Structural investigation of the capsular polysaccharide from Escherichia coli O9:K37 (A 84a).

The structure of the capsular polysaccharide from E. coli O9:K37 (A 84a) has been studied, using methylation analysis, Smith degradation, and graded acid hydrolysis. The configurations at the anomeric centres were assigned by 1H-n.m.r. spectroscopy of the polysaccharide and its derivatives and oligosaccharide fragments. The polysaccharide has the following trisaccharide repeating-unit which is unique in the E. coli series of capsular polysaccharides in possessing a 1-carboxyethylidene group as the sole acidic function. (Formula: see text) E. coli capsular polysaccharides have been classified into seventy-four serotypes. The structures of about twenty of these polysaccharides have been elucidated, one of which, K29, has been reported to contain a 1-carboxyethylidene group. In continuation of a programme aimed at establishing the structural basis for the serology and immunochemistry of the E. coli capsular antigens, we now report on the structure of the capsular polysaccharide from E. coli O9:K37.