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  • A. Roux, Y. Xu, J. - F. Heilier, M. - F. Olivier, E. Ezan, J. - C. Tabet, et C. Junot, « Annotation of the Human Adult Urinary Metabolome and Metabolite Identification Using Ultra High Performance Liquid Chromatography Coupled to a Linear Quadrupole Ion Trap-Orbitrap Mass Spectrometer », Analytical Chemistry, vol. 84, nᵒ 15, p. 6429-6437, août 2012.
    Résumé : Metabolic profiles of biofluids obtained by atmospheric pressure ionization mass spectrometry-based technologies contain hundreds to thousands of features, most of them remaining unknown or at least not characterized in analytical systems. We report here on the annotation of the human adult urinary metabolome and metabolite identification from electrospray ionization mass spectrometry (ESI-MS)-based metabolomics data sets. Features of biological interest were first of all annotated using the ESI-MS database of the laboratory. They were also grouped, thanks to software tools, and annotated using public databases. Metabolite identification was achieved using two complementary approaches: (i) formal identification by matching chromatographic retention times, mass spectra, and also product ion spectra (if required) of metabolites to be characterized in biological data sets to those of reference compounds and (ii) putative identification from biological data thanks to MS/MS experiments for metabolites not available in our chemical library. By these means, 384 metabolites corresponding to 1484 annotated features (6S9 in negative ion mode and 825 in positive ion mode) were characterized in human urine samples. Of these metabolites, 192 and 66 were formally and putatively identified, respectively, and 54 are reported in human urine for the first time. These lists of features could be used by other laboratories to annotate their ESI-MS metabolomics data sets.
    Mots-clés : acids, CSOB, database, discriminating signals, excretion, glucuronide, pattern-recognition, phase, POLE 3, resolution, spectra, sulfate.

  • A. Seyer, F. Fenaille, C. Féraudet-Tarisse, H. Volland, M. R. Popoff, J. - C. Tabet, C. Junot, et F. Becher, « Rapid Quantification of Clostridial Epsilon Toxin in Complex Food and Biological Matrixes by Immunopurification and Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry », Analytical Chemistry, vol. 84, nᵒ 11, p. 5103-5109, 2012.
    Résumé : Epsilon toxin (ETX) is one of the most lethal toxins produced by Clostridium species and is considered as a potential bioterrorist weapon. Here, we present a rapid mass spectrometry-based method for ETX quantification in complex matrixes. As a prerequisite, naturally occurring prototoxin and toxin species were first structurally characterized by top-down and bottom-up experiments, to identify the most pertinent peptides for quantification. Following selective ETX immunoextraction and trypsin digestion, two proteotypic peptides shared by all the toxin forms were separated by ultraperformance liquid chromatography (UPLC) and monitored by ESI-MS (electrospray ionization-mass spectrometry) operating in the multiple reaction monitoring mode (MRM) with collision-induced dissociation. Thorough protocol optimization, i.e., a 15 min immunocapture, a 2 h enzymatic digestion, and an UPLC-MS/MS detection, allowed the whole quantification process including the calibration curve to be performed in less than 4 h, without compromising assay robustness and sensitivity. The assay sensitivity in milk and serum was estimated at 5 ng·mL?1 for ETX, making this approach complementary to enzyme linked immunosorbent assay (ELISA) techniques.
    Mots-clés : CSOB, POLE 3.

  • L. Svilar, V. Stankov-Jovanovic, D. Lesage, H. Dossmann, et J. - C. Tabet, « High-resolution mass spectrometry and hydrogen/deuterium exchange study of mitorubrin azaphilones and nitrogenized analogues », Journal of Mass Spectrometry, vol. 47, nᵒ 8, p. 969-977, août 2012.
    Résumé : Azaphilones represent numerous groups of wild fungal secondary metabolites that exhibit exceptional tendency to bind to nitrogen atoms in various molecules, especially those containing the amine group. Nitrogenized analogues of mitorubrin azaphilones, natural secondary metabolites of Hypoxylon fragiforme fungus, have been detected in the fungal methanol extract in very low concentrations. Positive electrospray ionization interfaced with high-resolution mass spectrometry was applied for confirmation of the elemental composition of protonated species. Collision-induced dissociation (CID) experiments have been performed, and fragmentation mechanisms have been proposed. Additional information regarding both secondary metabolite analogue families has been reached by application of gas-phase proton/deuterium (H/D) exchanges performed in the collision cell of a triple quadrupole mass spectrometer. An incomplete H/D exchange with one proton less than expected was observed for both protonated mitorubrin azaphilones and their nitrogenized analogues. By means of the density functional theory, an appropriate explanation of this behavior was provided, and it revealed some information concerning gas-phase H/D exchange mechanism and protonation sites. Copyright (c) 2012 John Wiley & Sons, Ltd.
    Mots-clés : cd3co2d, cd3od, cid, CSOB, Cycloisomerization, D exchange, d2o, density, density functional theory, gas-phase, gas-phase H, hydrogen-deuterium exchange, ion-molecule reactions, lc-esi-ft, metabolite profiles, mitorubrins, ms, nd3, POLE 3.

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