Photoinduced long-lived charge transfer excited states in AT-DNA strands

The IR spectrum of a charge transfer (CT) excited electronic state in DNA has been computed for the first time, enabling assignment of the long-lived component of the transient IR spectrum of a d(AT)(9) single strand to an A -> T CT state. Experimentally, the CT state lifetime is much shorter than in the double strand, and our calculations explain this result using Marcus Theory.