PRIMARY FREE-RADICAL FORMATION IN RANDOMLY ORIENTED DNA - EPR SPECTROSCOPY AT 245 GHZ

245 GHz/8.7 T EPR spectroscopy has been applied for the first time to X-irradiated DNA equilibrated in different relative humidities and in frozen aqueous solution as well as to DNA components. Several primary and secondary radicals from nucleotides that are important with respec t to DNA-located radicals could be isolated and simulated: the guanine cation, the cytosine anion, the thymine anion, the thymine H addition radical and the thymine allyl radical. The most clear-cut evidence fo r a DNA radical component was for the guanine cation, both the cytosin e and the thymine anion being discernible. The guanine cation was foun d to be present in all DNA samples but was diminished in the frozen aq ueous solutions. The contribution of the thymine anion decreased with increasing hydration level.