Location of the O-methyl groups in the O polysaccharide of Pseudomonas syringae pv. phaseolicola

The O-methylation pattern of the O polysaccharide (OPS) of the lipopolysacc haride of Pseudomonas syringae pv. phaseolicola GSPB 1552 was revealed by m ethylation (CD3I) analysis, Smith degradation, and NMR spectroscopy. Togeth er with the major O repeats consisting of D-rhamnopyranose (D-Rhap) and D-f ucofuranose (D-Fucf), there are minor repeats (similar to 30%) containing 3 -O-methyl-D-rhamnose (D-acofriose), which is 2-substituted in the interior repeats and occupies the terminal non-reducing end of the OPS. It was sugge sted that the methylated O repeats are linked to each other nearby the non- reducing end of the OPS and that the 'biological' O repeat of the OPS has t he following structure: [GRAPHICS] (C) 2001 Elsevier Science Ltd. All rights reserved.