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  • Analytical Chemistry and Spectroscopy  (3)
  • Biochemistry  (2)
  • Wiley-Blackwell  (5)
  • Public Library of Science (PLoS)
  • Springer Nature
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Keywords
Publisher
  • Wiley-Blackwell  (5)
  • Public Library of Science (PLoS)
  • Springer Nature
Years
  • 1
    Electronic Resource
    Electronic Resource
    A spectroscopic study of the hydrogen bonding and π-π stacking interactions of harmane with quinoline (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 185-195 
    Details
    ISSN: 1075-4261
    Keywords: hydrogen bonding ; van der Waals ; betacarbolines ; benzopyridines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A spectroscopic (UV-vis, Fourier transform IR, steady state, and time-resolved fluorescence) study of the interactions of the ground and excited singlet states of harmane (1-methyl-9H-pyrido/3,4-b/indole) with quinoline has been carried out in cyclohexane, toluene, and buffered pH = 8.7 aqueous solutions. To analyze how the number of rings in the substrate influences these interactions, pyridine and phenanthridine have also been included in this study. In cyclohexane and toluene 1 : 1 stoichiometric hydrogen-bonded complexes are formed in both the ground and the excited singlet states. As the number of rings of the benzopyridines and the solvent polarity increase hydrogen-bonding interactions weaken and π-π van der Waals interactions become apparent. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 185-195, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Conformation of zearalenone in solution: A vicinal coupling constant and molecular mechanics study (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 665-667 
    Details
    ISSN: 0749-1581
    Keywords: Zearalenone ; Conformation in solution ; Vicinal coupling constants ; Molecular mechanics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vicinal coupling constants of stereochemical significance were obtained in four solvents for zearalenone and specifically deuteriated zearalenone. Comparison with values calculated for several conformations using molecular mechanics calculations indicates that zearalenone exists in a single conformation in solution. The solvent dependence observed for the H-9′ and H-10′ signals cannot be attributed to a conformational equilibrium.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280802
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  • 3
    Electronic Resource
    Electronic Resource
    Thermodynamic characterization of tautomeric equilibria by multinuclear magnetic resonance. Application to 3-hydroxypyridine (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 552-556 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; 15N NMR ; Variable temperature ; Tautomeric equilibria ; 3-Hydroxypyridine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A marked temperature dependence of the 13C and 15N chemical shifts of 3-hydroxypyridine in D2O (pD = 7.0) was observed. This dependence is explained in terms of thermally induced equilibrium shifts between the neutral form and the zwitterionic form of 3-hydroxypyridine. A method was developed to characterize the thermodynamics of the equilibria that are rapid on the NMR time scale, using the observed average 13C and 15N chemical shifts at different temperatures. This method was applied to the thermodynamics of the tautomerization equilibria of 3-hydroxypyridine. The equilibrium constants and the standard enthalpy change of the tautomerization equilibrium obtained by 13C and 15N methods agree very well with the results obtained by other spectroscopic methods.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310607
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical calculations of β-lactam antibiotics. III. AM1, MNDO, and MINDO/3 calculations of hydrolysis of β-lactam compound (azetidin-2-one ring) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 681-692 
    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: Semiempirical AM1, MINDO/3, and MNDO methods have been used in the study of the alkaline hydrolysis of β-lactam antibiotics through a base-catalyzed, acyl-cleavage, bimolecular mechanism. In this work, the hydroxyl ion has been chosen as nucleophilic agent and the azetidin-2-one ring like a model of β-lactam antibiotic. The MINDO/3 method does not predict correctly the energies of small rings. This, together with the fact that, like MNDO, it cannot detect the occurrence of hydrogen bonds, gives rise to uncertain estimates of energy barriers. The AM1 method can be considered the most suitable for studying the hydrolysis of β-lactam compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130603
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical calculations of β-lactam antibiotics. V. AM1 calculations of hydrolysis of cephalothin in gaseous phase and influence of the solvent (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 1545-1552 
    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: A comprehensive study on the gas-phase alkaline hydrolysis of cephalosporins by using the semiempirical AM1 method was carried out. Cephalothin was the model compound used on account of the presence of a good leaving group at C(3′). According to the results obtained, the hydrolysis process takes place via a twostep reaction mechanism that involves the formation of an intermediate with a fully open β-lactam ring that still preserves the acetate group. Likewise, the exo methylene end product is chiefly formed by nucleophilic attack on the β-lactam carbonyl group of cephalosporins containing a good leaving group at C(3′). On the other hand, the alternative mechanism involving hydrolysis of the ester function in the side chain at 3′ and subsequent hydrolysis of the resulting β-lactam yieds essentially the corresponding enamine. The presence of a first solvation layer consisting of five water molecules showed that, even though some potential barriers are slightly increased, the mechanism involved is identical to that of the gas-phase hydrolysis of this antibiotic. © John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540141217
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