ESR Study of Radiation-Induced Radicals in the Sugar-Phosphate Region of Nucleotides: II. PO42- Radical in a Crystal of Uridine 5′-Phosphate (Na Salt)

The PO42- radical in an irradiated single crystal of 5′-UMP (Na Salt) has been analyzed by ESR. The doublet structure is brought about by the isotropic31 P coupling (A = 20.6 G). The g-tensor is nearly axially symmetric $(g_{11}=2.0526,\ g_{\perp}=2.0048)$ . The radical is unstable at temperatures above 100 K. The radical is formed by the scission of the ${\rm C}_{5^{\prime}}-{\rm O}_{5^{\prime}}$ bond.