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  • Atomic, Molecular and Optical Physics  (377)
  • Wiley-Blackwell  (377)
  • 1
    Electronic Resource
    Electronic Resource
    Catecholamine interaction with anionic sites - A model study (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1225-1231 
    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: Interactions of catecholamines with acidic sites in the biophase are likely to be involved in the control of the receptors activity as well as in storage and transport mechanisms. In view of the importance of the phenomena a model study of ethanolamine-phosphate complexes was made. The electrostatic interaction energy surface was calculated in the charge density multipole expansion approximation with terms up to quadrupole. The consecutive minimal energy conformation shows the importance for the interaction with the biophase of the catechol ring steric and electronic relation to the side chain.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200607
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  • 2
    Electronic Resource
    Electronic Resource
    Implications of aminoacyladenylate conformations in the prebiotic polypeptide synthesis (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 139-148 
    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: Aminoacyladenylates play a central part in both protein enzymatic and polypeptide prebiotic synthesis. Previous general studies on aminoacyladenylate conformations were extended to some aspects related to polypeptide prebiotic synthesis. Major conclusions drawn from these quantum mechanical PCILO calculations are: (1) In the presence of an ammonium group the glycylphosphate system forms a double seven-membered ring. This folded conformation possesses an important rigidity. This occurs in neutral or acidic solutions. It agrees with experimental observations showing that there is no polymerization in this case, in the absence of catalyst. Thus the catalytic part of montmorillonite clays, which can break the ring by compensation of the anionic and cationic charges, can be understood. (2) When the amine group remains in its neutral form (in basic solutions), numerous stereo structures are allowed for the glycylphosphate stem, among which a ring of weak stability. This is still in good agreement with the observation of polycondensation at high pH without catalyst. (3) The phosphate linking system is flexible enough to allow the extension of the polypeptide chain between the clay layers. This is in accordance with the mechanism proposed by Paecht-Horowitz in which the phosphate is locked on the edge of the montmorillonite sheet.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200712
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  • 3
    Electronic Resource
    Electronic Resource
    Ab initio calculations on H transfer in the HF trimer (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 781-786 
    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: Systematic ab initio LCAO MO calculations with basis sets of increasing size have been performed to analyze the changes in relative stabilization energies of the two cyclic (D3h and C3h symmetry) and the noncyclic HF trimers. The results form the basis for a discussion of cyclic H-transfer reactions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270612
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical study of the geometry of Mn5 (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 231-236 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The geometry of Mn5 in rare gas matrices has been proposed to be a planar pentagon with 25 unpaired electrons. Simple unrestricted Hartree-Fock (UHF) calculations have been carried out using a basis of STO-6G for 1s, 2s, and 2p orbitals with STO-4G for 3s, 3p, 3d, 4s, and 4p in the HONDO5 program. The structure is optimized at the UHF level using the analytic gradient formalism for a planar pentagon. Binding energies and spinmixing are given for the optimized structure.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340827
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  • 5
    Electronic Resource
    Electronic Resource
    Investigation of tertiary structure of a series of DNA compact forms by the small-angle X-ray scattering methodPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 813-817 
    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 work describes the investigation of the space organization of DNA compact forms and DNA-protein complexes by the small-angle x-ray scattering method. A plane texture was disclosed in dehydrated DNP films. Compact DNA particles formed in the presence of poly(ethylene glycol) reveal ordered structures having a periodicity of 84 Å. Various morphological forms of crystals of CTA-DNA were used to obtain small-angle x-ray patterns of the single-crystal type.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170420
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the electrophilic attack. IX. Ab initio study of the C2H4 · HF molecular complexFor Part VIII, see Ref. 1. (1982)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 631-637 
    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: Several configurations of the C2H4 · HF molecular complex were studied using the 4-31G basis set. The most stable configuration was found to be the π hydrogen bonded complex. For this structure the interaction energy was computed employing a double-zeta basis plus polarization functions. The changes in electronic properties of the components C2H4 and HF due to complex formation were discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560220312
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational and MO studies of hydroxy-2-aminotetralins (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1121-1133 
    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: Attempting to explain the differences in the pharmacological profiles of the isomeric monohydroxy-and dihydroxy-2-aminotetralins (DHAT) which are potent dopaminergic agonists we have calculated the conformational energies of 2-aminotetralin and its N,N-dipropyl derivative using the QCFF/Pi and PCILO methods. Molecular electrostatic potential (MEP) maps based on ab initio (STO-3G) wave functions were computed for both dihydroxytetralins. Root-mean-square (rms) deviations from steric congruence between the enantiomeric 5,6- and 6,7-DHAT based either on atomic centers or on the minima in MEP near the putative points of attachment to the receptor are small, but may nevertheless be sufficient to cause differences in activity on subtypes of the dopamine receptor. N,N-dipropyl substitution influences the conformational energies of the skeleton and the preferences in the orientation of the propyl groups in the isomeric DHAT may be important for the interaction with the receptor. The HOMO energies of the isomeric HAT and DHAT do not correlate with their potencies.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230404
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  • 8
    Electronic Resource
    Electronic Resource
    The band description of materials with localizing orbitalsWork supported by the U. S. Department of Energy, BES-Materials Sciences, under contract W-31-109-ENG-38. (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 377-392 
    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: Density functional theory is a form of many body theory that maps the problem onto an equivalent single particle-like system by limiting to the ground state (or some limited ensemble). So it should be surprising that this ground state theory could have any relevance whatsoever to the excitation properties of a material, and yet it does when used carefully! However, the most interesting materials involve active orbitals that are at least partially localized in space, and this has profound effects both on the ground state and the excitation spectrum. My long term interest is in Ce and actinide compounds, where the popular concerns are mixed valence, heavy fermions, and the various forms of magnetic transitions. Band structure calculations can give a great deal of information concerning the mechanisms and degree of the localization as will be shown by examples using the Ce and U Ll2 structured materials and the Ce cubic Laves phase materials. There are some difficulties due to an incomplete knowledge of the functions involved that causes an underestimate of the local character. This will be illustrated and discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300735
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  • 9
    Electronic Resource
    Electronic Resource
    Supercomputing and supercomputers for science and engineering in general and for chemistry and biosciences in particularThis paper, presented at the conference, was partially published in Biological and Artificial Intelligence Systems, edited by E. Clementi and S. Chin, Eds. (ESCOM Science Publishers B.V., Leiden, The Netherlands, 1988). (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 35 (1989), S. 3-89 
    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: We start by pointing out relationships between production of information, global simulation, and supercomputing, thus placing our research activities in today's society context. Then we detail the evolution in hardware and software for 1CAP, our experimental supercomputer, which we claim to be especially well suited for supercomputing in science and engineering. A preliminary discussion of 1CAP/3090 (our latest experimental effort) is included. Many examples from different disciplines are provided to verify our assertions. We “prove” our point by presenting an example of global supercomputing. Starting with 3 nuclei and 10 electrons, building up to a single water molecule, then to a few hundred, we learn, for example, about Raman, infrared, and neutron scattering; we then move up to a few hundred thousand molecules to analyze particle flow and obstructions; finally we experiment, but only preliminarily, with a few million particles to learn more on nonequilibrium dynamics as in the Rayleigh-Benard systems. In this way, quantum mechanics is overlapped with statistical mechanics and expanded into microdynamics. The entire paper is finally reanalyzed from a different perspective, presenting rather systematically, even if most briefly, our ideas on “modern” computational chemistry, where quantum mechanics is as much needed as fluid dynamics and graphics. In this section the main computational techniques are analyzed in terms of computer programs and their associated flow diagrams to solve the basic equations using parallel supercomputers.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560350103
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  • 10
    Electronic Resource
    Electronic Resource
    A molecular orbital valence bond study of 3-methyl sydnone and 3-methyl pseudosydnone (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 153-166 
    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 pair-excitation-multiconfigurational-self-consistent-field (PEMCSCF) study with 10 configurations has been carried out on 3-methyl-1,2,4-oxadiazolin-5-one (3-methyl pseudosydnone) which has normal covalent bonds but is isoelectronic with 3-methyl sydnone for which no single covalent valence bond structure can be drawn. The PEMCSCF results were found to be very similar for the two isoelectronic compounds and an attempt was made to represent the bonding of the sydnone in only two simple molecular-orbital-valence-bond (MOVB) configurations using a Luken-type correlating orbital. A compact minimum basis of Slater-Transform-Preuss functions fitted by six cartesian gaussian orbitals (STP-6G) is used to express the compact representation for chemical comparison to experiment. The molecular geometry was gradient-optimized at the single determinantal level using a 6-31G extended basis set. “Orthonormal Resonance Analysis” is given for the two dominant configurations by noting that the Boys-Reeves configuration interaction algorithm is identical to the Pauling valence bond algorithm except for use of orthogonal molecular orbitals instead of atomic hybrid orbitals. This equivalence permits use of PEMCSCF atomic charges, bond orders, and dipole moments in a slightly modified valence bond interpretation of the unusual bonding of this compound. Although forcing a larger PEMCSCF problem into a minimum basis and only two configurations raises the energy, chemical interpretation is simplified. This comparison between a mesoionic compound and an isoelectric compound with normal bonding offers new understanding of the mesoionic effect.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382418
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