Energetics of the Radical Ions of the AT and AU Base Pairs: A Density Functional Theory (DFT) Study

Abstract

In this work, we present DFT calculations of the energetics of the base-pair anion and cation radicals of adenine−thymine (AT) and adenine−uracil (AU). At the B3LYP/6-31+G(d) level, we find that the adiabatic electron affinities (AEAs) are 0.30 eV for AT and 0.32 eV for AU. These values are both positive but slightly smaller than previously reported values for the AEA of guanine−cytosine (GC) and the hypoxanthine−cytosine base pair (IC). Furthermore, the AT and AU anion radical vertical electron detachment energies are also smaller than those of GC and IC, with that of AT only about half of GC's. For electron transfer between two identical isolated base pairs, the reorganization energies, λ, are calculated to be AT(0.76), AU(1.06), IC(1.25), and GC(1.31 eV). These results indicate that the AT base pair has a shallow trap depth and provides a favorable route for electron transfer, which explains previous experimental results that electron-transfer rates were higher in polydAdT than in polydGdC. Values of t...