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1 2005

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Repeating Unit Structure of Enterobacter sakazakii ZORB A 741 O-Polysaccharide

Szafranek J., Czerwicka M., Kumirska J., Paszkiewicz M., Łojkowska E.

Polish Journal of Chemistry

2005

Vol. 79 / nr 2

287-295

The O-specific polysaccharide from Enterobacter sakazakii cell was isolated and structurally characterized. Lipopolysaccharide (LPS) was obtained from cell mass by hot phenol- water extraction procedure. Mild acid hydrolysis followed by gel filtration provided pure O-antigen (OPS). Two-stage sugar analysis detected tyvelose, rhamnose and galactose in the molar ratio of 1:1:2, and their linkages were established by means of methylation analysis. Sugar configurations, D or L, were determined by gas-liquid chromatography on an achiral liquid phase for (S)-(+)-2-butyl glycosides. D configuration was determined for galactose and 3,6-dideoxy-mannose (tyvelose), but L for rhamnose. Repeating unit structure was deduced by analysis of 1H and 13C NMR spectra. 1H and 13C NMR resonances have been assigned by homonuclear (COSY, TOCSY) and heteronuclear (HSQC, HMBC) correlations spectra. Anomeric configurations were determined from anomeric proton chemical shifts and 3JH1-H2 and JC-H coupling constants. Sugar sequences were established from comparisons of specific carbon chemical shifts with those in literature, two-dimensional nuclear Overhauser effect spectroscopy (NOESY), and heteronuclear multiple-bond correlation experiments (HMBC). The repeating unit structure of Enterobacter sakazakii was found to be as: alfa-Tyvp _2 _3)-alfa-L-Rhap-(1--3)-alfa-D-Galp-(1_3)-alfa-D-Galp-(1_ _6 O-Ac