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
  • 1
    Electronic Resource
    Electronic Resource
    Molecular-orbital studies of the mechanism of xanthine oxidase-catalyzed oxidation of purines, especially 2-chloropurineSupported by the Robert A. Welch Foundation (Grant No. D-182) of Houston, Texas, and by the Texas Technological College (No. 191-4753). (1967)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 1 (1967), S. 699-719 
    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
    Description / Table of Contents: Les réactions de la 2-chloropurine et d'autre bases, catalysées par la xanthine oxidase, ont été étudiées avec des méthodes différentes basées sur l'idée des orbitales molécularies, telles que HMO, ω-SCF—HMO, et PPP. Ces études not démontré l'importance des indices de réactivité électronique pour comprendre les réactions d'enzymes. De plus il paraît possible de prédire la spécificité de l'enzyme d'une analyse systématique de la différence entre les sites de réactions prédits et observés dans des substrats avec des substituants 2- et 8-oxy.Les concepts de densité d'obritale de frontière, de superdélocalisabilité et d'énergie de localisation se sont avérés tres utiles. Les Méthodes différentes ont donné en général dees résultats consistants.
    Abstract: Ein genauses Studium der durch Xanthine-Oxidas katalysierten Reaktionen von 2-Chloropurin und anderen Basen mittels verschiedenen MO-Methoden, wie HMO, ω-SCF—HMO, PPP, zeigt dass die Enzymreaktionen in der Sprache von elektronischen Reaktivitätsindizes beschrieben werden können. Es scheint möglich das Enzymspezifizität von einer systematischen Analysis der Verschiedenheit zwischen theoretisch berechnbeten und observierten Reaktionslagen in Substraten Mit 2- und 8-oxy Substituenten vorherzusagen.De Regriffe der Grenzorbitaldichte, des Superdelokalisabilitäts und der Lokalisierungsenergie sind sich sehyr nützlich rewiesen. Verschiedence MO-Methoden gaben im allgemeinen übereinstimmende Resultate.
    Notes: A detailed study to the xanthine oxidase-catalyzed reactions of 2-chloropurine and other substrate bases with various molecular-orbital techniques such as HMO, ω-SCF—HMO, and ppp semiempirical SCF—LCAO—MO has shown that the enzyme reactions can be understood in terms of electronic reactivity indices. Furthermore, it appeared possible to suggest the enzyme specificity from a systematic analysis of discrepancy between mo theoretically predicted and observed reaction sites in substrates with 2- and 8-oxy substituents. In other words, the discrepancy does not necessarily indicate the failure of the MO melthodes for such substrates, but it is possible to utilize the result in correlating with binding specificity of the ES complex. This has been done specifically for 2-chloropurine.Among several electronic reacxtivity indices, frontier orbital density, superdelocalizability, and localization energy have been proved to be very useful. Diferent MO methods gave, in general, consistent results.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560010519
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Calculation of molecular geometries, relative conformational energies, dipole moments, and molecular electrostatic potential fitted charges of small organic molecules of biochemical interest by density functional theory (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 1483-1506 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Density functional theory is tested on a large ensemble of model compounds containing a wide variety of functional groups to understand better its ability to reproduce experimental molecular geometries, relative conformational energies, and dipole moments. We find that gradient-corrected density functional methods with triple-ζ plus polarization basis sets reproduce geometries well. Most bonds tend to be approximately 0.015 Å longer than the experimental results. Bond angles are very well reproduced and most often fall within a degree of experiment. Torsions are, on average, within 4 degrees of the experimental values. For relative conformational energies, comparisons with Hartree-Fock calculations and correlated conventional ab initio methods indicate that gradient-corrected density functionals easily surpass the Hartree-Fock approximation and give results which are nearly as accurate as MP2 calculations. For the 35 comparisons of conformational energies for which experimental data was available, the root mean square (rms) deviation for gradient-corrected functionals was approximately 0.5 kcal mol-1. Without gradient corrections, the rms deviation is 0.8 kcal mol-1, which is even less accurate than the Hartree-Fock calculations. Calculations with extended basis sets and with gradient corrections incorporated into the self-consistent procedure generate dipole moments with an rms deviation of 5%. Dipole moments from local density functional calculations, with more modest basis sets, can be scaled down to achieve roughly the same accuracy. In this study, all density functional geometries were generated by local density functional self-consistent calculations with gradient corrections added in a perturbative fashion. Such an approach generates results that are almost identical to the self-consistent gradient-corrected calculations, which require significantly more computer time. Timings on scalar and vector architectures indicate that, for moderately sized systems, our density functional implementation requires only slightly less computer resources than established Hartree-Fock programs. However, our density functional calculations scale much better and are significantly faster than their MP2 counterparts, whose results they approach. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540161206
    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...