Free Radicals from X-irradiated Single Crystals of Uridine-5′-phosphate Disodium Salt

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Abstract
X-irradiation of single crystals of UMP (disodium salt) at 10.degree.-300.degree. K as well as storage of irradiated crystals at 300.degree. K produces at least 7 different radical species. At 10.degree.-77.degree. K, the uracil base anion and a secondary alkoxy radical at the ribose-O3''-site are formed. The latter transforms into a C5''-centered alkylphosphate species at 110.degree.-130.degree. K which in turn decays at 180.degree.-220.degree. K under formation of a base 5-yl hydrogen addition radical. Irradiation at 300.degree. K additionally produces the base-located 6-yl radical together with a radical tentatively assigned to the doubly protonated base anion. Storage of crystals for several months results in decay of most of these species leaving a radical possibly located at C5'', of the ribose. The spectral parameters of these radicals are given and discussed.