Reduced Products and Hydrogen from X-Irradiated Air-Saturated Solutions of Cystamine and Cystine

Abstract

Hydrogen, in excess of track yields, and thiol are found in acidic cystamine sulfate solutions exposed, in air, to x-rays. These products are not found in basic solutions. Earlier work had shown that alkaline air-saturated cystamine solutions give sulfonic acid (taurine) in amounts of numerically close to $G_{{\rm OH}}$. Hydrogen peroxide in excess of track yields by amounts equal to 1/2 $G_{{\rm H}}$ was also found. Acidic solutions, however, give considerably more sulfonic acid at intermediate disulfide concentrations and no excess peroxide. The present results indicate the extra sulfonic acid, above $G_{{\rm OH}}$, to arise from oxidation by H, in part directly (possibly as ${\rm H}_{2}{}^{+}$) and in part via HO2. The latter part decreases steadily at higher disulfide concentrations as H are scavenged by disulfide, giving thiol, rather than by O2. Cystine, in neutral or acidic solution, gives sulfonic acid yields no greater than $G_{{\rm OH}}$ Concomitant hydrogen peroxide yields are near 1/2 $G_{{\rm...