An ESR and ESEEM study of long-lived radicals which cause mutation in irradiated mammalian cells

Abstract

Long-lived radicals (LLR) that exist in γ-ray-irradiated mammalian cells and have a very long lifetime such as 20 h induce mutation and transformation. The long-lived radicals in the irradiated mammalian cells were scavenged using AsA( L-ascorbic acid) as well as by EGCG((−)-epigallocatechin-3- O-gallate) after irradiation, accompanying the decrease in mutation in the irradiated cells. Determining the location of the long-lived radicals in the cells is therefore very important in order to elucidate the mechanism of the induction of mutation by the radicals. The electron spin echo envelope modulation (ESEEM) study indicates that the long-lived radicals are produced in the interior of the biopolymer coils where water molecules scarcely exist. Since DNA and its sugar chains are quite hydrophilic, the long-lived radicals are not produced in them. However, they are produced in proteins as a major content in cells that have several hydrophobic sites in their higher order structure. The long-lived radicals that cause mutations are not generated in DNA and/or in its sugar chains. However, they are probably produced in proteins.