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  • 1
    ISSN: 1432-2234
    Keywords: Molecular orbital ; Nitrosamine metabolism ; Monomethyl nitrosamine ; Methyldiazohydroxide ; Mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Monomethylnitrosamine and methyldiazohydroxide are two proposed N-nitrosamine metabolites, which are formally related by an N → O 1,3-proton shift. Their possible interconversion is an important reaction to investigate in elucidating the pathways involved in the decomposition of carcinogenic N-nitrosamines. Self-consistent field molecular orbital studies using a 4-21G basis set, in which solvation is treated using the supermolcule approach, have led to the proposal of a new low energy pathway for their interconversion; this mechanism involves protonation and the implicit involvement of at least two molecules of water.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computer aided molecular design 14 (2000), S. 307-316 
    ISSN: 1573-4951
    Keywords: bioreductive ; cyclophosphamides ; molecular orbital ; nitroimidazole ; tirapazamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyclophosphamides have been in clinical use as anti-cancer drugs for a long time and much research has been directed towards reducing their side effects. Here we have performed a theoretical investigation into the possibility of designing bioreductive analogues of cyclophosphamides. Our calculations have employed semiempirical molecular orbital AM1-SM2 and PM3-SM3 calculations, as implemented in MOPAC 93, which include a modified Born method for the treatment of solvation. We have investigated the effect of bioreductive activation on the β-elimination reaction that is central to the activation of cyclophosphamides. The approach was tested on two known bioreductive agents, including CB1954, and gave results in agreement with experiment. Non-local density functional calculations on CB1954 and its metabolites, including the radical anion, were in agreement with the semiempirical calculations. The calculations have identified a number of potentially novel bioreductive cyclophosphamides. In particular, our calculations identified compounds in which the initial one-electron reduction was not activating. Such compounds are likely to be more effective bioreductive agents, as the β-elimination will not compete under oxic conditions with the important re-oxidation required for the protection of oxic tissue.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A number of important reactions involved in the formation and metabolism of N-nitrosamines have been studied using a modified reaction field method which treats the solute quantum mechanically and the solvent as a polarized dielectric.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 159-169 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Electrostatic potentials calculated from AM1 wave functions have been compared with ab initio STO-3G values and qualitative agreement has been found. Atomic charges derived from AM1 electrostatic potentials for both experimental and AM1 optimized geometries are of comparable quality with STO-3G potential derived charges. These results suggest that the AM1 electrostatic potential may be useful both in its own right and also for deriving atomic charges for use in molecular dynamics studies.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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