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  • 1
    Electronic Resource
    Electronic Resource
    Use of the overlap multipole expansion for approximating molecular electrostatic potentials (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 15 (1979), S. 121-129 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular electrostatic potentials computed by the overlap-multipole-expansion procedure (OMTP) are compared to exact electrostatic potentials computed with the same Gaussian basis set, for different molecular species. It is shown that at distances of the molecule larger than 2.2 Å, the OMTP values compared to those of the exact ones are within an error of 0.5 kcal/mol. This error decreases with increasing distance. For distances below this limit the OMTP potentials may be used as a first indication of the trends of the molecule, provided the values to compare are not too close.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560150112
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  • 2
    Electronic Resource
    Electronic Resource
    A theoretical study of the selective alkali and alkaline-earth cation binding properties of valinomycin (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 109-116 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In an attempt to account for the selectivity displayed by valinomycin with respect to the binding of alkali metal cations, theoretical computations were performed of the interaction energies of this macrocyclic carrier with Na+, K+, Rb+, and Cs+. Subtracting from these interaction energies the corresponding dehydration energies of the cations yields a set of values of the energy balance, the ordering of which follows the ordering of the binding constants measured experimentally in polar solvents. The possibility of extending the procedure to the alkaline-earth cations Mg2+ and Ca2+ is examined.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200709
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  • 3
    Electronic Resource
    Electronic Resource
    On the electrostatic properties of papain in relation to its enzymatic activity (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 353-371 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrostatic potentials and fields created by the thiol protease, papain, are computed on the surface envelope of the protein and in the region of its active site using a technique based on accurate multipole expansions of the electron density of appropriately chosen subunits. The effect of binding counterions to the protein is considered specifically. The possible role of the “electrostatic environment” in the functioning of the enzyme is discussed and it is found that this environment can favor the proton transfer between Cys 25 and His 159 that is thought to initiate its mode of action, but that the reasons for this appear more complicated than earlier models would suggest.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240404
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  • 4
    Electronic Resource
    Electronic Resource
    Cation-ligand interactions: Reproduction of extended basis set Ab initio SCF computations by the SIBFA 2 additive procedure (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 757-771 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of the additive SIBFA 2 procedure, the intermolecular interaction energy is computed as a sum of five terms: ΔE = EMTP + Erep + Epol + ECT + Edisp. In order to assess the accuracy of the procedure to compute cation-ligand interactions, the interaction of alkali (Na+, K+) and alkaline-earth (Mg2+, Ca2+) cations with two representative ligands H2O and HCOO- has been studied and the results compared with those of ab initio SCF extended basis set computations. The additive procedure reproduces very satisfactorily the results of ab initio computations as concerns the numerical values of the interaction energies and the equilibrium cation-ligand distances, as well as the evolution of the energy components. A detailed study of these components at different distances helps, in particular, to delineate the relative weights of the charge-transfer and polarization contributions within the second-order energy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280610
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  • 5
    Electronic Resource
    Electronic Resource
    Zero-field splitting parameters in heterocyclic molecules II. Calculations using SCF, SCF CM and UHF wave functions (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 1055-1058 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030623
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 11 (1977), S. 701-701 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560110413
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio molecular-orbital study of the binding of ZnII with SH2 and SH- (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 779-791 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560140610
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  • 8
    Electronic Resource
    Electronic Resource
    Model studies on the active site of carbonic anhydrase: Ligand properties and CO2 binding (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 16 (1979), S. 641-653 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In view of building a workable molecular model of tetraliganded zinc at the active site of carbonic anhydrase, an ab initio SCF study using pseudopotentials is performed on Zn2+(OH2)n from n = 2 to 6, Zn2+(NH3)n-1 (OH2) for n = 2 and 4, Zn2+(NH3)2 (imidazole) (OH2), and their ionized species involving OH- or imidazolate, considering in particular the evolution of the properties of the ligands and of the bound cation upon increasing n and upon replacement of one ligand by another. (Comparison of NH3 and imidazole binding was made in a full SCF calculation.) The results obtained in the tetraliganded complex confirm that zinc binding facilitates water deprotonation more than imidazole deprotonation, so as to reverse the order of their intrinsic ease of ionization. A study of the approach of CO2 toward the active site is made in an electrostatic approximation using as models the most representative of the computed four-ligand complexes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560160319
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  • 9
    Electronic Resource
    Electronic Resource
    Computations of intermolecular interactions: Expansion of a charge-transfer energy contribution in the framework of an additive procedure. Applications to hydrogen-bonded systems (1982)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 199-215 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure is given to derive an explicit charge-transfer contribution from the Murrell-Randic-Williams formula, and to implement it in the framework of an additive procedure for the computation of intermolecular interaction energies, as a sum of electrostatic, repulsion, polarization, dispersion, and charge-transfer terms. Comparisons are performed between the radial and angular dependence of this term in model hydrogen-bonded systems, and that of the charge-transfer term resulting from SCF supermolecule computations. The evolution of the derived term can be matched very satisfactorily to that of an SCF counterpart when the counterpoise correction is taken into account. The underlying features governing the radial and angular evolution of the counterpoise and charge transfer terms are underlined.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560220118
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  • 10
    Electronic Resource
    Electronic Resource
    Intermolecular interactions: Elaboration on an additive procedure including an explicit charge-transfer contribution (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 29 (1986), S. 101-118 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An additive procedure is derived for the computation of intermolecular interactions, in which an explicit expression for the charge-transfer energy contribution ECT is implemented. In the total interaction energy, \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta E = E_{{\rm MTP}} + E_{{\rm pol}} + E_{{\rm CT}} + E_{{\rm disp}} + E_{{\rm rep}}, $$ \end{document} the electrostatic terms EMTP and Epol are calculated as in our previous treatment. The dispersion contribution is calibrated by reference to variation-perturbation computations on model systems and the repulsion contribution is computed as a sum of bond - bond, bond - lone pair, and lone pair - lone pair interactions. Tests of the procedure are given for representative hydrogen-bonded systems.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560290110
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