Thermodynamic Space of Chemical Reaction Networks (2407.11498v2)

Abstract: Living systems are usually maintained out of equilibrium and consume energy to sustain emergent organized states. Their robust functioning rely on a set of interconnected chemical reaction networks (CRN) in which the external energy supply often comes from fluxes that can keep some species concentrations constant. Hence, to capture the emergent complexity of living systems and the role of their non-equilibrium nature, it is fundamental to uncover constraints and properties of the CRNs underpinning their functions. In particular, while kinetics plays a key role in shaping detailed dynamical phenomena, the range of operations of these underlying CRNs is fundamentally constrained by thermodynamics. Here, we derive universal thermodynamic upper and lower bounds for species concentrations in a generic CRN operating within a given energy budget. The resulting region determines the thermodynamic space of the CRN, a concept we introduce in this work that determines the range of accessible concentrations for the chemical species involved at a given value of non-equilibrium driving. We obtain similar bounds for the affinities, shedding light on how global thermodynamic properties, such as the total dissipation, can limit local non-equilibrium quantities. We illustrate our results in various paradigmatic examples, the Schlogl model for bistability, a minimal self-assembly process, a paradigmatic system exhibiting chiral symmetry breaking, and a multi-molecular model for reaction-diffusion patterns, demonstrating how the onset of complex behaviors is intimately tangled with the presence of non-equilibrium conditions. By providing a general tool for analyzing CRNs, the presented framework constitutes a stepping stone to deepen our ability to predict complex out-of-equilibrium phenomena and design artificial chemical systems, starting from the sole knowledge of the underlying thermodynamic properties.