Structure analysis of glycosphingolipids using fast atom bombardment (FAB) techniques.

The results presented show, that with the aid of negative ion FAB MS native glycosphingolipids and especially gangliosides are amenable to sequence analysis. The preferred formation of pseudomolecular ions M-1 and of sialic acid containing fragments gives conclusive information on the number of sialic acids present and the sites of their attachment to the oligosaccharide backbone. Positive ion FAB MS of branched permethylated glycosphingolipids with up to 25 sugar units yielded pseudomolecular ions [M+Na]+ in excess of 6000 daltons, that allowed an exact calculation of carbohydrate constituents. Furthermore highly (Formula: see text) specific fragmentation patterns furnished information on number and positions of branching points as well as on the ceramide moiety. It can be anticipated, that FAB MS will be very useful in the analysis of more complex gangliosides carrying additional fucose or acyl residues and of even larger molecules with molecular weights up to 15,000 daltons.