Effects of contact and efficient charge transport in G4-DNA molecules

Abstract

We report a theoretical study highlighting the fundamental effects of contact between molecule and electrodes and of the off-diagonal disorder on the transport properties of guanine-quadruplex DNA (G4-DNA) molecules. On the basis of the effective tight-binding model which simulates charge transport through G4-DNA, the transmission coefficient and localization length are numerically calculated by using the transfer-matrix method. In contrast to the physical intuition that a strong coupling at the molecule-metal interface will lead to a large conductance, we find that the averaged transmission coefficient is decreased by increasing the coupling when the coupling strength surpasses a critical value and the optimal configuration of contact for efficient charge transport through G4-DNA is obtained. In addition, the localization length of G4-DNA, especially at band centers, is much larger than that of poly(G)-poly(cytosine) molecules, suggesting that G4-DNA is potentially better as a conducting molecular wire than double-stranded DNA molecules. Several effectively delocalized states can be found in realistic G4-DNA molecules at low temperatures. These results may provide perspectives for experimental work aimed at controlling charge transport through DNA-based nanodevices.