We have studied the electron affinities and ionization potentials for models of DNA. We conclude that removing an electron is most favorable on the PO4- groups; whereas, addition of an electron is most favorable on a nucleic acid. The computed electron affinities are 1.9, 4.8, 5.7, and 7.9 kcal/mol for adenine, cytosine, guanine, and thymine, respectively. Our best estimate of the IP for hydrated DNA is 4.5 eV and for hydrated DNA plus Na+ counter ions is 5.6 eV. (C) 2003 Elsevier Science B.V. All rights reserved.