γ-Irradiation of Lima Bean Protease Inhibitor in Dilute Aqueous Solutions

Two chromatographically separated fractions of lima beans protease inhibitor were irradiated under atmospheres of nitrogen, oxygen, and nitrous oxide and assayed for residual inhibitory capacity toward β-trypsin and α-chymotrypsin. Conventional exponential losses were observed under the conditions studied. The amino acid compositions of the inhibitors were also monitored after radiolysis. The results obtained showed that apparently minor differences in the three-dimensional structures of the inhibitors were sufficient to influence significantly the rates of destruction of their inhibitory capacities. Further, the modes of action of radiation on the inhibitors is complex: No simple relation between loss of biological activity and destruction of amino acid residues pertains.