Fish egg polysialoglycoproteins: structures of new sialooligosaccharide chains isolated from the eggs of Oncorhynchus keta (Walbaum). Fucose-containing units with oligosialyl groups

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Abstract
A series of acidic oligosaccharides alditols having different neutral core oligosaccharides were isolated from salmon egg polysialoglycoproteins by alkali-borohydride treatment followed by anion-exchange chromatography and Iatrobead chromatography. Their structures were determined by methylation analysis, molecular secondary ion mass spectrometry of underivatized oligosaccharides and enzymatic desialylation. The molecular secondary ion mass spectra of intact sialooligosaccharides exhibit pronounced quasi-molecular-ion peaks, (M + H)+, (M + Na)+, (M + 2Na-H)+, and/or (M + K)+, as well as some diagnostic sequence ion peaks. Of a number of oligosaccharide alditols, the following are novel: Fuc.alpha.1 .fwdarw. 3GalNAc.beta.1 .fwdarw. 3Gal.beta.1 .fwdarw. 4Gal.beta.1 .fwdarw. 3[(.fwdarw. -8NeuGc.alpha.2)n .fwdarw. 6]GalNAcol (n = 1-6). PMR spectra of these oligosaccharides are also reported and discussed.