Free radicals from single crystals of deoxyguanosine 5?-monophosphate (Na Salt) irradiated at low temperatures

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Abstract
Summary In single crystals of the DNA nucleotide 2′deoxyguanosine-5′phosphate (5′dGMP) X- orγ-irradiated at 4.2 K or 15 K, two primary radical species can be discriminated and assigned to the cation and anion of the guanine base,G(+) andG(−). Both species are unstable.G(−) partially transforms into a secondary radical at 4.2 K, the latter being the precursor to the dominant 300 K species formed by netH-addition to carbonC8. The secondary radical, together with another intermediate appearing at 77 K and perhaps connected with the anion decay could not be structurally identified. The guanine cationG(+) transforms upon annealing to temperatures above 77 K into a more stable species by deprotonation at positionN1.