Structure of the serotype f polysaccharide antigen of Streptococcus mutans

The structure of the serotype f polysaccharide antigen of Streptococcus mutans was determined by methylation analysis, periodate oxidation, and partial methanolysis, and the configuration of the anomeric linkages by 13C-n.m.r. spectroscopy, indicating the trisaccharide repeating unit----3)-alpha-L-Rhap-(1----2)-[alpha-D-Glcp-(1----3)]-alpha-L-+ ++Rhap- (1----. The structure of the backbone of the polysaccharide was confirmed by demonstrating immunological identity between the product of Smith degradation of the S. mutans serotype f antigen and the group A-variant streptococcal polysaccharide.