ESR STUDY OF RADICAL PROCESSES IN IRRADIATED DNA - THE EFFECT OF THE COMPLEXATION WITH CIS-DICHLORO DIAMINO PT(II)

The room temperature esr spectra of irradiated neat duplex hydrated, d ehydrated and thermally denaturated DNA are interpreted in terms of th e radicals formed by protonation of the thymine and cytosine anion rad icals, by deprotonation of the guanine cation radicals, by addition of OH radicals at C8 of guanine and by loss of a methyl hydrogen from th ymine. The complexation of DNA with cis-dichlorodiamino Pt(II) causes a drastic alteration of the radical distribution interpreted in terms of electron scavenging by the Pt(II) complex, a partial inhibition of the radical-cation chemistry of guanine, and enhancement of the reacti vity of thymine toward hydrogen abstractions.