STRUCTURE-ANALYSIS OF BRANCHED OLIGOSACCHARIDES USING POST-SOURCE DECAY IN MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

Post-source decay matrix-assisted laser desorption ionization (PSD-MAL DI) of sodium ion-attached branched oligosaccharides derived from glyc oproteins was demonstrated as a method of structure analysis by reflec tron time-of-flight (TOF) mass spectrometry. Mono-, di- and triantenna ry structures were investigated. The fragmentation patterns of these ( structurally related) substances as obtained in the positive-ion mode showed characteristic differences correlated with branching sites and linkage positions. Two-bond ring cleavages as known from fast atom bom bardment/collision-induced dissociation and IR laser desorption mass s pectrometry were also observed. Internal fragment ions formed by up to four consecutive cleavages were obtained with high intensity, allowin g the branching structure of complex carbohydrates to be identified. P SD-MALDI of oligosaccharides is characterized by high sensitivity, ver y good signal-to-noise ratios and high reproducibility of fragmentatio n patterns and signal intensities.