ESR study of radiation‐induced radicals in the sugar‐phosphate region of nucleotides. III. The alkoxy radical in deoxycytidine 5′‐phosphate

The unstable radical at 77 K in a gamma‐irradiated single crystal of deoxycytidine 5′‐phosphate was analyzed by ESR. A very anisotropic g tensor (g1=1.9997, g2=2.0095, and g3=2.0773) and two approximately equal β‐proton couplings with isotropic values of 8.0 G were interpreted to represent a radical of the O–CH2–R form. The radical is formed by the breakage of the phosphate–ester bond. The calculated spin densities on H(5′) and H′(5′) in the INDO MO approximation are in agreement with the observed couplings. The lack of any hydrogen bonding in the radical is believed to bring about much smaller β‐proton couplings from those previously observed and assigned to the same radical.

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