Electron Attachment Energies of the DNA Bases

Injection of electrons into the empty π* molecular orbitals of uracil and the DNA bases creates short-lived anion states whose energies have been determined by electron scattering. A common range of attachment energies into the lowest orbitals is observed in all the bases. Evidence for nuclear motion during the lifetimes of the anions is found in all the compounds except adenine. These properties of the bases as bridge sites along the π-stack of DNA, namely, the effective degeneracy of the anion energies and the strong excitation of vibration, are key parameters for theories of electron-transfer rate, some of which lead to inverse rather than exponentially decreasing bridge-length dependences.