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  • Analytical Chemistry and Spectroscopy  (6)
  • Computational Chemistry and Molecular Modeling  (2)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 171-187 
    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 method is presented for the rigorous computation of the electric potential of molecules of arbitrary shape, under the assumption of continuous linear dielectric media. The computational technique involves finding the distribution of induced polarization charge on the molecular surface, and proceeds by an application of the method of boundary elements. The surface, which separates the molecular interior (of low dielectric constant) from the highly polar solvent, is given a piece-wise analytic representation as a collection of curvilinear elements. Given a set of internal fixed charges, the distribution of polarization-charge is found as a continuous function over the surface elements, and the electric potential (including all polarization effects) is then easily computed at any point. The method is applied to a spherical interface, and to several small molecules of biological interest, including a hexapeptide. The resulting potentials show good convergence in all cases. The future application of the method to macromolecules is discussed.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 4-8 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ionic species [C12H11]+ has been formed by ion-molecule reactions in benzene at high pressure (˜0.5 Torr). This ion has been shown to be stable for at least 10-5 s and its structure has been inferred by a study of its unimolecular and collision induced fragmentations in both the first and second field free regions of the ZAB-2F mass spectrometer.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 735-738 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The apperrance of peaks at non-integral masses in linked scans, where the ratio B/E is kept constant, is shown to be caused by fragmentations of metastable ions occuring in the region between the magnetic and electric sectors. A formula is given for calculating the mass of the parent metastable ion and that of its daughter ion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 490-490 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extensive 13C and 15N labelling has shown that the molecular ions of 2-, 3- and 4-cyanopyridine with lifetimes up to 10-6 s eliminate hydrogen cyanide originating predominantly from the ring (˜65%). Moreover, this hydrogen cyanide loss occurs after an equilibrated positional interchange of the ring carbon atoms at positions interchange of the ring carbon atoms at positions 2, 4 and 6 via Dewar pyridine structures. In molecular ions with lifetimes of 10-6-10-5 s skeletal rearrangements have taken place in such a way that both nitrogen atoms have become equivalent prior to the loss of hydrogen cyanide. Arguments are put forward that this equivalence of nitrogen atoms is caused by the intermediacy of ions with a 1,4-dicyanobuta-1,3-diene structure. About 60% of these intermediate ions eliminate hydrogen cyanide in a fast process. The remaining 40% of these ions undergo ring closure again to a pyridine ring in which the carbon atoms of positions 2, 4 and 6 are positionally interchanged rapidly via Dewar pyridine structures followed by ring opening again and eventual loss of hydrogen cyanide. This interpretation of the 13C and 15N labelling results is further corroborated by a study of the loss of hydrogen cyanide from molecular ions of 1,4-dicyanobuta-1,3-diene labelled with 13C in both cyano groups.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 627-628 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The best operating conditions that yield maximum sensitivity at minimum source pressure have been evaluated for the chemical ionization source in a Kratos MS-25 mass spectrometer. The best reagent gas pressure is shown to be different for each gas and is significantly lower than is usually reported in the literature.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 172-176 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deuterium labelling and kinetic energy release measurements have shown that the initially enolic [M—C2H4]+ ions from o-hydroxybutyrophenone have rearranged to o-hydroxyacetophenone ions, if they eliminate a methyl radical.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 603-622 
    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 new method is presented for defining a smooth, triangulated analytic surface for biological molecules. The surface produced by the algorithm is well-suited for use with a recently developed polarizationcharge technique1 for the computation of the electrostatic potential of solvated molecules, and may also be used for calculations of molecular surface areas and volumes. The new method employs Connolly's definitions of contact, reentrant and saddle surface,2 but includes modifications that preclude the presence of self-interesting reentrant surface, and also insure a rigorous decomposition of contact regions into curvilinear finite elements. The triangulation algorithm may be used in conjunction with the electrostatic methods described previously to compute the electric potential of molecules of arbitrary shape in solution. Applications include the estimation of hydration enthalpies, computation of the electrostatic forces associated with solvation, estimation of interactions between separate charged species in solution, and computation of the three-dimensional form of the molecular electric potential. Test calculations are presented for a double-stranded dinucleotide, the polypeptide enkephalin, and the protein ferredoxin.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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