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Distinguishing Biotic vs. Abiotic Origins of ‘Bio’signatures: Clues from Messy Prebiotic Chemistry for Detection of Life in the Universe. Life (Basel) 2023; 13:life13030766. [PMID: 36983921 PMCID: PMC10058490 DOI: 10.3390/life13030766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 03/04/2023] [Accepted: 03/11/2023] [Indexed: 03/16/2023] Open
Abstract
It is not a stretch to say that the search for extraterrestrial life is possibly the biggest of the cosmic endeavors that humankind has embarked upon. With the continued discovery of several Earth-like exoplanets, the hope of detecting potential biosignatures is multiplying amongst researchers in the astrobiology community. However, to be able to discern these signatures as being truly of biological origin, we also need to consider their probable abiotic origin. The field of prebiotic chemistry, which is aimed at understanding enzyme-free chemical syntheses of biologically relevant molecules, could particularly aid in this regard. Specifically, certain peculiar characteristics of prebiotically pertinent messy chemical reactions, including diverse and racemic product yields and lower synthesis efficiencies, can be utilized in analyzing whether a perceived ‘signature of life’ could possibly have chemical origins. The knowledge gathered from understanding the transition from chemistry to biology during the origin of life could be used for creating a library of abiotically synthesized biologically relevant organic molecules. This can then be employed in designing, standardizing, and testing mission-specific instruments/analysis systems, while also enabling the effective targeting of exoplanets with potentially ‘ongoing’ molecular evolutionary processes for robust detection of life in future explorative endeavors.
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Arya A, Ray J, Sharma S, Cruz Simbron R, Lozano A, Smith HB, Andersen JL, Chen H, Meringer M, Cleaves HJ. An open source computational workflow for the discovery of autocatalytic networks in abiotic reactions. Chem Sci 2022; 13:4838-4853. [PMID: 35655880 PMCID: PMC9067619 DOI: 10.1039/d2sc00256f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/16/2022] [Indexed: 11/21/2022] Open
Abstract
A central question in origins of life research is how non-entailed chemical processes, which simply dissipate chemical energy because they can do so due to immediate reaction kinetics and thermodynamics, enabled the origin of highly-entailed ones, in which concatenated kinetically and thermodynamically favorable processes enhanced some processes over others. Some degree of molecular complexity likely had to be supplied by environmental processes to produce entailed self-replicating processes. The origin of entailment, therefore, must connect to fundamental chemistry that builds molecular complexity. We present here an open-source chemoinformatic workflow to model abiological chemistry to discover such entailment. This pipeline automates generation of chemical reaction networks and their analysis to discover novel compounds and autocatalytic processes. We demonstrate this pipeline's capabilities against a well-studied model system by vetting it against experimental data. This workflow can enable rapid identification of products of complex chemistries and their underlying synthetic relationships to help identify autocatalysis, and potentially self-organization, in such systems. The algorithms used in this study are open-source and reconfigurable by other user-developed workflows.
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Affiliation(s)
- Aayush Arya
- Department of Physics, Lovely Professional University Jalandhar Delhi-GT Road Phagwara Punjab 144411 India
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
| | - Jessica Ray
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
| | - Siddhant Sharma
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
- Department of Biochemistry, Deshbandhu College, University of Delhi New Delhi 110019 India
| | - Romulo Cruz Simbron
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
- Laboratorio de Investigación Fisicoquímica (LABINFIS), Universidad Nacional de Ingeniería Av. Túpac Amaru 210 Lima Peru
- Centro de Tecnologías de la Información y Comunicaciones (CTIC UNI), Universidad Nacional de Ingenieria Av. Túpac Amaru 210 Lima Peru
| | - Alejandro Lozano
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
- Unidad Profesional Interdisciplinaria de Biotecnología - Instituto Politécnico Nacional 550 Av. Acueducto 07340 Mexico City Mexico
| | - Harrison B Smith
- Earth-Life Science Institute, Tokyo Institute of Technology Tokyo Japan
| | - Jakob Lykke Andersen
- Department of Mathematics and Computer Science, University of Southern Denmark Campusvej 55 5230 Odense M Denmark
| | - Huan Chen
- National High Magnetic Field Laboratory Tallahassee Florida 32310 USA
| | - Markus Meringer
- German Aerospace Center (DLR) 82234 Oberpfaffenhofen Wessling Germany
| | - Henderson James Cleaves
- Blue Marble Space Institute of Science Seattle Washington 98104 USA
- Earth-Life Science Institute, Tokyo Institute of Technology Tokyo Japan
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3
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Sharma S, Arya A, Cruz R, Cleaves II HJ. Automated Exploration of Prebiotic Chemical Reaction Space: Progress and Perspectives. Life (Basel) 2021; 11:1140. [PMID: 34833016 PMCID: PMC8624352 DOI: 10.3390/life11111140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/15/2021] [Accepted: 10/18/2021] [Indexed: 12/12/2022] Open
Abstract
Prebiotic chemistry often involves the study of complex systems of chemical reactions that form large networks with a large number of diverse species. Such complex systems may have given rise to emergent phenomena that ultimately led to the origin of life on Earth. The environmental conditions and processes involved in this emergence may not be fully recapitulable, making it difficult for experimentalists to study prebiotic systems in laboratory simulations. Computational chemistry offers efficient ways to study such chemical systems and identify the ones most likely to display complex properties associated with life. Here, we review tools and techniques for modelling prebiotic chemical reaction networks and outline possible ways to identify self-replicating features that are central to many origin-of-life models.
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Affiliation(s)
- Siddhant Sharma
- Blue Marble Space Institute of Science, Seattle, WA 98154, USA; (S.S.); (A.A.); (R.C.)
- Department of Biochemistry, Deshbandhu College, University of Delhi, New Delhi 110019, India
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Aayush Arya
- Blue Marble Space Institute of Science, Seattle, WA 98154, USA; (S.S.); (A.A.); (R.C.)
- Department of Physics, Lovely Professional University, Jalandhar-Delhi GT Road, Phagwara 144001, India
| | - Romulo Cruz
- Blue Marble Space Institute of Science, Seattle, WA 98154, USA; (S.S.); (A.A.); (R.C.)
- Big Data Laboratory, Information and Communications Technology Center (CTIC), National University of Engineering, Amaru 210, Lima 15333, Peru
| | - Henderson James Cleaves II
- Blue Marble Space Institute of Science, Seattle, WA 98154, USA; (S.S.); (A.A.); (R.C.)
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
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4
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Yu P, Sterling AJ, Hein J. A Novel Automated Screening Method for Combinatorially Generated Small Molecules. J Chem Inf Model 2021; 61:1637-1646. [PMID: 33844913 DOI: 10.1021/acs.jcim.0c01462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A main challenge in the enumeration of small-molecule chemical spaces for drug design is to quickly and accurately differentiate between possible and impossible molecules. Current approaches for screening enumerated molecules (e.g., 2D heuristics and 3D force fields) have not been able to achieve a balance between accuracy and speed. We have developed a new automated approach for fast and high-quality screening of small molecules, with the following steps: (1) for each molecule in the set, an ensemble of 2D descriptors as feature encoding is computed; (2) on a random small subset, classification (feasible/infeasible) targets via a 3D-based approach are generated; (3) a classification dataset with the computed features and targets is formed and a machine learning model for predicting the 3D approach's decisions is trained; and (4) the trained model is used to screen the remainder of the enumerated set. Our approach is ≈8× (7.96× to 8.84×) faster than screening via 3D simulations without significantly sacrificing accuracy; while compared to 2D-based pruning rules, this approach is more accurate, with better coverage of known feasible molecules. Once the topological features and 3D conformer evaluation methods are established, the process can be fully automated, without any additional chemistry expertise.
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Affiliation(s)
- Pingshi Yu
- Department of Statistics, University of Oxford, 29 St Giles', Oxford OX1 2JD, U.K.,Department of Computer Science, University of Oxford, 15 Parks Road, Oxford OX1 3QD, U.K
| | - Alistair J Sterling
- Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Jotun Hein
- Department of Statistics, University of Oxford, 29 St Giles', Oxford OX1 2JD, U.K
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5
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Classification of the Biogenicity of Complex Organic Mixtures for the Detection of Extraterrestrial Life. Life (Basel) 2021; 11:life11030234. [PMID: 33809046 PMCID: PMC8001260 DOI: 10.3390/life11030234] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 03/02/2021] [Accepted: 03/07/2021] [Indexed: 11/17/2022] Open
Abstract
Searching for life in the Universe depends on unambiguously distinguishing biological features from background signals, which could take the form of chemical, morphological, or spectral signatures. The discovery and direct measurement of organic compounds unambiguously indicative of extraterrestrial (ET) life is a major goal of Solar System exploration. Biology processes matter and energy differently from abiological systems, and materials produced by biological systems may become enriched in planetary environments where biology is operative. However, ET biology might be composed of different components than terrestrial life. As ET sample return is difficult, in situ methods for identifying biology will be useful. Mass spectrometry (MS) is a potentially versatile life detection technique, which will be used to analyze numerous Solar System environments in the near future. We show here that simple algorithmic analysis of MS data from abiotic synthesis (natural and synthetic), microbial cells, and thermally processed biological materials (lab-grown organisms and petroleum) easily identifies relational organic compound distributions that distinguish pristine and aged biological and abiological materials, which likely can be attributed to the types of compounds these processes produce, as well as how they are formed and decompose. To our knowledge this is the first comprehensive demonstration of the utility of this analytical technique for the detection of biology. This method is independent of the detection of particular masses or molecular species samples may contain. This suggests a general method to agnostically detect evidence of biology using MS given a sufficiently strong signal in which the majority of the material in a sample has either a biological or abiological origin. Such metrics are also likely to be useful for studies of possible emergent living phenomena, and paleobiological samples.
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6
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Tran QP, Adam ZR, Fahrenbach AC. Prebiotic Reaction Networks in Water. Life (Basel) 2020; 10:E352. [PMID: 33339192 PMCID: PMC7765580 DOI: 10.3390/life10120352] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/05/2020] [Accepted: 12/06/2020] [Indexed: 02/07/2023] Open
Abstract
A prevailing strategy in origins of life studies is to explore how chemistry constrained by hypothetical prebiotic conditions could have led to molecules and system level processes proposed to be important for life's beginnings. This strategy has yielded model prebiotic reaction networks that elucidate pathways by which relevant compounds can be generated, in some cases, autocatalytically. These prebiotic reaction networks provide a rich platform for further understanding and development of emergent "life-like" behaviours. In this review, recent advances in experimental and analytical procedures associated with classical prebiotic reaction networks, like formose and Miller-Urey, as well as more recent ones are highlighted. Instead of polymeric networks, i.e., those based on nucleic acids or peptides, the focus is on small molecules. The future of prebiotic chemistry lies in better understanding the genuine complexity that can result from reaction networks and the construction of a centralised database of reactions useful for predicting potential network evolution is emphasised.
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Affiliation(s)
| | - Zachary R. Adam
- Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA;
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7
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Seyler L, Kujawinski EB, Azua-Bustos A, Lee MD, Marlow J, Perl SM, Cleaves II HJ. Metabolomics as an Emerging Tool in the Search for Astrobiologically Relevant Biomarkers. ASTROBIOLOGY 2020; 20:1251-1261. [PMID: 32551936 PMCID: PMC7116171 DOI: 10.1089/ast.2019.2135] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
It is now routinely possible to sequence and recover microbial genomes from environmental samples. To the degree it is feasible to assign transcriptional and translational functions to these genomes, it should be possible, in principle, to largely understand the complete molecular inputs and outputs of a microbial community. However, gene-based tools alone are presently insufficient to describe the full suite of chemical reactions and small molecules that compose a living cell. Metabolomic tools have developed quickly and now enable rapid detection and identification of small molecules within biological and environmental samples. The convergence of these technologies will soon facilitate the detection of novel enzymatic activities, novel organisms, and potentially extraterrestrial life-forms on solar system bodies. This review explores the methodological problems and scientific opportunities facing researchers who hope to apply metabolomic methods in astrobiology-related fields, and how present challenges might be overcome.
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Affiliation(s)
- Lauren Seyler
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Address correspondence to: Lauren Seyler, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 86 Water Street, Woods Hole, MA 02543, USA
| | - Elizabeth B. Kujawinski
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | - Armando Azua-Bustos
- Department of Planetology and Habitability, Centro de Astrobiología (CSIC-INTA), Madrid, Spain
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Michael D. Lee
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Exobiology Branch, NASA Ames Research Center, Moffett Field, California, USA
| | - Jeffrey Marlow
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
- Department of Biology, Boston University, Boston, Massachusetts, USA
| | - Scott M. Perl
- Geological and Planetary Sciences, California Institute of Technology/NASA Jet Propulsion Laboratory, Pasadena, California, USA
- Mineral Sciences, Los Angeles Natural History Museum, Los Angeles, California, USA
| | - Henderson James Cleaves II
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
- School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey, USA
- Geographical Research Laboratory, Carnegie Institution of Washington
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8
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Yi R, Tran QP, Ali S, Yoda I, Adam ZR, Cleaves HJ, Fahrenbach AC. A continuous reaction network that produces RNA precursors. Proc Natl Acad Sci U S A 2020; 117:13267-13274. [PMID: 32487725 PMCID: PMC7306801 DOI: 10.1073/pnas.1922139117] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Continuous reaction networks, which do not rely on purification or timely additions of reagents, serve as models for chemical evolution and have been demonstrated for compounds thought to have played important roles for the origins of life such as amino acids, hydroxy acids, and sugars. Step-by-step chemical protocols for ribonucleotide synthesis are known, but demonstrating their synthesis in the context of continuous reaction networks remains a major challenge. Herein, compounds proposed to be important for prebiotic RNA synthesis, including glycolaldehyde, cyanamide, 2-aminooxazole, and 2-aminoimidazole, are generated from a continuous reaction network, starting from an aqueous mixture of NaCl, NH4Cl, phosphate, and HCN as the only carbon source. No well-timed addition of any other reagents is required. The reaction network is driven by a combination of γ radiolysis and dry-down. γ Radiolysis results in a complex mixture of organics, including the glycolaldehyde-derived glyceronitrile and cyanamide. This mixture is then dried down, generating free glycolaldehyde that then reacts with cyanamide/NH3 to furnish a combination of 2-aminooxazole and 2-aminoimidazole. This continuous reaction network models how precursors for generating RNA and other classes of compounds may arise spontaneously from a complex mixture that originates from simple reagents.
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Affiliation(s)
- Ruiqin Yi
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Quoc Phuong Tran
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Sarfaraz Ali
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Isao Yoda
- Co-60 Radiation Facility, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Zachary R Adam
- Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721
- Blue Marble Space Institute of Science, Seattle, WA 98154
| | - H James Cleaves
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
- Blue Marble Space Institute of Science, Seattle, WA 98154
- Program in Interdisciplinary Studies, Institute for Advanced Study, Princeton, NJ 08540
| | - Albert C Fahrenbach
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia;
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9
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Bowman JC, Petrov AS, Frenkel-Pinter M, Penev PI, Williams LD. Root of the Tree: The Significance, Evolution, and Origins of the Ribosome. Chem Rev 2020; 120:4848-4878. [PMID: 32374986 DOI: 10.1021/acs.chemrev.9b00742] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ribosome is an ancient molecular fossil that provides a telescope to the origins of life. Made from RNA and protein, the ribosome translates mRNA to coded protein in all living systems. Universality, economy, centrality and antiquity are ingrained in translation. The translation machinery dominates the set of genes that are shared as orthologues across the tree of life. The lineage of the translation system defines the universal tree of life. The function of a ribosome is to build ribosomes; to accomplish this task, ribosomes make ribosomal proteins, polymerases, enzymes, and signaling proteins. Every coded protein ever produced by life on Earth has passed through the exit tunnel, which is the birth canal of biology. During the root phase of the tree of life, before the last common ancestor of life (LUCA), exit tunnel evolution is dominant and unremitting. Protein folding coevolved with evolution of the exit tunnel. The ribosome shows that protein folding initiated with intrinsic disorder, supported through a short, primitive exit tunnel. Folding progressed to thermodynamically stable β-structures and then to kinetically trapped α-structures. The latter were enabled by a long, mature exit tunnel that partially offset the general thermodynamic tendency of all polypeptides to form β-sheets. RNA chaperoned the evolution of protein folding from the very beginning. The universal common core of the ribosome, with a mass of nearly 2 million Daltons, was finalized by LUCA. The ribosome entered stasis after LUCA and remained in that state for billions of years. Bacterial ribosomes never left stasis. Archaeal ribosomes have remained near stasis, except for the superphylum Asgard, which has accreted rRNA post LUCA. Eukaryotic ribosomes in some lineages appear to be logarithmically accreting rRNA over the last billion years. Ribosomal expansion in Asgard and Eukarya has been incremental and iterative, without substantial remodeling of pre-existing basal structures. The ribosome preserves information on its history.
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Affiliation(s)
- Jessica C Bowman
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Anton S Petrov
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Moran Frenkel-Pinter
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Petar I Penev
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Loren Dean Williams
- Center for the Origins of Life, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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10
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Kauffman SA, Jelenfi DP, Vattay G. Theory of chemical evolution of molecule compositions in the universe, in the Miller–Urey experiment and the mass distribution of interstellar and intergalactic molecules. J Theor Biol 2020; 486:110097. [DOI: 10.1016/j.jtbi.2019.110097] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 11/25/2019] [Accepted: 11/28/2019] [Indexed: 11/29/2022]
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11
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Polyesters as a Model System for Building Primitive Biologies from Non-Biological Prebiotic Chemistry. Life (Basel) 2020; 10:life10010006. [PMID: 31963928 PMCID: PMC7175156 DOI: 10.3390/life10010006] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/22/2019] [Accepted: 01/10/2020] [Indexed: 12/14/2022] Open
Abstract
A variety of organic chemicals were likely available on prebiotic Earth. These derived from diverse processes including atmospheric and geochemical synthesis and extraterrestrial input, and were delivered to environments including oceans, lakes, and subaerial hot springs. Prebiotic chemistry generates both molecules used by modern organisms, such as proteinaceous amino acids, as well as many molecule types not used in biochemistry. As prebiotic chemical diversity was likely high, and the core of biochemistry uses a rather small set of common building blocks, the majority of prebiotically available organic compounds may not have been those used in modern biochemistry. Chemical evolution was unlikely to have been able to discriminate which molecules would eventually be used in biology, and instead, interactions among compounds were governed simply by abundance and chemical reactivity. Previous work has shown that likely prebiotically available α-hydroxy acids can combinatorially polymerize into polyesters that self-assemble to create new phases which are able to compartmentalize other molecule types. The unexpectedly rich complexity of hydroxy acid chemistry and the likely enormous structural diversity of prebiotic organic chemistry suggests chemical evolution could have been heavily influenced by molecules not used in contemporary biochemistry, and that there is a considerable amount of prebiotic chemistry which remains unexplored.
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Abstract
Using three supercomputers, we broke a record set in 2011, in the enumeration of non-isomorphic regular graphs by expanding the sequence of A006820 in the Online Encyclopedia of Integer Sequences (OEIS), to achieve the number for 4-regular graphs of order 23 as 429,668,180,677,439, while discovering several regular graphs with minimum average shortest path lengths (ASPL) that can be used as interconnection networks for parallel computers. The enumeration of 4-regular graphs and the discovery of minimal-ASPL graphs are extremely time consuming. We accomplish them by adapting GENREG, a classical regular graph generator, to three supercomputers with thousands of processor cores.
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13
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Lancet D, Zidovetzki R, Markovitch O. Systems protobiology: origin of life in lipid catalytic networks. J R Soc Interface 2019; 15:rsif.2018.0159. [PMID: 30045888 PMCID: PMC6073634 DOI: 10.1098/rsif.2018.0159] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 06/29/2018] [Indexed: 12/17/2022] Open
Abstract
Life is that which replicates and evolves, but there is no consensus on how life emerged. We advocate a systems protobiology view, whereby the first replicators were assemblies of spontaneously accreting, heterogeneous and mostly non-canonical amphiphiles. This view is substantiated by rigorous chemical kinetics simulations of the graded autocatalysis replication domain (GARD) model, based on the notion that the replication or reproduction of compositional information predated that of sequence information. GARD reveals the emergence of privileged non-equilibrium assemblies (composomes), which portray catalysis-based homeostatic (concentration-preserving) growth. Such a process, along with occasional assembly fission, embodies cell-like reproduction. GARD pre-RNA evolution is evidenced in the selection of different composomes within a sparse fitness landscape, in response to environmental chemical changes. These observations refute claims that GARD assemblies (or other mutually catalytic networks in the metabolism first scenario) cannot evolve. Composomes represent both a genotype and a selectable phenotype, anteceding present-day biology in which the two are mostly separated. Detailed GARD analyses show attractor-like transitions from random assemblies to self-organized composomes, with negative entropy change, thus establishing composomes as dissipative systems—hallmarks of life. We show a preliminary new version of our model, metabolic GARD (M-GARD), in which lipid covalent modifications are orchestrated by non-enzymatic lipid catalysts, themselves compositionally reproduced. M-GARD fills the gap of the lack of true metabolism in basic GARD, and is rewardingly supported by a published experimental instance of a lipid-based mutually catalytic network. Anticipating near-future far-reaching progress of molecular dynamics, M-GARD is slated to quantitatively depict elaborate protocells, with orchestrated reproduction of both lipid bilayer and lumenal content. Finally, a GARD analysis in a whole-planet context offers the potential for estimating the probability of life's emergence. The invigorated GARD scrutiny presented in this review enhances the validity of autocatalytic sets as a bona fide early evolution scenario and provides essential infrastructure for a paradigm shift towards a systems protobiology view of life's origin.
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Affiliation(s)
- Doron Lancet
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Raphael Zidovetzki
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, CA 92521, USA
| | - Omer Markovitch
- Origins Center, Center for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Groningen, the Netherlands.,Blue Marble Space Institute of Science, Seattle, WA, USA
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14
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Adaptive Properties of the Genetically Encoded Amino Acid Alphabet Are Inherited from Its Subsets. Sci Rep 2019; 9:12468. [PMID: 31462646 PMCID: PMC6713743 DOI: 10.1038/s41598-019-47574-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 07/08/2019] [Indexed: 01/11/2023] Open
Abstract
Life uses a common set of 20 coded amino acids (CAAs) to construct proteins. This set was likely canonicalized during early evolution; before this, smaller amino acid sets were gradually expanded as new synthetic, proofreading and coding mechanisms became biologically available. Many possible subsets of the modern CAAs or other presently uncoded amino acids could have comprised the earlier sets. We explore the hypothesis that the CAAs were selectively fixed due to their unique adaptive chemical properties, which facilitate folding, catalysis, and solubility of proteins, and gave adaptive value to organisms able to encode them. Specifically, we studied in silico hypothetical CAA sets of 3–19 amino acids comprised of 1913 structurally diverse α-amino acids, exploring the adaptive value of their combined physicochemical properties relative to those of the modern CAA set. We find that even hypothetical sets containing modern CAA members are especially adaptive; it is difficult to find sets even among a large choice of alternatives that cover the chemical property space more amply. These results suggest that each time a CAA was discovered and embedded during evolution, it provided an adaptive value unusual among many alternatives, and each selective step may have helped bootstrap the developing set to include still more CAAs.
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15
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Walker SI, Packard N, Cody GD. Re-conceptualizing the origins of life. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:rsta.2016.0337. [PMID: 29133439 PMCID: PMC5686397 DOI: 10.1098/rsta.2016.0337] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/26/2017] [Indexed: 06/07/2023]
Abstract
Over the last several hundred years of scientific progress, we have arrived at a deep understanding of the non-living world. We have not yet achieved an analogous, deep understanding of the living world. The origins of life is our best chance at discovering scientific laws governing life, because it marks the point of departure from the predictable physical and chemical world to the novel, history-dependent living world. This theme issue aims to explore ways to build a deeper understanding of the nature of biology, by modelling the origins of life on a sufficiently abstract level, starting from prebiotic conditions on Earth and possibly on other planets and bridging quantitative frameworks approaching universal aspects of life. The aim of the editors is to stimulate new directions for solving the origins of life. The present introduction represents the point of view of the editors on some of the most promising future directions.This article is part of the themed issue 'Reconceptualizing the origins of life'.
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Affiliation(s)
- Sara I Walker
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, AZ, USA
- Blue Marble Space Institute for Science, Seattle, WA, USA
| | | | - G D Cody
- Geophysical Laboratory, Carnegie Institution for Science, Washington, DC, USA
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