Electronic structure of bases in DNA duplexes characterized by resonant photoemission spectroscopy near the Fermi level

The electronic structure of bases in DNA duplexes was investigated by resonant photoemission spectroscopy near the Fermi level, in order to specify charge migration mechanisms. We observed a kinetic energy shift of N-KLL Auger electrons and an intensity enhancement of valence electrons on the resonant photoemission spectra for both poly(dG).poly(dC) and poly(dA).poly(dT) DNAs. These directly show the localized unoccupied states of the bases. We conclude that the charge hopping model is pertinent for electric conduction in a DNA duplex, when electrons pass through the unoccupied states.