Somatic antigens of shigella. Structural investigation on the O-specific polysaccharide chain of Shigella dysenteriae type 1 lipopolysaccharide.

The O-specific polysaccharide obtained from the lipopolysaccharide of Shigella dysenteriae type 1 (Shigella shiga) by mild acid hydrolysis followed by fractionation on Sephadex G-50 was found to be identical to that desribed by Morgan's group and was composed of L-rhamnose, D-galactose and N-acetyl-D-glycosamine in a ratio 2:1:1. On the basis of methylation analysis data the polysaccharide was proved to be a linear chain of monosaccharide residues in pyranose forms substituted at position 3, except for that of galactose substituted at position 2. Selective cleavage, based on the N-deacetylation reaction of the polymer, together with determination of linkage configurations by chromic anhydride oxidation showed that the O-specific polysaccharide is built up of repeating tetrasaccharide units whose proposed structure is given below -3)-alpha-L-Rhap (1-3)-alpha-L-Rhap(1-2)-alpha-D-Galp(1-3)-alphapD-GlcNAcp(1- where RHAP = rhamnopyranose, Galp = galactopyranose, and GlcNAcp = N-acetyl-glucosamine. The present findings confirmed the considerations of Heidelberger on the substitution patterns of L-rhamnose and D-galactose residues from the results of serological studies.