Association-Dissociation Behavior of Sesame a-Globulin in Electrolyte Solutions

The major protein fraction, a-globulin, of sesame seed CS’esamum indicum L.) contains subunits which are associated predominantly by hydrophobic interactions. Effects of various salts show the following effectiveness of anions in dissociating the proteins, SO,*< Cl< Br< C104< SCN4 I< CCl,COO-, the first two members being association-inducing ions. CC1,COONa is found to be the most effective among the series in causing dissociation. The cations Lit, Na+, K+, and Cs+ induce association, the order of effectiveness being Cs+ K+ > Na+ > IA+. The low concentration of salts (anions) necessary to induce dissociation does not involve a detectable change in protein conformation. The discrepancy between the effectiveness of the anions in dissociating the protein and the Hofmeister pattern of these ions has been discussed.