STRUCTURAL STUDIES OF THE VIBRIO-SALMONICIDA LIPOPOLYSACCHARIDE

The oligosaccharide part of the Vibrio salmonicida (strain NCMB 2262) lipopolysaccharide was isolated by mild acid hydrolysis followed by ge l-permeation chromatography. The structure was established mainly by m ethylation analysis, mass spectrometry, and NMR spectroscopy, It is co ncluded that the oligosaccharide has the following structure, in which L-alpha-D-Hep p is L-glycero-alpha-D-manno-heptopyranose, D-alpha-D-H epp is D-glycero-alpha-D-manno-heptopyranose, alpha-D-Fuc p4N is 4-ami no-4,6-dideoxy-alpha-D-galactopyranose alpha-NonA is 9-tetradeoxy-L-gl ycero-alpha-D-galacto-nonulosonic acid, BA is (R)-3-hydroxybutanoyl, a nd PEA is phosphoethanolamine. The substitution pattern of the branchi ng heptosyl residue was deduced from H-1 NMR chemical shifts and confo rmations of the branching region, obtained by molecular modelling, The absolute configuration for NonA was determined by NMR spectroscopy fr om NOE correlations to the neighbouring sugar and C-13 NMR chemical sh ift data, It could also be shown that assignments of nonulosonic acids with the D-glycero-L-galacto configuration, reported by previous inve stigators, are erroneous and should be changed to L-glycero-D-galacto. The oligosaccharide is assumed to be linked to the 5-position of a Kd o residue, phosphorylated in the 4-position as observed for other lipo polysaccharides from Vibrionaceae.