STRUCTURAL-ANALYSIS OF O-LINKED OLIGOSACCHARIDE-ALDITOLS BY ELECTROSPRAY-TANDEM MASS-SPECTROMETRY AFTER MILD PERIODATE-OXIDATION AND DERIVATIZATION WITH 2-AMINOPYRIDINE

O-linked oligosaccharide-alditols were analyzed by a combination of hi gh-performance liquid chromatography (HPLC) and electrospray-tandem ma ss spectrometry (ESI-MS/MS). First, oligosaccharide-alditols were trea ted with sodium meta-periodate under conditions where core N-acetylgal actosaminitol is specifically degraded. The resulting fragments were l abeled with 2-aminopyridine and purified on a reversed-phase column. P yridylamino oligosaccharides yielded protonated molecular ions in posi tive-ion ES-MS and gave Y-series sequence ions, arising from glycosidi c cleavages, by ESI-tandem mass spectrometry. Information on sugar seq uence and branching of oligosaccharides linked at C-6 and C-3 to the N -acetylgalactosaminitol can be obtained. A systematic study of various oligosaccharide-alditols demonstrated that this approach constitutes a powerful tool for the structural characterization of O-glycans avail able only in limited quantities. (C) 1998 Academic Press.