On the Possibility of Superfast Charge Transfer in DNA

TL;DR

This paper proposes that superfast charge transfer between DNA base pairs can occur, leading to quasi-equilibrium charge distributions, which explains the contradictory experimental observations of slow localization versus long-distance transfer.

Contribution

It introduces the hypothesis of superfast charge transitions in DNA, independent of the transfer mechanism, and compares charge transfer in dry versus solvated DNA.

Findings

Superfast charge transfer can establish quasi-equilibrium distributions in DNA.

Charge solvation in solution significantly reduces transfer rates.

Calculated distributions support the possibility of superfast tunneling of holes in DNA.

Abstract

Numerous experiments on charge transfer in DNA yield a contradictory picture of the transfer: on the one hand they suggest that it is a very slow process and the charge is almost completely localized on one Watson-Crick pair, but on the other hand they demonstrate that the charge can travel a very large distance. To explain this contradiction we propose that superfast charge transitions are possible between base pairs on individual DNA fragments resulting in the establishment of a quasi-equilibrium charge distribution during the time less than that of charge solvation. In other words, we hypothesize these states irrespective of the nature of a mechanism responsible for their establishment, whether it be a hopping mechanism, or a band mechanism, or superexchange, or polaron transport, etc., leaving aside the debates of which one is more advantageous. We discuss qualitative differences between the charge transfer in a dry DNA and that in a solution. In a solution, of great importance is the charge solvation which decreases the transfer rate $10^7 - 10^8$ times as compared with a dry DNA. We consider the conditions under which the superfast charge transfer in a DNA leading to quasi-equilibrium distributions of polarons in a duplex is possible. Comparison of calculated quasi-equilibrium distributions with the experiment testifies to the possibility of superfast tunnel transitions of a hole in a DNA duplex in a solution.