Polysaccharides from Peptostreptococcus anaerobius and structure of the species-specific antigen

Synthesis of Defined and Functionalized Glycans of Lipoteichoic Acid: A Cell Surface Polysaccharide from Clostridium difficile

Two structurally defined, functionalized glycans of lipoteichoic acid (LTA, also known as PS-III) from C. difficile, which have one or two repeating units of LTA linked to the core trisaccharide, were efficiently synthesized via a convergent [2 + 3] or [2 + 2 + 3] strategy. The α-linkage of both N-acetylglucosamine residues in the repeating unit were constructed with glycosyl imidates of azidosugars as donors, while the phosphodiester bridges between the oligosaccharides were fashioned using H-phosphonate chemistry. Both synthetic targets contained a 3-aminopropyl group at the core trisaccharide reducing end, facilitating their conjugation to other biomolecules to afford conjugates useful for various biological studies and applications.

Structural characterization of surface glycans from Clostridium difficile

Whole-cell high-resolution magic angle spinning (HR-MAS) NMR was employed to survey the surface polysaccharides of a group of clinical and environmental isolates of Clostridium difficile. Results indicated that a highly conserved surface polysaccharide profile among all strains studied. Multiple additional peaks in the anomeric region were also observed which prompted further investigation. Structural characterization of the isolated surface polysaccharides from two strains confirmed the presence of the conserved water soluble polysaccharide originally described by Ganeshapillai et al. which was composed of a hexaglycosyl phosphate repeat consisting of [→6)-β-D-Glcp-(1-3)-β-D-GalpNAc-(1-4)-α-D-Glcp-(1-4)-[β-D-Glcp(1-3]-β-D-GalpNAc-(1-3)-α-D-Manp-(1-P→]. In addition, analysis of phenol soluble polysaccharides revealed a similarly conserved lipoteichoic acid (LTA) which could be detected on whole cells by HR-MAS NMR. Conventional NMR and mass spectrometry analysis indicated that the structure of this LTA consisted of the repeat unit [→6)-α-D-GlcpNAc-(1-3)-[→P-6]-α-D-GlcpNAc-(1-2)-D-GroA] where GroA is glyceric acid. The repeating units were linked by a phosphodiester bridge between C-6 of the two GlcNAc residues (6-P-6). A minor component consisted of GlcpN-(1-3) instead of GlcpNAc-(1-3) in the repeat unit. Through a 6-6 phosphodiester bridge this polymer was linked to →6)-β-D-Glcp-(1-6)-β-D-Glcp-(1-6)-β-D-Glcp-(1-1)-Gro, with glycerol (Gro) substituted by fatty acids. This is the first report of the utility of HR-MAS NMR in the examination of surface carbohydrates of Gram positive bacteria and identification of a novel LTA structure from Clostridium difficile.

Studies on the skeletal cell wall of the cystocarpic stage of the red seaweed Iridaea undulosa B. Part II. Fractionation of the cell wall and methylation analysis of the inner core-fibrillar polysaccharides

In order to determine the structure of the fibrillar cell wall, the material isolated from cystocarpic thalli of the red seaweed Iridaea undulosa was fractionated using different media. While classical methods produced a scarce solubilization of material, the use of lithium salts in polar aprotic solvents (dimethylsulfoxide or N, N-dimethylacetamide), had successfully extracted higher amounts of material. The final residue from the Li(+)/DMSO extraction contains cellulose and a mannan, while that from the Li(+)/DMAc extraction contains only cellulose and traces of a galactan. Methylation analyses of both residues confirm the presence of those polysaccharides, and shows that the mannan is (1-->4)-linked. Treatment with proteases suggests that the protein is efficiently shielded from digestion. All the extracts and residues contain major amounts of (glyco)proteins and/or proteins, in agreement with a previous suggestion that they are of major importance in the structure of the cell wall.