Chiral symmetry breaking in a microscopic model with asymmetric autocatalysis and inhibition

Abstract

Asymmetric autocatalysis and inhibition have been proposed as key processes in the spontaneous emergence of chiral symmetry breaking in a prebiotic world. An elementary lattice model is formulated to simulate the kinetics of chiral symmetry breaking via autocatalysis and inhibition in a mixture of prochiral reactants, chiral products, and inert solvent. Starting from a chirally unbiased initial state, spontaneous symmetry breaking occurs in spite of equal a priori probability for creating either product enantiomer, and the coupled reaction-diffusion processes subsequently amplify the random early-stage symmetry breaking. The processes of reaction and diffusion are kinetically intertwined in a way leading to competition in the appearance of enantiomeric excess. An effective transition temperature can be identified below which spontaneous symmetry breaking appears. In the absence of inhibition, reactions are predominantly autocatalytic under both reaction control (fast diffusion, slow reaction) or diffusion control (fast reaction, slow diffusion) conditions. In the presence of inhibition, simulations with different system sizes converge to the same transition temperature under reaction control conditions, and in this limit the reactions are predominantly nonautocatalytic.

The Viedma Deracemization of Racemic Conglomerate Mixtures as a Paradigm of Spontaneous Mirror Symmetry Breaking in Aggregation and Polymerization

“…In agreement with a previous experimental report (ref. 18o), which shows a small ee that is of the opposite sign to that of the crystal mixture, the simulation for cluster‐to‐cluster aggregation reproduces this effect (i.e. in the steady state, the ee of monomers, dimers, and trimers has an opposite sign to that of the higher order clusters) that is absent when cluster‐to‐cluster aggregation is switched‐off (two columns right).…”

Spontaneous Deracemizations

“…The theoretical understanding of Viedma’s experiment is currently open to debate. ,,,,,,,,,− Nevertheless, the unquestionable nexus of agreement between all reports to date is that the higher solubility of the smaller crystals, the Gibbs–Thomson effect, , obtained through grinding, creates a supersaturated media for the larger crystals and that a steady state continuous distribution of visible crystal sizes and small crystal clusters down to the monomer must be obtained. This is most likely due to the fact that the mechanisms of crystal growth are modeled as reaction networks.…”

Molecular model for chirality phenomena

“…21 Despite the theoretical validity of this scheme, an experimental demonstration remained elusive until the discovery of the Soai reaction. 22,23 From a theoretical perspective, kinetic models 24 and lattice-based calculations 25,26 have provided mechanistic and microscopic insights into the Frank model. A recent theoretical modification of the Frank model suggests that chiral inhibition is not necessary to achieve biological homochirality.…”