Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Atomic, Molecular and Optical Physics  (6)
  • Nitrosamine metabolism  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Ab-initio molecular orbital studies on a new mechanism for the interconversion of monomethylnitrosamine and methyldiazohydroxide (1986)
    Springer
    Theoretical chemistry accounts 70 (1986), S. 421-427 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00531923
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Density functional calculation of quinone electrode potentials (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 677-687 
    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: Here, we have applied density functional methods, in combination with free energy hydration calculations, to calculate two-electron electrode potentials for quinones and naphthoquinones. While we find that the free-energy perturbation method, implemented within a molecular dynamics framework, is superior to the PM3 - SM3 continuum method for determining free energies of hydration, the computationally less expensive PM3 - SM3 method does perform well when there is not an internal hydrogen bond. Generally, all the density functional approaches investigated gave good energetics when applied to this problem, but the Beck '88 - Vosko - Wilk - Nusair combination of functionals for the exchange-correlation energy gave the best results. The density functional results are marginally better than the Møller-Plesset second-order perturbation results. Moreover, because the results are obtained using a thermodynamic cycle which involves taking differences in total energies, the results are not too dependent on the quadrature scheme used to calculate the exchange-correlation energy. By using semiempirically optimized geometries and the PM3 - SM3 method for determining free energies of hydration, it has been possible to calculate electrode potentials for a series of large molecules (naphthoquinones) to within about 30 mV of experiment. This result is extremely encouraging and shows that density functional methods offer great promise in the design of redox-active molecules such as bioreductive anticancer agents. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560605
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Theoretical calculation of electrode potentials: Electron-withdrawing compounds (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 293-310 
    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 electrode potential of 2,3-dicyanobenzoquinone in aqueous solution has been calculated relative to parabenzoquinone using a thermodynamic cycle approach that includes accurate gasphase ab initio calculations and calculation of differences in free energies of hydration using the free-energy perturbation method. The discrepancy between the calculated and experimental electrode potential is disappointingly large (99 mV) compared to previous studies using this approach. This, along with the experimental evidence, suggests that the experimental value itself is too large and that theoretical approaches may indeed be as reliable as experimental ones for determining redox properties of molecules such as 2,3-dicyanobenzoquinone. In the light of this discrepancy we have examined the variation of the results with the basis set, inclusion of electron correlation and changes in the parameters used in the molecular dynamics free-energy simulations. The results are shown to be dependent upon the torsional parameters and especially dependent upon the basis set or semiempirical method used to obtain the electrostatic potential-derived charges. The best charge set was determined using the ab initio criteria of completeness - as far as it can be applied to large molecules - and also by studying the effect of hydration on these charges. This was done by allowing the solvent to perturb the wave function prior to the electrostatic potential determination. Thus, 3-21G and 6-31G* basis sets were found to give satisfactory results. Similar results were obtained using semiempirical and ab initio geometries.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560410206
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Energetics of reactions involving radical species in solution: Calculation of relative electrode potentials for nitroimidazoles using density functional and continuum methods (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 59 (1996), S. 135-145 
    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: Nonlocal density functional calculations and a semiempirical modified Born method for computing free energies of hydration were used to calculate the electrode potentials for a series of nitroimidazoles to a mean accuracy of about 80 mV. The density functional calculations used the nonlocal Becke '88 functional for exchange and either the nonlocal Lee-Yang-Parr or the local Vosko-Wilk-Nusair functionals for correlation and were performed at the HF/3-21G geometry. The most suitable geometry for these calculations was determined from a survey of various semiempirical, Hartree-Fock (HF) and density functional methods, with a variety of basis sets. The HF/3-21G method was found to yield a very favorable compromise between speed and accuracy in the determination of the geometry of 2-nitroimidazole, but the small basis set density functional calculations performed very badly. Density functional atom-optimized basis sets were found to give better overall results than traditional Pople-type basis sets. The free energy of hydration calculations employed the AM1 SM2 method. Both the gas-phase energies and the free energies of hydration made a significant contribution to the computed electrode potential. Indeed, an inverse relationship was found between the gas-phase electron affinity and the difference in free energy of hydration between the neutral nitroimidazole and its radical anion. The protocol established here may be useful for investigating novel bioreductive agents. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Ab initio calculations relevant to the mechanism of chemical carcinogenesis by N-nitrosamines. I. The nitrosation of amines (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 167-181 
    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: Ab initio calculations have been carried out on the reaction of NO+ with amines, using a 4-21G basis set. The influence of solvation was investigated using one to three molecules of H2O. Geometry optimizations were carried out on reactants, products, and intermediates. The results show that loss of CH3+ is energetically favorable and this fact has implications with respect to the mechanism of carcinogenesis by dimethylnitrosamine.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260718
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A theoretical study of N-nitrosamine metabolites: Possible alkylating species in carcinogenesis by N,N'-dimethyl nitrosamine (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 751-762 
    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 results of ab initio calculations using a 4-21G basis set are reported for various possible metabolites of N,N'-dimethylnitrosamine. The relevance of these results to the nature of the alkylating agent is discussed. Although the calculations widen the range of possible alkylating agents that need to be considered, the diazonium ion appears to be the most likely candidate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300604
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Hydrated carbonium ions as possible nitrosamine metabolites: An ab initio study (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 123-131 
    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: Various isomers of CH3(H2O)n+ (where n = 1-3) have been studied using self-consistent field gradient techniques. The calculations have largely employed a split valence (4-21G) basis set, although the effects of polarization functions and electron correlation have been considered for a model system. A mechanism for the formation of CH3OH from CH3(H2O)n+, involving linear hydration chains, is proposed, and the relevance of the results to the various proposed pathways for the decomposition of nitrosamine metabolites is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320111
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...