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Accueil > Archives > Articles Scientifiques > Polysaccharides > Genre Escherichia

Structural determination of the O-antigenic polysaccharide from Escherichia coli O74

par Emmanuel Maes - publié le

by : K. Hanna M. Jonsson , Andrej Weintraub and Göran Widmalm (2009) Carbohydr. Res., 344, 1592-1595

ABSTRACT

The structure of the O-antigen polysaccharide (PS) from Escherichia coli O74 has been determined. Component analysis, together with 1H and 13C NMR spectroscopy as well as 1H,15N-HSQC experiments were employed to elucidate the structure. Inter-residue correlations were determined by 1H,1H-NOESY and 1H,13C-heteronuclear multiple-bond correlation experiments. The PS is composed of tetrasaccharide repeating units with the following structure :

→6)[β-D-Fucp3NAc-(1→3)]-α-D-GlcpNAc-(1→4)-β-D-GalpA-(1→3)-β-D-GlcpNAc-(1→

Cross-peaks of low intensity from an α-linked N-acetylglucosamine residue were present in the NMR spectra, and spectral analysis indicates that they originate from the penultimate residue in the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-glucosamine residue at its reducing end. The 1H, 13C and 15N NMR chemical shifts of the α- and β-anomeric forms of D-Fucp3-
NAc are also reported. The repeating unit of the E. coli O74 O-antigen is identical to that of the capsular polysaccharide from E. coli K45.