Hole interactions with molecular vibrations on DNA

TL;DR

This study investigates how holes interact with molecular vibrations in dry DNA, revealing long-lived localized holes with weak vibrational coupling, supporting a model of DNA as a chain of coupled quantum dots with Anderson localization.

Contribution

It provides a quantitative analysis of hole-vibrational interactions in dry DNA and supports a quantum dot chain model over metallic conduction.

Findings

Holes have a lifetime over 1 ms at room temperature.

Hole-vibrational coupling constant is approximately 0.2.

DNA behaves as a chain of coupled quantum dots with Anderson localization.

Abstract

We report on a study of the interactions between holes and molecular vibrations on dry DNA using photoinduced infrared absorption spectroscopy. Laser photoexcited (PE) 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 PE holes, we find the holevibrational coupling constant to be relatively small, 0.2. This interaction leads to a change in the conformational energy of 0.015 eV, which is too small to cause selftrapping 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 pseudo-random chain sequence of base pairs, in which Anderson localization prevents the formation of a metallic state.