Structural analysis of the O-specific polysaccharide from the lipopolysaccharide of Aeromonas veronii bv. sobria strain K49.

The O-specific polysaccharide obtained by mild-acid degradation of the lipopolysaccharide from Aeromonas veronii bv. sobria strain K49 was studied by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy. The sequence of the sugar residues was determined using (1)H,(1)H NOESY and (1)H,(13)C HMBC experiments. The O-specific polysaccharide was found to be a high molecular mass polysaccharide composed of repeating units of the structure: →2)-β-D-Quip3NAc-(1→3)-α-L-Rhap-(1→3)-α-L-Rhap-(1→2)-α-L-Rhap-(1→3)-α-D-FucpNAc-(1→ ESI MS confirmed the pentasaccharide structure of the repeating unit, as the molecular mass peaks seen in the spectrum differed by 812.34 u, a value corresponding to the calculated molecular mass of the O-unit.