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-DNA͒ 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 transfermatrix 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 poly͑G͒-poly͑cytosine͒ 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.

Structural fluctuations and quantum transport through DNA molecular wires: a combined molecular dynamics and model Hamiltonian approach

“…[10]- [13]. However, hole transfer experiments [14]- [20] as well as related theoretical work [21]- [25] in the chemical physics community strongly suggested that charge migration through DNA oligomers can be understood only in the context of a dynamical approach that includes the coupling of the electronic system to conformational degrees of freedom, resulting in fully or partially incoherent charge propagation.…”

“…6,7,8,9 for recent reviews. While most of the models originally used started from a static picture of the DNA structure, 10,11,12,13 it has become meanwhile clearer that charge migration through DNA oligomers attached to electrodes may only be understood in the context of a dynamical approach. 14,15,16,17,18,19,20,21 Hole transfer experiments 22,23,24,25,26 had already hinted at the strong influence of DNA structural fluctuations in supporting or hindering charge propagation.…”

Structural stability versus conformational sampling in biomolecular systems: Why is the charge transfer efficiency in G4-DNA better than in double-stranded DNA?

“…Guo et al [44,45] have recently shown using the Landauer theory (coherent transport) that G4-DNA exhibits much larger delocalization lengths at the band center compared to doublestranded poly(G) DNA. Surprisingly, it was also found out that the delocalization length can be even enhanced via environment-induced disorder through the backbones.…”

Electronic localization at mesoscopic length scales: different definitions of localization and contact effects in a heuristic DNA model

“…(i) The scaling between LL and PN, considering that PN embraces not only the system length, but also the number of chains, not all of them coupled to the contacts and taking part in the transmission. (ii) The quantitative agreement is not uniformly achieved along the entire energy range, particularly at the two anomalously large LL peaks, introduced by the backbones, but also present in other related systems like G4-DNA [48].…”