RADIOLYSIS OF METALLOTHIONEIN IN DEAERATED AND OXYGEN-SATURATED SOLUTIONS

Gamma radiolysis of metallothionein (MT) in phosphate-buffered solutions at pH 8.0 leads to the formation of intra- and intermolecular disulfide bridges as well as the release of chelated metal ions. When MT solutions deaerated with N-2 or saturated with N2O were irradiated, G values for RS(-) loss as determined by Ellman's reagent were 4.2 and 7.0, respectively, whereas those for dimerization were only 0.32 and 0.67. A short chain reaction existed in the decrease in RS(-) when radiolysis was performed in O-2-saturated solutions. The rate constants for reactions of MTs with OH radical and H2O2 were measured to be about 10(12) and 100 M(-1)s(-1) respectively. A mechanism for the radiolysis of MT-1 is proposed.