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  • 1
    Electronic Resource
    Electronic Resource
    Sequential product-ion spectra (MS3 and MS4) with array detection and reaction-intermediate scanning on a four-sector mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 553-559 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Frangmentation yields during high-energy collisionally activated decomposition (CAD) tandem mass spectrometie experiments are often low, due in part to the short time-period available for the fragmentations. Consequently, attempts at multi-stage mass spectrometry undeer high-energy CAD conditions can give unsatisfactory result when a conventional point detector is used. Arry detection dramatically improves the detection of ion currents of low abundance; we therefore incorporated arry detection in a variety of sequential product-ion ‘scanning’ experiments, including MS3 and MS4, using a BEBE instrument. The corresponding experiments were previously established on a BEqQ hybrid instrument. where the final stage of decomposition occurred under low-energy CAD conditions. The results from the hybrid were used as a basis of comparison for the results under high-energy CAD with array detection. On the BEBE instrument, the use of the array greatly enhanced the signal-to background ratio for second-and third-generation product-ion spectra, as compared to the use of the point detector on the instrument in several instances, the use of the array was criticaL to the success of the experiment on the four-sector instrument. For the peptides analyzed, the fragmentation patterns observed in the sequential product spectra were similar on the four-sector instrument and on the hybrid instrument, although the relative abundances differed between the high-and low energy CAD regimes. Reaction-intermediate scanning, involving two sequential decomposition step occurring on the microsecond high energy time scale, has also been implemented on the BEBE instrument. A New mode of reaction-intermediate scanning has also been implemented on the BEqQ hybrid instrument, permitting it to access sequential fragmentation when both occur under high-energy CAD conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060904
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  • 2
    Electronic Resource
    Electronic Resource
    Peroxidation of erythrocytes: FTIR spectroscopy studies of extracted lipids, isolated membranes, and intact cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 133-140 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Fourier transform infrared (FTIR) spectroscopy was used to directly monitor peroxidative damage to membrane phospholipid acyl chains in erythrocyte membranes. Samples were suspended in a mixed 2H2O/H2O buffer system, thereby producing a “spectral window” in the C-H stretching region of the infrared spectrum. A decrease in the number of acyl chain C=C bonds upon erythrocyte peroxidation was quantitated directly from the spectra of isolated membranes. Second-derivative spectroscopy permitted the conformationally sensitive membrane acyl chain methylene stretching modes to be separated from the protein (mostly hemoglobin) vibrations that dominate the spectra of intact cells. The sensitivity of these modes in erythrocytes was then determined in a series of thermotropic experiments. The effect of peroxidation upon the membrane acyl chain conformational order was monitored in isolated membranes and intact cells. No change in conformational order was detected upon peroxidation in intact cell and ghost spectra. In contrast, experiments with pure unsaturated phospholipids demonstrated that decreasing the C=C bond population results in increased conformational order. The finding of identical results for peroxidation versus control samples in isolated membranes (“ghosts”) validates the results observed for intact cells. FTIR technology permits the direct monitoring of conformational order in the acyl chains of intact cells. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bspy.350010207
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  • 3
    Electronic Resource
    Electronic Resource
    Fast atom bombardment tandem mass spectrometry of the anti-parasitic agent pentamidine and its oxygenated metabolites (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 549-556 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Although pentamidine (1,5-bis(4′-amidinophenoxy)pentane) is currently in use for the treatment of a variety of parasitic infections, including acquired immune deficiency syndrome-related Pneumocystis carinii pneumonia, its metabolism is still under investigation. Positive-ion fast atom bombardment mass spectrometry was used with high-energy collision-activated dissociation (CAD) and linked scanning at constant B/E to obtain tandem mass spectra of protonated molecules of pentamindine and seven synthetic oxygenated derivatives, which are known metabolites of pentamidine. Charge-initiated fragmentation produced abundant fragment ions of m/z 120 and 137 and loss of neutral ammonia from the protonated analyte that characterized the amidinophenoxy group. The structures of isomeric 2-hydroxypentamidine, 3-hydroxypentamidine and N-hydroxypentamidine could be distinguished based on charge-remote fragmentation that produced a series of fragment ions of the pentyl chain and permitted the exact location of the hydroxyl group in each molecule to be determined. Next, tandem mass spectra were obtained and the charge-initiated and charge-remote fragmentation discussed for four other metabolites of pentamidine, including N,N′-dihydroxypentamidine, 5-(4′-amidinophenoxy)pentanoic acid, 5-(4′-amidinophenoxy) pentan-1-ol, and p-hydroxybenzamidine. Finally, tandem mass spectrometry was used to identify pentamidine and three pentamidine metabolites contained in high-performance liquid chromatographic (HPLC) fractions from rat liver perfusate and rat urine following treatment with pentamidine. Pentamidine metabolites identified in rat urine and liver perfusate using mass spectrometry and HPLC retention times included 2-hydroxypentamidine, 3-hydroxypentamidine and 5-(4′-amidinophenoxy)pentanoic acid.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300405
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of serum cortisol by thermospray liquid chromatography/mass spectrometry: Comparison with gas chromatography/mass spectrometry (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 717-722 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of serum cortisol by thermospray liquid chromatography/mass spectrometry (LC/MS) has been assessed. The method incorporates stable isotope dilution and innumoadsorption extraction. [M + H]+ ions are monitored during LC/MS. The within-assay reproducibility is satisfactory (coefficient of variation 7% at a concentration of 190 ng ml-1), though inferior to that achieved with the (more lengthy) procedure of gas chromatography/mass spectrometry (GC/MS). Satisfactory agreement between LC/MS (y) and GC/MS (x) data was observed (y = 0.934x + 12.4 ng ml-1; r = 0.968; n = 14). It is concluded that the generation of precise reference data for the assessment of routine cortisol assays is at present better achieved by GC/MS. LC/MS, however, provides satisfactory quantitative data via a more simple and rapid method.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200141205
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid identification of drug metabolites with tandem mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 193-204 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method which involves the use of tandem mass spectrometry (MS/MS) for the identification of drug metabolites has been demonstrated with a triple quadrupole mass spectrometer. The method is based on the fact that metabolites usually retain various substructures of the original drug molecule. MS/MS is capable of rapidly identifying molecules with characteristic substructures without prior separation. It is shown that this method makes it possible to postulate possible drug metabolite structures rapidly and systematically without the use of standards. The MS/MS method, as it was applied to the identification of the metabolites of a new antiepileptic drug, zonisamide, is discussed. In this case it was possible to identify isomeric metabolites due to their differences in vaporization times off the probe and their different daughter spectra. The complementary uses of the neutral loss and parent scans for the determination of the site of metabolism is demonstrated. A new figure of merit, the limit of identification, is introduced. The amount of the epoxide metabolite of carbamazepine necessary for its reliable identification in urine was shown to be 0.4 ng/μl. The application of various techniques to confirm preliminary findings with this MS/MS method are described.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150403
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  • 6
    Electronic Resource
    Electronic Resource
    Laser desorption/fourier transform ion cyclotron resonance mass spectrometry: Digoxin, digitoxin, and their reduced and sugar-hydrolyzed metabolites (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 295-302 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of digoxin and digitoxin (the most widely prescribed drugs for treatment of congestive heart failure) and a complete set of their 14 dihydro- and sugar-hydrolyzed metabolites have been obtained via laser desorption/ionization with a Fourier transform ion cyclotron resonance (LD/FT/ICR) mass spectrometer. The most intense peak is typically the pseudomolecular [M + K]+ ion, but fragment ions corresponding to loss of 1--3 sugars and hydroxyls are also observed. LD/FT/ICR mass spectra for all 16 compounds were produced with a single set of sample and spectrometer parameters. No matrix peaks are present. Finally, LD/FT/ICR provides dynamic mass accuracy within ≈5 ppm throughout a mass range of 404 〈 m/z 〈 819.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150510
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  • 7
    Electronic Resource
    Electronic Resource
    On-line generation of fast atom bombardment spectra with particle beam liquid chromatography/mass spectrornetry interfaung (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 355-357 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180511
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  • 8
    Electronic Resource
    Electronic Resource
    University of Bristol, Spring School in Chemometrics, 5-10 April 1987 (1987)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 197-198 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180010308
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  • 9
    Electronic Resource
    Electronic Resource
    Source contributions to ambient aerosol calculated by discriminat partial least squares regression (PLS) (1988)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 2 (1988), S. 281-296 
    Details
    ISSN: 0886-9383
    Keywords: Partial least squares ; Receptor modelling ; Colinearities ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Partial least squares regression (PLS) is proposed for solving ir pollution source apportionment problems as an alternative method to the frequently used chemical mass balance technique. A discriminant PLS is used to calculate linear mixing proportions for a synthetic ambient aerosol data set where the truth is known. Without sacrificing orthogonality of the source profiles, PLS can resolve the emission sources and accurately predict the emission source contributions. Further extensions of the PLS approach to environmental receptor modelling are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180020406
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  • 10
    Electronic Resource
    Electronic Resource
    Capillary gas chromatography/mass spectrometry of cholesteryl esters with negative ammonia chemical ionization (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 131-140 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of both synthetic and naturally occurring (human plasma) cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300°C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140307
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