Structural characterization of the serotype O:5 O-polysaccharide antigen of the lipopolysaccharide of Escherichia coli O:5.

The structure of the antigenic O-polysaccharide component of the smooth lipopolysaccharide produced by Escherichia coli serotype O:5 was investigated by composition, methylation, and periodate oxidation methods, and by 1D and 2D nuclear magnetic resonance spectroscopy. The antigenic O-chain was determined to be a high molecular weight polysaccharide composed of repeating tetrasaccharide units containing 2-acetamido-2-deoxy-D-galactose, D-galactose, D-ribose, and 3-acetamido-3,6-dideoxy-D-glucose and having the structure -[-4)-beta-D-Galp-(1-3)-alpha-D-GalpNAc-(1-4)-beta-D-Quinp3NAc-(1- 3)-beta-D-Ribf-(1-]-.