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  • Articles  (18)
  • Analytical Chemistry and Spectroscopy  (11)
  • Biochemistry  (7)
  • 1990-1994  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Analysis of kerogens and kerogen precursors by flash pyrolysis in combination with isotope-ratio-monitoring gas chromatography-mass spectrometry (irm-GC-MS)Woods Hole Oceanographic Institution Contribution 8753. (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 476-488 
    Details
    ISSN: 0935-6304
    Keywords: Isotope ratio monitoring-Gas Chromatography-Mass Spectrometry (irm-GC-MS) ; Compound specific isotope analysis (CSIA) ; Pyrolysis ; Stable carbon isotopes ; Kerogen ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study describes the application of isotope ratio monitoring gas chromatography- mass spectrometry (irm-GC-MS) for compound-specific stable carbon isotopic analysis of aliphatic hydrocarbon and phenolic products from flash pyrolysis (800 °C, 20s) of natural biopolymers and sedimentary kerogens. As part of this work, we provide a detailed description of the analysis of complex samples, including approaches for peak integration, data handling and correction for derivative carbons. Several aliphatic and aromatic biopolymers are analyzed by irm-GC-MS in order to establish relationships between the isotopic signatures of pyrolysis products and those of their parent macromolecules. We also analyze a select group of kerogens and kerogen precursors of different ages and biopolymer compositions to evaluate the applicability of combined pyrolysis/irm-GC-MS to complex geochemical mixtures. Our findings suggest that, in spite of the wide degree of heterogeneity, the isotopic values of individual aliphatic and phenolic pyrolysis products determined by irm-GC-MS can be related to the isotopic composition of the total organic carbon in kerogens and used to trace its biological sources. This study also highlights the need for optimum chromatographic separation in order to fully realize the potential of compound specific isotope analyses.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240170615
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  • 2
    Electronic Resource
    Electronic Resource
    Structural characterization of the cyanelle peptidoglycan of Cyanophora paradoxa by 252Cf plasma desorption mass spectrometry and fast atom bombardment/tandem mass spectrometryDedicated to Professor Peter Krenmayr on the occasion of his retirement from the Technical University of Vienna. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 524-536 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A strategy for the structural characterization of the four major NaBH4-reduced peptidoglycan monomers derived from muramidase-digested peptidoglycan from the cyanelles of the flagellate Cyanophora paradoxa Korschikoff is described. Initial molecular weight determination of these glycopeptides was performed by positive and negative ion plasma desorption mass spectrometry. Due to the presence of two pairs of disaccharide tripeptide and disaccharide tetrapeptide monomers differing in mass by 112 units, respectively, an as yet unknown peptidoglycan modification either at the carbohydrate or at the peptide moiety was assumed. β-Elimination of the disaccharide unit from the unreduced peptidoglycan monomers yielded the corresponding (modified) N1-lactyltripeptides and -tetrapeptides, respectively. These peptides, N-terminally blocked with lactic acid, unambiguously showed the modification to be located on the peptide moiety. By positive ion fast atom bombardment/hybrid tandemmass spectrometry of the reduced peptidoglycan monomers as well as of the corresponding deglycosylated monomers (= N1-lactylpeptides) the modification was determined to be linked to the glutamic acid moiety. Based on combined data from plasma desorption mass spectrometry, tandem mass spectrometry, accurate mass measurement and amino acid analysis of the acid hydrolysate after derivatization with o-phthaldialdehyde by high-performance liquid chromatography we could establish the structure of the modification as N-acetylputrescine. Finally, the confirmation of the linkage of the glutamic acid to diaminopimelic acid via the γ-COOH was based on the presence of a-type peptide backbone fragment ions in the positive ion plasma desorption mass spectra of the modified N1-lactylpeptides.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200220906
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study of some nitriles: Intramolecular hydrogen bonds and anomeric effect (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 722-729 
    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: An ab initio study of 3-chloro-, 3-hydroxy-, 3-mercapto-, and 3-amino-propanenitrile and 4-chloro-bu- tanenitrile was carried out at several levels of theory. The calculated stabilities and geometrical trends are interpreted in terms of the effects of intramolecular hydrogen bonds and anomeric interactions, and compared with available experimental data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130607
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  • 4
    Electronic Resource
    Electronic Resource
    Semiempirical study of compounds with O-H—O intramolecular hydrogen bond (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 860-866 
    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: Application of MNDO, AM1, PM3, MNDO/H, and MNDO/M methods to a set of compounds with intramolecular hydrogen bonds suggested that none of these methods accurately modeled the characteristics of the hydrogen bonds. Since the MNDO/H and MNDO/M methods work well for intermolecular hydrogen bonds, we followed their example and modified MNDO for intramolecular hydrogen bonds by altering the empirical core-core repulsion energy function for all pairs of atoms involved in intramolecular O-H—O bonds. The resulting modified method models the behavior of these bonds quite well, especially as regards their geometry and the barrier to proton transfer. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130710
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  • 5
    Electronic Resource
    Electronic Resource
    Parametrization of a force field for studying some beta-lactams (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 455-465 
    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 molecular mechanics force field for studying some beta-lactams was developed from ab initio and experimental data. The optimized parameters allowed accurate calculation of the geometries of both the compounds on which the parametrization was based and others on which the validity of the predictions was checked. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150409
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular mechanics study of conformational trends in simple alcohols and ethers. II. Intramolecular hydrogen bonding (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 851-859 
    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: In this article we present an extension of our modified MM2(80) force field MM2MOD in which a potential function for hydrogen bonding in alcohols and ethers is included. The results of applying MM2(85), MM2(87), and MM2MOD on ethylene glycol, 2-methoxyethanol and 1,3-propanediol are reported and compared with available experimental data and ab initio results. It is concluded that hydrogen bonding plays an important role in determining the molecular conformations of these systems. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130709
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  • 7
    Electronic Resource
    Electronic Resource
    13C NMR data for several cyclolignans (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 868-875 
    Details
    ISSN: 0749-1581
    Keywords: Cyclolignans ; 13C NMR ; 2D H—C correlations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR shielding data for 100 naturally occurring and hemisynthetic cyclolignans are tabulated. Some of them have been compiled from the literature. The data have been assigned on the basis of 2D heteronuclear 1H-13C correlations.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310915
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of carbonyl substituents on the barrier to rotation in N-ethyl-N-methylamides (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 451-454 
    Details
    ISSN: 0749-1581
    Keywords: Rotation barrier in amides ; N-Ethyl-N-methylamides ; Substituent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The barriers to rotation about the C(O)—N bond for 13 α-alkyl- and α-halo-substituted N-theyl-N-methylamides were determined by 1H NMR spectroscopy at coalescence temperature. Plots of Gibbs free energy (ΔG°) and Gibbs energy of activation (ΔG
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310507
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  • 9
    Electronic Resource
    Electronic Resource
    13C NMR data for abieta-7,13-diene diterpenoids (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 841-844 
    Details
    ISSN: 0749-1581
    Keywords: Abieta-7,13-dienes ; Diterpenoids ; 13C NMR ; 2D 1H—13C shift correlations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR data for several abieta-7,13-diene diterpenoids are reported. The most significant effects caused by the change in the stereochemistry at C-4 and other structural modifications are discussed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310910
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  • 10
    Electronic Resource
    Electronic Resource
    13C NMR spectra of eudesmane derivativesPart IV in the series 13C NMR Spectra of Sesquiterpenes. For Parts I-III, see Ref. 1. (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 678-681 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; 1H NMR ; Sesquiterpenes Eudesmanes ; Epoxides ; Substituent effects ; γ-Effect ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectral data of 18 eudesmane derivatives, mainly acids and esters of natural and synthetic origin, are reported, and the γ-effect of the epoxide ring in two diastereoisomeric epoxy esters is discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300719
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