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 the charge between different base pairs and interaction $\lambda$ with the local environment, which attempts to trap the charge. To determine which interaction dominates, we investigate charge quantum states in various ${\left(GC\right)}_n$ sequences choosing DNA parameters such as to satisfy experimental data for the balance of charge-transfer rates $G^{+}\leftrightarrow G_n^{+}$; $n=2,3$ [Lewis et al., Nature (London) 406, 51 (2000)]. We show that experimental data can be consistent with theory only under an assumption of $b⪡\lambda$, which implies that charge is typically localized within a single $G$ base. Consequently any DNA sequence, including the stack of identical base pairs, behaves more like an insulating material than a molecular conductor.

• Received 24 July 2008

DOI:https://doi.org/10.1103/PhysRevB.78.073106