Equilibrium and non-equilibrium furanose selection in the ribose isomerisation network

TL;DR

This study combines NMR and statistical mechanics to explore how temperature gradients influence the prevalence of furanose over pyranose in prebiotic chemistry, revealing non-equilibrium conditions favoring furanose formation.

Contribution

It introduces a novel approach to understanding sugar isomer distributions by integrating experimental data with models of non-equilibrium thermodynamics, highlighting the role of temperature gradients.

Findings

Furanose can be favored over pyranose at high temperatures at equilibrium.

Non-equilibrium steady states can enhance furanose populations beyond equilibrium limits.

Optimal dissipation conditions maximize furanose selection, matching hydrothermal vent environments.

Abstract

The exclusive presence of $\beta$-D-ribofuranose in nucleic acids is still a conundrum in prebiotic chemistry, given that pyranose species are substantially more stable at equilibrium. However, a precise characterisation of the relative furanose/pyranose fraction at temperatures higher than about 50$^{\,\rm o}$C is still lacking. Here, we employ a combination of NMR measurements and statistical mechanics modelling to predict a population inversion between furanose and pyranose at equilibrium at high temperatures. More importantly, we show that a steady temperature gradient may steer an open isomerisation network into a non-equilibrium steady state where furanose is boosted beyond the limits set by equilibrium thermodynamics. Moreover, we demonstrate that nonequilibrium selection of furanose is maximum at optimal dissipation, as gauged by the temperature gradient and energy barriers for isomerisation. The predicted optimum is compatible with temperature drops found in hydrothermal vents associated with extremely fresh lava flows on the seafloor.