Chromatographic determination of the D- and L-amino acid residues in pneumococcal C-polysaccharide.

The configurations of the amino acids in pneumococcal C-polysaccharide have been determined chromatographically after acid hydrolysis. The amino acids were coupled with an L-amino acid N-carboxyanhydride for formation of the corresponding L-Dand L-L-dipeptides; these derivatives were separated by ion exchange chromatography on an amino acid analyzer. The amount of racemization of alanine which occurred during the hydrolysis was determined by measurement of the amount of tritium incorporated into the amino acid after hydrolysis of the C-polysaccharide in tritiated HCl. After correction for the amount of D or L isomer formed by racemization, it was concluded that the content of D-alanine was variable (25 to 33%) in the three preparations of pneumococcal C-polysaccharide studied. Each of the preparations contained glutamic acid (100% D isomer) and lysine (100% L isomer).