Electrospray tandem mass spectrometry of lexitropsins

Several compounds, representative of the class of lexitropsins, were analyz ed by electrospray tandem mass spectrometry. The study of the fragmentation s of the protonated molecular species ([M + H](+)) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compo unds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of s everal compounds, and the MS/MS and MS/MS/MS spectra of the deuterated comp ounds, were obtained. Accurate mass measurements helped elucidate the struc tures of smaller fragment ions. Low-energy collision-induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and ide ntification of this class of compounds. Main fragmentation pathways occur b y cleavage of the peptide bond followed by the elimination of the substitut ed pyrrole ring, and their elucidation will facilitate structural character ization of new lexitropsins. Copyright (C) 2001 John Wiley & Sons, Ltd.