The role of copper and iron ions in the γ-radiolysis of DNA.: Part 1.: EPR studies at cryogenic temperatures

The gamma-radiolysis of frozen aqueous solutions of DNA has been studied by EPR. The effect of transition metal ions Fe(III) and Cu(II) up to 5 mM concentration emerged in lowering of the total radical production in DNA. The loss of 5-thymyl radical (TH)-T-. was mainly observed (on annealing to 203 K) giving evidence that less radical anion of thymine was formed and that no electron transfer from C.- to thymine was revealed in the system. Fe(III) ions are more efficient in the DNA protection than Cu(II) ions. The specific binding sites of iron ions appear to be thymine base. (C) 1998 Elsevier Science Ltd. All rights reserved.