COLLISION-INDUCED DISSOCIATION OF BRANCHED OLIGOSACCHARIDE IONS WITH ANALYSIS AND CALCULATION OF RELATIVE DISSOCIATION THRESHOLDS

Collision-induced dissociation (CID) is used in an external source Fou rier transform mass spectrometer (FTMS) equipped with matrix-assisted laser desorption/ionization (MALDI) to study a number of complex, bran ched oligosaccharides. The relative dissociation thresholds for variou s oligosaccharide fragmentation pathways have been calculated in terms of kinetic and center-of-mass frame energy. For two isomers of difuco syllacto-N-hexaose, the loss of the fucose sugar is always the lowest energy fragment observed and occurs at the same energy for both isomer s when the oligosaccharide is coordinated to a sodium ion. When the ol igosaccharide is complexed to cesium, the threshold for the removal of the fucose moiety increases, indicating that the cesium is involved i n a coordination complex that stabilizes the sugar. MS/MS/MS is perfor med on a sugar, mannose core, which does not readily fragment during M ALDI. In all the sugars examined, CID produces additional structural i nformation relative to MALDI/FTMS.