Association of optically active ions III: diastereomeric ion pair formation in histidine-glutamic acid mixtures

Conductometric titrations of equimolar mixtures of L-glutamic acid and L-histidine indicate that these species interact more strongly than L-glutamic acid with D-histidine in dilute solution. The presence of ion pairs is confirmed by the UV spectrum of these solutions. No such stereospecific interactions were found between L-glutamic acid and L-lysine or L-ornithine. The conductometric titration curves of these compounds are identical with that of L-glutamic acid with the DL mixture of the basic amino acids.