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

Summary

X-irradiation of single crystals of uridine-5′-phosphate (disodium salt) between 10 and 300 K as well as storage of irradiated crystals at 300 K produces at least seven different radical species. Between 10 and 77 K, the uracil base anion and a secondary alkoxy radical at the ribose-O_3′-site are formed. The latter transforms into a C_5′-centred alkylphosphate species between 110 and 130 K which in turn decays between 180 and 220 K under formation of a base 5-yl hydrogen addition radical. Irradiation at 300 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 C_5′ of the ribose. The spectral parameters of these radicals are given and discussed.