Effect of radiation on cis-dichlorodiammineplatinum (II) and DNA in aqueous solution

The radiolysis of cis-dichlorodiammineplatinum (II) (cis-PDD) was studied in order to better understand the mechanisms by which it acts as a radiation sensitizer. The Pt(I) intermediate formed by e- aq reduction of cis-PDD loses both chlorides rapidly, interacts with O2 to form a Pt-oxygen adduct, reacts with the hydroxyl radical adduct of thymine and the peroxy radical of t-butanol, and disproportionates to platinum metal and trans-PDD. The Pt (III) intermediate formed by OH oxidation of cis-PDD likely disproportionates to cis-PDD and Pt(IV) complexes. In a biological model, radiation-induced 3H-thymine base residue release from DNA is found to be inhibited by cis-PDD.