A PROPOSED MODEL FOR ELECTRON CONDUCTION IN DNA-BASED UPON PAIRWISE ANION PI-STACKING - ELECTRON-AFFINITIES AND IONIZATION-POTENTIALS OF THE HYDROGEN-BONDED BASE-PAIRS

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 affi nities 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 thermodynamic ally feasible in biological systems. During anion formation, calculati ons show geometry changes which affect the noncovalent hydrogen bonds and pi stacking interactions. A model for rapid electron transfer thro ugh the pi-system inherent in the base pairs is postulated. This mecha nism is based upon the separation of the system into two distinct port ions: a tunneling down the backbone and a pairwise donor-acceptor proc ess through the pi-way. (C) 1998 Elsevier Science S.A. All rights rese rved.