title: Structural analysis of a novel sialic-acid-containing trisaccharide from Rhodobacter capsulatus 37b4 lipopolysaccharide.
abstract: Sialic-acid-containing lipopolysaccharides from Rhodobacter capsulatus 37b4 (S-form lipopolysaccharide), KB-1 (R-type lipopolysaccharide) and Sp 18 (deep R-type lipopolysaccharide) were investigated for the linkage and substitution of sialic acids. Methylation analysis and behaviour towards acid and enzymic hydrolysis indicated a non-reducing terminal location of sialic acids in the R-type lipopolysaccharide of strain Sp 18, whereas an internal, chain-linked location of sialic acids was found in the lipopolysaccharides of strains 37b4 and KB-1. For these latter strains, methylation analysis revealed a substitution of sialic acids by other sugars at position 7 for strain 37b4 and positions 4 and 7 for strain KB-1. In accordance with the chain-linked position of sialic acids, mild hydrolysis of R. capsulatus 37b4 lipopolysaccharide with acetic acid released a trisaccharide with sialic acid at the reducing terminus. Structural investigation of this trisaccharide by methylation analysis, 1H- and 13C-NMR spectroscopy revealed the presence of the disaccharide Gal1-6Glc at the non-reducing end, probably with an alpha-anomeric configuration of the galactose residue, i.e. melibiose, beta-glycosidically linked to position 7 of sialic acid. Therefore the structure Gal alpha 1-6Glc beta 1-7Neu5Ac is proposed for this core oligosaccharide from R. capsulatus 37b4 lipopolysaccharide.
authors.affiliation: Max-Planck-Institut für Immunbiologie, Freiburg, Federal Republic of Germany.
authors.forename: J H
authors.initials: JH
authors.lastname: Krauss
authors.forename: K
authors.initials: K
authors.lastname: Himmelspach
authors.forename: G
authors.initials: G
authors.lastname: Reuter
authors.forename: R
authors.initials: R
authors.lastname: Schauer
authors.forename: H
authors.initials: H
authors.lastname: Mayer
mesh_terms: D002240:Carbohydrate Sequence; D008401:Gas Chromatography-Mass Spectrometry; D008070:Lipopolysaccharides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008745:Methylation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019158:N-Acetylneuraminic Acid; D010084:Oxidation-Reduction; D010504:Periodic Acid; D016354:Rhodobacter capsulatus / Q000737:chemistry*; D012794:Sialic Acids / Q000032:analysis*; D014312:Trisaccharides / Q000737:chemistry*
chemical_list: D008070:Lipopolysaccharides; D012794:Sialic Acids; D014312:Trisaccharides; D010504:Periodic Acid; D019158:N-Acetylneuraminic Acid