title: Oxidation half-reaction of aqueous nucleosides and nucleotides via photoelectron spectroscopy augmented by ab initio calculations.
abstract: Oxidative damage to DNA and hole transport between nucleobases in oxidized DNA are important processes in lesion formation for which surprisingly poor thermodynamic data exist, the relative ease of oxidizing the four nucleobases being one such example. Theoretical simulations of radiation damage and charge transport in DNA depend on accurate values for vertical ionization energies (VIEs), reorganization energies, and standard reduction potentials. Liquid-jet photoelectron spectroscopy can be used to directly study the oxidation half-reaction. The VIEs of nucleic acid building blocks are measured in their native buffered aqueous environment. The experimental investigation of purine and pyrimidine nucleotides, nucleosides, pentose sugars, and inorganic phosphate demonstrates that photoelectron spectra of nucleotides arise as a spectral sum over their individual chemical components; that is, the electronic interactions between each component are effectively screened from one another by water. Electronic structure theory affords the assignment of the lowest energy photoelectron band in all investigated nucleosides and nucleotides to a single ionizing transition centered solely on the nucleobase. Thus, combining the measured VIEs with theoretically determined reorganization energies allows for the spectroscopic determination of the one-electron redox potentials that have been difficult to establish via electrochemistry.
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States.
authors.forename: Christi A
authors.initials: CA
authors.lastname: Schroeder
authors.forename: Eva
authors.initials: E
authors.lastname: Pluhařová
authors.forename: Robert
authors.initials: R
authors.lastname: Seidel
authors.forename: William P
authors.initials: WP
authors.lastname: Schroeder
authors.forename: Manfred
authors.initials: M
authors.lastname: Faubel
authors.forename: Petr
authors.initials: P
authors.lastname: Slavíček
authors.forename: Bernd
authors.initials: B
authors.lastname: Winter
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Bradforth
mesh_terms: D004247:DNA / Q000737:chemistry*; D009711:Nucleotides / Q000737:chemistry*; D010084:Oxidation-Reduction; D056951:Photoelectron Spectroscopy; D011687:Purines / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory; D014867:Water / Q000737:chemistry
chemical_list: D009711:Nucleotides; D011687:Purines; D011743:Pyrimidines; D014867:Water; D004247:DNA; C030986:pyrimidine; C030985:purine