Life has most likely originated as a consequence of processes taking place in non-equilibrium conditions (e.g. in the proximity of deep-sea thermal vents) selecting states of matter that would have been otherwise unfavorable at equilibrium. Here we present a simple chemical network in which the selection of states is driven by the thermodynamic necessity of dissipating heat as rapidly as possible in the presence of a thermal gradient: states participating to faster reactions contribute the most to the dissipation rate, and are the most populated ones in non-equilibrium steady-state conditions. Building upon these results, we show that, as the complexity of the chemical network increases, the velocity of the reaction path leading to a given state determines its selection, giving rise to non-trivial localization phenomena in state space. A byproduct of our studies is that, in the presence of a temperature gradient, thermophoresis-like behavior inevitably appears depending on the transport properties of each individual state, thus hinting at a possible microscopic explanation of this intriguing yet still not fully understood phenomenon.

The exclusive presence of β-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 °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.

Exposing a solution to a temperature gradient can lead to the accumulation of particles on either the cold or warm side. This phenomenon, known as thermophoresis, has been discovered more than a century ago and yet its microscopic origin is still debated. Here, we show that thermophoresis can be observed in any system such that the transitions between different internal states are modulated by temperature and such that different internal states have different transport properties. We establish thermophoresis as a genuine non-equilibrium effect, whereby a system of currents in real and internal space that is consistent with the thermodynamic necessity of transporting heat from warm to cold regions. Our approach also provides an expression for the Soret coefficient, which decides whether particles accumulate on the cold or on the warm side, that is associated to the correlation between the energies of the internal states and their transport properties, that instead remain system specific quantities. Finally, we connect our results to previous approaches based on close-to-equilibrium energetics. Our thermodynamically consistent approach thus encompasses and generalizes previous findings.

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Exposing a solution to a temperature gradient can lead to the accumulation of particles on either the cold or warm side. This phenomenon is known as thermophoresis, and its microscopic origin is still debated. Here, we show that thermophoresis can be observed in any system having internal states with different transport properties, and temperature-modulated rates of transitions between the states. These internal degrees of freedom might be configurational, chemical or velocity states. We also derive an expression for the Soret coefficient, which decides whether particles accumulate on the cold or warm side. Our framework can be applied to any chemical reaction system diffusing in a temperature gradient. It also captures the possibility to observe a sign inversion of the Soret coefficient as the competition between chemical and velocity states. We establish thermophoresis as a genuine non-equilibrium effect, originating from internal microscopic currents consistent with the necessity of transporting heat from warm to cold regions.