Charge and Excitation Transfer Through DNA

There is a long-standing interest in the question of charge and excitation transfer through DNA. This largely resulted from an attempt to protect or to sensitize DNA against the effects of ionizing radiation in radiotherapy. The concept of 

In recent years, the interest in hole and electron transfer has so dramatically increased that it is no longer possible to report details adequately in the limited space available here. Therefore, attention is drawn to some reviews (Grinstaff 1999 Symons 1997 Giese 2000 Schuster 2000 O Neill and Barton 2004 Kawai and Majima 2004 Schuster and Landman 2004 Nakatani and Saito 2004 Douki et al. 2004). 

Long-range charge transfer by tunneling can be described by Eq. (76), where k is the rate of charge transfer, p the attenuation coefficient that qualifies the 

Lower p values around 0.6 0.1 were observed for the charge transfer from excited 2-aminopurine to G through interlacing adenines (Wan et al. 2000) and in DNA hairpins (Lewis et al. 1997 Lewis and Letsinger 1998 for a review see Lewis et al. 2001). 

The power parameter q equals 2 for unbiased diffusive hopping from the donor to the acceptor, and between 1 and 2 for a direction-biased random walk process (Priyadarshy et al. 1996). 

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Abstract. We consider here the theoretical and quantum chemical description of the photoexcitated states in DNA duplexes. We discuss the motivation and limitations of an exciton model and use this as the starting point for more detailed excited state quantum chemical evaluations. In particular, we focus upon the role of interbase proton transfer between Watson/Crick pairs in localizing an excitation and then quenching it through intersystem crossing and charge transfer. 

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