Structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O12

The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O12. Its structure was studied by sugar analysis using GLC of the alditol acetates and (S)-2-octyl glycosides, methylation analysis, Smith degradation, and 1H and 13C NMR spectroscopy, including 2D 1H–1H COSY, TOCSY, ROESY, 1H–13C HSQC, and HMBC experiments. It was found that the polymer is a neutral heteropolysaccharide and has a branched heptasaccharide repeating unit with the following structure:

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