Emergence of homochirality in large molecular systems

TL;DR

This paper demonstrates that large molecular systems are likely to develop homochirality through a phase transition, extending classic models to complex, multi-species networks and confirming this with numerical and theoretical analysis.

Contribution

It extends Frank's model to large, complex chemical networks and proves a robust phase transition towards homochirality using random matrix theory.

Findings

Large molecular systems undergo a phase transition to homochirality.

Homochirality emergence is linked to the number of chiral species.

The transition is robust and generic in large non-equilibrium networks.

Abstract

The selection of a single molecular handedness, or homochirality across all living matter, is a mystery in the origin of life. Frank's seminal model showed in the fifties how chiral symmetry breaking can occur in non-equilibrium chemical networks. However, an important shortcoming in this classic model is that it considers a small number of species, while there is no reason for the prebiotic system, in which homochirality first appeared, to have had such a simple composition. Furthermore, this model does not provide information on what could have been the size of the molecules involved in this homochiral prebiotic system. Here, we show that large molecular systems are likely to undergo a phase transition towards a homochiral state, as a consequence of the fact that they contain a large number of chiral species. Using chemoinformatics tools, we quantify how abundant are chiral species in the chemical universe of all possible molecules of a given length. Then, we propose that Frank's model should be extended to include a large number of species, in order to possess the transition towards homochirality as confirmed by numerical simulations. Finally, using random matrix theory, we prove that large non-equilibrium reaction networks possess a generic and robust phase transition towards a homochiral state.