A proposed model for electron conduction in DNA based upon pairwise anion π stacking: electron affinities and ionization potentials of the hydrogen bonded base pairs

Abstract

The values of the electron affinities (EAs) and ionization potentials (IPs) of the Watson–Crick hydrogen-bonded base pairs were calculated using the AM1-multiconfiguration configuration interaction (AM1-MCCI) method. This procedure was previously used to verify the electron affinities of the monomers determined from half wave reduction potentials. The electron affinities of the DNA base pairs differ by only 180 meV (4 kcal/mol). This makes rapid electron transport in DNA thermodynamically feasible in biological systems. During anion formation, calculations show geometry changes which affect the noncovalent hydrogen bonds and π stacking interactions. A model for rapid electron transfer through the π-system inherent in the base pairs is postulated. This mechanism is based upon the separation of the system into two distinct portions: a tunneling down the backbone and a pairwise donor–acceptor process through the π-way.