DNA DOUBLE-HELIX-MEDIATED LONG-RANGE ELECTRON-TRANSFER

A theoretical analysis based upon large-scale self-consistent Hartree- Fock calculations at a semiempirical quantum theory level (CNDO/S) is performed to investigate long-range electron transfer in a donor-DNA-a cceptor molecule, where the donor and acceptor moieties are tethered t o the DNA. The pi-stacked base pairs are found to dominate the long-ra nge electronic coupling. Despite the pi-electron mediated coupling, th e exponential distance decay constant of the electron transfer rate is similar to 1.2-1.6 Angstrom(-1), values typical of electron transfer proteins. The calculated long-range electron transfer rate of the orde r of 10(6) s(-1) for a metal-to-metal distance of 21 Angstrom is found to be in agreement with kinetic measurements by Meade and Kayyem. Bas ed on the current analysis, the pi-electrons dominate the long-range e lectronic coupling interactions in DNA, but they do not lead to one-di mensional molecular wire-like properties. (C) 1996 John Wiley & Sons, Inc.