Remote cis-syn-thymine [2+2] dimers are not repaired by radical cations migrating in duplex DNA

A series of DNA oligomers was prepared containing an anthraquinone derivative linked to a 5'-end, a cis-syn-[2 + 2]thymine dimer and strategically located GG steps. These compounds were designed to test the claim that one-electron oxidation of the DNA leads to repair of remote thymine dimers. Irradiation of the anthraquinone leads to remote damage at the 5'-G of GG steps that are positioned both before and after the thymine dimer, but there is no detectable (<3%) repair of the thymine dimer. These findings are in contrast to a previous series of reports in which repair of the thymine dimer is reported to occur 40 times more efficiently than reaction at GG steps when the remote one-electron oxidation is initiated by irradiation of a covalently linked Rh-containing metallointercalator.