STRUCTURAL-ANALYSIS OF PERMETHYLATED OLIGOSACCHARIDES BY ELECTROSPRAYTANDEM MASS-SPECTROMETRY

Electrospray tandem mass spectrometry used in conjunction with reverse d-phase liquid chromatography was applied to characterize permethylate d oligosaccharides. N-Acetylhexosamine-containing carbohydrates yielde d under these conditions protonated molecular ions which underwent ext ensive fragmentation, even under low-energy collision-induced dissocia tion. MS/MS spectra of [M + H](+) ions are characterized by simple fra gmentation patterns which result from cleavage of the glycosidic bonds and thus allow a straightforward interpretation, A systematic study o f various oligosaccharides showed that information on sugar sequence a nd branching could be obtained. The nature of the substituent linked i n position 3 of HexNAc-containing fragments could easily be assigned a s the result of a specific secondary fragmentation process, The nature of some internal fragments was established on the basis of MS/MS spec tra of derivatives O-18-labeled at the reducing end. Furthermore, MS/M S experiments carried out on fragment ions were proven to be useful fo r the structural characterization of oligosaccharide subunits, Thus, t his approach constitutes a powerful tool for the structural assignment of moieties derived from larger glycans.