Radiation Damage to Nucleosides and Nucleotides. III. A C 4 -Centered Radical in the Ribose Moiety of Uridine-5 prime -Phosphate Single Crystals

Abstract

Single crystals of the disodium salt of UMP were irradiated with 4.0-MeV electrons at 270.degree. K and studied by ESR spectroscopy. A particular resonance not fully analyzed was investigated. The resonance exhibited typical features for interactions with 1 .alpha. proton (principal values -28.6, -19.0 and -8.7 G) and 2 .beta. protons with about 13 and 48 G isotropic splitting. A detailed comparison with crystallography implied the resonance may be ascribed to a radical formed by a ribose-ring opening with the spin density centered mainly at C4''. A possible relationship to a radical in 2''-deoxycytidine hydrochloride single crystals with very similar spectral characteristics is discussed.