title: An experimental and theoretical core-level study of tautomerism in guanine.
abstract: The core level photoemission and near edge X-ray photoabsorption spectra of guanine in the gas phase have been measured and the results interpreted with the aid of high level ab initio calculations. Tautomers are clearly identified spectroscopically, and their relative free energies and Boltzmann populations at the temperature of the experiment (600 K) have been calculated and compared with the experimental results and with previous calculations. We obtain good agreement between experiment and the Boltzmann weighted theoretical photoemission spectra, which allows a quantitative determination of the ratio of oxo to hydroxy tautomer populations. For the photoabsorption spectra, good agreement is found for the C 1s and O 1s spectra but only fair agreement for the N 1s edge.
authors.affiliation: Sincrotrone Trieste, in Area Science Park, I-34012 Basovizza (Trieste), Italy.
authors.forename: Oksana
authors.initials: O
authors.lastname: Plekan
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Feyer
authors.forename: Robert
authors.initials: R
authors.lastname: Richter
authors.forename: Marcello
authors.initials: M
authors.lastname: Coreno
authors.forename: Gemma
authors.initials: G
authors.lastname: Vall-Llosera
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Prince
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Trofimov
authors.forename: Irina L
authors.initials: IL
authors.lastname: Zaytseva
authors.forename: Tatyana E
authors.initials: TE
authors.lastname: Moskovskaya
authors.forename: Evgeniy V
authors.initials: EV
authors.lastname: Gromov
authors.forename: Jochen
authors.initials: J
authors.lastname: Schirmer
mesh_terms: D000042:Absorption; D002244:Carbon / Q000737:chemistry; D006147:Guanine / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D009696:Nucleic Acids / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D009696:Nucleic Acids; D006147:Guanine; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen