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Parity-violating energy differences and the origin of biomolecular homochirality

Authors
Journal
Journal of Theoretical Biology
0022-5193
Publisher
Elsevier
Publication Date
Volume
119
Issue
4
Identifiers
DOI: 10.1016/s0022-5193(86)80196-5
Disciplines
  • Biology
  • Chemistry

Abstract

The violation of parity by the weak interactions ensures that enantiomeric chiral molecules have inequivalent energies. These parity-violating energy differences have been calculated, using ab initio methods, for the series of α-amino acids glycine, alanine, valine, serine and aspartic acid, and for a set of polypeptide/protein fragments in both the α-helix and β-sheet secondary structures. In each case the energy differences are found to favour the existence of the natural left-handed l-enantiomers over their unnatural mirror-image right-handed d-enantiomers. The variation of the parity-violating energy difference along a prebiotic reaction path leading to the formation of a possible precursor of alanine has also been determined. Under equilibrium conditions the energy difference is found to preferentially select the stereochemical reaction channel corresponding to the eventual formation of l-alanine rather than that for its unnatural d-enantiomer. The significance of these results in accounting for the prebiotic origins of the terrestrial biomolecular homochirality are discussed.

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