Polysaccharides Type 37 capsular, structure

Type IV Pneumococcus Specific Polysaccharide.—This capsular material110 ([ck]d + 33°, water) has been hydrolyzed and shown to contain units of D-glucose and N-acetyl-hexosamine. Its structure has not yet been studied. 

In 1967, Heidelberger, Stacey et al. reported the purification, some structural features, and the chemical modification of the capsular polysaccharide from Pneumococcus Type I. Difficulties of direct hydrolysis of the polysaccharide were overcome and it was possible to identify some of the fragments in the hy-drolyzate. At least six products resulted from nitrous acid deamination. Two were disaccharides, which were identified, and sequences of linked sugar units were proposed. As modification of the polysaccharide decreased the amounts of antibody precipitated by anti-pneumococcal Type I sera, the importance of the unmodified structural features in contributing to the specificity of the polysaccharide was indicated. 

By 1945, Stacey speculated about the possibility of a structural relationship between Pneumococcus capsular polysaccharides and those produced by other organisms. With Miss Schliichterer, he had examined the capsular polysaccharide of Rhizobium radicicolum. This polysaccharide gave a precipitin reaction in high dilution, not only with Type III Pneumococcus antiserum, but also mixed with antisera from other Pneumococcus types. The chemical evidence indicated that the polysaccharide resembled the specific polysaccharides of Types I and II Pneumococcus. A decade later, the acidic capsular polysaccharide from Azoto-bacter chroococcum, a soil organism, was studied. It, too, produced serological cross-reactions with certain pneumococcal specific antisera. Although the molecular structure of the polysaccharide was not established, adequate evidence was accumulated to show a structural relationship to Type III Pneumococcus-specific polysaccharide. This was sufficiently close to account for the Type III serological cross-relationship. 

There are solitary examples of other alditol phosphates as components of this class of polymers. Arabinitol 1-phosphate is part of the S. pneumoniae type 17F capsular polysaccharide. o-Glucitol 6-phosphate is a component of the group-specific polysaccharide from group B Streptococcus, which has a most unusual, ramified structure. In a polysaccharide from Nocardia... 

Despite their popularity, aluminium-based adjuvants suffer from several drawbacks. They tend to effectively stimulate only the humoral arm of the immune response. They cannot be frozen or lyophylized, as either process promotes destruction of their gel-based structure. In addition, aluminium-based products display poor or no adjuvanticity when combined with some antigens (e.g. typhoid or Haemophilus influenzae type b capsular polysaccharides). 

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-... 

Oxidation of the carboxyl-reduced and acetylated Pneumococcus type 2 capsular polysaccharide revealed that only one L-rhamnose residue in the hexasaccharide repeating-unit, later demonstrated to have the structure 60, was oxidized and, consequently, /3-L-linked.156 Replacement of 2,3,6-tri-O-methyl-D-glucose in the methylation analysis of the original polysaccharide by 2,3,4,6-tetra-O-methyl-D-glucose in that of the oxidized polysaccharide established that this L-rhamnose residue is linked to 0-4 of a D-glucose residue. The analysis also showed that it was an L-rhamnose residue in the chain (and not the branching L-rhamnose residue) that was /3-linked. 

Further examples of modified Smith degradation, in which the polyalcohol is methylated prior to hydrolysis under mild conditions, uronic acid degradation, and /3-elimination preceded by oxidation have been reported in connection with structural studies on the Klebsiella type 28 (Ref. 182), 57 (Ref. 183), 59 (Ref. 142), and 81 (Ref. 184) capsular polysaccharides. 

The revised377 structure of the type 14 capsular polysaccharide is shown in formula 39. The precursors of the polymer were identified378 as UDP-Glc, UDP-Gal, and UDP-GlcNAc. Incorporation of a glycosyl group from... 

K. Leontein, B. Lindberg, J. Lonngren, and D. J. Carlo, Structural studies of the capsular polysaccharide from Streptococcus pneumoniae Type 12 A, Carbohydr. Res., 114 (1983) 257-266. 

B. Lindberg and K. Samuelson, The Klebsiella type 38 capsular polysaccharide identification of 3-deoxy-L-g-(ycCTO-pentulosonic acid and structural studies, Carbohydr. Res., 30 (1973) 63-70. 

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