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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of phospholipid molecular species in rat lung as dinitrobenzoate diglycerides by electron capture negative chemical ionization mass spectrometry (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 573-578 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of electron capture negative ion desorption chemical ionization mass spectrometry was demonstrated in the analysis of phospholipid molecular species at the 1,3-dinitrobenzoate (DNB) diglyceride derivative. Modification of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) by phospholipase C treatment and acylation of the resultant diglyceride with 3,5-dinitrobenzoylchloride afforded separation of the alkylacyl, alkenylacyl, and diacyl dinitrobenzoate subclasses by thin-layer chromatography (TLC). Separation of alkylacyl DNB into individual molecular species by reverse-phase high-performance liquid chromatography (RPHPLC) was demonstraed. Electron capture desorption chemical ionization of individual molecular species (10-25 ng) from a direct probe yielded a mass spectrum characterized by an intense molecular anion. This molecular anion was the base peak of the spectrum accounting for greater than 80% of the total ionization. From this molecular anion the total carbon number and degree of unsaturation of the fatty chains could be determined. Analysis of fatty acid content of the molecular species allowed unequivocal assignment of structure for the alkyl ether phospholipids. Using selected ion monitoring as little as 0.5 pmol of these species could be detected with a signal-to-noise ratio ≥3. This technique was useful in the analysis of low picomolar amounts of molecular species of ether phospholipids in the rat lung. Given an appropriate internal standard, analysis of dynamic changes in turnover, metabolism and precursor product relationships could be undertaken.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200141007
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative analysis of platelet activating factor using fast atom bombardment/tandem mass spectrometry (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 439-444 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure is described for the quantitative determination of platelet activating factor (PAF) using stable isotope dilution and fast atom bombardment/tandem mass spectrometry. Low-energy collisional activation of the [M + H]+ ion of PAF yields a single daughter ion of m/z 184, characteristic of phosphocholine derivatives. For precise and accurate quantification the internal standard is (2H3)acetyl-hexadecyl PAF, which yields an analogous daughter ion of m/z 185. Quantitative analyses are based on limited mass-range parent ion scanning with transmission of daughters of m/z 184 and 185 during alternate scans; all scans are accumulated into a single data file to facilitate determination of the analyte/internal standard response ratio. Analysis of authentic hexadecyl PAF indicates a low-picogram detection limit. The method has been applied to the determination of PAF in preparations of human neutrophils stimulated by addition of a calcium ionophore. Concentrations of PAF of 7-17 ng/106 cells were observed, in keeping with earlier reports. The method has been validated by standard addition and dilution experiments. Comparison of data obtained by the new procedure and those obtained by a method involving gas chromatography/electron capture mass spectromery of dephosphorylated and derivatized PAF showed excellent agreement.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180613
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of glutathione conjugates by fast atom bombardment/tandem mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 615-621 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200151107
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  • 4
    Electronic Resource
    Electronic Resource
    Improved detection of glucuronide and glutathione conjugates with thermospray ionization following esterification (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 371-376 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Analysis by thermospray of glucuronide and glutathione conjugates as the corresponding methyl-, propyl-, or hexyl esters is demonstrated to yield a remarkable increase in positive pseudomolecular ion production and to result in a dramatic improvement in detectability of these thermally labile compounds as intact molecular structures. In the most extreme examples a 450-fold increase in the [M + NH4]+ ion intensity was observed for mycophenolic acid glucuronide bis-propyl esters vs. the native conjugate and an 860-fold increase in the [M + H]+ ion intensity was achieved for acetaminophen glutathione bis-hexyl ester vs. the native conjugate. Following esterification, seventeen of the eighteen glucuronide esters analyzed demonstrated an increase in totalion-current yield ranging from 1.1- to 8.3-fold while eighteen of the twenty-one glutathione esters examined demonstrated an increase in totalion-current yield from 2.0- to 26.3-fold. For both types of conjugates a trend in increased relative abundance of the positive pseudomolecular ion intensity is observed as the hydrophobicity of the ester increases from methyl to hexyl. For the glutathione conjugate esters, the [M + H]+ ion represented the base peak in the mass spectra of the majority of samples analyzed. This approach improves the protonated- or ammoniated-molecular-ion abundances of the conjugates to such an extent that it provides a means for unambiguous molecular weight assignments to be made. Although the exact mechanism(s) for the observed phenomenon is not known, it appears that the improvement in sensitivity for the conjugate esters over the corresponding native conjugates involves an increase in pseudomolecular-ion stability and also in part an increased ionization efficiency of the esterified molecule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080506
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  • 5
    Electronic Resource
    Electronic Resource
    Collisionally activated decomposition of modified peptides using a tandem hybrid instrument (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 31-33 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analyses are described of small peptides and related compounds using a tandem hybrid mass spectrometer of BEQQ geometry. Collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment, was performed in the radio frequency (rf)-only quadrupole. Interpretation of fragmentation was greatly facilitated by analysis of labeled analogs, obtained by 18O exchange of carboxyl oxygens. N-Acetylation was also valuable although significant changes in fragmentation resulted from derivatization. Daughter ion spectra of [M + H]+ ions of angiotensin III showed diagnostic fragmentations throughout the peptide chain.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160106
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  • 6
    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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