Driving Force Dependence of Electron Transfer Dynamics in Synthetic DNA Hairpins

The driving force dependence of photoinduced electron-transfer dynamics in duplex DNA has been investigated for 16 synthetic DNA hairpins in which an acceptor chromophore serves as a linker connecting two complementary oligonucleotide arms containing a single donor nucleobase located either adjacent to the linker or separated from the linker by two unreactive base pairs. The rate constants for both charge separation and charge recombination processes have been determined by means of subpicosecond time-resolved transient absorption spectroscopy and the results analyzed using quantum mechanical Marcus theory. This analysis provides intimate details about electron-transfer processes in DNA including the distance dependence of the electronic coupling between the acceptor and nucleobase donor and the solvent and nuclear reorganization energies.