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

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 ( M̄ w ). A detailed study was also carried out to determine the optimum conditions for this method. The M̄ w , values of the polymers were determined by the sedimentation equilibrium method; it was found that the pentachlorophenyl active ester gave M̄ w values of up to 11, 500 but the mixed anhydride and carbodiimide methods gave M̄ 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.