Structure determination of the O-antigenic polysaccharide from the enteroinvasive Escherichia coli 0136

The structure of the O-antigen polysaccharide of the lipopolysaccharide fro m the enteroinvasive Escherichia coli O136 has been elucidated. The composi tion of the repeating unit was established by sugar and methylation analysi s together with H-1 and C-13 NMR spectroscopy. Two-dimensional nuclear Over hauser effect spectroscopy (NOESY) and heteronuclear multiple-bond correlat ion experiments were used to deduce the sequence. The absolute configuratio n for the nonulosonic acid (NonA) could be determined using spin-spin coupl ing constants, C-13 chemical shifts and NOESY. The anomeric configuration o f the NonA was determined via vicinal and geminal C-13,'H coupling constant s. The structure of the repeating unit of the polysaccharide from E. coli O 136 is as follows, in which beta-NonpA is 5,7-diacetamido-3,5,7,9-tetradeox y-L-glycero-beta-L-manno-nonulosonic acid:-->4)-beta-NonpA-(2-4)-beta-D-Gal p-(1-4)-beta-D-GlcpNAc(1-->.