Negative ion electrospray mass spectrometry of neutral underivatized oligosaccharides

Negative-ion electrospray mass spectrometry (ES-MS) with collision-induced dissociation (CID) and MS/MS scanning on a quadrupole-orthoganal time-of-ni ght instrument provide a sensitive means for structural analysis of neutral underivatized oligosaccharides. Molecular mass information can be readily obtained from the dominant [M - H](-) ions in the ES mass spectrum formed w ith subnanomole amounts of oligosaccharides, and similar sensitivity is ava ilable from CID-MS/MS to give structural details. The CID spectra of 14 oli gosaccharides demonstrated that sequence and partial linkage information ca n be derived and isomeric structures can be differentiated. Series of C-typ e fragment ions give sequence information while the double glycosidic D-typ e cleavage of a 3-linked GlcNAc or Glc and the saccharide ring fragmentatio n of the (0,2)A-type from 4-linked GlcNAc or Glc can provide partial linkag e information. The distinctive D- and A-cleavages are important for differe ntiation of oligosaccharide type 1 and type 2 chains and to define the bloo d group H, Le(a), Le(X), Le(b), and Le(y) determinants carried by their fuc osylated analogues.