Polypeptides with known repeating sequences of amino acids. Comparison of several methods used for the synthesis of poly-γ-D- and L-glutamylglycine and investigation of its serological reaction with antianthrax immune serum

Abstract

To make a comparison of some of the various polymerization methods, poly-γ-D-and L-glutamylglycine were synthesized through the mixed anhydride, carbodiimide, and pentachlorophenyl active ester methods. This last method proved to be best, on the basis of weight-average molecular weights (M^-_w). A detailed study was also carried out to determine the optimum conditions for this method. The M^-_w, values of the polymers were determined by the sedimentation equilibrium method; it was found that the pentachlorophenyl active ester gave M^-_w values of up to 11, 500 but the mixed anhydride and carbodiimide methods gave M^-_w, values of only about 1000. Tests with rabbit antianthrax immune serum showed that neither D- nor L-isomer precipitated with the antiserum, but that, both were able to inhibit the precipitation of the antiserum by anthrax polypeptide. In addition, the D-polymer gave more inhibition than the L, which would indicate a specificity of the antibody for D-glutamic acid residues.