Life 2018, 8(2), 21; https://doi.org/10.3390/life8020021
Homochirality through Photon-Induced Denaturing of RNA/DNA at the Origin of Life
Karo Michaelian ORCID
Department of Nuclear Physics and Application of Radiations, Instítuto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, México, D.F. 01000, Mexico
Received: 27 April 2018 / Revised: 22 May 2018 / Accepted: 22 May 2018 / Published: 6 June 2018
(This article belongs to the Special Issue The Origin of Chirality in Life (Chiral Symmetry Breaking))
Abstract
Since a racemic mixture of chiral nucleotides frustrates the enzymeless extension of RNA and DNA, the origin of homochirality must be intimately connected with the origin of life. Homochirality theories have elected to presume abiotic mechanisms for prebiotic enantiomer enrichment and post amplification, but none, so far, has been generally accepted. Here I present a novel hypothesis for the procurement of homochirality from an asymmetry in right- over left-circularly polarized photon-induced denaturing of RNA and DNA at the Archean ocean surface as temperatures descended below that of RNA and DNA melting. This asymmetry is attributed to the small excess of right-handed circularly polarized submarine light during the afternoon, when surface water temperatures were highest and thus most conducive to photon-induced denaturing, and to a negative circular dichroism band extending from 230 to 270 nm for small oligos of RNA and DNA. Because D-nucleic acids have greater affinity for L-tryptophan due to stereochemistry, and because D-RNA/DNA+L-tryptophan complexes have an increased negative circular dichroism band between 230 and 270 nm, the homochirality of tryptophan can also be explained by this hypothesis. A numerical model is presented, demonstrating the efficacy of such a mechanism in procuring homochirality of RNA or DNA from an original racemic solution in as little as 270 Archean years.
Keywords: homochirality; origin of life; non-equilibrium thermodynamics; photon dissipation; RNA; DNA; tryptophan
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