Circular dichroism of the O-specific polysaccharide of Vibrio cholerae O1 and some related derivatives.
The O-specific polysaccharide (O-SP) of Vibrio cholerae O1 is a homopolymer of alpha-(1 --> 2)-linked 4-amino-4, 6-dideoxy-D-mannopyranose whose amino group is acylated with 3-deoxy-L-glycero-tetronic acid [N-(3-deoxy-L-glycero- tetronyl)-alpha-D-perosamine]. The circular dichroism (CD) of the O-SP as well as of a number of N-acyl (formyl, acetyl, 4-hydroxybutyl, 3-deoxy-L-and D-glycero-tetronyl) derivatives of methyl alpha-glycosides of 4-amino-4,6-dideoxy-D-mannopyranose (methyl alpha-D-perosaminide) has been studied for solutions in water, acetonitrile and 1,1,1-trifluoroethanol. The strong solvent dependence of the sign and intensity of the CD observed for the monosaccharide amides bearing achiral acyl groups is explained by solvent-mediated change of the orientation of the amido group relative to the proximal hydroxyl group at C-3. A change in the population of the nonplanar conformers with a pyramidal arrangement of bonds at the amido nitrogen has also been considered. The effect of solvents upon the CD spectra of compounds bearing chiral N-acyl substituents is less pronounced than that of their counterparts bearing achiral N-acyl substituents. The sign of the CD for the O-SP was found negative in all solvents used. This result is in agreement with the negative sign of the CD of the n --> pi electron transition observed, independent of the solvent, for the monosaccharide derivative containing the L-glycero-3-deoxytetronamido group, and the positive sign found for its D-glycero-counterpart.
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NICHD, Laboratory of Developmental and Molecular Immunity, National Institutes of Health, Bethesda, MD 20892, USA.
Szu
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Gotoh
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Kovác
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D000097:Acetonitriles; D000577:Amides / Q000737:chemistry; D002942:Circular Dichroism; D008358:Mannose / Q000031:analogs & derivatives / Q000737:chemistry; D019081:O Antigens / Q000737:chemistry* / Q000276:immunology; D012995:Solubility; D014270:Trifluoroethanol; D014734:Vibrio cholerae / Q000737:chemistry* / Q000276:immunology; D014867:Water
D000097:Acetonitriles; D000577:Amides; D019081:O Antigens; D014867:Water; C057033:4-amino-4,6-dideoxy-D-mannose; D014270:Trifluoroethanol; D008358:Mannose; C032159:acetonitrile