Structure determination of oligosaccharides isolated from Cad erythrocyte membranes by permethylation analysis and 500-MHz 1H-NMR spectroscopy

Abstract

Alkaline borohydride reductive cleavage (beta-elimination) of glycophorin A isolated from one individual of the rare blood group Cad, resulted in the release of six acidic oligosaccharide-alditols which were separated by high-performance liquid chromatography (HPLC) on an alkyl amine silicagel column. The structure of four of them has been determined by the application of methanolysis analysis and 1H-NMR spectroscopy at 500 MHz. The structures and relative amounts were as follows: oligosaccharide 1: NeuAc(alpha2-3)Gal(beta1 - 3)GalNAcol (3.5%); oligosaccharide 3: GalNAc(beta1-4)[NeuAc(alpha2-3)]Gal(beta1-3)GalNAc-ol (10.5%); oligosaccharide 5: NeuAc(alpha2-3)Gal(beta1-3)[NeuAc(alpha2-6)]GalNAc-ol (10.4%); oligosaccharide 6: GalNAc(beta1-4)[NeuAc(alpha2-3)]Gal(beta1-3)[NeuAc(alpha2-6)]GalNAc-ol (71.2%). The two other oligosaccharides (2 and 4) were obtained in very low amount. The major pentasaccharide (oligosaccharide 6) carries the blood group Cad determinant and is a potent inhibitor of human anti-Sda antibody.