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Abstract

Collision-induced dissociation of peptide ions yields „sequence” ions arising from dissociations of the peptide backbone. Recently, Biemann and his collaborators have elucidated fragment ions involving cleavage of all or part of the side-chains, and have characterized them as remote-site fragmentations of the type investigated for other molecular species by Gross et al. The present work reports results of experiments conducted using a tandem, hybrid mass spectrometer, and devoted to investigating whether remote-site fragmentations (including side-chain cleavages for peptide ions) can be observed for collision energies substantially lower than the keV range used previously. It was found that (laboratory-frame) collision energies of at least 200 eV, and preferably greater, are required for the formation of such fragments. At collision energies in this range the transmission efficiency of the qQ assembly is much lower than for the more usual range of a few tens of eV; this drop in transmission efficiency becomes increasingly severe with increasing mass of the precursor.