Hopping, in DNA

Bixon M, Jortner J (2001) Hole trapping, detrapping and hopping in DNA. J Phys Chem A 105 10322-10328... 

An energy level scheme for photoinitiated hole hopping in DNA is shown in Figure 16. Photoinduced electron transfer between the singlet acceptor and the nearest guanine, creates the initial hole on guanine, which can then undergo... 

Bixon M., Giese B., Wessely S., LangenbacherT., Michel-Beyerle M.E., Jortner J., Long-range charge hopping in DNA, Proc. Natl. Acad. Sci. USA, 1999,96,11713-11716. 

As with conductivity measurements, methods and results of theoretical treatments of CT in DNA have varied significantly. Mechanisms invoking hopping, tunneling, superexchange, or even band delocalization have been proposed to explain CT processes in DNA (please refer to other reviews in this text). Significantly, many calculations predicted that the distance dependence of CT in DNA should be comparable to that observed in the a-systems of proteins [26]. This prediction has not been realized experimentally. The dichotomy between theory and experiment may be related to the fact that many early studies gave insufficient consideration to the unique properties of the DNA molecule. Consequently, CT models derived for typical conductors, or even those based on other biomolecules such as proteins, were not adequate for DNA. 

Investigations of the kinetics of hole transfer in DNA by means of pulse radiolysis of synthetic ODNs have provided details about the hole transfer process, especially over 1 /is, including the multi-step hole transfer process. Based on the investigation of the kinetics of hole transfer in DNA, development of the DNA nanoelectronic devices is now expected. An active application of the hole transfer process is also desirable from a therapeutical point of view, since hole transfer may play a role in improvement of quantum yield and selectivity of DNA scission during photodynamic therapy. The kinetics of the hole transfer process is now being revealed, although there is still much research to be performed in this area. The kinetics of adenine hopping is another area of interest that should be explored in the future. 

Incorporation of an artificial flavin nucleobase and of a cyclobutane pyrimidine dimer building block into DNA DNA double strands, DNArPNA hybrid duplexes, and DNA-hairpins, provided compelling evidence that an excess electron can hop through DNA to initiate dimer repair even at a remote site. The maximum excess electron transfer distance realised so far in these defined Donor-DNA-Acceptor systems is 24 A. New experiments are now in progress to clarify whether even larger transfer distances can be achieved. 

Recent experiments have demonstrated the operation of the hole hopping mechanism between G bases in DNA.145,481 In these experiments, Norrish I photocleavage of an acylated nucleoside in a syn-... 

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. 

Giese B (2000) Long-distance charge transport in DNA the hopping mechanism. Acc Chem Res 33 631-636 and references therein... 

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