Radiation-induced luminescence in DNA: evidence for long-range electron migration

The radiation-induced "in-pulse" luminescence emission from solid DNA containing either metronidazole or a highly electron-affinic 5-nitrofuran in the range 3-2000 (w:w) base pairs per additive molecule has been investigated in vacuo at 293 K using electron pulses of energy below 260 keV. The luminescence intensity at 450 nm from DNA decreases with increasing content of the additive in the sample and approaches a limiting level at high concentrations of the additives. At these higher concentrations the limiting value represents about 50% of that observed from DNA alone. It is shown that the efficiency of the additives in reducing the luminescence intensity is dependent upon their redox potential E1(7); this dependence is consistent with these additives acting as electron acceptors. It is concluded that the ability of the electron acceptors to reduce the luminescence is related to the electron affinity of E1(7) of the acceptors and electron migration distances of at least 300 base pairs are proposed.