Electron transfer in DNA

Excess Electron Transfer in DNA PNA Hybrid Double Strands. . 200... 

Keywords Electron Tansfer m Energy Transfer m Through-Bond Coupling m Superexchange m Molecular Wires m Solvent-Mediated Electron Transfer m Electron Transfer in DNA m Charge Separation m Electron Transfer Through H-Bonds... 

With regard to electron transfer in DNA radical anions (as opposed to HT in the radical cations), the hopping mechanism involves the intermediacy of radical anions of the Cand Tbases which have similar reduction potentials. Since one of these bases is present in each base pair, it is predicted that ET proceeding by the hopping mechanism would not be sequence dependent.1451 This important prediction has yet to be verified. 

Bixon and Jortner, Rosch and Voityuk, Olofsson and Larsson, Berlin, Burin, Siebbeles, and Ratner, Orlandi and their coworkers [4, 8, 19-31] have explored the energetics and base-base interactions associated with hole and electron transfer in DNA base-pair stacks. They find nearest-neighbor coupling inter-... 

When estimating the energetics of excess electron transfer in DNA via differences of electron affinities (EA) of nucleobases B in WCP trimers 5 -XBY-3 [92], we found the EA values of bases to decrease in the order C T A>G. The destabihzing effect of the subsequent base Y is more pronounced than that of the preceding base X. As strongest electron traps, we predicted the sequences 5 -XCY-3 and 5 -XTY-3, where X and Y are pyrimidines C and T. These triads exhibit very similar EA values, and therefore, the corresponding anion radical states should be approximately in resonance, favoring efficient transport of excess electrons in DNA [92]. 

The rate and extent of electron and hole migration within DNA had been a topic of intense experimental [1] and theoretical [2] interest and dispute. However, as other chapters in this volume point out, the overall picture is now becoming increasingly understood. Several earlier reviews have dealt with the radiation damage to DNA and subsequent chemical processes including electron and hole transfer [3]. This chapter will focus on recent contributions to hole and electron transfer in DNA from high-energy radiation studies. We first present a brief overview on electron transfer processes in DNA from radiation studies and describe in more detail our most recent results on electron and hole transfer in DNA at low temperatures. 

Fig. 9 Plots of the transfer rates of electrons, holes, and overall DNA radicals at 77 K vs hydration levels lower axis) as well as vs the distance between DNA ds s (upper axis). Values of D s are estimated from the work of Lee et al. [39]. The results show that as amorphous (glassy) hydration increases up to T=22 D20/nucleotide, D s increases and transfer rate decreases. At T=30 D20/nucleotide, the ice is formed, and leaves the actual amorphous hydration level at around 14 D20/nucleotide with the remainder in the ice phase. The plot clearly shows equivalent transfer rates for both hydration levels at 14 and 30 D20/nucleotide. This result suggests that Djs plays an important role in hydration-dependent hole and electron transfer in DNA [7dj. Reprinted with permission from the J. Phys. Chem. Copyright (2001) American Chemical Society...

Cai et al. compared electron transfer from one-electron reduced DNA base radicals to MX in D2O glasses with H2O glasses at 77 K [7c]. A slightly smaller value of p for electron transfer in DNA in H2O over D2O media was ob-... 

Anderson RF, Wright GA (1999) Energetics and rate of electron transfer in DNA from base radial anions to electron-affinic intercalators in aqueous solution. Phys Chem Chem Phys 1 4827-4831 Anderson RF, Patel KB, Wilson WR (1991) Pulse radiolysis studies of electron migration in DNA from DNA base-radical anions to nitroacridine intercalators in aqueous solution. J Chem Soc Faraday Trans 87 3739-3746... 

Cai Z, Sevilla MD (2000) Electron spin resonance study of electron transfer in DNA inter-double-strand tunneling processes. J PhysChem B 104 6942-6949 Cai Z, Sevilla MD (2003) Electron and hole transfer from DNA base radicals to oxidized products of guanine in DNA. Radiat Res 159 411-419... 

Cai Z, Gu Z, Sevilla MD (2001) Electron spin resonance study of electron and hole transfer in DNA effects of hydration, aliphatic amine cations and histone proteins. J Phys Chem B 105 6031-6041 Cai Z, Li X, Sevilla MD (2002) Excess electron transfer in DNA effect of base sequence and proton transfer. J Phys Chem B 106 2755-2762... 

Fukui K, Tanaka K (1997) Distance dependence of photoinduced electron transfer in DNA. Angew Chem Int Ed 37 158-161... 

Voityuk AA, Michel-Beyerle M-E, Rosch N (2001) Energetics of excess electron transfer in DNA. Chem Phys Lett 342 231-238... 

Fig. 4.6.9. Electron transfer in DNA hairpins capped with a stilbene diether derivative as the charge donor D.

Finally, we should note that there is a vast literature regarding the study of hole and electron transfer in DNA using a variety of experimental methods other than ESR spectroscopy of irradiated samples. Recent reviews regarding these other methods should be consulted for further information. 

Cai Z, Sevilla MD. (2000) Electron spin resonance study of electron transfer in DNA Inter-double-strand tunneling processes. J Phys Chem B 104 6942-6949. 

Giese B. Electron transfer in DNA. Curr. Opin. Chem. Biol. 2002 6 612-618. 

Figure 4 Schematic representation of a doubly metallated DNA duplex used to probe photoinduced electron transfer in DNA (26).

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