On the Origins of Life's Homochirality: Inducing Enantiomeric Excess with Spin-Polarized Electrons

TL;DR

This paper proposes that spin-polarized electrons generated by UV irradiation of magnetite deposits in early Earth lakes could have driven enantioselective prebiotic chemistry, potentially explaining the origin of biological homochirality.

Contribution

It introduces a novel hypothesis linking the CISS effect and spin-polarized electrons to the emergence of homochirality in prebiotic chemistry.

Findings

Spin-polarized electrons can induce enantioselective reduction reactions.

The CISS effect provides a mechanism for chiral symmetry breaking.

Magnetite deposits could have generated these electrons in early Earth environments.

Abstract

Life as we know it is homochiral, but the origins of biological homochirality on early Earth remain elusive. Shallow closed-basin lakes are a plausible prebiotic environment on early Earth, and most are expected to have significant sedimentary magnetite deposits. We hypothesize that UV (200-300nm) irradiation of magnetite deposits could generate hydrated spin-polarized electrons sufficient to induce chirally selective prebiotic chemistry. Such electrons are potent reducing agents that drive reduction reactions where the spin polarization direction can alter enantioselectively the reaction kinetics. Our estimate of this chiral bias is based on the strong effective spin-orbit coupling observed in the chiral-induced spin selectivity (CISS) effect, as applied to energy differences in reduction reactions for different isomers. In the original CISS experiments, spin selective electron transmission through a monolayer of dsDNA molecules is observed at room temperature - indicating a strong coupling between molecular chirality and electron spin. We propose that the chiral symmetry breaking due to the CISS effect, when applied to reduction chemistry, can induce enantioselective synthesis on the prebiotic Earth and thus facilitate the homochiral assembly of life's building blocks.