Electron Affinities of AT AU and GC

In order to establish a donor acceptor mechanism for electron transport in DNA, values for the electron affinities and ionization potentials of the hydrogen-bonded base pairs are required. As early as 1962 the importance of such interactions was considered  

From molecular orbital calculations on the adenosine-thymidine and guanosine-cytidine base pairs of DNA. the second pair is both a better electron acceptor 

In 1998 the Ea of AT, AU, and GC were calculated using the CURES-EC method. These were the first to give positive values for the electron affinities. Subsequently, all the calculations emphasize the positive nature of the Ea. The CURES-EC Ea are given in Table 12.9 and compared with the experimental values for the individual bases and values calculated using the density functional theory available in 2002 [52-54]. Although the density functional values are lower than the CURES-EC values, the difference between the Ea of GC and AT is about the same, 0.20 eV. This activation energy is very small for an electron transfer reaction. This difference supports the possibility of thermal activation of electron conduction. 

TABLE 12.9 Electron Affinities (in eV) of Purines and Pyrimidines and Watson Crick Hydrogen-Bonded Base Pairs 

Guani ne-Cytosine(-) Global minimum Gua ni ne-Cytosine(-) planar 

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