Water-Controlled Keto–Enol Tautomerization of a Prebiotic Nucleobase

Abstract

Barbituric acid is believed to be a proto-RNA nucleobase that was used for biological information transfer on prebiotic earth before DNA and RNA in their present forms evolved. Nucleobases have various tautomeric forms and the relative stability of these forms is critical to their biological function. It has been shown that barbituric acid has a tri-keto form in the gas phase and an enol form in the solid state. However, its dominant tautomeric form in aqueous medium that is most relevant for biology has been investigated only to a limited extent and the findings are inconclusive. We have used multiple approaches, namely, molecular dynamics, quantum chemistry, NMR, and IR spectroscopy to determine the most stable tautomer of barbituric acid in solution. We find a delicate balance in the stability of the two tautomers, tri-keto and enol, which is tipped toward the enol as the extent of solvation by water increases.

Heterogeneous chemistry of methyl ethyl ketone on mineral oxide surfaces: impacts of relative humidity and nitrogen dioxide on product formation

“…Water may also act as a catalyst for the KET step. 69,70 Higher relative humidity conditions such as those simulated in these experiments produce a strong H-bonded-water network with MEK molecules, 71 and on the surface as supported by the FTIR spectra of MEK-exposed a-Fe 2 O 3 at 80% RH (Fig. S3 †).…”