Polaron Hopping in Nano-scale Poly(dA)-Poly(dT) DNA

Unexpected large charge transfer rate mediated by adenine in twisted DNA structure

DNA exhibits remarkable charge transfer ability, which is crucial for its biological functions and potential electronic applications. The charge transfer process in DNA is widely recognized as primarily mediated by guanine, while the contribution of other nucleobases is negligible. Using the tight-binding models in conjunction with first-principles calculations, we investigated the charge transfer behavior of homogeneous GC and AT pairs. We found that the charge transfer rate of adenine significantly changes. With overstretching, the charge transfer rate of adenine can even surpass that of guanine, by as much as five orders of magnitude at a twist angle of around 26°. Further analysis reveals that it is attributed to the turnover of the relative coupling strength between homogeneous GC and AT base pairs, which is caused by the symmetry exchange between the two highest occupied molecular orbitals of base pairs occurring at different twist angles. Given the high degree of flexibility of DNA in vivo and in vitro conditions, these findings prompt us to reconsider the mechanism of biological functions concerning the charge transfer in DNA molecules and further open the potential of DNA as a biomaterial for electronic applications.

Charge transport in a double-stranded DNA: Effects of helical symmetry and long-range hopping

Within a tight-binding framework, we examine conformation-dependent charge transport properties of the DNA double-helix, including helical symmetry and the possibility of multiple charge conduction pathways. Using techniques based on the Green's function method, we inspect changes in the localization properties of DNA in the presence of long-range hopping, with varying disorder strength. We study three characteristic DNA sequences, two periodic and one random. We observe that, in all cases, due to disorder-induced delocalization, the localization length variation is similar. We also investigate the effect of backbone energetics on current-voltage (I-V) responses, using the Landauer-Büttiker formalism. We find that, in the presence of helical symmetry and long-range hopping, due to environmental effects, DNA can undergo a phase transition from semiconductor to insulator.

Charge transfer mechanisms in DNA at finite temperatures: From quasiballistic to anomalous subdiffusive charge transfer

We address various regimes of charge transfer in DNA within the framework of the Peyrard-Bishop-Holstein model and analyze them from the standpoint of the characteristic size and timescales of the electronic and vibrational subsystems. It is demonstrated that a polaron is an unstable configuration within a broad range of temperatures and therefore polaronic contribution to the charge transport is irrelevant. We put forward an alternative fluctuation-governed charge transfer mechanism and show that the charge transfer can be quasiballistic at low temperatures, diffusive or mixed at intermediate temperatures, and subdiffusive close to the DNA denaturation transition point. Dynamic fluctuations in the vibrational subsystem is the key ingredient of our proposed mechanism which allows for explanation of all charge transfer regimes at finite temperatures. In particular, we demonstrate that in the most relevant regime of high temperatures (above the aqueous environment freezing point), the electron dynamics is completely governed by relatively slow fluctuations of the mechanical subsystem. We argue also that our proposed analysis methods and mechanisms can be relevant for the charge transfer in other organic systems, such as conjugated polymers, molecular aggregates, α-helices, etc.