect to experiment of order 2 kcal/mol, 0.15 eV, and 2 kcal/mol, respectively, for atomization energies, ionization potentials, and proton affinities. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 633-644 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Density-Functional method, with Linear Combination of Atomic Orbitals, has been applied to eight crystals: the lattice equilibrium parameters, and the lattice formation energies have been calculated at the Hartree-Fock level (HF), at the hybrid Hartree-Fock Density-Functional level (DFT/HF), and at the Kohn-Sham Density-Functional level (DFT). The band structures and the electronic charge distributions calculated at the DFT and HF levels are compared. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 767-797 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We obtain an analytic expression for the total energy of a metallic cluster formed by N atoms of valence v and with net charge Q, by solving variationally the extended Thomas-Fermi version of density functional theory within the spherical jellium model. The energy is expressed as an expansion (mass formula) in decreasing powers of the cluster radius RI = rsZ1/3, with Z = vN, and rs, the one electron radius of the bulk, \documentclass{article}\pagestyle{empty}\begin{document}$$ E\left( {r_s ,Z,Q} \right) = \sum\limits_{n = - 2}^3 {a_n \left( {r_s } \right)Z^{n/3} + Q\sum\limits_{n = 0}^2 {W_n \left( {r_s } \right)Z^{ - n/3} + \frac{1}{2}\frac{{Q2}}{{R_I + d\left( {r_s } \right)}},} } $$\end{document} and the coefficients of this mass formula are functions of rs. Contributions of volume (RI3), surface (RI2), curvature (RI), constant (RI0), (1/RI), and (1/RI2) are clearly separated in the formula. The Chemical potential, work function, electron affinity, and ionization potential are easily obtained for neutral and charged clusters of any electronic density in the metallic range. A general estimation of the critical size for stability against electron detachment of negatively charged clusters is also obtained. The stability of highly charged clusters against fragmentation is also studied. © John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 957-961 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability of the local density approximation (LDA) and of corresponding gradient corrections (for the exchange and correlation energy) for the treatment of the hydrogen bond is investigated. As test systems, we consider the water dimer and the H2O…HX complexes (X = F, Cl, Br): Using an LCAO scheme, their equilibrium geometries and interaction energies are ćalculated and compared with experimental data and with other calculations. We obtain that the LDA gives the geometries in qualitative agreement with other data, whereas the energies are overestimated. The use of the gradient corrections (GC) according to Becke and Perdew leads to a significant improvement of the geometry, and especially of the interaction energies. The calculations indicate further that LDA + GC should also be able to describe weaker intermolecular interactions than the usual hydrogen bond. Finally, a short discussion of the charge distribution and the dipole moments of the H2O…HX complexes is performed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 398-406 
    ISSN: 1040-452X
    Keywords: Preimplantation embryo ; Insulin ; IGFs ; Protein synthesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Previously constructed protein databases for two stages of preimplantation mouse embryogenesis, the compacted eight-cell stage and the fully expanded blastocyst stage, have been used to analyze the effects of insulin, IGF-I, and IGF-II on protein synthesis in these developmental stages. Proteins were labeled by placing, for 2 hr, synchronous cohorts of 35-50 embryos into human tubal fluid (HTF) medium containing L-[35S]-methionine (1 mCi/ml) in the presence or absence of one of the growth factors. The embryos were then washed with medium and lysed. Samples were processed for 2-D gel analysis. For each embryonic stage and each growth factor, four or five experimental replicates were done and the gel images were compared using the PDQUEST system. Using the computer-assisted analysis, we were able to identify proteins that showed a statistically significant (P 〈 0.05) change in synthesis. At the eight-cell stage of development insulin caused increased synthesis of two proteins and decreased synthesis in three proteins. Insulin-treated blastocyst stage embryos exhibited an increased synthesis in eight proteins and decreased synthesis for one protein. The effect of IGF-I at the eight-cell stage of development was mostly inhibitory; the synthesis of only one protein increased and the synthesis of five proteins showed a decrease. Similar results were obtained with blastocyst stage embryos; four proteins demonstrated an increase in synthesis while 14 proteins showed a decrease. Eight-cell stage embryos incubated with IGF-II had seven proteins with a decreased synthesis, although in blastocyst stage embryos, nine proteins showed increased synthesis. However, seven IGF response proteins were found to be proteins that showed significant changes in isotope incorporation during the eight-cell to blastocyst stage of development (Shi et al., 1993). In all, 54 proteins were affected, and these were unique; thus, protein synthesis in preimplantation mouse embryos is influenced by insulin and the IGFs, and further, each growth factor affects specific proteins. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 61-70 
    ISSN: 1059-910X
    Keywords: Salivary gland ; Diabetes ; Insulin ; Electron microscopy ; Streptozotocin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Effects of experimental diabetes on rat submandibular glands have been documented, but earlier reports suggested that diabetes caused an extensive cellular degeneration and a replacement of the parenchymal cells by fibrous connective tissue. Such observations, however, are difficult to reconcile with the relatively normal physiological responsiveness of the gland (Anderson and Suleiman, 1989). This study, therefore, reexamined the histological, histochemical and ultrastructural effects of streptozotocin-induced diabetes on rat submandibular glands. The tissues were examined at 3 weeks, and 3 and 6 months after the induction of diabetes, and compared with glands from age-matched controls by both light and electron microscopy. Light microscopically, the proportional volumes of the acini and granular ducts remained constant in control rats at about 48% and 38% respectively. In diabetic animals the volume density of the acini increased progressively to 62%, whereas that of the granular ducts decreased to 20%. The diameter and number of granular ducts were reduced in diabetic animals, but acinar cell profile area was only affected 6 months after the induction of diabetes. Ultrastructurally, there was an accumulation of lipid in the acinar cells and, with increasing duration of diabetes, the number of autophagic structures in both the acini and the granular ducts increased. Although there was evidence of some cellular degeneration it was never excessive. Morphometry showed that the volume density of secretory granules within the acinar cells was unaffected, but there was a significant reduction in the volume density of secretory granules within the granular ducts. Thus, in the rat submandibular gland the greatest effect of streptozotocin-induced diabetes was to cause hypotrophic changes in the cells of the granular ducts. The relative contributions of a direct effect of insulin insufficiency and the hypogonadal effects of diabetes, however, are not known. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 12-22 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The suitability of the two most widely used strategies to compute semiempirical MEPs is examined. For this purpose, MEP minima, electrostatic charges, and dipoles for a large number of molecules were computed at the AM1, MNDO, and PM3 levels using both the NDDO strategy developed by Ferenczy, Reynolds, and Richards and our own quasi-ab initio method. Results demonstrate that the quasi-ab initio is preferred over the NDDO method for the computation of MEP minima. It is also found that the best set of semiempirical charges and dipoles are obtained using either the AM1 NDDO or the MNDO quasi-ab initio methods. In these two cases, the quality of the results is fully comparable with 6-31G* values. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 54-60 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Explicitly correlated Gaussian functions have been used in variational calculations on the ground state of the helium atom. The major problem of this application, as well as in other applications of the explicitly correlated Gaussian functions to compute electronic energies of atoms and molecules, is the optimization of the nonlinear parameters involved in the variational wave function. An effective Newton-Raphson optimization procedure is proposed based on analytic first and second derivatives of the variational functional with respect to the Gaussian exponents. The algorithm of the method and its computational implementation is described. The application of the method to the helium atom shows that the Newton-Raphson procedure leads to a good convergence of the optimization process. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 90-104 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We described various technical aspects in applying reaction field theories using continuum models to practical problems. It was investigated how solvent-dependent properties of solute molecules are influenced by the following factors: difference in quantum-chemical description of solute-solvent (continuum dielectric) interaction, difference in values of empirically determinable parameters such as atomic radii to define a size of a cavity created in a dielectric to accommodate a solute, and difference in the sophistication level of molecular orbital calculation, including electron correlation and different parameter sets (MNDO, AM1, and PM3). Through these investigations, the better parameter sets were found to evaluate accurately physicochemically important parameters such as hydration enthalpy. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 132-143 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio MP2/6-31G*//MP2/6-31G* and semiempirical AM1 and PM3 calculations on a series of differently substituted α-oxo-ketenes are used to investigate E/Z-isomerism and rotational barriers in these molecules. Sterically crowded derivatives are found to exist solely as s-E conformers. The unusual stability of these derivatives thus can be attributed to their inability to adopt the s-Z conformation required for the normal α-oxo-ketene reactions. With respect to structures and energies, the PM3 method (especially in the case of highly crowded molecules) is found to be less reliable than AM1. Ab initio HF/3-21G and PM3 vibrational frequencies appear to be of sufficient accuracy for a distinction between s-Z and s-E conformers. In this respect, the AM1 method appears less reliable. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 200-207 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Atomic charges derived from a recently described approach to the very rapid computation of AM1 electrostatic potentials (ESP) accurately parallel, but are ca. 20% smaller than, the corresponding HF/6-31G* values. The dipole moments computed from the AM1 charges are virtually identical to those derived directly from the wave function and in rather better agreement with the experimental values than those computed using the HF/6-31G* charges. Unlike other approaches to the semiempirical calculation of ESP-derived charges, the present method also yields near HF/6-31G* quality potentials close to the molecular periphery. For medium-sized organic molecules (40-100 basis functions), the method is approximately two orders of magnitude faster than those involving prior deorthogonalization of AM1 wave function and explicit computation of the full ESP integral matrix. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 233-240 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Rigid inhibitors suffer a smaller loss of conformational entropy when they bind to a macromolecular receptor than their acyclic counterparts. They can also be useful for elucidating pharmacophores due to their reduced conformational space and may be more amenable to synthesis. Computational approaches to rational drug design should therefore take these factors into consideration when suggesting possible compounds. We describe how an acyclic chain which links two parts of a receptor site can be ‘braced’ using ring templates. The acyclic chains may be produced from a number of sources, including lattices or the structures of known inhibitors. The resulting structures contain a rich variety of isolated and fused ring systems, which provide many useful molecular skeletons for subsequent inhibitor design. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 251-268 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A general force field type of calculation has been devised in connection with MM3 to treat 1,2- and 1,4-diketones, both when they are not conjugated (as in derivatives of glyoxal) and when they are conjugated (as in derivatives of ortho- and para-benzoquinone). The molecular structures, moments of inertia, dipole moments, and vibrational spectra have been examined for about 15 compounds, some in several conformations. Ab initio calculations (6-31G*) have been used to determine quantities that have not been previously defined by experiment. In general, the force field permits the calculation of the structures with high accuracy, and the spectroscopic and conformational energy data with fair accuracy. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 313-321 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Effective core potential (ECP) and full-electron (FE) calculations for MoS4-2, MoO4-2, and MoOCl4 compounds were analyzed. Geometry parameters, binding energies, charge distributions, and topological properties of the electronic density were studied for Mo—L bonds (L = S, O, Cl). Results clearly indicate that those approaches that include valence plus 4s and 4p electrons (ECP2 methods) are able to reproduce the topological properties of Mo—L bonds, charge distributions, and geometries with respect to those obtained by FE methods. ECP methods that consider only the 4d and 5s valence electrons (ECP1) fail in the calculation of molecular properties. The use of 5p functions in ECP1 approaches produces a negative Mulliken charge on Mo. Bader's charges give more consistent results than Mulliken's ones. A new parameter for measuring the degree of ionicity is proposed. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 346-350 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The equilibrium geometries, excitation energies, force constants, and vibrational frequencies of the low-lying electronic states X2B1, 2A1, 2B2, and 2A2 of the PF2 radical have been calculated at the MRSDCI level with a double zeta plus polarization basis set. Our calculated geometry, force constants, and vibrational frequencies for the X2B1 state are in good agreement with experimental data. The electronic transition moments, oscillator strengths for the 2A1 → X2B1 and 2A2 → X2B1 transitions, and radiative lifetimes for the 2A1 and 2A2 states are calculated based on the MRSDCI wave functions. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 351-373 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A coarse-grain parallel implementation of the free energy perturbation (FEP) module of the AMBER molecular dynamics program is described and then demonstrated using five different molecular systems. The difference in the free energy of (aqueous) solvation is calculated for two monovalent cations ΔΔGaq(Li+ Δ Cs+), and for the zero-sum ethane-to-ethane′ perturbation ΔΔGaq(CH3—methyl—X → X—methyl—CH3), where X is a ghost methyl. The difference in binding free energy for a docked HIV-1 protease inhibitor into its ethylene mimetic is examined by mutating its fifth peptide bond, ΔG(CO—NH → CH=CH). A potassium ion (K+) is driven outward from the center of mass of ionophore salinomycin (SAL-) in a potential of mean force calculation ΔGMeOH(SAL- · K+) carried out in methanol solvent. Parallel speedup obtained is linearly proportional to the number of parallel processors applied. Finally, the difference in free energy of solvation of phenol versus benzene, ΔΔGoct(phenol → benzene), is determined in water-saturated octanol and then expressed in terms of relative partition coefficients, Δ log(Po/w). Because no interprocessor communication is required, this approach is scalable and applicable in general for any parallel architecture or network of machines. FEP calculations run on the nCUBE/2 using 50 or 100 parallel processors were completed in clock times equivalent to or twice as fast as a Cray Y-MP. The difficulty of ensuring adequate system equilibrium when agradual configurational reorientation follows the mutation of the Hamiltonian is discussed and analyzed. The results of a successful protocol for overcoming this equilibration problem are presented. The types of molecular perturbations for which this method is expected to perform most efficiently are described. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 405-423 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The vibrational spectra of oligomers of thiophene are treated theoretically with the main purpose of deriving information for the interpretation of the infrared and Raman spectra of the polymer and isotopic derivatives. We report the results of a series of semiempirical MNDO calculations on the structure and vibrational properties of oligothiophenes, and we compare the calculated MNDO Pulay scaled force field of the monomer with an empirical harmonic force field that we have obtained by least squares refinement on nine isotopic derivatives. The scaling factors obtained were transferred from thiophene for the computation of the vibrational spectrum and the phonon dispersion curves of the polymer. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 475-475 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 507-523 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A fast computer algorithm is presented for complete analytical calculation of van der Waals surfaces and volumes. Connolly's analytical algorithms, computing second- and third-order atomic spheres overlaps, are shown to give insufficient numerical approximations of the exact van der Waals surfaces and volumes. The presented algorithm computes overlaps of any order. Practical situations frequently involve six-order overlaps. Analytical computed surfaces and volumes of 63 chemicals are compared with Monte Carlo measured values. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 488-506 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An efficient methodology, further referred to as ICM, for versatile modeling operations and global energy optimization on arbitrarily fixed multimolecular systems is described. It is aimed at protein structure prediction, homology modeling, molecular docking, nuclear magnetic resonance (NMR) structure determination, and protein design. The method uses and further develops a previously introduced approach to model biomolecular structures in which bond lengths, bond angles, and torsion angles are considered as independent variables, any subset of them being fixed. Here we simplify and generalize the basic description of the system, introduce the variable dihedral phase angle, and allow arbitrary connections of the molecules and conventional definition of the torsion angles. Algorithms for calculation of energy derivatives with respect to internal variables in the topological tree of the system and for rapid evaluation of accessible surface are presented. Multidimensional variable restraints are proposed to represent the statistical information about the torsion angle distributions in proteins. To incorporate complex energy terms as solvation energy and electrostatics into a structure prediction procedure, a “double-energy” Monte Carlo minimization procedure in which these terms are omitted during the minimization stage of the random step and included for the comparison with the previous conformation in a Markov chain is proposed and justified. The ICM method is applied successfully to a molecular docking problem. The procedure finds the correct parallel arrangement of two rigid helixes from a leucine zipper domain as the lowest-energy conformation (0.5 Å root mean square, rms, deviation from the native structure) starting from completely random configuration. Structures with antiparallel helixes or helixes staggered by one helix turn had energies higher by about 7 or 9 kcal/mol, respectively. Soft docking was also attempted. A docking procedure allowing side-chain flexibility also converged to the parallel configuration starting from the helixes optimized individually. To justdy an internal coordinate approach to the structure prediction as opposed to a Cartesian one, energy hypersurfaces around the native structure of the squash seeds trypsin inhibitor were studied. Torsion angle minimization from the optimal conformation randomly distorted up to the rms deviation of 2.2 Å or angular rms deviation of l0° restored the native conformation in most cases. In contrast, Cartesian coordinate minimization did not reach the minimum from deviations as small as 0.3 Å or 2°. We conclude that the most promising detailed approach to the protein-folding problem would consist of some coarse global sampling strategy combined with the local energy minimization in the torsion coordinate space. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 95
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 627-632 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An important area of research in computational biochemistry is the design of molecules for specific applications. The design of these molecules, which depends on the accurate determination of their three-dimensional structure, can be formulated as a global optimization problem. In this article, we present results from the application of a new conformation searching method based on direct search methods. We compare these results to some earlier results using genetic algorithms and simulated annealing. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 97
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The consistency of three density functional computational implementations (DMol, DGauss, and deMon) are compared with high-level Hartree-Fock and Møller-Plesset (MP) calculations for triazene (HN=NNH2) and formyl triazene (HN=NNHCOH). Proton affinities on all electronegative sites are investigated as well as the geometries of the neutral and protonated species. Density functional calculations employing the nonlocal gradient corrections show agreement with MP calculations for both proton affinities and geometries of neutral and protonated triazenes. Local spin density approximation DMol calculations using numerical basis sets must employ an extended basis to agree with other density functional codes using analytic Gaussian basis sets. The lowest energy conformation of triazene was found to be nonplanar; however, the degree of nonplanarity, as well as some bond lengths, is dependent on the basis set, electron correlation treatment, and methods used for the calculation. © 1994 by John Wiley & Sons, Inc.This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 899-916 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We describe a method for locating clusters of geometrically similar conformers in ensembles of chemical conformations. We first calculate the pairwise interconformational distance matrix in either torsional or Cartesian space and then use an agglomerative, single-link clustering method to define a hierarchy of clusterings in the same space. Especially good clusterings are distinguished by high values of the separation ratio: the ratio of the shortest intercluster distance to the characteristic threshold distance defining the clustering. We also discuss other statistics. The method has been embodied in a program called XCluster, which can display the distance matrix, the hierarchy of clusterings, and the clustering statistics in a variety of formats. XCluster can also write out the clustered conformations for subsequent or simultaneous viewing with a molecular visualization program. We demonstrate the sorts of insight that this approach affords with examples obtained from conformational search and molecular dynamics procedures. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 937-946 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The methodology of conformational potential energy (hyper)surface (PES) elucidation is the subject of this article. The decomposition of the recently developed software CICADA and its implementation in the distributed environment using PVM (parallel virtual machine) is presented. CICADA has been chosen for the parallelization because of its ability to elucidate systematically the low-energy areas of PES in polynomial time. This makes the method applicable on larger systems which are beyond the scope of the grid search. To show the level of parallelization, conformational PES of two molecules, cyclohexane and terminally blocked alanine, have been studied by the distributed version, D-CICADA, and results have been compared to those of the sequential version. D-CICADA was tested on several virtual machines composed of DEC and Sun workstations. The timing shows good efficiency for both the decomposition of the original algorithm and the PVM environment. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 997-1012 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present a novel algorithm of constrained, overdamped dynamics to study the long-time properties of peptides, proteins, and related molecules. The constraints are applied to an all-atom model of the molecule by projecting out all components of the nonbonding interactions which tend to alter fixed bond lengths and angles. Because the overdamped dynamical equations are first order in time, the constraints are satisfied by inversion of a banded matrix at each timestep, which is computationally efficient. Thermal effects are included through a Langevin noise term in the equation of motion. Because high-frequency components of the motion have been eliminated, the timestep of the algorithm is determined by the nonbonding forces, which are two to three orders of magnitude weaker than the bonding forces. Using polyalanine as a test example, we demonstrate that trajectories simulating a microsecond of motion can be run about 103 times faster than an equivalent molecular dynamics simulation. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...