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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of impurities in a synthetic renin substrate peptide by fast-atom bombardment mass spectrometry and hybrid tandem mass spectrometry (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 314-319 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Fast-atom bombardment mass spectrometry of a synthetic renin substrate decapeptide (Pro-His-Pro-Phe-His-Leu-Val-Ile-His-D-Lys) indicated the presence of several of side-products, including a component 12 Da higher in mass. Low-energy collisionally activated decomposition analyses were performed using a hybrid tanden, instrument and demonstrated that the heavier side product had two components, in which the structural modification was either at the N- or the C-terminus. Additional analyses of the N-acetyl derivative indicated that for each component the strucutrual modification blcoked a site of N-acetylation. It is suggested that the formation of these side products is attributable to the generation of formaldehyde, during removal of the histidine protecting group (benzyloxymethyl), which reacts with the N-terminus of the peptide to give an imidazolidinone structure or with the D-lysine ε-amine group to yield an imine. While the precise genesis of the side-products remains speculative, it is clear that the combined strategy of derivatization and tandem mass spectrometry has allowed structural conclusions concerning individual components of an isobaric mixture.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030912
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  • 2
    Electronic Resource
    Electronic Resource
    Introduction to computer-assisted experimentation. Kenneth L. ratzlaff. Wiley-Interscience: New York, NY, 1987. 438 pp + figs and tables. $44.95 (1987)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 1 (1987), S. iv 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290010213
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Application of liquid chromatography/thermospray mass spectrometry to studies on the formation of glutathione and cysteine conjugates from monomethylcarbamate metabolites of bambuterol (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 360-363 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Liquid chromatography/thermospray mass spectrometry (LC/TSP-MS) has been used to identify and study the rates of formation of S-(N-methylcarbamoyl) cysteine and S-(N-methylcarbamoyl)glutathione as products of the in vitro reaction of cysteine and glutathione, respectively, with two monomethylcarbamate metabolites of the bronchodilator pro-drug bambuterol. The conjugates of interest afforded MH+ species and yielded abundant structurally informative fragment ions which were employed in the development of quantitative, selected-ion monitoring assays. It is concluded that LC/TSP-MS represents a rapid and convenient approach to the direct aqueous-phase analysis of the class of S-(N-alkylcarbamoyl) conjugates of cysteine and glutathione.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290031012
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and applications of isotopically labelled compounds (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 195-195 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020909
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  • 5
    Electronic Resource
    Electronic Resource
    The use of alkoxycarbonyl derivatives for the mass spectral analysis of drug-thioether metabolites. Studies with the cysteine, mercapturic acid and glutathione conjugates of acetaminophen (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 637-647 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkoxycarbonyl derivatives of the cysteine-, N-acetylcysteine- and glutathione conjugates of acetaminophen have been prepared in aqueous buffer solutions and their chromatographic and mass spectrometric properties examined. Structurally informative fragmentation patterns of the cysteine- and N-acetylcysteine derivatives were obtained when their methyl esters were subjected to analysis by direct insertion chemical ionization (CH4) mass spectrometry, although field desorption and liquid secondary ion mass spectrometric techniques were required in order to obtain satisfactory spectral data for derivatives of the glutathione adduct. Treatment of ethoxycarbonyl derivatives of the three acetaminophen metabolites with N-methyltrifluoroacetamide-based silylating reagents led to the formation of a common volatile product which was ideally suited to analysis by gas chromatography/electron impact mass spectrometry. A mechanism is proposed for the formation of this novel derivative, which appears to possess a benzo-1,3-thioxalane structure, and its mass spectral characteristics are reported. Finally, the utility of alkoxycarbonyl derivatives for the analysis of drug - thioether conjugates in biological fluids is discussed in terms of their advantages for aqueous phase derivatization, purification by high-performance liquid chromatography and characterization by mass spectrometry.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200151202
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  • 6
    Electronic Resource
    Electronic Resource
    Studies on the biotransformation of ketamine. II - quantitative significance of the N-demethylation pathway in rats in vivo determined by a novel stable isotope technique (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 401-404 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to determine the fraction of an intravenous bolus dose of ketamine which is metabolized in vivo to the corresponding N-desmethyl compound, norketamine, a novel stable isotope technique was developed and applied to a study in rats. Co-injection of equimoiar amounts of deuterium-labeled ketamine and unlabeled norketamine to four animals, followed by gas chromatographic/mass spectrometric analysis of both the administered compounds and deuterium-labeled norketamine in plasma yielded pharmacokinetic data from which the fraction of the parent drug subjected to N-demethylation (fm) was calculated from AUC data to be 36.8 ± 2.4%. It is concluded that this stable isotope co-administration technique represents a powerful approach to the determination of fm, in that the pharmacokinetics of the metabolite of interest, given as the preformed compound and generated in vivo, are determined simultaneously. This experimental design thus obviates the influence of time-dependent changes in metabolite clearance which may complicate the interpretation of studies performed using the classical cross-over design.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180607
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  • 7
    Electronic Resource
    Electronic Resource
    Applications of tandem mass spectrometry to the characterization of derivatized glutathione conjugates. Studies with S-(N-Methylcarbamoyl)-glutathione, a metabolite of the antineoplastic agent N-methylformamide (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 51-56 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Daughter ion spectra are reported for [M + H]+ ions generated by fast atom bombardment mass spectrometry of S-(N-methylcarbamoyl)glutathione (1) and a series of alkoxycarbonyl methyl ester derivatives thereof. Structurally informative, even-electron fragment ions, which serve to define the nature of both the xenobiotic and peptide components of the conjugate, are observed in the collisionally activated dissociation (CAD) spectra of 1 and its ethoxy- and benzyloxycarbonyl methyl esters. Studies with the t-butyloxycarbonyl (tBOC) methyl ester derivative, on the other hand, indicated that the tBOC group exerts a powerful directing influence on the CAD process, and that the major daughter ions in this case are associated with cleavage of the tBOC functionality itself and are of little diagnostic value. Of the derivatives examined, the benzyloxycarbonyl congener, which may be generated readily from 1 in aqueous media, is judged to be the most useful from the standpoints of ease of formation, desirable high-performance liquid chromatographic properties, and informative mass spectral fragmentation characteristics under CAD conditions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160110
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