Modeling hole transfer in DNA. II. Molecular basis of charge transport in the DNA chain

摘要

A theoretical multiconfigurational second-order perturbation method, CASPT2, has been employed to determine the binding energies and electronic couplings for all pairs of stacked canonical nucleobases in the standard conformation of the B-DNA. The existence and relevance of conical intersections mediating the hole transfer process has been shown in different systems in vacuo and, by using hybrid QM/MM techniques, in a more realistic biological environment, formed by a double helix of 18 oligomers of DNA surrounded by water molecules. The present results support, therefore, the cooperative micro-hopping mechanism proposed in a previous work for the migration of the hole between adjacent π-stacked 2'-deoxycytidine 5'-monophosphate (dCMP) or alternate 2'-deoxyadenosine 5'-monophosphate and dCMP oligonucleotides.