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Symmetry
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Chirality and the Origin of Life
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Chirality and the Origin of Life

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 9725

Special Issue Editor

Prof. Dr. Yannick Vallée

E-Mail Website
Guest Editor
Departement of Chimie Moleculaire, Univ. Grenoble Alpes, Campus, F-38058 Grenoble, France
Interests: prebiotic chemistry; organic chemistry

Special Issue Information

Dear Colleagues,

Chirality is so important in the chemistry of life that it was unavoidable that the very first metabolism (or proto-metabolism) that was set up on primitive Earth would very quickly, perhaps immediately, become asymmetrical. What would have been strands of nucleic acids built on the basis of racemic sugars? Peptides made from mixtures of L and D amino acids? Could they have organized themselves enough to carry out the many stages of the incredible journey towards a living cell? What we know of current life leads us to answer no to these questions. This Special Issue is devoted to this fundamental questioning on the relationship between chirality and the origin of life. It will welcome regular research papers, reviews, and short communications in this field. Relevant topics include the chirality of small molecules (the so called “bricks of life”) and polymers; relationships between the symmetry of various types of molecules and/or polymers, “chiral assemblies”; the role of mineral surfaces in the development of non-racemic mixtures, chiral amplification; the discovery of non-racemic chiral molecules in space and studies on their impact on the setting of a proto-metabolism when they landed on primitive Earth; as well as any question about the roots of the current asymmetry of life in simple processes, whether physical, chemical, or biochemical.

Prof. Dr. Yannick Vallée
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Origin of Life
  • Prebiotic Chemistry
  • Astrobiology
  • Chirality
  • Chiral amplification

Published Papers (3 papers)

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20 pages, 3641 KiB  
Article
Racemic Phospholipids for Origin of Life Studies
by Emiliano Altamura, Arnaud Comte, Alice D’Onofrio, Charlotte Roussillon, Dimitri Fayolle, René Buchet, Fabio Mavelli, Pasquale Stano, Michele Fiore and Peter Strazewski
Symmetry 2020, 12(7), 1108; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12071108 - 03 Jul 2020
Cited by 13 | Viewed by 3578
Abstract
Although prebiotic condensations of glycerol, phosphate and fatty acids produce phospholipid esters with a racemic backbone, most experimental studies on vesicles intended as protocell models have been carried out by employing commercial enantiopure phospholipids. Current experimental research on realistic protocell models urgently requires [...] Read more.
Although prebiotic condensations of glycerol, phosphate and fatty acids produce phospholipid esters with a racemic backbone, most experimental studies on vesicles intended as protocell models have been carried out by employing commercial enantiopure phospholipids. Current experimental research on realistic protocell models urgently requires racemic phospholipids and efficient synthetic routes for their production. Here we propose three synthetic pathways starting from glycerol or from racemic solketal (α,β-isopropylidene-dl-glycerol) for the gram-scale production (up to 4 g) of racemic phospholipid ester precursors. We describe and compare these synthetic pathways with literature data. Racemic phosphatidylcholines and phosphatidylethanolamines were obtained in good yields and high purity from 1,2-diacylglycerols. Racemic POPC (rac-POPC, (R,S)-1-palmitoyl-2-oleoyl-3-phosphocholine), was used as a model compound for the preparation of giant vesicles (GVs). Confocal laser scanning fluorescence microscopy was used to compare GVs prepared from enantiopure (R)-POPC), racemic POPC (rac-POPC) and a scalemic mixture (scal-POPC) of (R)-POPC enriched with rac-POPC. Vesicle morphology and size distribution were similar among the different (R)-POPC, rac-POPC and scal-POPC, while calcein entrapments in (R)-POPC and in scal-POPC were significantly distinct by about 10%. Full article
(This article belongs to the Special Issue Chirality and the Origin of Life)
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23 pages, 422 KiB  
Hypothesis
A Few Experimental Suggestions Using Minerals to Obtain Peptides with a High Concentration of L-Amino Acids and Protein Amino Acids
by Dimas A. M. Zaia and Cássia Thaïs B. V. Zaia
Symmetry 2020, 12(12), 2046; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12122046 - 10 Dec 2020
Cited by 7 | Viewed by 2421
Abstract
The peptides/proteins of all living beings on our planet are mostly made up of 19 L-amino acids and glycine, an achiral amino acid. Arising from endogenous and exogenous sources, the seas of the prebiotic Earth could have contained a huge diversity of biomolecules [...] Read more.
The peptides/proteins of all living beings on our planet are mostly made up of 19 L-amino acids and glycine, an achiral amino acid. Arising from endogenous and exogenous sources, the seas of the prebiotic Earth could have contained a huge diversity of biomolecules (including amino acids), and precursors of biomolecules. Thus, how were these amino acids selected from the huge number of available amino acids and other molecules? What were the peptides of prebiotic Earth made up of? How were these peptides synthesized? Minerals have been considered for this task, since they can preconcentrate amino acids from dilute solutions, catalyze their polymerization, and even make the chiral selection of them. However, until now, this problem has only been studied in compartmentalized experiments. There are separate experiments showing that minerals preconcentrate amino acids by adsorption or catalyze their polymerization, or separate L-amino acids from D-amino acids. Based on the [GADV]-protein world hypothesis, as well as the relative abundance of amino acids on prebiotic Earth obtained by Zaia, several experiments are suggested. The main goal of these experiments is to show that using minerals it is possible, at least, to obtain peptides whose composition includes a high quantity of L-amino acids and protein amino acids (PAAs). These experiments should be performed using hydrothermal environments and wet/dry cycles. In addition, for hydrothermal environment experiments, it is very important to use one of the suggested artificial seawaters, and for wet/dry environments, it is important to perform the experiments in distilled water and diluted salt solutions. Finally, from these experiments, we suggest that, without an RNA world or even a pre genetic world, a small peptide set could emerge that better resembles modern proteins. Full article
(This article belongs to the Special Issue Chirality and the Origin of Life)
16 pages, 2190 KiB  
Hypothesis
Symmetry Breaking of Phospholipids
by Michele Fiore and René Buchet
Symmetry 2020, 12(9), 1488; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12091488 - 10 Sep 2020
Cited by 9 | Viewed by 2940
Abstract
Either stereo reactants or stereo catalysis from achiral or chiral molecules are a prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausibly organic syntheses of phospholipids under prebiotic conditions with special attention paid to the starting materials as pro-chiral dihydroxyacetone [...] Read more.
Either stereo reactants or stereo catalysis from achiral or chiral molecules are a prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausibly organic syntheses of phospholipids under prebiotic conditions with special attention paid to the starting materials as pro-chiral dihydroxyacetone and dihydroxyacetone phosphate (DHAP), which are the key molecules to break symmetry in phospholipids. The advantages of homochiral membranes compared to those of heterochiral membranes were analysed in terms of specific recognition, optimal functions of enzymes, membrane fluidity and topological packing. All biological membranes contain enantiomerically pure lipids in modern bacteria, eukarya and archaea. The contemporary archaea, comprising of methanogens, halobacteria and thermoacidophiles, are living under extreme conditions reminiscent of primitive environment and may indicate the origin of one ancient evolution path of lipid biosynthesis. The analysis of the known lipid metabolism reveals that all modern cells including archaea synthetize enantiomerically pure lipid precursors from prochiral DHAP. Sn-glycerol-1-phosphate dehydrogenase (G1PDH), usually found in archaea, catalyses the formation of sn-glycerol-1-phosphate (G1P), while sn-glycerol-3-phosphate dehydrogenase (G3PDH) catalyses the formation of sn-glycerol-3-phosphate (G3P) in bacteria and eukarya. The selective enzymatic activity seems to be the main strategy that evolution retained to obtain enantiomerically pure lipids. The occurrence of two genes encoding for G1PDH and G3PDH served to build up an evolutionary tree being the basis of our hypothesis article focusing on the evolution of these two genes. Gene encoding for G3PDH in eukarya may originate from G3PDH gene found in rare archaea indicating that archaea appeared earlier in the evolutionary tree than eukarya. Archaea and bacteria evolved probably separately, due to their distinct respective genes coding for G1PDH and G3PDH. We propose that prochiral DHAP is an essential molecule since it provides a convergent link between G1DPH and G3PDH. The synthesis of enantiopure phospholipids from DHAP appeared probably firstly in the presence of chemical catalysts, before being catalysed by enzymes which were the products of later Darwinian selection. The enzymes were probably selected for their efficient catalytic activities during evolution from large libraries of vesicles containing amino acids, carbohydrates, nucleic acids, lipids, and meteorite components that induced symmetry imbalance. Full article
(This article belongs to the Special Issue Chirality and the Origin of Life)
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