Separation of partially desialylated branched oligosaccharide isomers containing {alpha}(2<-3)- and {alpha}(2<-6)-linked Neu5Ac

The following two tri-sialylated triantennary oligosaccharides,which differ only in the linkage of the Neu5Ac to the uppermostbranch were, individually, partially desialylated to produceall possible di- and mono-sialylated isomers. A tetra-sialylated triantennary isomer, which contained an (26)-linkedNeu5Ac to the GlcNAc on branch III, was also converted to allpossible trisialylated isomers by mild acid hydrolysis as previouslydescribed (Roher et al., Anal Biochem., 212, 7–16, 1993).The resulting branch isomers were separated using high-pH anion-exchangechromatography (HPAEC). Structures were assigned to peak fractionson the basis of the previously described effect of (26)- and(23)-linked Neu5Ac on the elution order of branched lactosamine-typeoligosaccharides (Townsend et al., Anal Biochem., 182, 1–8,1989). No differences in the acid lability of the Neu5Ac linkageto either Gal ((23) or (26)) or GlcNAc ((26)) were observed.Our studies show that chemical desialylation and HPAEC is auseful approach to prepare and identify all possible sialylatedbranch isomers and should prove useful for defining the branchspecificity of sialyltransferases and sialidases. high-pH anion-exchange chromatography pulsed electrochemical detection sialidases sialylated oligosaccharides sialyltransferases