Structure elucidation of the O-antigenic polysaccharide from the enteroaggregative Escherichia coli strain 62D(1)

The O-antigen polysaccharide of the lipopolysaccharide from the enteroaggre gative Escherichia coli strain 62D(1) has been determined. Sugar and methyl ation analysis together with H-1 and C-13 NMR spectroscopy revealed the com ponents of the repeating unit. Two-dimensional NOESY and heteronuclear mult iple-bend correlation experiments were used to deduce the sequence. H-1 and C-13 NMR spectra indicate heterogeneity in the polysaccharide. Methylation analysis and H-1 NMR spectra of native and Smith-degraded material show th at the majority (65%) of the repeating units has the following structure: -->2)-beta-D-Quip3NAc-(1-->3)-alpha-L-Rhap-(1-->3)-beta-D -Galp-(1-->3)-alp ha-D-FucpNAc-(1-->alpha-D-Galp [GRAPHICS] Minor resonances in the NMR spectra are consistent with the presence of rep eating units which lack the alpha-D-Galp terminal residue (35%).