A C_5′-centred Deoxyribose Radical in Single Crystals of 5-chloro-and 5-bromodeoxyuridine X-irradiated at Low Temperatures

Summary

X-irradiation at 77 K and subsequent warming to 150 K of single crystals of 5-chloro- and 5-bromodeoxyuridine produces a radical located at position C_5′ of the deoxyribose moiety. The radical exhibits identical spectral properties in both crystal systems. It is characterized by interaction of the unpaired electron with an α-proton (−17·0, −8·7, −33·7 G), a β-proton (18·6, 21·3, 17·5 G) as well as an OH-proton (4·8, 7·9, 12·8 G). The principal values of the g-tensor are 2·0034, 2·0049 and 2·0042. The spectral parameters are discussed in relation to those of the same or similar radicals in other nucleosides (-tides).