Chiral Polymerization in Open Systems From Chiral-Selective Reaction Rates

TL;DR

This paper explores how prebiotic homochirality could arise solely from chiral-selective reaction rates in open polymerization systems without autocatalysis or explicit enantiomeric inhibition, suggesting moderate chiral bias suffices.

Contribution

It demonstrates that moderate chiral selectivity in reaction rates can produce significant homochirality in open systems, expanding understanding of prebiotic chiral symmetry breaking.

Findings

Moderate chiral bias (<10%) can generate high chiral excess.

Chiral selectivity in reaction rates is sufficient without autocatalysis.

Homochirality could emerge under early Earth conditions with small rate differences.

Abstract

We investigate the possibility that prebiotic homochirality can be achieved exclusively through chiral-selective reaction rate parameters without any other explicit mechanism for chiral bias. Specifically, we examine an open network of polymerization reactions, where the reaction rates can have chiral-selective values. The reactions are neither autocatalytic nor do they contain explicit enantiomeric cross-inhibition terms. We are thus investigating how rare a set of chiral-selective reaction rates needs to be in order to generate a reasonable amount of chiral bias. We quantify our results adopting a statistical approach: varying both the mean value and the rms dispersion of the relevant reaction rates, we show that moderate to high levels of chiral excess can be achieved with fairly small chiral bias, below 10%. Considering the various unknowns related to prebiotic chemical networks in early Earth and the dependence of reaction rates to environmental properties such as temperature and pressure variations, we argue that homochirality could have been achieved from moderate amounts of chiral selectivity in the reaction rates.