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.