Enhancement of transport in DNA-like systems induced by backbone disorder

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.

Role of photoresponse of π electrons in light-driven DNA dissociations

The role of photoresponse of π electrons in light-driven DNA dissociations is theoretically studied. A new model combining the Peyrard-Bishop-Dauxois model and the charge ladder model is first proposed. Then the evolutions of π-electronic states and H-bond stretching in the light-driven DNA dissociations are studied. The results show that light irradiation will induce ultrafast charge redistribution among bases, leading to the precursory insulator-to-metallic transition. This electronic transition will assist DNA to dissociate. Effects of screened Coulomb interactions on dissociation dynamics is emphatically discussed. Finally, it is also found that light-driven DNA dissociation preferentially occurs in the adenine-thymine-rich region rather than the guanine-cytosine-rich region.

Enhancement of the thermoelectric figure of merit in DNA-like systems induced by Fano and Dicke effects

We report a theoretical study highlighting the thermoelectric properties of biological and synthetic DNA molecules.

Localization phenomena in a DNA double-helix structure: a twisted ladder model

In this work we propose a model for the DNA double helix within the tight-binding framework that incorporates the helicity of the molecules. We have studied the localization properties of three DNA sequences, the periodic poly(dG)-poly(dC) and poly(dA)-poly(dT) sequences and the random ATGC sequence (where A is adenine, T is thymine, G is guanine, and C is cytosine), all of which are coupled to the backbone with random site energies representing the environmental fluctuations. We observe that due to the helicity of DNA, electron transport is greatly enhanced and there exists an almost disorder-strength-independent critical value of the hopping integral, which accounts for the helicity of DNA, for which the electronic states become maximally extended. We have also investigated the effect of backbone energetics on the transmission and I-V characteristics of DNA.

Influence of backbone on the charge transport properties of G4-DNA molecules: a model-based calculation

We put forward a model Hamiltonian to describe the influence of backbone energetics on charge transport through guanine-quadruplex DNA (G4-DNA) molecules. Our analytical results show that an energy gap can be produced in the energy spectrum of G4-DNA by hybridization effects between the backbone and the base and by on-site energy difference of the backbone from the base. The environmental effects are investigated by introducing different types of disorder into the backbone sites. Our numerical results suggest that the localization length of G4-DNA can be significantly enhanced by increasing the backbone disorder degree when the environment-induced disorder is sufficiently large. There exists a backbone disorder-induced semiconducting-metallic transition in short G4-DNA molecules, where G4-DNA behaves as a semiconductor if the backbone disorder is weak and behaves as a conductor if the backbone disorder degree surpasses a critical value.