Structure of the O-specific side chain of the Escherichia coli O128 lipopolysaccharide

The O-specific polysaccharide isolated from Escherichia coli O128 lipopolysaccharide contains d-galactose, l-fucose, and 2-acetamido-2-deoxy-d-galactose in the molar ratios 2:1:2. The primary structure of the O-specific polysaccharide from E. coli was established by compositional analysis, methylation analysis, together with 1H and 13C NMR spectroscopy including two-dimensional shift-correlated and one-dimensional NOE spectroscopy. The polysaccharide moiety was found to consist of a tetrasaccharide backbone containing d-galactose and 2-acetamido-2-deoxy-d-galactose, with l-fucose as a side chain in a branched pentasaccharide repeating unit having the following structure: