Hole Interactions with Molecular Vibrations on DNA

Ales Omerzu, Matjaz Licer, Tomaz Mertelj, Viktor V. Kabanov, and Dragan Mihailovic

Department of Complex Matter, Institute Jozef Stefan, Jamova 39, 1000 Ljubljana, Slovenia

We report on a study of the interactions between holes and molecular vibrations on dry DNA using photoinduced infrared absorption spectroscopy. Laser photoexcited holes are found to have a room-temperature lifetime in excess of >1 ms, clearly indicating the presence of localization. However, from a quantitative model analysis of the frequency shifts of vibrational modes caused by the holes, we find the hole-vibrational coupling constant to be relatively small, 0.2. This interaction leads to a change in the conformational energy of E0~0.015 eV, which is too small to cause self-trapping at room temperature. We conclude that, at least in the dry (A) form, DNA is best understood in terms of a double chain of coupled quantum dots arising from the pseudorandom chain sequence of base pairs, in which Anderson localization prevents the formation of a metallic state.

Email: ales.omerzu@ijs.si

Address: Department of Complex Matter, Institute Jozef Stefan, Jamova 39, 1000 Ljubljana, Slovenia