SEPARATION OF PARTIALLY DESIALYLATED BRANCHED OLIGOSACCHARIDE ISOMERSCONTAINING ALPHA(2-]3)-LINKED AND ALPHA(2-]6)-LINKED NEU5AC

The following two tri-sialylated triantennary oligosaccharides, which differ only in the linkage of the Neu5Ac to the uppermost branch were, individually, partially desialylated to produce all possible di- and mono-sialylated isomers.[GRAPHICS] A tetra-sialylated triantennary iso mer, which contained an alpha(2-->6)-linked Neu5Ac to the GlcNAc on br anch III, was also converted to all possible trisialylated isomers by mild acid hydrolysis as previously described (Roher et al., Anal. Bioc hem., 212, 7-16, 1993). The resulting branch isomers were separated us ing high-pH anion-exchange chromatography (HPAEC), Structures were ass igned to peak fractions on the basis of the previously described effec t of alpha(2-->6)- and alpha(2-->3)-linked Neu5Ac on the elution order of branched lactosamine-type oligosaccharides (Townsend et al., Anal, Biochem,, 182, 1-8, 1989). No differences in the acid lability of the Neu5Ac linkage to either Gal (alpha(2-->3) or alpha(2-->6)) or GlcNAc (alpha(2-->6)) were observed, Our studies show that chemical desialyl ation and HPAEC is a useful approach to prepare and identify all possi ble sialylated branch isomers and should prove useful for defining the branch specificity of sialyltransferases and sialidases.