Long-lived radicals of amino acids induced by X-ray radiation are the source of hydrogen peroxide in aqueous medium

Abstract

The formation of long-lived radicals in the solutions of casein and its hydrolysate with an equimolar mixture of amino acids was compared by measuring the X-ray-induced chemiluminescence. It was shown that free amino acids constituting the protein produce long-lived radicals. It was demonstrated that some amino acids (Leu, Ile, Val, Ser, Trp, Met, Pro, Arg, Gly, Phe) emit light of visible spectrum over a long period of time after the irradiation, which indicates the generation of long-lived radicals of these amino acids. The half-life times of these radicals are several hours. Dissolving irradiated dry amino acids capable of luminescing over a long time gives rise to the formation of hydrogen peroxide in aqueous medium.