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  • Digitale Medien  (18)
  • Analytical Chemistry and Spectroscopy  (18)
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  • Digitale Medien  (18)
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  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200141007
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  • 2
    Digitale Medien
    Digitale Medien
    Electron capture negative ion chemical ionization analysis of arachidonic acid (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 175-178 
    Details
    ISSN: 0887-6134
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A highly sensitive (subpicomole level) and structural specific method for the analysis of arachidonic acid esterified to complex glycerophospholipids has been developed using combined capillary gas chromatography and mass spectrometry. The methodology is based upon the formation of the pentafluorobenzyl ester of arachidonic acid, which is efficiently ionized using electron capture negative ion chemical ionization conditions to yield an abundant carboxylate anion at m/z 301. Quantification is carried out following hydrolysis of the complex glycerophospholipid in the presence of a known amount of (2H8) araachidonic acid. The use of this method is illustrated by the quantification of arachidonic acid within the glycerophospholipid classes isolated from resident peritoneal macrophage cells isolated from HS mice.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200150309
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  • 3
    Digitale Medien
    Digitale Medien
    Low-energy fast atom bombardment tandem mass spectrometry of monohydroxy substituted unsaturated fatty acids (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 465-473 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The low-energy collision-induced dissociation (CID) of the carboxylate anions generated by fast atom bombardment ionization of monohydroxy unsaturated fatty acids derived from oleic, linoleic, linolenic and arachidonic acids were studied in a tandem quadrupole mass spectrometer. The collisional activation spectra revealed structurally informative ions as to the position of the hydroxyl substituent in relationship to the sites of unsaturation. Five mechanisms are proposed for the fragmentation of hydroxy substituted unsaturated fatty acids and are dependent upon the presence of α- or β-unsaturation sites. These mechanisms include charge-remote allylic fragmentation, charge-remote vinylic fragmentation, charge-driven allylic fragmentation, charge-driven vinylic fragmentation, and homolytic fragmentation by an oxy-Cope rearrangement process. The assignment of specific fragmentation pathways was supported in many instances with deuterium-labeled analogs. Although no single fragmentation mechanism appears to predominate, a rational approach to the interpretation of these CID spectra is proposed. The CID spectra of unknown compounds could be used to establish the hydroxyl substituent position in relationship to certain sites of unsaturation but would not be indicative of all double bond locations. The oxy-Cope rearrangement is specific for a structural unit, namely the 3-hydroxy-1,5-diene moiety.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200220808
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  • 4
    Digitale Medien
    Digitale Medien
    Fast atom bombardment analysis of arachidonic acid-containing phosphatidylcholine molecular species (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 71-76 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fast atom bombardment (FAB) mass spectrometry was evaluated as a means for the characterization of molecular species of glycerophosphocholines (GPC) from HL60 cells. Previous reports of phospholipid molecular species analysis have suggested that several inherent problems with FAB could limit its analytical usefulness in such an application. The GPC-related secondary ions produced by the FAB experiment were found to be dependent on the matrix employed. Triethanolamine was found to minimize mass-related discrimination in ion emission when mixtures were studied; and furthermore, this matrix maintained 60% maximal ion current after 12 minutes as compared to a glycerol matrix which diminished to 10% maximal ion current. Using triethanolamine, the major GPC species in HL60 cells prelabeled with (2H8) arachidonic acid were found to be 16:0a16:1, 16:0e/18:1, 16:0a/18:1, 18:1a/18:1 and 18:0a/18:1.† It was possible to identify the minor GPC species containing arachidonic acid only after partial purification by reverse-phase high-performance liquid chromatography. Comparison of the 2H8/2H0 enrichment data estimated by FAB with data obtained by gas chromatographic/mass spectral analysis of arachidonic acid following GPC hydrolysis revealed that the precision of FAB was less precise than gas chromatography/mass spectrometry. Yet the FAB technique did allow the observation of one unexpected molecular species (18:1a/20:4) due to the fact that the GPC was not degraded to simpler species prior to analysis. In this respect, the two strategies of molecular species analysis complement each other.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200130205
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  • 5
    Digitale Medien
    Digitale Medien
    The exchange of [18O]-H2O with the aromatic oxygen atoms of catecholamine metabolites (1980)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1980), S. 345-348 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Catechol oxygen atoms can be exchanged with oxygen-18 atoms in [18O]-H2O under acidic conditions. The catechol oxygen atoms in L-3, 4-dihydroxyphenylalanine both underwent significant exchange with water when heated in 3 N HC1 at 150 °C for 20 days. Under the same conditions of heat and strong acid, vanillylmandelic acid was degarded to homovanillic and dihydroxyphenylacetic acid in two hours. Exchange of the catechol oxygen with the solvent occurred simultaneously with degradation. This degradation of vanillylmandelic acid formally involves reductive cleavage of the aliphatic hydroxyl in a reaction which is probably general for compounds of similar structure. An analogous, although slower, degradation of dihydroxyphenyllactic acid to dihydroxyphenylpropionic acid accompanied by catechol oxygen atom exchange was observed. Direct exchange of catechol oxygen atoms and degradation of appropriate precursor molecules are two facile methods for the preparation of oxygen-18 labelled compounds containing the catechol moiety.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200070806
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  • 6
    Digitale Medien
    Digitale Medien
    Preparation of oxygen-18-labeled lipoxygenase metabolites of arachidonic acid (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 714-718 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Plasma pseudocholinesterase and porcine liver esterase were used to catalyse the incorporation of the stable isotope oxygen-18 into the carboxyl moiety of lipoxygenase metabolites of arachidonic acid. This simple method produces eicosanoid products containing two oxygen-18 atoms; but the enzymes studied were found to display large substrate specificity in the efficiencies at which oxygen-18 could be incorporated into the lipoxygenase metabolites. Furthermore, [18O2]LTB4 was found not to back exchange during in vitro incubation with human neutrophils. The methods involved for stable isotope incorporation are simple, efficient and produce highly enriched species in a short time. By varying the type of esterase, the amount of esterase or the length of incubation highly enriched species of all eicosanoids tested could be prepared.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200121208
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  • 7
    Digitale Medien
    Digitale Medien
    Collision-induced dissociation of carboxylate anions from derivatized 5-lipoxygenase metabolites of arachidonic acid (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 9-18 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The low-energy collision-induced dissociations (CID) of carboxylate anions derived from pentafluorobenzyl ester, trimethylsilyl ether derivatives of four arachidonic acid metabolites of the 5-lipoxygenase pathway have been determined. These molecules include leukotriene B4 (LTB4), a potent chemotactic factor for the human neutrophil; 20-carboxy-LTB4, an inactive metabolite; 5-hydroxyeicosatetraenoic acid (5-HETE), a useful marker of 5-lipoxygenase activity within cells; and 5-hydroxyeicosanoic acid (5-HEA), which has been previously used for the quantitation of leukotriene E4. The carboxylate anion of 5-HEA (m/z 399) was found to decompose by the loss of trimethylsilanol as well as the loss of 146 u corresponding to the loss of trimethylsilanol followed by acrolein, a process specific for 5-hydroxy-containing saturated fatty acids. The loss of trimethylsilanol by a remote site mechanism is the major transition observed for the 5-HETE carboxylate anion (m/z 391). The ion formed (m/z 301) further decomposes by the loss of CO2 (m/z 257). The loss of trimethylsilanol is also seen at m/z 389 after collisional activation of the carboxylate anion of LTB4 (m/z 479) by a complex charge-driven mechanism, not the remote site fragmentation mechanism as expected. The loss of an olefinic proton possibly from carbon-7 is involved as well as an oxygen atom derived from the carboxylic acid moiety. The loss of two trimethylsilanol neutral molecules gives rise to ions seen at m/z 299. Isotopic labeling studies revealed that two isobaric ions are present at m/z 299. Both of these ions involve the loss of trimethylsilanol from the carbon-12 position according to remote site mechanisms, but only one has lost the olefinic proton at carbon-7 and, therefore, likely originates from the further decomposition of the ion (m/z 389) described above. An additional ion seen at m/z 317 is attributed to the loss of trimethylsilyl ether (TMS-O-TMS) following a charge-driven mechanism involving the oxygen atom at carbon-12. The 20-carboxy-LTB4 carboxylate anion (m/z 689) decomposes primarily through the loss of one and two tri-methylsilanol moieties, but the base peak (m/z 491) is due to the loss of pentafluorobenzyl alcohol. This ion, likely a ketene, further gives rise to three ions by the sequential loss of one and two trimethylsilanols and TMS-O-TMS. All collision-induced decompositions of the carboxylate anions of these eicosanoids are characterized by losses of small neutral molecules from the derivatizing groups (TMS and pentafluorobenzyl) and little fragmentation of the carbon backbone.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200220103
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  • 8
    Digitale Medien
    Digitale Medien
    Quantitation of 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) produced by human polymorphonuclear leukocytes using electron capture ionization gas chromatography/mass spectrometry (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 249-253 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Arachidonic acid can be enzymatically oxidized at the terminal methyl group by the cytochrome P450 system found in several tissues and cells, including the human polymorphonuclear leukocyte. The ω-hydroxy metabolite, 20- hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) has recently been found to have interesting and diverse biological activities. Accurate measurement of quantities of this metabolite using physical chemical methods has not been previously described, but is necessary to assess biosynthesis of this eicosanoid from endogenous arachidonic acid. A procedure is described to quantitate 20-HETE produced by the human polymorphonuclear leukocyte following physiological stimulation using (18O2)carboxy-20-HETE as internal standard. Since the human neutrophil produces relatively small amounts of this eicosanoid, such a study required substantial sensitivity in the quantitative assay. Following stimulation of the neutrophil, cell extracts and supernatants were purified by reverse-phase high-performance liquid chromatography, catalytically reduced then derivatized to the pentafluorobenzyl ester, trimethylsilyl ethers before electron capture ionization gas chromatography/mass spectrometry. Using selected ion monitoring, the amount of 20-HETE present in a biological extract could be detected when as little as 60 pg per sample were available. Following stimulation of the human neutrophil with formyl-methionyl-leucyl-phenylalanine (0.1 μM), platelet activating factor (0.1 μM) as well as with the calcium ionophore A23187 (2 μM), 20-HETE was generated from endogenous arachidonate in concentrations of 1.2, 1.3 and 5.7 pg per 106 cells, respectively.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200210505
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  • 9
    Digitale Medien
    Digitale Medien
    Incorporation of stable isotope-labeled arachidonic acid into cellular phospholipid molecular species and analysis by fast atom bombardment tandem mass spectrometry (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 562-571 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The source of arachidonic acid metabolized to eicosanoids by 5-lipoxygenase was studied in a cultured neoplastic mast cell using a stable isotope tracer and tandem mass spectrometry strategy. Selected reaction monitoring and fast atom bombardment were used to analyze eight major arachidonate molecular species of glycerophosphocholine, nine major molecular species of glycerophosphoethanolamine, three major species of glycerophosphoinositol, and three major glycerophosphoserine molecular species. Incubation of the mast cells with (2H8)arachidonic acid led to a time-dependent isotopic incorporation in each of these molecular species. Following stimulation with calcium ionophore A23187, the isotope incorporation of leukotriene B4 (LTB4) was found to be higher than that of the major arachidonate-containing glycerophospholipid molecular species. The isotope incorporation of LTB4 was similar to that found for free arachidonic acid present in the unstimulated cell. In order to prevent direct labeling of the intracellular, free arachidonic acid pool, (2H4)linoleic acid was added to the culture medium as a biochemical precursor of labeled arachidonic acid. There was a time-dependent increase of the specific incorporation of labeled arachidonic acid into each of the phospholipid molecular species of each lipid class after incubation with (2H4)linoleic acid. Importantly, (2H4)linoleic acid incubation also resulted in deuterium-labeled arachidonic acid in the free arachidonic acid, intracellular pool. The arachidonic acid isotopic incorporation in this pool very closely correlated with the isotopic incorporation of LTB4 (correlation coefficient 0.97) synthesized after A23187 stimulation, while the isotopic incorporation of the extracellularly released, not esterified arachidonic acid, after stimulation, did not. These studies show that fast atom bombardment and tandem mass spectrometry can be used to follow incorporation of stable isotope-labeled arachidonic acid into complex mixtures of glycerophospholipids. This approach is relatively sensitive in being able to assess incorporation of 10% or less of the minor lipid pool.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200230906
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  • 10
    Digitale Medien
    Digitale Medien
    Special feature: Perspective. Lipid mediators, leukotrienes and mass spectrometryThis Perspective was derived in large part from a plenary lecture given by the author at the 42nd Annual Conference on Mass Spectrometry and Allied Topics, 1 June 1994, Chicago, IL, USA. (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 5-16 
    Details
    ISSN: 1076-5174
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jms.1190300104
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