STRUCTURE-ANALYSIS OF ACETYLATED AND NON-ACETYLATED O-LINKED MUC1-GLYCOPEPTIDES BY POST-SOURCE DECAY MATRIX-ASSISTED LASER DESORPTION IONIZATION MASS-SPECTROMETRY/

We have investigated the potential of structural elucidation of O-link ed glycopeptides by post-source decay matrix-assisted laser desorption ionization mass spectrometry (PSD-MALDI-MS). In order to establish de tailed fragmentation patterns and to dissect fragment ions with and wi thout carbohydrate content, the same O-linked MUC1-derived glycopeptid es with acetylated and non acetylated sugars were analysed and compare d, Furthermore, we were interested to examine possible differences in the fragmentation between glycopeptides with acetylated and non-acetyl ated sugars, The obtained PSD-MALDI-MS spectra showed a rather complet e set of fragmentation data which allows us to localize the glycan on the peptide, in parallel with sequencing a short glycan and the backbo ne peptide, Fragmentations of the sugars were dominated by inter-ring cleavages at the glycosidic bond, Intra-ring cleavage did also occur f rom the non-reducing end, but to a much lower extent, The fragmentatio n of the peptide backbone was not changed either by acetylated or non- acetylated sugars, Glycosylated peptide fragments occurred as fully gl ycosylated fragment ions, partially deglycosylated ions and completely deglycosylated ions, and was not influenced by the acetylation of sug ars, However, differences occurred in the quality and quantity of frag ment ions from the non-reducing end of the glycan part when comparing acetylated with non-acetylated glycopeptides. (C) 1997 by John Wiley & Sons, Ltd.