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  • 1995-1999  (1)
  • 1985-1989  (2)
  • Analytical Chemistry and Spectroscopy  (3)
  • 1
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The positive ion fast atom bombardment (FAB) mass spectra of oligosaccharides related to D-xylan and D-glucurono-D-xylans were investigated. Although the mass spectra of the underivatized oligosaccharides are relatively weak, they still offer reliable information on the molecular weight of these compounds from their [M + H]+ and [M + H + glycerol]+ ions. Esterification, glycosidation and/or partial methylation improve the relative abundances of the molecular and fragment ions with respect to those of the glycerol matrix. The mass spectra of these derivatized compounds also allow the determination of the mass of the monosaccharide units by the occurrence of more abundant and characteristic fragment ions. The differently linked D-xylobioses of the (1 → 2), (1 → 3) and (1 → 4) type cannot be distinguished on the basis of their mass spectra alone. The collisional activation (CA) spectra of the [M + H + glycerol]+ adduct ions, however, revealed that an unequivocal determination of the type of linkage in these isomers is possible. The small values of the discrepancy factors in the FAB CA spectra prove that CA mass spectrometry is, also in combination with FAB ionization, the most precise of the current mass spectrometric techniques.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The protonated and sodium cationized pseudomolecular ions of a series of reducing and non-reducing oligosaccharides possessing aldopentopyranosyl, 6-deoxyaldohexopyranosyl, ketohexofuranosyl, 4-O-methyl glucuronopyranosyl methyl ester and N-acetyl 2-deoxyglucopyranosylamine units were studied using collision-induced dissociation (CID) fast atom bombardment (FAB) mass spectrometry. The CID spectra of the [M + H]+ ions provide information about the sequence of the monosaccharide units, while dissociation of the [M + Na]+ ions by two-bond ring cleavage processes gives rise to fragment ions which allow differentiation of 1 → 2 and 1 → 4 linkages. The influence of the structure of the constituent monosaccharides on the dissociation of the [M + H]+ and [M + Na]+ ions is discussed. An unusual type of fragmentation, which we suggest involves the elimination of internal monosaccharides residues, has not only been observed in the FAB mass spectra but also in the unimolecular decomposition and CID spectra of both [M + H]+ ions and oxonium ions from several oligosaccharides containing monosaccharide residues with different masses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0749-1581
    Keywords: Xylotriosides ; 29Si NMR ; 1H NMR ; 13C NMR ; 2D Homo- and hetero-nuclear NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 29 and 13C NMR spectra of all possible pertrimethylsilylated β-D-xylopyranosyl-substituted methyl 4-O-β-D-xylopyranosyl-β-D- XYLOPYRANOSIDES ARE ASSIGNED BY HETERONUCLEAR 1H-X 2D NMR chemical shift correlation experiments, where X = C or Si. It is shown that the 29Si NMR spectra can be used for identification of the glycosidation site and ring assignments. The silicon chemical shifts do not follow any simple rule that would allow empirical assignment.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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