Elucidation, capsular polysaccharides

A structural study on lipid A and the O-specific polysaccharide of the lipopoly-saccharide from a clinical isolate of Bacteroides vulgatus from a patient with Crohn s disease was conducted by Hashimoto and coworkers [39]. They separated two potent virulence factors, capsular polysaccharide (CPS) and lipopolysaccharide (LPS), from a clinical isolate of B. vulgatus and characterized the structure of CPS. Next, they elucidated the strucmres of O-antigen polysaccharide (OPS) and lipid A in the LPS. LPS was subjected to weak acid hydrolysis to produce the lipid A fraction and polysaccharide fraction. Lipid A was isolated by PLC, and its structure was determined by MS and NMR. 

The separation and identification of disaccharides is often an important step in the elucidation of the structure of a natural polysaccharide, and Percival484 has published useful data on the O-trimethyl-silyl derivatives of a variety of disaccharides and their reduction products. In some instances, the trimethylsilyl ethers of the disaccharide alditols have lower retention times than those of the disaccharide derivatives. The per-O-trimethylsilyl derivatives of gentiobi-itol and maltitol were encountered in studies on the structure of Pneumococcus Type II capsular polysaccharide.4843... 

The work of Baddiley and collaborators256 259 on teichoic acids provides excellent examples of the use of deamination in the elucidation of oligosaccharide structure. For example, when treated with nitrous acid (see Scheme 9), the hexasaccharide 140, the repeating unit of the Pneumococcus Type XA capsular polysaccharide, gave 2-... 

One clear example of the importance of capsular polysaccharides is in the symbiotic relationship between nitrogen-fixing rhizobial bacteria and leguminous plants, where MS has played a central role in helping elucidate structures. Here we aim to highlight, using the specific example of bacterial K-antigen studies, the central role of modern mass-spectrometric techniques in polysaccharide analysis. 

The 6-trityl ether of methyl 3-tosyl-D-glucopyranoside was employed by Goebel and coworkers for the unequivocal synthesis of methyl 2,4-dimethyl- 9-D-glucopyranoside. This synthesis was an important link in elucidating the structure of the capsular polysaccharide of Type III pneumococcus. 

In structural studies on the capsular polysaccharide of Klebsiella K-type 9, a number of acidic and neutral oligosaccharides were isolated by ion-exchange chromatography. The homogeneities and structures of the preparations were established by g.l.c.-m.s. of the permethylated oligosaccharide alditols. The structure of the oligosaccharides was also determined by methylation analyses. The same technique was used in the structural elucidation of the capsular polysaccharide of Klebsiella K-type 47. 

K62 (23), have been elucidated, mostly using a combination of methylation analysis. Smith degradation, partial hydrolysis with acid, and H n.m.r. spectroscopy. In some cases e.g. Klebsiella serotypes K13, K25, and K37), depolymerization of the polysaccharides was accomplished by glycanase activities associated with particles of Klebsiella bacteriophages. Serological cross-reactions also revealed similarities in the structures of certain capsular polysaccharides for example, the polysaccharide from Klebsiella serotype K13 (18) cross-reacted with that from Klebsiella serotype K2, which has an identical structure except for the absence of the terminal 3,4-0-(l-carboxyethylidene)-P-D-galactopyranosyl residue. 

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