Abstract
We have provided evidence that long lived radicals (LLRs), produced by ionizing radiation, are highly mutagenic and transforming in mammalian cells. LLRs are effectively scavenged by vitamin C or by epigallocatechin-3-O-gallate (EGCG). LLRs are not involved in lethality or induction of chromosome aberrations. ESR spectra of LLRs produced in irradiated Syrian hamster embryo (SHE) cells were precisely analyzed. We now report results of experiments that define the relative amounts of LLR in DNA and proteins and identify the major protein radical as sulfinyl radicals (R-CH2-S-O). LLRs yields of 99.8% are produced in proteins. We also identified a new type of LLR as H-added phenylalanine radicals. While our evidence does not rule out the possibility of important biological consequences of low-level, LLRs created by radiation in molecules besides proteins, it implicates protein radicals as playing a key role in genetic effects of ionizing radiation. We suggest that these novel radicals, wherever they reside, need to be considered in explanations of biological sequela of radiation. [J Radiat Res 44:379 (2003)]
