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The Origin of Chirality in Life (Chiral Symmetry Breaking)

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A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Origin of Life".

Deadline for manuscript submissions: closed (31 August 2019) | Viewed by 18836

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Special Issue Editor

Prof. Dr. Josep M. Ribó

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Guest Editor

Departament de Quimica Inorgànica I Orgànica, Seccció d’Orgànica, Universitat de Barcelona, E-08028 Barcelona, Spain
Interests: supramolecular chirality; chirality and origin of life

Special Issue Information

Dear Colleagues,

The actual state-of-the-art in chiral symmetry breaking is based on autocatalytic networks working in compartmentalized open systems. Such physico-chemical scenarios show strong similarities with those proposed for the emergence of catalytic polymers and replicators. In spite of this, there is a lack of discussion whether biological homochirality represents, in the origin of life, a simple contingency or is an advantage for the emergence of biological complexity, either because of the dissipation of chemical entropy and/or due to informational entropy reasons.

This Special Issue deals with matters that range from the formation of simple chiral compounds and the formation of chiral biases from the racemic composition in astrobiological scenarios, through the decisive planetary stages of the formation of functional polymers, and to the first primordial biological phase transitions. The call for papers extends from physical chemistry to synthetic biology, and has the aim to discuss the chirality “question” between all research fields involved in the study of the origin of life. Critical reviews, with the goal to disseminate and communicate new advances concerning chirality to research groups working in other fields, are welcome. Furthermore, probably experts on the research of the several stages of chemical evolution, even during the primordial major transitions, have questions and opinions, never before published, on the paradoxical role of biological homochirality, which are worthy of presentation to the origin of life community.

Prof. Dr. Josep M. Ribó
Guest Editor

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Keywords

Astrobiology
Autocatalytic sets
Chiral replicators
Coupled networks Enantioselective autocatalysis
Spontaneous chiral symmetry breaking
Prebiotic Chemistry Worlds

Published Papers (4 papers)

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Research

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24 pages, 408 KiB

Open AccessArticle

Computing the Parameter Values for the Emergence of Homochirality in Complex Networks

by Andrés Montoya, Elkin Cruz and Jesús Ágreda

Life 2019, 9(3), 74; https://doi.org/10.3390/life9030074 - 15 Sep 2019

Cited by 3 | Viewed by 2801

Abstract

The goal of our research is the development of algorithmic tools for the analysis of chemical reaction networks proposed as models of biological homochirality. We focus on two algorithmic problems: detecting whether or not a chemical mechanism admits mirror symmetry-breaking; and, given one of those networks as input, sampling the set of racemic steady states that can produce mirror symmetry-breaking. Algorithmic solutions to those two problems will allow us to compute the parameter values for the emergence of homochirality. We found a mathematical criterion for the occurrence of mirror symmetry-breaking. This criterion allows us to compute semialgebraic definitions of the sets of racemic steady states that produce homochirality. Although those semialgebraic definitions can be processed algorithmically, the algorithmic analysis of them becomes unfeasible in most cases, given the nonlinear character of those definitions. We use Clarke’s system of convex coordinates to linearize, as much as possible, those semialgebraic definitions. As a result of this work, we get an efficient algorithm that solves both algorithmic problems for networks containing only one enantiomeric pair and a heuristic algorithm that can be used in the general case, with two or more enantiomeric pairs. Full article

(This article belongs to the Special Issue The Origin of Chirality in Life (Chiral Symmetry Breaking))

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16 pages, 656 KiB

Open AccessArticle

Entropic Analysis of Mirror Symmetry Breaking in Chiral Hypercycles

by David Hochberg and Josep M. Ribó

Life 2019, 9(1), 28; https://doi.org/10.3390/life9010028 - 15 Mar 2019

Cited by 18 | Viewed by 3079

Abstract

Replicators are fundamental to the origin of life and evolvability. Biology exhibits homochirality: only one of two enantiomers is used in proteins and nucleic acids. Thermodynamic studies of chemical replicators able to lead to homochirality shed valuable light on the origin of homochirality and life in conformity with the underlying mechanisms and constraints. In line with this framework, enantioselective hypercyclic replicators may lead to spontaneous mirror symmetry breaking (SMSB) without the need for additional heterochiral inhibition reactions, which can be an obstacle for the emergence of evolutionary selection properties. We analyze the entropy production of a two-replicator system subject to homochiral cross-catalysis which can undergo SMSB in an open-flow reactor. The entropy exchange with the environment is provided by the input and output matter flows, and is essential for balancing the entropy production at the non-equilibrium stationary states. The partial entropy contributions, associated with the individual elementary flux modes, as defined by stoichiometric network analysis (SNA), describe how the system’s internal currents evolve, maintaining the balance between entropy production and exchange, while minimizing the entropy production after the symmetry breaking transition. We validate the General Evolution Criterion, stating that the change in the chemical affinities proceeds in a way as to lower the value of the entropy production. Full article

(This article belongs to the Special Issue The Origin of Chirality in Life (Chiral Symmetry Breaking))

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14 pages, 373 KiB

Open AccessArticle

Homochirality through Photon-Induced Denaturing of RNA/DNA at the Origin of Life

by Karo Michaelian

Life 2018, 8(2), 21; https://doi.org/10.3390/life8020021 - 06 Jun 2018

Cited by 9 | Viewed by 6135

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. Full article

(This article belongs to the Special Issue The Origin of Chirality in Life (Chiral Symmetry Breaking))

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Review

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21 pages, 1988 KiB

Open AccessReview

The Astrophysical Formation of Asymmetric Molecules and the Emergence of a Chiral Bias

by Adrien D. Garcia, Cornelia Meinert, Haruna Sugahara, Nykola C. Jones, Søren V. Hoffmann and Uwe J. Meierhenrich

Life 2019, 9(1), 29; https://doi.org/10.3390/life9010029 - 16 Mar 2019

Cited by 29 | Viewed by 6095

Abstract

The biomolecular homochirality in living organisms has been investigated for decades, but its origin remains poorly understood. It has been shown that circular polarized light (CPL) and other energy sources are capable of inducing small enantiomeric excesses (ees) in some primary biomolecules, such as amino acids or sugars. Since the first findings of amino acids in carbonaceous meteorites, a scenario in which essential chiral biomolecules originate in space and are delivered by celestial bodies has arisen. Numerous studies have thus focused on their detection, identification, and enantiomeric excess calculations in extraterrestrial matrices. In this review we summarize the discoveries in amino acids, sugars, and organophosphorus compounds in meteorites, comets, and laboratory-simulated interstellar ices. Based on available analytical data, we also discuss their interactions with CPL in the ultraviolet (UV) and vacuum ultraviolet (VUV) regions, their abiotic chiral or achiral synthesis, and their enantiomeric distribution. Without doubt, further laboratory investigations and upcoming space missions are required to shed more light on our potential extraterrestrial molecular origins. Full article

(This article belongs to the Special Issue The Origin of Chirality in Life (Chiral Symmetry Breaking))

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