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  • Inorganic Chemistry  (41)
  • Life and Medical Sciences  (29)
  • Computational Chemistry and Molecular Modeling  (10)
  • Physical Chemistry  (9)
  • Wiley-Blackwell  (89)
  • Annual Reviews
  • Oxford University Press
  • Springer
  • 1980-1984
  • 1975-1979  (89)
  • 1950-1954
  • 1978  (89)
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  • Wiley-Blackwell  (89)
  • Annual Reviews
  • Oxford University Press
  • Springer
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  • 1980-1984
  • 1975-1979  (89)
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 815-838 
    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 theoretical approach to study the enthalpy variations occurring during an enzymatic reaction is presented. The structural modifications of the enzyme-substrate complex along the reaction path are distinguished as macro- and microdeformations. Macrodeformations, which concern primarily the approach of the substrate to the enzyme and the release of the reaction products and arise from nonbonded interactions, are treated with an empirical method for computing the energy of a macromolecule. Microdeformations, which are local displacements driven by variations of the electronic structure and its energy and involve only a limited portion of the complex, are treated with the ab initio SCF-LCAO-MO method. The reaction path is idealized as a sequence of major steps: at each step, first the empirical program REFINE is used to calculate the geometry of the system for that step, then the energy of an appropriate subsystem is computed ab initio with the program IBMOL, using the geometry provided by REFINE and applying small concerted atomic displacements. Thus along the entire reaction path one can obtain an energy profile computed with the ab initio method and compatible with the structure of the whole complex. This approach was applied here to the first steps of the reaction of proteolysis catalyzed by papain. The formation of an ion pair ImH+ …S- between the side chains of residues His-159 and Cys-25 was examined in detail. The results show that the instability of the ion pair decreases by ˜ 11.5 kcal/mol when the interactions with residues Asn-175 and Ala- 160 are taken into account; the instability is further decreased by ˜2 kcal/mol after a partial geometry optimization. The energies of the noncovalent enzyme-substrate complex and of the tetrahedral intermediate were computed, considering N-methyl acetamide (NMA) as model substrate and representing papain with the residues Cys-25, His-159, Gln-19, and Ala-160. The interaction energy of the noncovalent complex is -3.8 kcal/mol, compared to the value of +7.4 kcal/mol for the CH3S- -NMA complex. The tetrahedral intermediate is found to be less stable than the noncovalent complex by 27 and 38.5 kcal/mol, respectively, for the papain-NMA and the CH3S- -NMA systems. While these rather large energy differences are possibly due to the incorrect geometry of the tetrahedral intermediate and optimization of the structure is required, it appears that the interactions with the various protein residues represent a very important stabilization factor, which lowers the onthalpy variations during the reaction.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 97 (1978), S. 371-380 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Early passage mouse embryo fibroblasts, mouse 3T3 cell lines, and early passage diploid human fibroblasts grew to higher cell densities in tissue culture medium supplemented with serum than in medium supplemented with defibrinogenated platelet-poor plasma (PPP). Unlike the mouse cells, the human fibroblasts displayed this differential growth response only in the presence of hypophysiologic concentrations of calcium. The addition of heat-treated extracts of human platelets to PPP-supplemented medium stimulated the replication of both the normal mouse cells and early passage human embryo fibroblasts.Human or mouse fibroblasts transformed by either retroviruses or by SV40, including SV40 infected “serum revertants” and “flat transformants,” grew to equal cell densities in medium supplemented with either serum or PPP. Infection of Balb/c-3T3 cells with SV40 rapidly induced them to grow in PPP-supplemented medium demonstrating that the ability of SV40-transformed cell lines to proliferate in PPP-supplemented medium does not arise from the cell culture selection procedures usually employed to obtain stable virus-transformed cell lines. 3T3 cells infected but not transformed by retroviruses do not replicate in PPP-supplemented medium demonstrating that reduction of the growth requirement for the platelet growth factor(s) by retroviruses is a transformation-specific response. Cell cultures that did not proliferate well in PPP-supplemented medium did not form tumors when inoculated into athymic nude mice. Many, although not all, of the lines which grew well in PPP medium were tumorigenic in nude mice. Together, these findings indicate that: (1) normal fibroblast-like cells display a growth requirement for factor(s) present in serum but not found in PPP; (2) this serum specific growth factor is derived from platelets; (3) a primary response to viral transforming genes is a reduction in the growth requirement for these platelet-derived factors; and (4) cells that have a reduced requirement for the platelet-derived growth factor are often tumorigenic.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 10 (1978), S. 783-804 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of hydroxyl radicals with eight substituted aromatic hydrocarbons and four olefins were studied utilizing the flash photolysis-resonance fluorescence technique. The rate constants were measured at 298°K using either Ar or He as the diluent gas. The values of the rate constants (k × 1012) in the units of cm3/molec. sec are (a) OH + o-xylene → products: (12.9±3.8), 20 torr He; (13.0±0.3), 20 torr Ar; (12.4±0.1), 200 torr He;(b) OH + m-xylene → products: (15.6±1.4), 3 torr Ar; (19.4±0.8), 20 torr Ar; (21.4±0.2), 20 torr He; (20.3±1.9), 200 torr Ar; (20.6±1.3), 200 Torr He;(c) OH + p-xylene → products: (8.8±1.2), 3 torr Ar; (10.1±1.0), 20 torr He; (10.5±0.6), 200 torr He;(d) OH + ethyl benzene → products: (7.50±0.38), 3 torr He; (7.06±0.26), 20 torr He; (7.95±0.28), 200 torr He;(e) OH + n-propylbenzene → products: (6.40±0.36), 20 torr He; (5.86±0.16), 200 torr He;(f) OH + isopropylbenzene → products: (7.79±0.40), 200 torr He;(g) OH + hexafluorobenzene → products: (0.221±0.020), 20 torr He; (0.219±0.016) 200 torr He;(h) OH + n-propyl pentafluorobenzene → products: (2.52±0.54), 3 torr He; (3.01±0.76), 20 torr He; (3.06±0.24), 200 torr He;(i) OH + propylene → products: (25.6±1.2), 20 torr He; (26.3±1.2), 200 torr He;(j) OH + 1-butene → products: (29.6±1.9), 3 torr He; (29.4±1.4), 20 torr He;(k) OH + cis-2-butene → products: (43.2±4.1), 3 torr He; (42.6±2.5), 20 torr He;(l) OH + tetramethylethylene → products: (56.9±1.3), 20 torr He.
    Additional Material: 15 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 439 (1978), S. 265-274 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Hydrates of Na2PHO3, Phase Relations and Crystallographic InvestigationsDehydration of Na2PHO3,5 H2O to the respective anhydrous salt was investigated by thermogravimetry and differential thermal analysis. In the course of dehydration an intermediate lower hydrate is formed, Na2PHO3,0.5 H2O. Single crystals of this phase were grown from solution. Na2PHO3,0.5 H2O is rhombohedral, space group R32, R3m or R3m, with a = 18.918(5) Å and α = 33.00(2)°. - The crystal structure of Na2PHO3,5 H2O was redetermined. The pentahydrate is orthorhomic, space group Pnm21, with a = 7.190(1), b = 6.447(1), c = 9.230(2) Å. The structure consists of layers of Na-coordinating polyhedra which share edges and vertices. The layers are connected to a threedimensional structure by hydrogen bonds of the water molecules.
    Notes: Die Dehydratisierung von NaaPHO3 · 5 H2O zum wasserfreien Salz wurde mit Thermogravimetrie und Differentialthermoanalyse untersucht. Die Entwässerung verläuft über die Stufe eines intermediären niederen Hydrates, Na2PHO3 · 0,5 H2O. Einkristalle des Hemihydrates konnten aus Lösung gezüchtet werden; es kristallisiert rhomboedrisch, Raumgruppe R32, R3m oder R3m, mit a = 18,918(5) ß und α = 33,00(2)°. - Die Kristallstruktur von Na2PHO3 · 5 H2O wurde neu bestimmt. Das Pentahydrat kristallisiert orthorhombisch, Raumgruppe Pnm21 mit a = 7,109(1), b = 6,447(1), c = 9,230(2) Å. Die Struktur ist aus Schichten von kanten- und eckenverknüpften Na-Koordinationspolyedern aufgebaut. Die Schichten werden durch Wasserstoffbrückenbindungen der Wassermoleküle zu einem dreidimensionalen Strukturverband verknüpft.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 10 (1978), S. 453-459 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the thermal decomposition of trans-1,2-dicyanocyclobutane, which yields only vinyl cyanide, have been studied in the temperature range of 570°-660°K using a stirred-flow reactor. The reaction was found to be first order and homogeneous with rate constants represented by the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}k{\rm (sec}^{- 1} {\rm) =}{{{\rm (16}{\rm .0} \pm {\rm 0}{\rm .3)} - {\rm (52}{\rm .9} \pm {\rm 0}{\rm .8)}} \mathord{\left/ {\vphantom {{{\rm (16}{\rm .0} \pm {\rm 0}{\rm .3)} - {\rm (52}{\rm .9} \pm {\rm 0}{\rm .8)}} \theta}} \right. \kern-\nulldelimiterspace} \theta} $$\end{document} where θ = 2.303 RT kcal/mol. The Arrhenius parameters are considerably higher than previously reported. On the assumption of a biradical mechanism the results are consistent with a cyano stabilization energy of ∼5 kcal/mol, in good agreement with the results of recent studies of related systems.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 289-297 
    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 paper, MC-SCF and CI methods have been explored for the calculation of ground- and excited-state energies of some aromatic heterocycles in the PPP framework. A new algorithm for solving the orbital equations in MC-SCF theory has been suggested and its performance has been compared with the conventional gradient optimization technique. Energies of first few transitions have been calculated and compared with rather extensive CI results.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 523-528 
    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
    Additional Material: 3 Ill.
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  • 8
    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: Many-body (diagrammatic) perturbation theory (MBPT), coupled-pair many-electron theory (CPMET), and configuration interaction (CI) are investigated with particular emphasis on the importance of quadruple excitations in correlation theories. These different methods are used to obtain single, double, and quadruple excitation contributions to the correlation energy for a series of molecules including CO2, HCN, N2, CO, BH3, and NH3. It is demonstrated that the sum of double and quadruple excitation diagrams through fourth-order perturbation theory is usually quite close to the CPMET result for these molecules at equilibrium geometries. The superior reliability of the CPMET model as a function of internuclear separation is illustrated by studying the 1∑g+ potential curve of Be2. This molecule violates the assumption common to nondegenerate perturbation theory that only a single reference function is important and this causes improper behavior of the potential curve as a function of R. This is resolved once the quadruple excitation terms are fully included by CPMET.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 747-755 
    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 calculations are presented for the [F-; e+] and [CN-; e+] complexes. Positron affinities of 4.99 and 3.79 eV are obtained for F- and CN-, respectively. The excitation energies to the low-lying excited states of the positron complexes are also calculated.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 779-791 
    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: This paper reports an ab initio molecular-orbital (MO) study of binding of SH2 and SH- with ZnII. The mechanism of binding of ZnII with these ligands is investigated using a detailed analysis of the energy decomposition and of the electronic distribution. The dependence of the results on the choice of the basis set for sulfur (in particular the effect of incorporation of diffuses p and d orbitals) on the geometry of ligand binding, the binding energy, and the proton affinity of SH- are investigated. Comparison made with the corresponding results concerning the binding of OH2, OH-, and NH3 shows that sulfur binding is less favorable although more covalent. Both sulfur ligands show a marked preference for angular conformations for binding with the metal ion. The effect of ZnII binding on the ease of deprotonation of H2S is quite similar to the corresponding effect found earlier for H2O.
    Additional Material: 2 Ill.
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