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  • Wiley-Blackwell  (24)
  • National Academy of Sciences  (15)
  • 1995-1999  (24)
  • 1985-1989  (15)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 507-520 
    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: Multireference configuration interaction (MR-CI) calculations using energy-selected and complete-active-space reference configurations are compared for a large-basis-set treatment of the (H2)2 van der Waals complex in a T geometry. Procedures for estimating truncation errors arising from energy threshold selection of configuration state functions and for extrapolating to the full CI limit are tested by comparisons with untruncated calculations and with the full CI energy. The results of these tests show that great care is required in the use of the correction and extrapolation formulas. Optimization of the orbitals of the reference wave function (compared to the use of SCF orbitals) is found to produce order-of-magnitude improvement in the results.
    Additional Material: 5 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 409-420 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Presented in this paper is a finite element method for the analysis of nonlinear oscillations which exhibit periodic response. The basic idea of the method is to recast the initial value problem as a boundary value problem in which the domain (that is, period) may be unknown. We apply the method to study the free response of the conservative oscillator ü + mu + ∊f(u)=0, where m is either - 1, 0 or 1, f(u) is an odd nonlinear function, and ∊ need not be small. The harmonically forced case, ü + mu + ∊f(u) = Psin Ωt, is also considered, and it is shown that the superharmonic response can be efficiently calculated using this technique.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987), S. 31-38 
    ISSN: 0886-1544
    Keywords: microtubule assembly ; proleolysis ; Vinca drugs ; Zn2+-induced assembly ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Limited proteolysis of tubulin with subtilisin results in cleavage of both the α and β subunits, releasing small peptides from the C-terminal ends. At 37°C the digested tubulin assembles into polymorphic structures: microtubules with attached ribbons in the presence of GTP, rings in the presence of GDP, and protofilament spirals in the presence of vinblastine. Undigested tubulin does not assemble under these conditions. Rings and Vinca-induced spiral structures are assembled from undigested tubulin only when microtubule-associated proteins, high Mg2+ concentrations, or polycations are present. Thus, cleavage with subtilisin affects assembly in a manner similar to the addition of these agents. It appears that binding of positively charged substances may act by neutralizing the charge on the highly acidic C-terminal regions of the α- and β-subunits, while cleavage with subtilisin produces the same effect by removing these peptides. Undigested and subtilisin-digested tubulin form sheets of protofilaments in the presence of Zn2+, which indicates that the binding sites for the 2-3 Zn2+ ions necessary to induce sheet formation do not reside in the C-terminal regions of the monomers.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 918-926 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A negative ion chemical ionization (NICI) gas chromatographic/mass spectrometric method is described for the identification of 15 valproic acid (VPA) metabolites as their pentafluorobenzyl derivatives. Samples analyzed were serum, urine and saliva taken from a volunteer on VPA at steady state and also given selected doses of (2H6)VPA. Metabolite peaks were identified by comparison to synthetic standards. All the metabolites, like the parent drug, produced abundant [M - 181]- ions, except 3-keto VPA, which gave an [M - 181 - CO2]- ion. Using the NICI method, two new VPA metabolites were identified. One of these metabolites was characterized as 4′-keto-2-ene VPA by synthesis, while the second one appeared to be a positional isomer of 4′-keto-2-ene VPA. The sensitivity of the method was also sufficient to detect metabolites of VPA in saliva. The ratio of the levels of (Z)-2-ene VPA to (E)-2-ene VPA was much greater in saliva than in serum, suggesting stereoselective plasma protein binding or transport of these two metabolites. The lower limit of detection for the quantification of VPA in serum or saliva was 2 ng ml-1.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 485-491 
    ISSN: 0886-1544
    Keywords: PMN chemotaxis ; PMN storage ; PMN locomotion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous studies of the storage of polymorphonuclear leukocytes (PMNs) have used an empirical approach to define “optimal” conditions. To date, no storage conditions have been described which satisfactorily preserve the chemotactic function of PMNs beyond 24 h. In an effort to define the precise nature of the storage lesion, we studied the chemotactic locomotion of freshly isolated PMNs and PMNs which had been suspended in citrate-phosphate-dextrose-adenine (CPD-Al) plasma and stored in PVC bags, at 20-22°C for 24 h. We used time-lapse video recording and computer image analysis to quantitate the motion of PMNs migrating under agarose. The positions of individual motile cells were traced at 1-min intervals for 5 min. The following parameters were used to quantitate migration: (1) speed (distance/min), (2)) persistence of locomotion index (velocity/speed), (3) orientation angle (the angle of the vector describing the next displacement of a cell relative lo a direct line toward the chemoattractant), and (4) chemotropic index (cosine of the orientation angle). After 24 h of storage, the following changes were observed: (1) fewer cells migrated, (2) (he speed of migrating cells was reduced by 25%, (3) the persistence of locomotion index decreased by 7%, which indicates that migrating cells made slightly more/wider turns, and (4) the chemotropic index was decreased by 30%, which indicates that migrating cells were less accurate in their orientation toward the chemoattractant. Apparently, the storage of PMNs selectively impairs the ability of some cells to orient accurately in a chemotactic gradient and changes the distribution of these locomotor parameters within the population.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0006-3592
    Keywords: buffer exchange ; chromatography ; flow filtration ; dialysis, counter current ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are three major methods for buffer exchange of proteins at industrial scale: size exclusion chromatography (SEC), tangential flow filtration (TFF), and countercurrent dialysis (CCD). In order to determine the optimal technology for a given process, a study was done to compare these technologies on a technological and economic basis. This comparison required that new mathematical models be developed which enable the common features of each unit operation to be directly compared. The new concept of a diavolume equivalent for SEC, defined as the inverse of the fractional loading, was also introduced to aid in this comparison. Variables that were examined for each unit operation included range of buffer exchange, dilution of protein solution, yield, buffer requirements, total operating time, throughput, plant space, capital, raw materials, and labor costs. It was found that TFF and CCD have a greater range of buffer exchange than SEC. TFF also provides the advantage that concentration of the protein can readily be accomplished in the same step. For processes of equal batch size and yield, TFF and CCD also provide a two- to five- fold improvement in each of the remaining variables. The major economic advantage in using TFF and CCD over SEC is the decreased plant size required for manufacturing and thus the longer term use of existing facilities. Situations where SEC (or CCD) would be favored over TFF are when protein denaturation occurs in TFF but does not occur in SEC. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 138 (1989), S. 367-374 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Black people have a higher propensity than caucasions toward essential hypertension. To explore the possibility that this racial difference relates to cellular Ca2+ metabolism, we measured 45Ca2+ washout and uptake and cytosolic free concentration of Ca2+ [Ca2+], in serially passed skin fibroblasts from normotensive black and white males. Depending on the experimental conditions, 45Ca2+ washout in these cells was described by either two or three exponential functions, whereas 45Ca2+ uptake was described only by a two-exponent function. There were no racial differences in 45Ca2+ uptake and washout of unstimulated fibroblasts. However, stimulation by human serum resulted in an increase in the 45Ca2+ washout that was higher in fibroblasts from blacks than from whites. The racial differences were expressed primarily by higher values of the apparent washout rate constant (k1) of 45Ca2+ from the largest and most rapidly exchangeable cellular pool. The effect of human serum was not related to its origin (blacks vs. whites). In 2 mM Ca2+ medium and 10% serum from blacks, the respective k1 (mean ± SEM; × 10-2/min) values for fibroblasts from blacks and whites were 89.68 ± 5.23 and 73.29 ± 4.0; in the presence of 10% serum from whites, the k1 values for cells from blacks and whites were 84.14 ± 2.80 and 76.36 ± 3.23 (overall significance of P .01). In Ca2+-deficient medium in the presence of 10% human serum, the k1 for fibroblasts from blacks and whites were 115.57 ± 3.76 and 102.15 ± 3.30 (P 〈 .05). Serum substantially increased the 45Ca2+ uptake in fibroblasts from both blacks and whites; however, racial differences were not observed. Basal levels of [Ca2+], were not different in fibroblasts of blacks vs. whites (46.8 ± 6.8 and 43.2 ± 7.1 nM for blacks and whites, respectively). However, the peak response of Ca2+ transients for cell stimulated by 5% human serum was significantly higher in blacks than whites (blacks = 963 ± 213, whites = 481 ± 162 nM; P = .0286). We conclude that Ca2+ regulation is different in serum-stimulated fibroblasts from blacks and whites and that, at least in part, this difference may relate to a greater agonist-induced mobilization of Ca2+ in fibroblasts from blacks.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Transforming growth factor-beta (TGF-β) purified from platelets is a potent growth inhibitor of several normal epithelial cell types in culture. In contrast, some carcinoma cell lines derived from tumors of these same tissues are resistant to this factor. Using recombinant human TGF-β, the authors have confirmed these results with six normal human epidermal keratinocyte strains and four human epidermal squamous carcinoma cell lines. However, the sensitivity of normal cells to TGF-β was found to depend on the culture conditions. When grown in a specialized nutrient medium supplemented with pituitary extract, keratinocytes were completely inhibited by the addition of 0.3 ng/ml TGF-β. In contrast, when their growth was supported by cocultivation with 3T3 fibroblast feeder cells, 30- to 100-fold higher concentrations of TGF-β were required to achieve comparable growth inbibition. This differential sensitivity occurred despite the fact that in both culture systems TGF-β in the culture medium had a half-life of about 50 minutes, becoming tightly bound to the surface of the culture dish. Bound TGF-β proved to be biologically active and stable for about a week in the absence of 3T3 feeder cells. Incubating 3T3 cells on TGF-β-coated dishes, however, resulted in nearly quantitative removal and degradation of the TGF-β within 2 days, permitting normal rates of keratinocyte growth. The binding of TGF-β to surfaces and the ability of fibroblasts to attenuate its inhibitory activity for epithelial cells must be considered when evaluating in vitro models and in planning strategies for the use of this factor in vivo.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 221-228 
    ISSN: 0894-3230
    Keywords: solvent effects ; hydroxide ; oximates ; phosphorus(V) esters ; nucleophilicity ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Second-order rate constants of reactions of OH-, 2,3-butanedionemonooximate and 2-hydroxybenzaldoximate ions with aryl phosphate, phosphinate and thioarylphosphinate esters go through minima with decreasing water content of aqueous acetonitrile, tert-butyl alcohol and N-methyl-2-pyrrolidone. For reactions in H2O-MeCN the solvent effects are analyzed in terms of activity coefficients of the anionic nucleophiles and transition states. In the drier solvents partial desolvation of the nucleophiles increases rates. Nucleophilicities of several oximates and inorganic anions are compared in water. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 405-408 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact induced fragmentations observed in the mass spectra of eight 1,4-diene-3-ketopregnane steroids are described. The effect of hydroxyl substituents in positions 11β, 17α and 21, on the typical fragmentation pattern is analysed; in particular the ‘long range’ effect of the 17α-hydroxy group on the relative abundance of the ions m/z 121 and 122 is confirmed using specific deuterium labelling.
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