The complete structure of the capsular polysaccharide from Streptococcus sanguis 34

A complete structure for the capsular polysaccharide of Streptococcus sanguis 34, which is responsible for coaggregation of this bacterium with Actinomyces viscosus T14V, an important step in the formation of dental plaque, is proposed, based partly on the 1H-n.m.r. spectrum, which was assigned by 2-dimensional COSY, homonuclear Hartmann-Hahn spectroscopy, and nuclear Overhauser effects. A phosphoric diester linkage was identified from the 31P-n.m.r. spectrum, and the linkage was determined from long range 1H-31P correlation spectroscopy. The proposed structure is supported both by methylation analysis before and after dephosphorylation and by g.l.c.-m.s. of the phosphorylated monosaccharides as their trimethylsilyl derivatives, isolated by partial hydrolysis of the polysaccharide. The structure is composed of repeating linear hexasaccharide units joined by a phosphoric diester linkage, i.e., [----PO4(-)----6)-alpha-D-GalpNAc-(1----3)-beta-L-Rhap-(1----4)-be ta -D-Glcp- (1----6)-beta-D-Galf-(1----6)-beta-D-GalpNAc-(1----3)-alpha-D-Galp -(1----]n.