Free radicals from lyophilized 'dry' DNA bombarded with heavy-ions as studied by electron spin resonance spectroscopy.

Purpose: To investigate the number and species of free radicals from dry DNA after bombardment with heavy-ions at low temperature in comparison with X-irradiation at 77K by electron spin resonance (ESR) spectroscopy. Materials and methods: Solid DNA samples were either X-irradiated at 77K as cylinder samples or heavy-ion-bombarded (LET range 1500-12400keV/mu m) at the Gesellschaft fur Schwerionenforschung (GSI Darmstadt) as very thin tablets. Data acquisition was on a Bruker ESP 380 ESR-spectrometer (X-band, 9.5 GHz). Data analysis involved computer treatment of spectra. Results: Spectra from heavy-ion-bombarded samples were found to reveal the same free radical species with about the same relative contributions for most components as those from X-irradiated samples at comparable doses. Only two components, a thymine allyl radical and a C1' deoxyribose located species, were enhanced after heavy-ion bombardment. Dose effects in both cases involved a higher relative amount of deoxyribose-derived free radica...