Hydrated electrons induce the formation of interstrand cross-links in DNA modified by cisplatin adducts

Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel electrophoresis analysis demonstrates the formation of cisplatin-interstrand crosslinks from the cisplatin-intrastrand species. The rate constant per base for the reaction between hydrated electrons and the double-stranded oligonucleotides with and without cisplatin containing a mismatched region was determined by pulse radiolysis to be 7 × 10(9) and 2 × 10(9) M(−1) s(−1), respectively. These results provide a better understanding of the radiosensitizing effect of cisplatin adducts in hypoxic tumors and of the formation of interstrand crosslinks, which are difficult for cells to repair.