title: Comprehensive core-level study of the effects of isomerism, halogenation, and methylation on the tautomeric equilibrium of cytosine.
abstract: Core-level X-ray photoemission and near-edge X-ray absorption fine structure spectra of 5-methylcytosine, 5-fluorocytosine, and isocytosine are presented and discussed with the aid of high-level ab initio calculations. The effects of the methylation, halogenation, and isomerization on the relative stabilities of cytosine tautomers are clearly identified spectroscopically. The hydroxy-oxo tautomeric forms of these molecules have been identified, and their quantitative populations at the experimental temperature are calculated and compared with the experimental results and with previous calculations. The calculated values of Gibbs free energy and Boltzmann population ratios are in good agreement with the experimental results characterizing tautomer equilibrium.
authors: Sincrotrone Trieste, in Area Science Park, Basovizza (Trieste) I-34149, Italy. vitaliy.feyer@elettra.trieste.it
authors: Vitaliy
authors: V
authors: Feyer
authors: Oksana
authors: O
authors: Plekan
authors: Antti
authors: A
authors: Kivimäki
authors: Kevin C
authors: KC
authors: Prince
authors: Tatyana E
authors: TE
authors: Moskovskaya
authors: Irina L
authors: IL
authors: Zaytseva
authors: Dmitriy Yu
authors: DY
authors: Soshnikov
authors: Alexander B
authors: AB
authors: Trofimov