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  • Atomic, Molecular and Optical Physics  (173)
  • Wiley-Blackwell  (173)
  • 1990-1994  (92)
  • 1980-1984  (69)
  • 1965-1969  (12)
  • 1955-1959
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  • Wiley-Blackwell  (173)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1225-1231 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 139-148 
    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.
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  • 3
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 631-637 
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1121-1133 
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 153-166 
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 287-298 
    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: In flow tube studies of the quenching of O2(b1Σg+), broad band emission of O2(b):M collision complexes was found to appear under the discrete rotational lines of the 0-0 band of the b1Σg+ → a1Δg electric quadrupole transition at higher oxygen pressures and on addition of foreign gases. Bimolecular rate constants for the collision-induced emission processes have been derived from the ratio of the intensities of the discrete lines and the continuum as well as from low-resolution measurements of the relative intensities of the b → a and b → X bands as a function of O2 and added gas pressure. They range from ≈10-21 cm3 s-1 for He to ≈4 × 10-19 cm3 s-1 for PCl3 vapor.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 657-666 
    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 large values of d = 3N, the radial distribution function of an N-particle system is sharply peaked near the hyperradius rm = (d - 2)/2k0, where k0≡(2/E/)1/2. This fact allows an approximate separation of the hyperradius, leading to many-dimensional hydrogenlike radial solutions. Kindred applications to dimensional scaling are also discussed, where d = DN, with D the spatial dimension. For the large D regime, illustrative analytic formulas are obtained giving the energy and effective nuclear charge for the lowest few S states of the helium atom.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 15-42 
    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 define the algebrant, a mathematical generalization of the determinant, the immanant, the permanent, and the Schur functions. Algebrants are classified as multilinear matrix functions or multicomponent symmetrized tensors. In applications, such as N-electron quantum mechanics, where extensive computation is required, it is vital to reduce computational effort, e.g., the well-known N-factorial problem. We derive certain mathematical properties that can be incorporated in efficient computing algorithms for algebrants. Foremost is our “elimination theorem,” which allows (in important special cases) zeros to be introduced into an algebrant in close analogy with Gaussian elimination for determinants. Savings accruing from such elimination can be substantial. We show examples from Matsen's spin-free quantum chemistry where elimination effectively removes the N-factorial problem that has hitherto stifled possible applications.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 567-572 
    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 local model for the following reaction path is suggested. Exploratory calculations on simple isomerization reactions are undertaken. A local version of Hammond's postulate is proposed and tested on some model systems.
    Additional Material: 2 Ill.
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