Structural studies utilizing 13C-enrichment of the O-antigen polysaccharide from the enterotoxigenic Escherichia coli O159 cross-reacting with Shigella dysenteriae type 4.

The structure of the O-antigen polysaccharide from Escherichia coli O159 has been determined using primarily NMR spectroscopy of the 13C-enriched polysaccharide. The sequence of the sugar residues could be determined by heteronuclear multiple bond connectivity NMR experiments. The polysaccharide is composed of a pentasaccharide repeating unit with the following structure: [sequence: see text] Matrix assisted laser desorption ionization mass spectrometry was performed on intact lipopolysaccharide and from the resulting molecular mass the O-antigen part was estimated to contain approximately 23 repeating units. Cross-reactivity of this O-antigen to that of Shigella dysenteriae type 4 was confirmed using enzyme-linked immunoabsorbant assay.