An ab initio DFT Characteristics of Tautomeric Properties of Hydroxyl Radical Modified Nucleosides in Polar and Non-Polar Environments

Abstract

Abstract DFT ab initio calculations of 22 free radical derived nucleosides analogs were performed in gas phase and water solution. Most of studied compounds exist mainly in expected amino- and keto- forms. However, there were found few important exceptions: enol-amino tautomer of 2-OH-adenosine is dominant in apolar environment, while in polar solution keto-amino isomer become more probable; 8-oxo-guanosine is to be represented as a mixture of two tautomers: 6,8-diketo and 6-enol-8-keto with disfavoring of the latter in polar conditions, 5-OH-cytidine adopts imino-keto form in non-polar surroundings but water stabilizes amino-keto isomer reverting order of these tautomers, cytidine glycol in apolar and polar conditions is represented mainly by keto-imino form, but more polar environment increase percentage of amino-keto tautomer not reverting their order, 6-hydroxy-5,6-dihydroxycytidine in both polar and non-polar conditions adopts keto-imino form, which dominates over keto-amino one, 5-hydroxy-5,6-dihydro-cytosine in non-polar conditions exists as keto-imino tautomer while polar conditions favors keto-amino form.