Excess electron transfer in flavin-capped, thymine dimer-containing DNA hairpins

The transfer of an excess electron through DNA was investigated with DNA hairpins, which contain a flavin cap functioning as an electron donor. A thymine dimer with an open backbone acts as the electron acceptor. The dimer translates the electron capture into a strand break, which is readily detectable by HPLC. Analysis of four hairpins, in which the distance between the flavin donor and the dimer acceptor was systematically increased, revealed a flat distance dependence of the repair efficiency supporting the view that excess electrons hop through DNA using intermediate A–T base pairs as temporary charge carriers.