Structural comparison of the O6 specific polysaccharides from E. coli O6:K2:H1, E. coli O6:K13:H1, and E. coli O6:K54:H10.

Two distinct forms of the O6 antigen (LPS) from E. coli were analysed using 1H and 13C NMR spectroscopy. Their structures were found to be [formula: see text] In the O6-specific polysaccharide from E. coli O6:K2 and O6:K13, X is beta-D-Glc p, as had previously been shown for the O6 polysaccharide from E. coli O6:K15; in the O6 specific polysaccharide from E. coli O6:K54, X is beta-D-Glc pNAc.

Somatic antigens of Pseudomonas aeruginosa. The structure of O-specific polysaccharide chains of P. aeruginosa O:3(a),c and O:3a,d,e lipopolysaccharides.

On mild acid degradation of Pseudomonas aeruginosa O:3(a),c, O:3a,d,e and O:3(a),d,f lipopolysaccharides O-specific polysaccharides were isolated. The trisaccharide repeating units of O:3(a),c and O:3a,d,e polysaccharides contained 2-acetamido-2,6-dideoxy-D-galactose and 2,3-(1-acetyl-2-methyl-2-imidazolino-5, 4)-2,3-dideoxy-D-mannuronic acid, which were identified previously as the constituents of P. aeruginosa O:3a,b and O:3a,d O-specific polysaccharides, as well as 2,3-diacetamido-2, 3-dideoxyl-L-guluronic acid, which has never before been found in nature. The last monosaccharide was identified without being isolated in the free state, by means of 13C nuclear magnetic resonance spectroscopy. The structures of O:3(a),c and O:3a,d,e polysaccharides were established by selective hydrogen fluoride solvolysis followed by modification of the trisaccharides obtained and analysis of the 13C nuclear magnetic resonance spectra at each modification stage. The polysaccharides possessed similar structures of repeating units differing from each other in the anomeric configuration of the N-acetylfucosamine residue only: leads to 4)DManImU-(beta 1 leads to 4) LGul(NAc)2U(alpha 1 leads to 3)DFucNAc(beta 1-and leads to 4)DManImU(beta 1 leads to 4)LGul(NAc)2U(alpha 1 leads to 3)DFucNAc(alpha 1-, where DManImU = 2,3-(1-acetyl-2-methyl-2-imidazolino-5,4)-2,3-dideoxy-D-mannuronic acid, LGul(NAc)2U = 2,3-diacetamido-2,3-dideoxy-L-guluronic acid, DFucNAc = 2-acetamido-2,6-dideoxy-D-galactose. The same components were detected in the O:3(a),d,f polysaccharide but not in the same stoichiometric ratio; this polysaccharide possessed no regular structure. The immunochemical study of lipopolysaccharides of all five P. aeruginosa O:3 serotypes showed a definite interrelation between their serological properties and structures of the corresponding O-specific polysaccharides.

Somatic antigens of Shigella. The structure of the specific polysaccharide of Shigella newcastle (Sh. flexneri type 6) lipopolysaccharide.

The specific polysaccharide was obtained from the lipopolysaccharide of Shigella newcastle by mild acid hydrolysis and further purified by permeation chromatography on Sephadex G-50. It was found to consist of L-rhamnose, 2-acetamido-2-deoxy-D-galactose, D-galacturonic acid residues and O-acetyl groups in the molar ratios of 2:1:1:1. On the basis of 1H and 13C nuclear magnetic resonance spectroscopy, methylation analysis, partial acid hydrolysis, Smith degradation, and chromium trioxide oxidation, the following structure can be assigned to the repeating oligosaccharide unit of the polysaccharide:-4)DGalA(beta 1-3)DGalNAc-(beta 1-2)LAc3Rha(alpha 1-2)LRha(alpha 1-, where GalA = galacturonic acid. GalNAc = N-acetylgalactosamine, Ac3Rha = 3-O-acetylrhamnose. The structural and immunochemical data presented prove that Sh. newcastle lipopolysaccharide belongs to a 'non-classical' type of somatic antigens with acidic O-specific polysaccharide chains.