Homochirality Originates from the Handedness of Helices.

Abstract

Homochirality is a common feature of amino acids and carbohydrates, and its origin is still unknown. Meanwhile, right-handed helices are ubiquitous in nature. Are these two phenomena intrinsically correlated? Here, we propose that homochirality of amino acids and nucleotide sugars originated from the handedness of helices. We show that right-handed 310-helix and α-helix favor the l-chiral form for amino acids, but for deoxyribose sugars, right-handed helices prefer the d-chiral form instead. Our analyses unveil strong cooperativity effects dominated by electrostatic interactions. This work not only resolves the mystery of homochirality by providing a unified explanation for the origin of homochirality in proteins and DNA using helical secondary structures as the root cause but also ratifies the Principle of Chirality Hierarchy, in which the chirality of a higher hierarchy dictates that of lower ones. Possible applications of this work to asymmetric synthesis and macromolecular assembly are discussed.