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Abstract

The O−specific polysaccharide, obtained by mild acid degradation of Citrobacrer 016 lipopolysaccharide, consists of D−glucose, D−galactose, 2−acetamido−2−deoxy−˜−galactosgel,y cerol and phosphate in the ratios 2 : 2:2 : 1 :l. Selective cleavage of the polysaccharide was carried out by Smith degradation, N−deacetylation−deamination and dephosphorylation with 48 % hydrofluoric acid, which was accompanied by unexpected splitting of one of the glycosidic linkages. The structures of the oligosaccharides thus obtained were established using 'H− and I3C−NMR spectroscopy, including one−dimensional NOE, two−dimensional rotating−frame NOE, homonuclear and heteronuclear 'qC,lH correlation spectroscopy, and, for the Smith degradation product, positive− and negative−ion−mode fast−atom−bombardment MS and MSMS with collision−induced dissociation. On the basis of these data and the results of methylation analysis, it was concluded that the O−specific polysaccharide has the following repeating unit structure