A molecular insight into the photophysics of barbituric acid, a candidate for canonical nucleobases’ ancestor

Abstract

This work investigates the photophysics of barbituric acid at different pH conditions using ab initio methods. Our calculations ascribe the most intense bands at ca. 260 nm at neutral pH...

Water-Controlled Keto–Enol Tautomerization of a Prebiotic Nucleobase

“…The conclusions about the structure of BA in solution will be useful to biologists, especially origin-oflife scientists, to understand the role of BA as a pre-RNA nucleobase. In particular, for scientists studying the properties of BA (e.g., photophysics 24 ) in solution, the study suggests that the enol form of BA be considered. While textbooks generally present the structure of BA in its keto form, 49−51 our study indicates that in the biological context, the enol structure is perhaps a more apt representation of BA.…”

“…Studies modeling the aqueous environment as a dielectric continuum suggest that, in comparison to the isolated molecules, the stability of the keto form in solution decreases by ∼3 kcal/mol with respect to the enol tautomer, although the keto form continues to be the most stable even in water. , The results depend on the solvation model used and in one continuum study there is nearly no effect on the relative stability of keto and enol tautomers due to solvation . A very recent continuum study similarly concludes that the keto form is dominant in aqueous solution . The effect of explicit water molecules on the relative stabilities of BA tautomers has been studied using DFT calculations by considering three water molecules complexed with BA.…”

“…17 A very recent continuum study similarly concludes that the keto form is dominant in aqueous solution. 24 The effect of explicit water molecules on the relative stabilities of BA tautomers has been studied using DFT calculations by considering three water molecules complexed with BA. At the M06/6-31 + G(d,p) level of theory, the keto tautomer was found to be more stable than the second most stable tautomer by ∼10 kcal/mol.…”