Structure and conformational studies of the disaccharides derived from the inner core of the lipopolysaccharide isolated from Sinorhizobium fredii SMH12.

The structure and conformational behaviour of the core region of the lipopolysaccharide isolated from Sinorhizobium fredii SMH12, a wide-ranging host bacterium isolated from nodulated soybean plants growing in Vietnam, have been studied. A mixture of oligosaccharides was isolated from the lipopolysaccharide by mild hydrolysis followed by size-exclusion chromatography. The structures were determined by sugar analysis, ESI-MS/MS and NMR studies. Conformational analysis was performed by molecular dynamics calculations and compared with the NMR spectroscopic data. The results indicate that the core oligosaccharide contains a disaccharide made up of α-D-glucopyranuronic acid (1→4)-linked to D-Kdo. In solution, this disaccharide exists as an equilibrium of three different structures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)