Determination of sequence and linkage of tissue oligosaccharides in caprine beta-mannosidosis by fast atom bombardment, collisionally activated dissociation tandem mass spectrometry.

Fast atom bombardment, collisionally activated dissociation tandem mass spectrometry (FAB-CAD-MS/MS), combined with p-aminobenzoic acid ethyl ester (ABEE) derivatization, were used to confirm the sequence and linkage pattern of subnanomolar amounts of the previously characterized three major thyroid gland oligosaccharides accumulated in caprine beta-mannosidosis. Positive ion FAB-CAD-MS/MS of both the [M + H]+ and [M + Na]+ ions from the ABEE derivatized oligosaccharides produced product ions derived from cleavage of the glycosidic bonds which allowed the sequences to be determined. Several fragments resulting from cleavages across the sugar ring permitted the assignment, in some cases, of the linkage positions between the sugar residues. The natriated molecule yielded several fragments of this type which were not observed when the protonated molecule was selected as the precursor ion. Use of these techniques gave the complete sequence and linkage characterization of the disaccharide and complete sequence and partial linkage information for the two higher oligosaccharides.