Adenine hole transfer from

Fig. 14 Reaction profile diagram for the hole transfer from a guanine radical cation (G +) to a distant GGG sequence via the activated hopping mechanism, which also involves adenines (A) as charge carriers...

N. (2004) Environmental fluctuabons fadlitate electron-hole transfer from guanine to adenine in DNA pi stacks. Angewandte Chernie International Edition, 43, 624-627. 

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. 

Calculation of As was carried out for hole transfer in finite DNA duplexes in water, in which one strand includes a G3(T) G3 sequence, n = 0-6, where G and T are, respectively, guanine and thymine nucleotide bases (in the complementary strand, of course, G and T are paired respectively, with cytosine and adenine bases) [23], The D and A sites (the solute) were taken as the middle unit of each G3 triad, or as alternative models for the n = 0 case, using one or both of the inner members of the G3 units). These structures lead to D/A sites in contact or separated by intervening bases ranging in number from 1 to 8. Using a base stacking separation of 3.4 A yields rDA = (m+ 1) (3.4 A), m = 0-8 (an estimate closely supported by detailed molecular force field calculations). 

Scheme 2. Hole and spin transfer (ht) in the electron-loss path after y-irradiation of DNA. It should be noted that extensive recombination occurs after the initial ionizations. This scheme assumes that last recombination is equally efficient for all cationic radicals. Net hole transfer occurs ftom the adenine, cytosine and thymidine base cation radicals to guanine and from the sugar phosphate backbone to the...

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