The O‐Specific Polysaccharide Chain of <i>Campylobacter fetus</i> Serotype B Lipopolysaccharide is a <scp>d</scp>‐Rhamnan Terminated with 3‐<i>O</i> ‐Methyl‐<scp>d</scp>‐Rhamnose (<scp>d</scp>‐Acofriose)

Abstract

An O-specific polysaccharide was liberated from Campylobacter fetus subsp. fetus serotype B lipopolysaccharide by mild acid hydrolysis followed by gel chromatography. This polysaccharide was found to contain D-rhamnose and 3-O-methyl-D-rhamnose (D-Rha3Me, D-acofriose) in a ratio of approximately 24:1, as well as lipopolysaccharide core constituents. The structure of the polysaccharide was studied by 1H-NMR and 13C-NMR spectroscopy, which included two-dimensional COSY, rotating-frame NOE spectroscopy (ROESY), and computer-assisted analysis of the 13C-NMR spectrum. Methylation analysis using [2H3]methyl iodide and Smith degradation followed by GLC/MS of the derived acetylated oligosaccharide-alditols was used to determine the location of D-acofriose. The O-specific polysaccharide is linear, consists on average of 12 disaccharide repeating units, and is terminated by a residue of D-acofriose. The following structure of the D-rhamnan chain was established: [sequence: see text]