WeO-04
THE NEGATIVE-ION SPECTRA OF PEPTIDES THAT CONTAIN AMINO ACID RESIDUES WHICH UNDERGO FACILE SIDE-CHAIN CLEAVAGE
Simon T. Steinborner and John H. Bowie
Department of Chemistry, The University of Adelaide, South Australia, 5005, Australia
Both positive- and negative-ion spectra of small peptides produce backbone fragmentations which typically reveal the amino acid sequence. However, spectra of [M-H]- ions (unlike those of MH+ ions) show side-chain cleavage which enable the identification of a particular residue. For certain residues (eg. Ser, Thr, Asp, Asn, Glu and Gln) the side-chain fragmentations (eg. loss of CH2O for Ser and H2O for Asp) may be so pronounced that backbone cleavage is either diminished or is absent.1
We will show that in larger peptides, side-chain cleavage not only dominates the negative-ion spectra but induces internal backbone cleavage.
1. Steinborner, S.T. and Bowie, J.H., Rapid Commun. Mass Spectrom., (1996), 10, 1243 and references cited therein.