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  • Computational Chemistry and Molecular Modeling  (11)
  • Chemistry  (7)
  • computer simulation  (2)
  • Molecular conformation  (1)
  • 1
    ISSN: 1432-2234
    Keywords: Molecular electrostatic potential ; Multipole expansion ; Localized orbitals ; Molecular conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An improvement of a multipole expansion based on localized orbitals and termed LMTP is presented and its ability to generate accurate electrostatic potentials is demonstrated. The possibilities of using this expansion in studying the potential of different conformational states of a molecule without the necessity of recalculating its molecular wavefunction is described and the construction of macromolecular potentials by the superposition of the potentials of subunits is reconsidered.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular engineering 5 (1995), S. 1-9 
    ISSN: 1572-8951
    Keywords: Protein structure ; computer simulation ; membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A strategy for modelling transmembrane α-helix bundles has been investigated. Results concerning the rotational orientations of the helices are described and perspectives for extensions of the method are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1077-1103 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Systematic theoretical modeling of symmetric DNA oligomers, carried out earlier for the B conformation, is now extended to A-DNA. In contrast to the previous results, it is found that A-DNA shows no multiplicity of low-energy substate conformations. The possibilities of the Jumna algorithm are subsequently applied to studying deformations of the oligomers. Controlled winding and stretching deformations are used to study how the two allomorphs and different base sequences absorb such external stress. The results help explain the internal mechanics of the DNA double helix and the extent to which fine structure influences this behavior. The results point to some differences between the A and B double helices, but also to many similarities. Sequence effects on flexibility are relatively limited compared to their impact on optimal energy conformations. It is also shown that the conformational substates detected for B-DNA oligomers are preserved under deformation, but have little influence on its energetics. © 1992 John Wiley & Sons, Inc.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 171-183 
    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 investigation is carried out of the influence of counterions bound to yeast tRNAPhe on the electrostatic potential and steric accessibility of this macromolecule. Two types of cations are considered, the Mg2+ ions located in the crystal of tRNAPhe, with their waters of hydration, and Na+ ions, which are positioned by theoretical estimation. Possible effects of the counterions on the chemical reactivity of tRNAPhe are pointed out.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1451-1461 
    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 potential of the triple helix poly(dT)·tpoly(dA)·poly(dT) is calculated, and the results are examined in relation to those obtained for its component double and single helical parts. For the double helix presenting the standard Watson-Crick hydrogen bonds, the deepest potentials are formed on the side of the major groove, a situation similar to that observed in the A-DNA duplex. For the double helix presenting Hoogsteen-type hydrogen bonds the deepest potentials lie in the major groove, on the side of the pyrimidine strand. In the triple helix the deepest potentials are located in the major groove in a narrow zone over the thymine bases of the Watson-Crick pair.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    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 extent of reactivity of a guanine in B-DNA toward aflatoxin B1 depends on the base sequence surrounding that purine in the double helix. In order to account for this variability, we have computed the ASIF (accessible surface integrated field) index for the N7 atom (at which the reaction occurs) of guanine in a G—C pair surrounded on both sides by different types of base pairs in a model oligohelix. When the conformation of the helix is maintained in the B-DNA form, the correlation ASIF reactivity is limited. A study is performed showing the influence on the ASIF index of different departures from the regular B-DNA conformation, likely to occur in a double helix. It is shown that the correlation ASIF reactivity can be strongly improved by allowing some local departures from this regular arrangement.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 15 (1979), S. 271-280 
    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 offers a unified presentation of the main ring conformers of the diol expoxides, triol carbonium ions, and tetrols related to the “bay-region” benzo ring of carcinogenic metabolites of PAH and brings forward quantitative information through ab initio SCF computations about their relative energies. It substantiates and evaluates the energy of the syn epoxide-OH4 hydrogen bond and, on the contrary, refutes the significance of an O⃛H—O or an O-⃛H—O bond in the triol carbonium ions. It provides an explanation for the similar rates of acid-catalyzed hydrolysis of the syn and anti diol expoxides. It evaluates the stabilization of the triol carbonium ions due to the presence of a neighboring double bond and accounts for the spontaneous opening of protonated epoxides. Finally it accounts for cis hydrolysis of the syn diol epoxide and trans hydrolysis of the anit diol epoxide under acid conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 161-170 
    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: Molecular electrostatic potentials are calculated for a single phospholipid molecule (1,2-dilauroyl-phosphatidylethanolamine) and for its model monolayer. For the single molecule the magnitudes of the positive and negative potentials associated with the amino and phosphate groups of the polar head are comparable. For the monolayer a dominantly positive surface potential is obtained.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 16 (1979), S. 175-188 
    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 quantum-mechanical model study, aided by classical potential calculations, of the formation of adducts between the candidate ultimate carcinogen benzo(a)pyrene diol epoxide and the amino groups of guanine, adenine, and cytosine is presented. An explanation for the preferential reactivity of guanine is proposed and conformational aspects of adduct formation are discussed for both nucleosides and B-DNA.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 259-272 
    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 for calculating the molecular electrostatic potentials on surface envelopes surrounding macromolecules is presented. This new representation of potential is employed in studying B-DNA double helices and, from the results, deductions are drawn on the interaction specificities of B-DNA with electrophiles.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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