Strong Localization of Positive Charge in DNA

TL;DR

This paper investigates the microscopic mechanisms of positive charge transfer in DNA, showing that charge tends to localize within a single base, making DNA more insulating than conductive.

Contribution

The study demonstrates that charge localization in DNA is dominated by environmental interactions, challenging the assumption of delocalized charge transfer in DNA sequences.

Findings

Charge is typically localized within a single G site.

DNA behaves more like an insulator than a conductor.

Experimental data supports the dominance of environmental trapping over pi-stacking.

Abstract

Microscopic mechanisms of positive charge transfer in DNA remain unclear. A quantum state of electron hole in DNA is determined by the competition of a pi-stacking interaction $b$ smearing a charge between different base pairs and interaction $\lambda$ with the local environment which attempts to trap charge. To determine which interaction dominates we investigated charge quantum states in various $(GC)_{n}$ sequences choosing DNA parameters satisfying experimental data for the balance of charge transfer rates $G^{+} \leftrightarrow G_{n}^{+}$, $n=2,3$ \cite{FredMain}. We show that experimental data can be consistent with theory only under an assumption $b\ll \lambda$ meaning that charge is typically localized within a single $G$ site. Consequently any DNA sequence including the one consisting of identical base pairs behaves more like an insulating material than a molecular conductor.