Long-range charge hopping in DNA

Abstract

The fundamental mechanisms of charge migration in DNA are pertinent for current developments in molecular electronics and electrochemistry-based chip technology. The energetic control of hole (positive ion) multistep hopping transport in DNA proceeds via the guanine, the nucleobase with the lowest oxidation potential. Chemical yield data for the relative reactivity of the guanine cations and of charge trapping by a triple guanine unit in one of the strands quantify the hopping, trapping, and chemical kinetic parameters. The hole-hopping rate for superexchange-mediated interactions via two intervening AT base pairs is estimated to be 10 9 s ؊1 at 300 K. We infer that the maximal distance for hole hopping in the duplex with the guanine separated by a single AT base pair is 300 ؎ 70 Å. Although we encounter constraints for hole transport in DNA emerging from the number of the mediating AT base pairs, electron transport is expected to be nearly sequence independent because of the similarity of the reduction potentials of the thymine and of the cytosine.

Stepwise regulation of hole transport in DNA by control of triplex formation

“…As shown in Figure 4A, photoirradiation of Duplex II caused efficient cleavage at all GG sites, even at the GG 6 doublet, indicating that the hole injected from the AQ chromophore arrived at the GG 6 site. 38 Addition of the 15-mer ODN 7 to Duplex II to form Triplex III dramatically reduced cleavage at the GG 6 site, while the GG 4 and GG 5 sites were still cleaved. This result strongly suggests that hole transport between the GG 5 and GG 6 sites was suppressed effectively by the binding of ODN 7 to form a partial triplex, whereas the hole injected by the AQ photosensitizer could still migrate to the GG 5 site.…”

“…[1][2][3][4][5][6][7][8][9] On the basis of this promising hole transport ability of DNA duplexes and the intrinsic fact that DNA forms highly organized structures, DNA is recognized as a potential candidate material for nanoscale molecular devices. [10][11][12][13][14][15][16][17][18] To utilize DNA duplexes in this way, DNA duplexes need to be equipped with an on/off switching functionality of their hole transport efficiency.…”

Vibronic couplings and coherent electron transfer in bridged systems

“…Time resolved spectroscopy and steady state oxidative damage analyses point toward an incoherent multistep hopping mechanism, 49,60,[76][77][78][79][80][81][82] in which the hole migrates essentially by hopping between G neighboring sites, 59 with the possibility of tunnelling over short distances, when two G sites are separated by two or almost three A and/or T sites. The hopping process is in most of the cases slow, thus limiting potential applications to nano-scale electronic devices, 83,84 but since significant enhancements of HT rates have been observed both by including in the strand modified nucleobases, with a lower oxidation potentials than natural ones, or by using sequences consisting of blocks of homopurine sequences, 85,86 research in the field is still very active.…”

Diffusion Approach to Long Distance Charge Migration in DNA: Time-Dependent and Steady-State Analytical Solutions for the Product Yields

“…Both the problem and the approach to its solution are similar to the one solved earlier for random charge injection. 6 The probability of finding the hole at the nth trapping site W(n) is obtained in the form (13) that further turns into eq 13a in the diffusion-controlled case of k t ≫ k (ω→∞).…”