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Hyde AS, House CH. Prebiotic thiol-catalyzed thioamide bond formation. GEOCHEMICAL TRANSACTIONS 2024; 25:5. [PMID: 39098875 PMCID: PMC11299287 DOI: 10.1186/s12932-024-00088-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 06/20/2024] [Indexed: 08/06/2024]
Abstract
Thioamide bonds are important intermediates in prebiotic chemistry. In cyanosulfidic prebiotic chemistry, they serve as crucial intermediates in the pathways that lead to the formation of many important biomolecules (e.g., amino acids). They can also serve as purine and pyrimidine precursors, the two classes of heterocycle employed in genetic molecules. Despite their importance, the formation of thioamide bonds from nitriles under prebiotic conditions has required large excesses of sulfide or compounds with unknown prebiotic sources. Here, we describe the thiol-catalyzed formation of thioamide bonds from nitriles. We show that the formation of the simplest of these compounds, thioformamide, forms readily in spark-discharge experiments from hydrogen cyanide, sulfide, and a methanethiol catalyst, suggesting potential accumulation on early Earth. Lastly, we demonstrate that thioformamide has a Gibbs energy of hydrolysis ( Δ G r ∘ ) comparable to other energy-currencies on early Earth such as pyrophosphate and thioester bonds. Overall, our findings imply that thioamides might have been abundant on early Earth and served a variety of functions during chemical evolution.
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Affiliation(s)
- Andrew S Hyde
- Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, 16802, PA, USA.
| | - Christopher H House
- Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, 16802, PA, USA
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2
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Wehbi S, Wheeler A, Morel B, Minh BQ, Lauretta DS, Masel J. Order of amino acid recruitment into the genetic code resolved by Last Universal Common Ancestor's protein domains. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.13.589375. [PMID: 38659899 PMCID: PMC11042313 DOI: 10.1101/2024.04.13.589375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The current "consensus" order in which amino acids were added to the genetic code is based on potentially biased criteria such as absence of sulfur-containing amino acids from the Urey-Miller experiment which lacked sulfur. Even if inferred perfectly, abiotic abundance might not reflect abundance in the organisms in which the genetic code evolved. Here, we instead exploit the fact that proteins that emerged prior to the genetic code's completion are likely enriched in early amino acids and depleted in late amino acids. We identify the most ancient protein-coding sequences born prior to the archaeal-bacterial split. Amino acid usage in protein sequences whose ancestors date back to a single homolog in the Last Universal Common Ancestor (LUCA) largely matches the consensus order. However, our findings indicate that metal-binding (cysteine and histidine) and sulfur-containing (cysteine and methionine) amino acids were added to the genetic code much earlier than previously thought. Surprisingly, even more ancient protein sequences - those that had already diversified into multiple distinct copies in LUCA - show a different pattern to single copy LUCA sequences: significantly less depleted in the late amino acids tryptophan and tyrosine, and enriched rather than depleted in phenylalanine. This is compatible with at least some of these sequences predating the current genetic code. Their distinct enrichment patterns thus provide hints about earlier, alternative genetic codes.
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Affiliation(s)
- Sawsan Wehbi
- Genetics Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Andrew Wheeler
- Genetics Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona, 85721, USA
| | - Benoit Morel
- Computational Molecular Evolution Group, Heidelberg Institute for Theoretical Studies, Heidelberg, Germany
| | - Bui Quang Minh
- School of Computing, Australian National University, Canberra, ACT, Australia
| | - Dante S Lauretta
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
| | - Joanna Masel
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
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3
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Rimmer PB, Shorttle O. A Surface Hydrothermal Source of Nitriles and Isonitriles. Life (Basel) 2024; 14:498. [PMID: 38672768 PMCID: PMC11051382 DOI: 10.3390/life14040498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 03/22/2024] [Accepted: 03/29/2024] [Indexed: 04/28/2024] Open
Abstract
Giant impacts can generate transient hydrogen-rich atmospheres, reducing atmospheric carbon. The reduced carbon will form hazes that rain out onto the surface and can become incorporated into the crust. Once heated, a large fraction of the carbon is converted into graphite. The result is that local regions of the Hadean crust were plausibly saturated with graphite. We explore the consequences of such a crust for a prebiotic surface hydrothermal vent scenario. We model a surface vent fed by nitrogen-rich volcanic gas from high-temperature magmas passing through graphite-saturated crust. We consider this occurring at pressures of 1-1000bar and temperatures of 1500-1700 ∘C. The equilibrium with graphite purifies the leftover gas, resulting in substantial quantities of nitriles (0.1% HCN and 1ppm HC3N) and isonitriles (0.01% HNC) relevant for prebiotic chemistry. We use these results to predict gas-phase concentrations of methyl isocyanide of ∼1 ppm. Methyl isocyanide can participate in the non-enzymatic activation and ligation of the monomeric building blocks of life, and surface or shallow hydrothermal environments provide its only known equilibrium geochemical source.
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Affiliation(s)
- Paul B. Rimmer
- Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, UK
| | - Oliver Shorttle
- Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
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4
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Rodriguez LE, Altair T, Hermis NY, Jia TZ, Roche TP, Steller LH, Weber JM. Chapter 4: A Geological and Chemical Context for the Origins of Life on Early Earth. ASTROBIOLOGY 2024; 24:S76-S106. [PMID: 38498817 DOI: 10.1089/ast.2021.0139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Within the first billion years of Earth's history, the planet transformed from a hot, barren, and inhospitable landscape to an environment conducive to the emergence and persistence of life. This chapter will review the state of knowledge concerning early Earth's (Hadean/Eoarchean) geochemical environment, including the origin and composition of the planet's moon, crust, oceans, atmosphere, and organic content. It will also discuss abiotic geochemical cycling of the CHONPS elements and how these species could have been converted to biologically relevant building blocks, polymers, and chemical networks. Proposed environments for abiogenesis events are also described and evaluated. An understanding of the geochemical processes under which life may have emerged can better inform our assessment of the habitability of other worlds, the potential complexity that abiotic chemistry can achieve (which has implications for putative biosignatures), and the possibility for biochemistries that are vastly different from those on Earth.
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Affiliation(s)
- Laura E Rodriguez
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA. (Current)
| | - Thiago Altair
- Institute of Chemistry of São Carlos, Universidade de São Paulo, São Carlos, Brazil
- Department of Chemistry, College of the Atlantic, Bar Harbor, Maine, USA. (Current)
| | - Ninos Y Hermis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Department of Physics and Space Sciences, University of Granada, Granada Spain. (Current)
| | - Tony Z Jia
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- Blue Marble Space Institute of Science, Seattle, Washington, USA
| | - Tyler P Roche
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Luke H Steller
- Australian Centre for Astrobiology, and School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, Australia
| | - Jessica M Weber
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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5
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Cohen ZR, Ding D, Zhou L, DasGupta S, Haas S, Sinclair KP, Todd ZR, Black RA, Szostak JW, Catling DC. Natural soda lakes provide compatible conditions for RNA and membrane function that could have enabled the origin of life. PNAS NEXUS 2024; 3:pgae084. [PMID: 38505692 PMCID: PMC10949909 DOI: 10.1093/pnasnexus/pgae084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/31/2024] [Indexed: 03/21/2024]
Abstract
The origin of life likely occurred within environments that concentrated cellular precursors and enabled their co-assembly into cells. Soda lakes (those dominated by Na+ ions and carbonate species) can concentrate precursors of RNA and membranes, such as phosphate, cyanide, and fatty acids. Subsequent assembly of RNA and membranes into cells is a long-standing problem because RNA function requires divalent cations, e.g. Mg2+, but Mg2+ disrupts fatty acid membranes. The low solubility of Mg-containing carbonates limits soda lakes to moderate Mg2+ concentrations (∼1 mM), so we investigated whether both RNAs and membranes function within these lakes. We collected water from Last Chance Lake and Goodenough Lake in Canada. Because we sampled after seasonal evaporation, the lake water contained ∼1 M Na+ and ∼1 mM Mg2+ near pH 10. In the laboratory, nonenzymatic, RNA-templated polymerization of 2-aminoimidazole-activated ribonucleotides occurred at comparable rates in lake water and standard laboratory conditions (50 mM MgCl2, pH 8). Additionally, we found that a ligase ribozyme that uses oligonucleotide substrates activated with 2-aminoimidazole was active in lake water after adjusting pH from ∼10 to 9. We also observed that decanoic acid and decanol assembled into vesicles in a dilute solution that resembled lake water after seasonal rains, and that those vesicles retained encapsulated solutes despite salt-induced flocculation when the external solution was replaced with dry-season lake water. By identifying compatible conditions for nonenzymatic and ribozyme-catalyzed RNA assembly, and for encapsulation by membranes, our results suggest that soda lakes could have enabled cellular life to emerge on Earth, and perhaps elsewhere.
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Affiliation(s)
- Zachary R Cohen
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Dian Ding
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Lijun Zhou
- Department of Biochemistry and Biophysics and Penn Institute for RNA Innovation, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Saurja DasGupta
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Sebastian Haas
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
| | - Kimberly P Sinclair
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
| | - Zoe R Todd
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
- Department of Chemistry and Department of Astronomy, University of Wisconsin, Madison, WI 53706, USA
| | - Roy A Black
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Jack W Szostak
- Howard Hughes Medical Institute, Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - David C Catling
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
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6
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Ahmad W, Kumar S, Verma M. Heterogeneous photocatalytic degradation of antiviral drug didanosine mediated by rose bengal and TiO 2 nanoparticles. ANAL SCI 2024; 40:175-184. [PMID: 37847356 DOI: 10.1007/s44211-023-00446-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 09/27/2023] [Indexed: 10/18/2023]
Abstract
There is a great concern among the researcher to remove the problem of the persistent organic pollutants in wastewater. Pharmaceutical agrochemical and personal care products are generally considered Persistent organic pollutants. Therefore, it is a matter of concern to develop new techniques how to remove these pollutants safely at low cost. This study mainly focuses on the commonly used antiviral drug didanosine and one most commonly used dye rose bengal. In this study, an organic dye rose bengal and TiO2 nanoparticles have been used in combination with UV light to achieve the photodegradation of selected pharmaceutical products and the dye was also degraded by using TiO2 Nanoparticles. The formation of three oxidation products was detected by using a very popular separation technique thin layer and column chromatography. The isolated photoproduct was characterized by using advanced characterization techniques like FTIR (Fourier transform infrared spectroscopy), UV Spectroscopy, and Proton and 13C NMR (Nuclear Magnetic Resonance spectroscopy). The role of singlet oxygen as an active species in this reaction was confirmed by using D2O as a reaction medium. The role of singlet oxygen in this photochemical reaction was also established by the addition of sodium azide. The TiO2 nanophotocatalyst efficiently degrade the didanosine and rose bengal in the presence of the UV light. In the TiO2-induced photocatalytic degradation of didanosine and dyes, the hydroxyl and superoxide radical anion play a prominent role. The finding of this manuscript is very useful to develop an efficient low-cost method for the treatment of wastewater contaminated by antiviral drugs, similar pharmaceutical products and dyes. This study was also very helpful to establish a plausible mechanism behind the phototoxicity of the didanosine.
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Affiliation(s)
- Waseem Ahmad
- Department of Chemistry, Graphic Era (Deemed to be University), Dehradun, 248002, India.
| | - Sanjay Kumar
- Department of Food Science and Technology, Graphic Era (Deemed to be University), Dehradun, India
| | - Monu Verma
- Department of Food Science and Technology, Graphic Era (Deemed to be University), Dehradun, India
- Water-Energy Nexus Laboratory, Department of Environmental Engineering, University of Seoul, Seoul, 02504, Republic of Korea
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7
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Harold SE, Warf SL, Shields GC. Prebiotic dimer and trimer peptide formation in gas-phase atmospheric nanoclusters of water. Phys Chem Chem Phys 2023; 25:28517-28532. [PMID: 37847315 DOI: 10.1039/d3cp02915h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023]
Abstract
Insight into the origin of prebiotic molecules is key to our understanding of how living systems evolved into the complex network of biological processes on Earth. By modelling diglycine and triglycine peptide formation in the prebiotic atmosphere, we provide a plausible pathway for peptide growth. By examining different transition states (TSs), we conclude that the formation of diglycine and triglycine in atmospheric nanoclusters of water in the prebiotic atmosphere kinetically favors peptide growth by an N-to-C synthesis of glycines through a trans conformation. Addition of water stabilizes the TS structures and lowers the Gibbs free activation energies. At temperatures that model the prebiotic atmosphere, the free energies of activation with a six water nanocluster as part of the TS are predicted to be 16 kcal mol-1 relative to the prereactive complex. Examination of the trans vs. cis six water transition states reveals that a homodromic water network that maximizes the acceptor/donor nature of the six waters is responsible for enhanced kinetic favorability of the trans N-to-C pathway. Compared to the non-hydrated trans TS, the trans six-water TS accelerates the reaction of diglycine and glycine to form triglycine by 13 orders of magnitude at 217 K. Nature uses the trans N-to-C pathway to synthesize proteins in the ribosome, and we note the similarities in hydrogen bond stabilization between the transition state for peptide synthesis in the ribosome and the transition states formed in nanoclusters of water in the same pathway. These results support the hypothesis that small oligomers formed in the prebiotic atmosphere and rained onto earth's surface.
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Affiliation(s)
- Shannon E Harold
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA.
| | - Skyler L Warf
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA.
| | - George C Shields
- Department of Chemistry, Furman University, Greenville, South Carolina 29613, USA.
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8
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Subbotin V, Fiksel G. Exploring the Lipid World Hypothesis: A Novel Scenario of Self-Sustained Darwinian Evolution of the Liposomes. ASTROBIOLOGY 2023; 23:344-357. [PMID: 36716277 PMCID: PMC9986030 DOI: 10.1089/ast.2021.0161] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 12/03/2022] [Indexed: 06/18/2023]
Abstract
According to the Lipid World hypothesis, life on Earth originated with the emergence of amphiphilic assemblies in the form of lipid micelles and vesicles (liposomes). However, the mechanism of appearance of the information molecules (ribozymes/RNA) accompanying that process, considered obligatory for Darwinian evolution, is unclear. We propose a novel scenario of self-sustained Darwinian evolution of the liposomes driven by ever-present natural phenomena: solar UV radiation, day/night cycle, gravity, and the formation of liposomes in an aqueous media. The central tenet of this scenario is the liposomes' encapsulation of the heavy solutes, followed by their gravitational submerging in the water. The submerged liposomes, being protected from the damaging UV radiation, acquire the longevity necessary for autocatalytic replication of amphiphiles, their mutation, and the selection of those amphiphilic assemblies that provide the greatest membrane stability. These two sets of adaptive compositional information (heavy content and amphiphilic assemblies design) generate a population of liposomes with self-replication/reproduction properties, which are amendable to mutation, inheritance, and selection, thereby establishing Darwinian progression. Temporary and spatial expansion of this liposomal population will provide the basis for the next evolutionary step-a transition of accidentally entrapped RNA precursor molecules into complex functional molecules, such as ribozymes/RNA.
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Affiliation(s)
- Vladimir Subbotin
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Gennady Fiksel
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan, USA
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9
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Wallner M, Jarraya M, Olsson E, Ideböhn V, Squibb RJ, Ben Yaghlane S, Nyman G, Eland JH, Feifel R, Hochlaf M. Abiotic molecular oxygen production-Ionic pathway from sulfur dioxide. SCIENCE ADVANCES 2022; 8:eabq5411. [PMID: 35984889 PMCID: PMC9390983 DOI: 10.1126/sciadv.abq5411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Molecular oxygen, O2, is vital to life on Earth and possibly also on exoplanets. Although the biogenic processes leading to its accumulation in Earth's atmosphere are well understood, its abiotic origin is still not fully established. Here, we report combined experimental and theoretical evidence for electronic state-selective production of O2 from SO2, a chemical constituent of many planetary atmospheres and one that played an important part on Earth in the Great Oxidation Event. The O2 production involves dissociative double ionization of SO2 leading to efficient formation of the [Formula: see text] ion, which can be converted to abiotic O2 by electron neutralization or by charge exchange. This formation process may contribute substantially to the abundance of O2 and related ions in planetary atmospheres, such as the Jovian moons Io, Europa, and Ganymede. We suggest that this sort of ionic pathway for the formation of abiotic O2 involving multiply charged molecular ion decomposition may also exist for other atmospheric and planetary molecules.
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Affiliation(s)
- Måns Wallner
- University of Gothenburg, Department of Physics, Origovägen 6B, 412 58 Gothenburg, Sweden
| | - Mahmoud Jarraya
- Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Spectroscopie Atomique, Moléculaire et Applications—LSAMA, 2092 Tunis, Tunisia
- Université Gustave Eiffel, COSYS/IMSE, 5 Bd Descartes, 77454 Champs sur Marne, France
| | - Emelie Olsson
- University of Gothenburg, Department of Physics, Origovägen 6B, 412 58 Gothenburg, Sweden
| | - Veronica Ideböhn
- University of Gothenburg, Department of Physics, Origovägen 6B, 412 58 Gothenburg, Sweden
| | - Richard J. Squibb
- University of Gothenburg, Department of Physics, Origovägen 6B, 412 58 Gothenburg, Sweden
| | - Saida Ben Yaghlane
- Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Spectroscopie Atomique, Moléculaire et Applications—LSAMA, 2092 Tunis, Tunisia
| | - Gunnar Nyman
- University of Gothenburg, Department of Chemistry and Molecular Biology, Kemigården 4, 412 96 Gothenburg, Sweden
| | - John H.D. Eland
- Oxford University, Department of Chemistry, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK
| | - Raimund Feifel
- University of Gothenburg, Department of Physics, Origovägen 6B, 412 58 Gothenburg, Sweden
| | - Majdi Hochlaf
- Université Gustave Eiffel, COSYS/IMSE, 5 Bd Descartes, 77454 Champs sur Marne, France
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Sources of Nitrogen-, Sulfur-, and Phosphorus-Containing Feedstocks for Prebiotic Chemistry in the Planetary Environment. LIFE (BASEL, SWITZERLAND) 2022; 12:life12081268. [PMID: 36013447 PMCID: PMC9410288 DOI: 10.3390/life12081268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 08/13/2022] [Accepted: 08/17/2022] [Indexed: 11/21/2022]
Abstract
Biochemistry on Earth makes use of the key elements carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (or CHONPS). Chemically accessible molecules containing these key elements would presumably have been necessary for prebiotic chemistry and the origins of life on Earth. For example, feedstock molecules including fixed nitrogen (e.g., ammonia, nitrite, nitrate), accessible forms of phosphorus (e.g., phosphate, phosphite, etc.), and sources of sulfur (e.g., sulfide, sulfite) may have been necessary for the origins of life, given the biochemistry seen in Earth life today. This review describes potential sources of nitrogen-, sulfur-, and phosphorus-containing molecules in the context of planetary environments. For the early Earth, such considerations may be able to aid in the understanding of our own origins. Additionally, as we learn more about potential environments on other planets (for example, with upcoming next-generation telescope observations or new missions to explore other bodies in our Solar System), evaluating potential sources for elements necessary for life (as we know it) can help constrain the potential habitability of these worlds.
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11
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Sahai N, Adebayo S, Schoonen MA. Freshwater and Evaporite Brine Compositions on Hadean Earth: Priming the Origins of Life. ASTROBIOLOGY 2022; 22:641-671. [PMID: 35447041 DOI: 10.1089/ast.2020.2396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The chemical composition of aqueous solutions during the Hadean era determined the availability of essential elements for prebiotic synthesis of the molecular building blocks of life. Here we conducted quantitative reaction path modeling of atmosphere-water-rock interactions over a range of environmental conditions to estimate freshwater and evaporite brine compositions. We then evaluated the solution chemistries for their potential to influence ribonucleotide synthesis and polymerization as well as protocell membrane stability. Specifically, solutions formed by komatiite and tonalite (primitive crustal rocks) weathering and evaporation-rehydration (drying-wetting) cycles were studied assuming neutral atmospheric composition over a wide range of values of atmospheric partial pressure of CO2 (PCO2) and temperatures (T). Solution pH decreased and total dissolved concentrations of inorganic P, Mg, Ca, Fe, and C (PT, MgT, CaT, FeT, and CT) increased with increasing PCO2. The PCO2 and T dictated how the solution evolved with regard to minerals precipitated and ions left in solution. At T = 75°C and PCO2 < 0.05 atm, the concentration ratio of magnesium to calcium ion concentrations (Mg2+/Ca2+) was < 1 and predominantly metal aluminosilicates (including clays), dolomite, gibbsite, and pyrite (FeS2) precipitated, whereas at PCO2 > 0.05 atm, Mg2+/Ca2+ was > 1 and mainly magnesite, dolomite, pyrite, chalcedony (SiO2), and kaolinite (Al2Si2O5) precipitated. At T = 75°C and PCO2 > 0.05 atm, hydroxyapatite (HAP) precipitated during weathering but not during evaporation, and so, PT increased with each evaporation-rehydration cycle, while MgT, CaT, and FeT decreased as other minerals precipitated. At T = 75°C and PCO2 ∼5 atm, reactions with komatiite provided end-of-weathering solutions with high enough Mg2+ concentrations to promote RNA-template directed and montmorillonite-promoted nonenzymatic RNA polymerization, but incompatible with protocell membranes; however, montmorillonite-promoted RNA polymerization could proceed with little or no Mg2+ present. Cyclically evaporating/rehydrating brines from komatiite weathering at T = 75°C and PCO2 ∼5 atm yielded the following: (1) high PT values that could promote ribonucleotide synthesis, and (2) low divalent cation concentrations compatible with amino acid-promoted, montmorillonite-catalyzed RNA polymerization and with protocell membranes, but too low for template-directed nonenzymatic RNA polymerization. For all PCO2 values, Mg2+ and PT concentrations decreased, whereas the HCO3- concentration increased within increasing temperature, due to the retrograde solubility of the minerals controlling these ions' concentrations; Fe2+ concentration increased because of prograde pyrite solubility. Tonalite weathering and cyclical wetting-drying reactions did not produce solution compositions favorable for promoting prebiotic RNA formation. Conversely, the ion concentrations compatible with protocell emergence, placed constraints on PCO2 of early Earth's atmosphere. In summary: (1) prebiotic RNA synthesis and membrane self-assembly could have been achieved even under neutral atmosphere conditions by atmosphere-water-komatiite rock interactions; and (2) constraints on element availability for the origins of life and early PCO2 were addressed by a single, globally operating mechanism of atmosphere-water-rock interactions without invoking special microenvironments. The present results support a facile origins-of-life hypothesis even under a neutral atmosphere as long as other favorable geophysical and planetary conditions are also met.
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Affiliation(s)
- Nita Sahai
- School of Polymer Science and Polymer Engineering and University of Akron, Akron, Ohio, USA
- Department of Geoscience, University of Akron, Akron, Ohio, USA
- Integrated Bioscience Program, University of Akron, Akron, Ohio, USA
| | - Segun Adebayo
- School of Polymer Science and Polymer Engineering and University of Akron, Akron, Ohio, USA
| | - Martin A Schoonen
- Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, New York, USA
- Department of Geosciences, Stony Brook University, Stony Brook, New York, USA
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12
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Colman DR, Labesse G, Swapna G, Stefanakis J, Montelione GT, Boyd ES, Royer CA. Structural evolution of the ancient enzyme, dissimilatory sulfite reductase. Proteins 2022; 90:1331-1345. [PMID: 35122336 PMCID: PMC9018543 DOI: 10.1002/prot.26315] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 01/29/2022] [Indexed: 07/21/2023]
Abstract
Dissimilatory sulfite reductase is an ancient enzyme that has linked the global sulfur and carbon biogeochemical cycles since at least 3.47 Gya. While much has been learned about the phylogenetic distribution and diversity of DsrAB across environmental gradients, far less is known about the structural changes that occurred to maintain DsrAB function as the enzyme accompanied diversification of sulfate/sulfite reducing organisms (SRO) into new environments. Analyses of available crystal structures of DsrAB from Archaeoglobus fulgidus and Desulfovibrio vulgaris, representing early and late evolving lineages, respectively, show that certain features of DsrAB are structurally conserved, including active siro-heme binding motifs. Whether such structural features are conserved among DsrAB recovered from varied environments, including hot spring environments that host representatives of the earliest evolving SRO lineage (e.g., MV2-Eury), is not known. To begin to overcome these gaps in our understanding of the evolution of DsrAB, structural models from MV2.Eury were generated and evolutionary sequence co-variance analyses were conducted on a curated DsrAB database. Phylogenetically diverse DsrAB harbor many conserved functional residues including those that ligate active siro-heme(s). However, evolutionary co-variance analysis of monomeric DsrAB subunits revealed several False Positive Evolutionary Couplings (FPEC) that correspond to residues that have co-evolved despite being too spatially distant in the monomeric structure to allow for direct contact. One set of FPECs corresponds to residues that form a structural path between the two active siro-heme moieties across the interface between heterodimers, suggesting the potential for allostery or electron transfer within the enzyme complex. Other FPECs correspond to structural loops and gaps that may have been selected to stabilize enzyme function in different environments. These structural bioinformatics results suggest that DsrAB has maintained allosteric communication pathways between subunits as SRO diversified into new environments. The observations outlined here provide a framework for future biochemical and structural analyses of DsrAB to examine potential allosteric control of this enzyme.
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Affiliation(s)
- Daniel R. Colman
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana 59717
| | - Gilles Labesse
- Centre de Biochimie Structurale, CNRS UMR 5048, Montpellier, France 34090
| | - G.V.T. Swapna
- Dept of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers The State University of New Jersey, Piscataway, NJ, 08854 USA
| | | | - Gaetano T. Montelione
- Department of Chemistry and Chemical Biology, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Eric S. Boyd
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana 59717
| | - Catherine A. Royer
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180
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13
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Bolton SG, Pluth MD. Efficient inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by sulfuration with solubilized elemental sulfur. Free Radic Biol Med 2022; 185:46-51. [PMID: 35470062 DOI: 10.1016/j.freeradbiomed.2022.03.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/29/2022] [Accepted: 03/31/2022] [Indexed: 02/07/2023]
Abstract
Hydrogen sulfide (H2S), carbon monoxide (CO), and nitric oxide (NO) have garnered increasing scientific interest in recent decades due to their classifications as members of the gasotransmitter family of signaling molecules. Due to the versatility of sulfur redox chemistry in biological systems, H2S specifically is being studied for its ability to modulate cellular redox environments, particularly through the downstream production of oxidized sulfur species. A major mechanism of this regulation is through a posttranslational modification known as persulfidation, where oxidized sulfur atoms are appended to free cysteine in proteins. Currently, it is difficult to discern the activity of H2S itself versus these oxidized sulfur species, particularly sulfane sulfur (S0). We have previously developed a method of solvating S8, a source of pure S0, to more accurately study persulfidation and sulfuration in general. Here, we apply this pure S0 to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which has previously been shown to be inhibited by S0-containing polysulfides via persulfidation. Using solvated S0, we demonstrate that native, reduced GAPDH can be completely inhibited by sulfuration with S0. Further, oxidized GAPDH activity cannot be rescued using S0, demonstrating that it is the oxidation of reduced GAPDH by S0 that curtails its activity. We also compare inhibition of GAPDH by pure S0 to different polysulfides and demonstrate the modulating effects that pendant alkyl groups have on GAPDH inhibition. These results highlight the promise of this novel, simplified system for the study of S0.
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Affiliation(s)
- Sarah G Bolton
- Department of Chemistry and Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, Institute of Molecular Biology, University of Oregon, Eugene, OR, 97403, USA
| | - Michael D Pluth
- Department of Chemistry and Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, Institute of Molecular Biology, University of Oregon, Eugene, OR, 97403, USA.
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14
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Microbial Diversity and Sulfur Cycling in an Early Earth Analogue: From Ancient Novelty to Modern Commonality. mBio 2022; 13:e0001622. [PMID: 35258328 PMCID: PMC9040765 DOI: 10.1128/mbio.00016-22] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Life emerged and diversified in the absence of molecular oxygen. The prevailing anoxia and unique sulfur chemistry in the Paleo-, Meso-, and Neoarchean and early Proterozoic eras may have supported microbial communities that differ from those currently thriving on the earth’s surface. Zodletone spring in southwestern Oklahoma represents a unique habitat where spatial sampling could substitute for geological eras namely, from the anoxic, surficial light-exposed sediments simulating a preoxygenated earth to overlaid water column where air exposure simulates oxygen intrusion during the Neoproterozoic era. We document a remarkably diverse microbial community in the anoxic spring sediments, with 340/516 (65.89%) of genomes recovered in a metagenomic survey belonging to 200 bacterial and archaeal families that were either previously undescribed or that exhibit an extremely rare distribution on the current earth. Such diversity is underpinned by the widespread occurrence of sulfite, thiosulfate, tetrathionate, and sulfur reduction and the paucity of sulfate reduction machineries in these taxa. Hence, these processes greatly expand lineages mediating reductive sulfur-cycling processes in the tree of life. An analysis of the overlaying oxygenated water community demonstrated the development of a significantly less diverse community dominated by well-characterized lineages and a prevalence of oxidative sulfur-cycling processes. Such a transition from ancient novelty to modern commonality underscores the profound impact of the great oxygenation event on the earth’s surficial anoxic community. It also suggests that novel and rare lineages encountered in current anaerobic habitats could represent taxa that once thrived in an anoxic earth but have failed to adapt to earth’s progressive oxygenation.
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15
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Ranjan S, Kufner CL, Lozano GG, Todd ZR, Haseki A, Sasselov DD. UV Transmission in Natural Waters on Prebiotic Earth. ASTROBIOLOGY 2022; 22:242-262. [PMID: 34939825 PMCID: PMC8968845 DOI: 10.1089/ast.2020.2422] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Ultraviolet (UV) light plays a key role in surficial theories of the origin of life, and numerous studies have focused on constraining the atmospheric transmission of UV radiation on early Earth. However, the UV transmission of the natural waters in which origins-of-life chemistry (prebiotic chemistry) is postulated to have occurred is poorly constrained. In this work, we combine laboratory and literature-derived absorption spectra of potential aqueous-phase prebiotic UV absorbers with literature estimates of their concentrations on early Earth to constrain the prebiotic UV environment in marine and terrestrial natural waters, and we consider the implications for prebiotic chemistry. We find that prebiotic freshwaters were largely transparent in the UV, contrary to assumptions in some models of prebiotic chemistry. Some waters, such as high-salinity waters like carbonate lakes, may be deficient in shortwave (≤220 nm) UV flux. More dramatically, ferrous waters can be strongly UV-shielded, particularly if the Fe2+ forms highly UV-absorbent species such as FeCN64-. Such waters may be compelling venues for UV-averse origin-of-life scenarios but are unfavorable for some UV-dependent prebiotic chemistries. UV light can trigger photochemistry even if attenuated through photochemical transformations of the absorber (e.g., eaq- production from halide irradiation), which may have both constructive and destructive effects for prebiotic syntheses. Prebiotic chemistries that invoke waters that contain such absorbers must self-consistently account for the chemical effects of these transformations. The speciation and abundance of Fe2+ in natural waters on early Earth is a major uncertainty and should be prioritized for further investigation, as it played a major role in UV transmission in prebiotic natural waters.
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Affiliation(s)
- Sukrit Ranjan
- Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Physics and Astronomy, Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, Evanston, Illinois, USA
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Address correspondence to: Sukrit Ranjan, Department of Physics and Astronomy, Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 1800 Sherman Avenue, 6th Floor, Evanston, IL 60601, USA
| | - Corinna L. Kufner
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
| | | | - Zoe R. Todd
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
| | - Azra Haseki
- Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Harvard College, Cambridge, Massachusetts, USA
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16
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Bouillaud F. Sulfide Oxidation Evidences the Immediate Cellular Response to a Decrease in the Mitochondrial ATP/O2 Ratio. Biomolecules 2022; 12:biom12030361. [PMID: 35327553 PMCID: PMC8944965 DOI: 10.3390/biom12030361] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/16/2022] [Accepted: 02/16/2022] [Indexed: 11/25/2022] Open
Abstract
The present article will not attempt to deal with sulfide per se as a signaling molecule but will aim to examine the consequences of sulfide oxidation by mitochondrial sulfide quinone reductase in mammalian cells. This oxidation appears first as a priority to avoid self-poisoning by endogenous sulfide and second to occur with the lowest ATP/O2 ratio when compared to other mitochondrial substrates. This is explained by the injection of electrons in the respiratory chain after complex I (as for succinate) and by a sulfur oxidation step implying a dioxygenase that consumes oxygen but does not contribute to mitochondrial bioenergetics. Both contribute to increase cellular oxygen consumption if sulfide is provided below its toxic level (low µM). Accordingly, if oxygen supply or respiratory chain activity becomes a limiting factor, small variations in sulfide release impact the cellular ATP/ADP ratio, a major metabolic sensor.
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Affiliation(s)
- Frédéric Bouillaud
- Institut Cochin, INSERM, CNRS, Université de Paris, F75014 Paris, France
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17
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From amino acid mixtures to peptides in liquid sulphur dioxide on early Earth. Nat Commun 2021; 12:7182. [PMID: 34893619 PMCID: PMC8664857 DOI: 10.1038/s41467-021-27527-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 11/18/2021] [Indexed: 01/01/2023] Open
Abstract
The formation of peptide bonds is one of the most important biochemical reaction steps. Without the development of structurally and catalytically active polymers, there would be no life on our planet. However, the formation of large, complex oligomer systems is prevented by the high thermodynamic barrier of peptide condensation in aqueous solution. Liquid sulphur dioxide proves to be a superior alternative for copper-catalyzed peptide condensations. Compared to water, amino acids are activated in sulphur dioxide, leading to the incorporation of all 20 proteinogenic amino acids into proteins. Strikingly, even extremely low initial reactant concentrations of only 50 mM are sufficient for extensive peptide formation, yielding up to 2.9% of dialanine in 7 days. The reactions carried out at room temperature and the successful use of the Hadean mineral covellite (CuS) as a catalyst, suggest a volcanic environment for the formation of the peptide world on early Earth. Peptide bond formation is one of the key biochemical reactions needed for the formation of life, but is thermodynamically unfavoured in water. Here, the authors report on the possibility of complex oligomer formation in liquid sulphur dioxide which may have existed on early Earth at the emergence of life.
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18
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Liu Z, Wu LF, Kufner CL, Sasselov DD, Fischer WW, Sutherland JD. Prebiotic photoredox synthesis from carbon dioxide and sulfite. Nat Chem 2021; 13:1126-1132. [PMID: 34635812 PMCID: PMC7611910 DOI: 10.1038/s41557-021-00789-w] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 08/17/2021] [Indexed: 11/16/2022]
Abstract
Carbon dioxide (CO2) is the major carbonaceous component of many planetary atmospheres, which includes the Earth throughout its history. Carbon fixation chemistry-which reduces CO2 to organics, utilizing hydrogen as the stoichiometric reductant-usually requires high pressures and temperatures, and the yields of products of potential use to nascent biology are low. Here we demonstrate an efficient ultraviolet photoredox chemistry between CO2 and sulfite that generates organics and sulfate. The chemistry is initiated by electron photodetachment from sulfite to give sulfite radicals and hydrated electrons, which reduce CO2 to its radical anion. A network of reactions that generates citrate, malate, succinate and tartrate by irradiation of glycolate in the presence of sulfite was also revealed. The simplicity of this carboxysulfitic chemistry and the widespread occurrence and abundance of its feedstocks suggest that it could have readily taken place on the surfaces of rocky planets. The availability of the carboxylate products on early Earth could have driven the development of central carbon metabolism before the advent of biological CO2 fixation.
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Affiliation(s)
- Ziwei Liu
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - Long-Fei Wu
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - Corinna L Kufner
- Harvard-Smithsonian Center for Astrophysics, Massachusetts, MA, USA
| | | | - Woodward W Fischer
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - John D Sutherland
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
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19
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Xu J, Green NJ, Russell DA, Liu Z, Sutherland JD. Prebiotic Photochemical Coproduction of Purine Ribo- and Deoxyribonucleosides. J Am Chem Soc 2021; 143:14482-14486. [PMID: 34469129 PMCID: PMC8607323 DOI: 10.1021/jacs.1c07403] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
The
hypothesis that life on Earth may have started with a heterogeneous
nucleic acid genetic system including both RNA and DNA has attracted
broad interest. The recent finding that two RNA subunits (cytidine,
C, and uridine, U) and two DNA subunits (deoxyadenosine, dA, and deoxyinosine,
dI) can be coproduced in the same reaction network, compatible with
a consistent geological scenario, supports this theory. However, a
prebiotically plausible synthesis of the missing units (purine ribonucleosides
and pyrimidine deoxyribonucleosides) in a unified reaction network
remains elusive. Herein, we disclose a strictly stereoselective and
furanosyl-selective synthesis of purine ribonucleosides (adenosine,
A, and inosine, I) and purine deoxynucleosides (dA and dI), alongside
one another, via a key photochemical reaction of thioanhydroadenosine
with sulfite in alkaline solution (pH 8–10). Mechanistic studies
suggest an unexpected recombination of sulfite and nucleoside alkyl
radicals underpins the formation of the ribo C2′–O bond.
The coproduction of A, I, dA, and dI from a common intermediate, and
under conditions likely to have prevailed in at least some primordial
locales, is suggestive of the potential coexistence of RNA and DNA
building blocks at the dawn of life.
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Affiliation(s)
- Jianfeng Xu
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, U.K
| | - Nicholas J Green
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, U.K
| | - David A Russell
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, U.K
| | - Ziwei Liu
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, U.K
| | - John D Sutherland
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, U.K
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20
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Rimmer PB, Thompson SJ, Xu J, Russell DA, Green NJ, Ritson DJ, Sutherland JD, Queloz DP. Timescales for Prebiotic Photochemistry Under Realistic Surface Ultraviolet Conditions. ASTROBIOLOGY 2021; 21:1099-1120. [PMID: 34152196 PMCID: PMC8570677 DOI: 10.1089/ast.2020.2335] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Ultraviolet (UV) light has long been invoked as a source of energy for prebiotic chemical synthesis, but experimental support does not involve sources of UV light that look like the young Sun. Here we experimentally investigate whether the UV flux available on the surface of early Earth, given a favorable atmosphere, can facilitate a variety of prebiotic chemical syntheses. We construct a solar simulator for the UV light of the faint young Sun on the surface of early Earth, called StarLab. We then attempt a series of reactions testing different aspects of a prebiotic chemical scenario involving hydrogen cyanide (HCN), sulfites, and sulfides under the UV light of StarLab, including hypophosphite oxidation by UV light and hydrogen sulfide, photoreduction of HCN with bisulfite, the photoanomerization of α-thiocytidine, the production of a chemical precursor of a potentially prebiotic activating agent (nitroprusside), the photoreduction of thioanhydrouridine and thioanhydroadenosine, and the oxidation of ethanol (EtOH) by photochemically generated hydroxyl radicals. We compare the output of StarLab to the light of the faint young Sun to constrain the timescales over which these reactions would occur on the surface of early Earth. We predict that hypophosphite oxidation, HCN reduction, and photoproduction of nitroprusside would all operate on the surface of early Earth in a matter of days to weeks. The photoanomerization of α-thiocytidine would take months to complete, and the production of oxidation products from hydroxyl radicals would take years. The photoreduction of thioanhydrouridine with hydrogen sulfide did not succeed even after a long period of irradiation, providing a lower limit on the timescale of several years. The photoreduction of thioanhydroadenosine with bisulfite produced 2'-deoxyriboadenosine (dA) on the timescale of days. This suggests the plausibility of the photoproduction of purine deoxyribonucleotides, such as the photoproduction of simple sugars, proceeds more efficiently in the presence of bisulfite.
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Affiliation(s)
- Paul B. Rimmer
- Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
- Address correspondence to: Paul B. Rimmer, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
| | | | - Jianfeng Xu
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | | | | | | | - Didier P. Queloz
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
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21
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Clark BC, Kolb VM, Steele A, House CH, Lanza NL, Gasda PJ, VanBommel SJ, Newsom HE, Martínez-Frías J. Origin of Life on Mars: Suitability and Opportunities. Life (Basel) 2021; 11:539. [PMID: 34207658 PMCID: PMC8227854 DOI: 10.3390/life11060539] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/28/2021] [Accepted: 06/01/2021] [Indexed: 02/07/2023] Open
Abstract
Although the habitability of early Mars is now well established, its suitability for conditions favorable to an independent origin of life (OoL) has been less certain. With continued exploration, evidence has mounted for a widespread diversity of physical and chemical conditions on Mars that mimic those variously hypothesized as settings in which life first arose on Earth. Mars has also provided water, energy sources, CHNOPS elements, critical catalytic transition metal elements, as well as B, Mg, Ca, Na and K, all of which are elements associated with life as we know it. With its highly favorable sulfur abundance and land/ocean ratio, early wet Mars remains a prime candidate for its own OoL, in many respects superior to Earth. The relatively well-preserved ancient surface of planet Mars helps inform the range of possible analogous conditions during the now-obliterated history of early Earth. Continued exploration of Mars also contributes to the understanding of the opportunities for settings enabling an OoL on exoplanets. Favoring geochemical sediment samples for eventual return to Earth will enhance assessments of the likelihood of a Martian OoL.
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Affiliation(s)
| | - Vera M. Kolb
- Department of Chemistry, University of Wisconsin—Parkside, Kenosha, WI 53141, USA;
| | - Andrew Steele
- Earth and Planetary Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA;
| | - Christopher H. House
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, State College, PA 16807, USA;
| | - Nina L. Lanza
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (N.L.L.); (P.J.G.)
| | - Patrick J. Gasda
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (N.L.L.); (P.J.G.)
| | - Scott J. VanBommel
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA;
| | - Horton E. Newsom
- Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 88033, USA;
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22
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Murphy CL, Biggerstaff J, Eichhorn A, Ewing E, Shahan R, Soriano D, Stewart S, VanMol K, Walker R, Walters P, Elshahed MS, Youssef NH. Genomic characterization of three novel Desulfobacterota classes expand the metabolic and phylogenetic diversity of the phylum. Environ Microbiol 2021; 23:4326-4343. [PMID: 34056821 DOI: 10.1111/1462-2920.15614] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/24/2021] [Accepted: 05/27/2021] [Indexed: 12/01/2022]
Abstract
We report on the genomic characterization of three novel classes in the phylum Desulfobacterota. One class (proposed name Candidatus 'Anaeroferrophillalia') was characterized by heterotrophic growth capacity, either fermentatively or utilizing polysulfide, tetrathionate or thiosulfate as electron acceptors. In the absence of organic carbon sources, autotrophic growth via the Wood-Ljungdahl (WL) pathway and using hydrogen or Fe(II) as an electron donor is also inferred for members of the 'Anaeroferrophillalia'. The second class (proposed name Candidatus 'Anaeropigmentia') was characterized by its capacity for growth at low oxygen concentration, and the capacity to synthesize the methyl/alkyl carrier CoM, an ability that is prevalent in the archaeal but rare in the bacterial domain. Pigmentation is inferred from the capacity for carotenoid (lycopene) production. The third class (proposed name Candidatus 'Zymogenia') was characterized by fermentative heterotrophic growth capacity, broad substrate range and the adaptation of some of its members to hypersaline habitats. Analysis of the distribution pattern of all three classes showed their occurrence as rare community members in multiple habitats, with preferences for anaerobic terrestrial, freshwater and marine environments over oxygenated (e.g. pelagic ocean and agricultural land) settings. Special preference for some members of the class Candidatus 'Zymogenia' for hypersaline environments such as hypersaline microbial mats and lagoons was observed.
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Affiliation(s)
- Chelsea L Murphy
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - James Biggerstaff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Alexis Eichhorn
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Essences Ewing
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Ryan Shahan
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Diana Soriano
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Sydney Stewart
- Department of Animal Sciences, Oklahoma State University, Stillwater, OK, USA
| | - Kaitlynn VanMol
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Ross Walker
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Payton Walters
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Mostafa S Elshahed
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
| | - Noha H Youssef
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA
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23
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Green NJ, Xu J, Sutherland JD. Illuminating Life's Origins: UV Photochemistry in Abiotic Synthesis of Biomolecules. J Am Chem Soc 2021; 143:7219-7236. [PMID: 33880920 PMCID: PMC8240947 DOI: 10.1021/jacs.1c01839] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Indexed: 01/15/2023]
Abstract
Solar radiation is the principal source of energy available to Earth and has unmatched potential for the synthesis of organic material from primordial molecular building blocks. As well as providing the energy for photochemical synthesis of (proto)biomolecules of interest in origins of life-related research, light has also been found to often provide remarkable selectivity in these processes, for molecules that function in extant biology and against those that do not. As such, light is heavily implicated as an environmental input on the nascent Earth that was important for the emergence of complex yet selective chemical systems underpinning life. Reactivity and selectivity in photochemical prebiotic synthesis are discussed, as are their implications for origins of life scenarios and their plausibility, and the future directions of this research.
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Affiliation(s)
- Nicholas J. Green
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge
Biomedical Campus, Cambridge CB2 0QH, U.K.
| | - Jianfeng Xu
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge
Biomedical Campus, Cambridge CB2 0QH, U.K.
| | - John D. Sutherland
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge
Biomedical Campus, Cambridge CB2 0QH, U.K.
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24
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Banfalvi G. Prebiotic Pathway from Ribose to RNA Formation. Int J Mol Sci 2021; 22:ijms22083857. [PMID: 33917807 PMCID: PMC8068141 DOI: 10.3390/ijms22083857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/31/2021] [Accepted: 04/06/2021] [Indexed: 01/12/2023] Open
Abstract
At the focus of abiotic chemical reactions is the synthesis of ribose. No satisfactory explanation was provided as to the missing link between the prebiotic synthesis of ribose and prebiotic RNA (preRNA). Hydrogen cyanide (HCN) is assumed to have been the principal precursor in the prebiotic formation of aldopentoses in the formose reaction and in the synthesis of ribose. Ribose as the best fitting aldopentose became the exclusive sugar component of RNA. The elevated yield of ribose synthesis at higher temperatures and its protection from decomposition could have driven the polymerization of the ribose-phosphate backbone and the coupling of nucleobases to the backbone. RNA could have come into being without the involvement of nucleotide precursors. The first nucleoside monophosphate is likely to have appeared upon the hydrolysis of preRNA contributed by the presence of reactive 2′-OH moieties in the preRNA chain. As a result of phosphorylation, nucleoside monophosphates became nucleoside triphosphates, substrates for the selective synthesis of genRNA.
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Affiliation(s)
- Gaspar Banfalvi
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, 1 Egyetem Square, 4010 Debrecen, Hungary
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Clark BC, Kolb VM. Macrobiont: Cradle for the Origin of Life and Creation of a Biosphere. Life (Basel) 2020; 10:life10110278. [PMID: 33198206 PMCID: PMC7697624 DOI: 10.3390/life10110278] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 11/09/2020] [Accepted: 11/09/2020] [Indexed: 02/06/2023] Open
Abstract
Although the cellular microorganism is the fundamental unit of biology, the origin of life (OoL) itself is unlikely to have occurred in a microscale environment. The macrobiont (MB) is the macro-scale setting where life originated. Guided by the methodologies of Systems Analysis, we focus on subaerial ponds of scale 3 to 300 m diameter. Within such ponds, there can be substantial heterogeneity, on the vertical, horizontal, and temporal scales, which enable multi-pot prebiotic chemical evolution. Pond size-sensitivities for several figures of merit are mathematically formulated, leading to the expectation that the optimum pond size for the OoL is intermediate, but biased toward smaller sizes. Sensitivities include relative access to nutrients, energy sources, and catalysts, as sourced from geological, atmospheric, hydrospheric, and astronomical contributors. Foreshores, especially with mudcracks, are identified as a favorable component for the success of the macrobiont. To bridge the gap between inanimate matter and a planetary-scale biosphere, five stages of evolution within the macrobiont are hypothesized: prebiotic chemistry → molecular replicator → protocell → macrobiont cell → colonizer cell. Comparison of ponds with other macrobionts, including hydrothermal and meteorite settings, allows a conclusion that more than one possible macrobiont locale could enable an OoL.
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Affiliation(s)
- Benton C. Clark
- Space Science Institute, Boulder, CO 80301, USA
- Correspondence:
| | - Vera M. Kolb
- Department of Chemistry, University of Wisconsin—Parkside, Kenosha, WI 53141, USA;
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Li Y, Li Y, Liu Y, Wu Y, Wu J, Wang B, Ye H, Jia H, Wang X, Li L, Zhu M, Ding H, Lai Y, Wang C, Dick J, Lu A. Photoreduction of inorganic carbon(+IV) by elemental sulfur: Implications for prebiotic synthesis in terrestrial hot springs. SCIENCE ADVANCES 2020; 6:6/47/eabc3687. [PMID: 33208363 PMCID: PMC7673799 DOI: 10.1126/sciadv.abc3687] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
Terrestrial hydrothermal systems have been proposed as alternative birthplaces for early life but lacked reasonable scenarios for the supply of biomolecules. Here, we show that elemental sulfur (S0), as the dominant mineral in terrestrial hot springs, can reduce carbon dioxide (CO2) into formic acid (HCOOH) under ultraviolet (UV) light below 280 nm. The semiconducting S0 is indicated to have a direct bandgap of 4.4 eV. The UV-excited S0 produces photoelectrons with a highly negative potential of -2.34 V (versus NHE, pH 7), which could reduce CO2 after accepting electrons from electron donors such as reducing sulfur species. Simultaneously, UV light breaks sulfur bonds, benefiting the adsorption of charged carbonates onto S0 and assisting their photoreduction. Assuming that terrestrial hot springs covered 1% of primitive Earth's surface, S0 at 10 μM could have produced maximal 109 kg/year HCOOH within 10-cm-thick photic zones, underlying its remarkable contributions to the accumulation of prebiotic biomolecules.
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Affiliation(s)
- Yanzhang Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yan Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yi Liu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yifu Wu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Junqi Wu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Bin Wang
- Sinopec Beijing Research Institute of Chemical Industry, Beijing 100013, People's Republic of China
| | - Huan Ye
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Haoning Jia
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Xiao Wang
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Linghui Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Meixiang Zhu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Hongrui Ding
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yong Lai
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Changqiu Wang
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Jeffrey Dick
- The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, People's Republic of China
| | - Anhuai Lu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, People's Republic of China
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Bolton SG, Pluth MD. Modified cyclodextrins solubilize elemental sulfur in water and enable biological sulfane sulfur delivery. Chem Sci 2020; 11:11777-11784. [PMID: 34123204 PMCID: PMC8162768 DOI: 10.1039/d0sc04137h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
An important form of biological sulfur is sulfane sulfur, or S0, which is found in polysulfide and persulfide compounds as well as in elemental sulfur. Sulfane sulfur, often in the form of S8, functions as a key energy source in the metabolic processes of thermophilic Archaean organisms found in sulfur-rich environments and can be metabolized both aerobically and anaerobically by different archaeons. Despite this importance, S8 has a low solubility in water (∼19 nM), raising questions of how it can be made chemically accessible in complex environments. Motivated by prior crystallographic data showing S8 binding to hydrophobic motifs in filamentous glycoproteins from the sulfur reducing Staphylothermus marinus anaerobe, we demonstrate that simple macrocyclic hydrophobic motifs, such as 2-hydroxypropyl β-cyclodextrin (2HPβ), are sufficient to solubilize S8 at concentrations up to 2.0 ± 0.2 mM in aqueous solution. We demonstrate that the solubilized S8 can be reduced with the common reductant tris(2-carboxyethyl)phosphine (TCEP) and reacts with thiols to generate H2S. The thiol-mediated conversion of 2HPβ/S8 to H2S ranges from 80% to quantitative efficiency for Cys and glutathione (GSH). Moreover, we demonstrate that 2HPβ can catalyze the Cys-mediated reduction of S8 to H2S in water. Adding to the biological relevance of the developed systems, we demonstrate that treatment of Raw 264.7 macrophage cells with the 2HPβ/S8 complex prior to LPS stimulation decreases NO2 - levels, which is consistent with known activities of bioavailable H2S and sulfane sulfur. Taken together, these investigations provide a new strategy for delivering H2S and sulfane sulfur in complex systems and more importantly provide new insights into the chemical accessibility and storage of S0 and S8 in biological environments.
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Affiliation(s)
- Sarah G Bolton
- Department of Chemistry and Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, Institute of Molecular Biology, University of Oregon Eugene OR 97403 USA
| | - Michael D Pluth
- Department of Chemistry and Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, Institute of Molecular Biology, University of Oregon Eugene OR 97403 USA
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Kovalenko SP. Physicochemical Processes That Probably Originated Life. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162020040093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Neubeck A, Freund F. Sulfur Chemistry May Have Paved the Way for Evolution of Antioxidants. ASTROBIOLOGY 2020; 20:670-675. [PMID: 31880469 PMCID: PMC7232690 DOI: 10.1089/ast.2019.2156] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The first organisms on the young Earth, just 1-1.5 billion years old, were likely chemolithoautotrophic anaerobes, thriving in an anoxic world rich in water, CO2, and N2. It is generally assumed that, until the accumulation of O2 in the atmosphere, life was exempted from the oxidative stress that reactive oxygen species (ROS) impose on hydrocarbon-based life. Therefore, it is perplexing to note that life on the early Earth already carried antioxidants such as superoxide dismutase enzymes, catalase, and peroxiredoxins, the function of which is to counteract all forms of ROS, including H2O2. Phylogenetic investigations suggest that the presence of these enzymes in the last universal common ancestor, far predating the great oxygenation event (GOE) sometime between 2.3 and 2.7 billion years ago, is thought to be due to the appearance of oxygen-producing microorganisms and the subsequent need to respond to the appearance of ROS. Since the metabolic enzymes that counteract ROS have been found in all domains of life, they are considered of primitive origin. Two questions arise: (1) Could there be a nonbiological source of ROS that predates the oxygenic microbial activity? (2) Could sulfur, the homologue of oxygen, have played that role? Reactive sulfur species (RSS) may have triggered the evolution of antioxidants such that the ROS antioxidants started out as "antisulfur" enzymes developed to cope with, and take advantage of, various forms of RSS that were abundantly present on the early Earth.
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Affiliation(s)
- Anna Neubeck
- Department of Palaeobiology, Uppsala University, Uppsala, Sweden
- Address correspondence to: Anna Neubeck, Department of Palaeobiology, Uppsala University, Geocentrum, Villavägen 16, SE-752 36 Uppsala, Sweden
| | - Friedemann Freund
- Space Biosciences Research (Code SCR), NASA Ames Research Center, Mountain View, California
- SETI Institute, Carl Sagan Center, Mountain View, California
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Colman DR, Lindsay MR, Amenabar MJ, Fernandes-Martins MC, Roden ER, Boyd ES. Phylogenomic analysis of novel Diaforarchaea is consistent with sulfite but not sulfate reduction in volcanic environments on early Earth. THE ISME JOURNAL 2020; 14:1316-1331. [PMID: 32066874 PMCID: PMC7174415 DOI: 10.1038/s41396-020-0611-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/28/2020] [Accepted: 02/04/2020] [Indexed: 12/27/2022]
Abstract
The origin(s) of dissimilatory sulfate and/or (bi)sulfite reducing organisms (SRO) remains enigmatic despite their importance in global carbon and sulfur cycling since at least 3.4 Ga. Here, we describe novel, deep-branching archaeal SRO populations distantly related to other Diaforarchaea from two moderately acidic thermal springs. Dissimilatory (bi)sulfite reductase homologs, DsrABC, encoded in metagenome assembled genomes (MAGs) from spring sediments comprise one of the earliest evolving Dsr lineages. DsrA homologs were expressed in situ under moderately acidic conditions. MAGs lacked genes encoding proteins that activate sulfate prior to (bi)sulfite reduction. This is consistent with sulfide production in enrichment cultures provided sulfite but not sulfate. We suggest input of volcanic sulfur dioxide to anoxic spring-water yields (bi)sulfite and moderately acidic conditions that favor its stability and bioavailability. The presence of similar volcanic springs at the time SRO are thought to have originated (>3.4 Ga) may have supplied (bi)sulfite that supported ancestral SRO. These observations coincide with the lack of inferred SO42- reduction capacity in nearly all organisms with early-branching DsrAB and which are near universally found in hydrothermal environments.
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Affiliation(s)
- Daniel R Colman
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT, 59717, USA
| | - Melody R Lindsay
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT, 59717, USA
| | - Maximiliano J Amenabar
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT, 59717, USA
| | | | - Eric R Roden
- Department of Geoscience, University of Wisconsin, Madison, WI, USA
- NASA Astrobiology Institute, Mountain View, CA, USA
| | - Eric S Boyd
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT, 59717, USA.
- NASA Astrobiology Institute, Mountain View, CA, USA.
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31
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Becker S, Feldmann J, Wiedemann S, Okamura H, Schneider C, Iwan K, Crisp A, Rossa M, Amatov T, Carell T. Unified prebiotically plausible synthesis of pyrimidine and purine RNA ribonucleotides. Science 2020; 366:76-82. [PMID: 31604305 DOI: 10.1126/science.aax2747] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/21/2019] [Accepted: 08/21/2019] [Indexed: 12/15/2022]
Abstract
Theories about the origin of life require chemical pathways that allow formation of life's key building blocks under prebiotically plausible conditions. Complex molecules like RNA must have originated from small molecules whose reactivity was guided by physico-chemical processes. RNA is constructed from purine and pyrimidine nucleosides, both of which are required for accurate information transfer, and thus Darwinian evolution. Separate pathways to purines and pyrimidines have been reported, but their concurrent syntheses remain a challenge. We report the synthesis of the pyrimidine nucleosides from small molecules and ribose, driven solely by wet-dry cycles. In the presence of phosphate-containing minerals, 5'-mono- and diphosphates also form selectively in one-pot reactions. The pathway is compatible with purine synthesis, allowing the concurrent formation of all Watson-Crick bases.
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Affiliation(s)
- Sidney Becker
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.,Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Jonas Feldmann
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany
| | - Stefan Wiedemann
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany
| | - Hidenori Okamura
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.,Institute for Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Christina Schneider
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany
| | - Katharina Iwan
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.,Centre for Translational Omics, University College London, Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Antony Crisp
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany
| | - Martin Rossa
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany
| | - Tynchtyk Amatov
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.,Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Thomas Carell
- Center for Integrated Protein Science, Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.
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32
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Recent Results on Computational Molecular Modeling of The Origins of Life. FOUNDATIONS OF COMPUTING AND DECISION SCIENCES 2020. [DOI: 10.2478/fcds-2020-0003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
In the last decade of research in the origins of life, there has been an increase in the interest on theoretical molecular modeling methods aimed to improve the accuracy and speed of the algorithms that solve the molecular mechanics and chemical reactions of the matter. Research on the scenarios of prebiotic chemistry has also advanced. The presented work attempts to discuss the latest computational techniques and trends implemented so far. Although it is difficult to cover the full extent of the current publications, we tried to orient the reader into the modern tendencies and challenges faced by those who are in the origins of life field.
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Nunn AVW, Guy GW, Botchway SW, Bell JD. From sunscreens to medicines: Can a dissipation hypothesis explain the beneficial aspects of many plant compounds? Phytother Res 2020; 34:1868-1888. [PMID: 32166791 PMCID: PMC7496984 DOI: 10.1002/ptr.6654] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 01/16/2020] [Accepted: 02/16/2020] [Indexed: 12/17/2022]
Abstract
Medicine has utilised plant‐based treatments for millennia, but precisely how they work is unclear. One approach is to use a thermodynamic viewpoint that life arose by dissipating geothermal and/or solar potential. Hence, the ability to dissipate energy to maintain homeostasis is a fundamental principle in all life, which can be viewed as an accretion system where layers of complexity have built upon core abiotic molecules. Many of these compounds are chromophoric and are now involved in multiple pathways. Plants have further evolved a plethora of chromophoric compounds that can not only act as sunscreens and redox modifiers, but also have now become integrated into a generalised stress adaptive system. This could be an extension of the dissipative process. In animals, many of these compounds are hormetic, modulating mitochondria and calcium signalling. They can also display anti‐pathogen effects. They could therefore modulate bioenergetics across all life due to the conserved electron transport chain and proton gradient. In this review paper, we focus on well‐described medicinal compounds, such as salicylic acid and cannabidiol and suggest, at least in animals, their activity reflects their evolved function in plants in relation to stress adaptation, which itself evolved to maintain dissipative homeostasis.
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Affiliation(s)
- Alistair V W Nunn
- Research Centre for Optimal Health, Department of Life Sciences, University of Westminster, London, UK
| | | | - Stanley W Botchway
- STFC, UKRI & Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Jimmy D Bell
- Research Centre for Optimal Health, Department of Life Sciences, University of Westminster, London, UK
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Sasselov DD, Grotzinger JP, Sutherland JD. The origin of life as a planetary phenomenon. SCIENCE ADVANCES 2020; 6:eaax3419. [PMID: 32076638 PMCID: PMC7002131 DOI: 10.1126/sciadv.aax3419] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 11/22/2019] [Indexed: 05/03/2023]
Abstract
We advocate an integrative approach between laboratory experiments in prebiotic chemistry and geologic, geochemical, and astrophysical observations to help assemble a robust chemical pathway to life that can be reproduced in the laboratory. The cyanosulfidic chemistry scenario described here was developed by such an integrative iterative process. We discuss how it maps onto evolving planetary surface environments on early Earth and Mars and the value of comparative planetary evolution. The results indicate that Mars can offer direct evidence for geochemical conditions similar to prebiotic Earth, whose early record has been erased. The Jezero crater is now the chosen landing site for NASA's Mars 2020 rover, making this an extraordinary opportunity for a breakthrough in understanding life's origins.
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Affiliation(s)
- Dimitar D. Sasselov
- Department of Astronomy, Harvard University, 60 Garden St., Cambridge, MA 02138, USA
- Corresponding author.
| | - John P. Grotzinger
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - John D. Sutherland
- MRC Laboratory of Molecular Biology, Francis Crick Ave., Cambridge CB2 0QH, UK
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Toner JD, Catling DC. A carbonate-rich lake solution to the phosphate problem of the origin of life. Proc Natl Acad Sci U S A 2020; 117:883-888. [PMID: 31888981 PMCID: PMC6969521 DOI: 10.1073/pnas.1916109117] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Phosphate is central to the origin of life because it is a key component of nucleotides in genetic molecules, phospholipid cell membranes, and energy transfer molecules such as adenosine triphosphate. To incorporate phosphate into biomolecules, prebiotic experiments commonly use molar phosphate concentrations to overcome phosphate's poor reactivity with organics in water. However, phosphate is generally limited to micromolar levels in the environment because it precipitates with calcium as low-solubility apatite minerals. This disparity between laboratory conditions and environmental constraints is an enigma known as "the phosphate problem." Here we show that carbonate-rich lakes are a marked exception to phosphate-poor natural waters. In principle, modern carbonate-rich lakes could accumulate up to ∼0.1 molal phosphate under steady-state conditions of evaporation and stream inflow because calcium is sequestered into carbonate minerals. This prevents the loss of dissolved phosphate to apatite precipitation. Even higher phosphate concentrations (>1 molal) can form during evaporation in the absence of inflows. On the prebiotic Earth, carbonate-rich lakes were likely abundant and phosphate-rich relative to the present day because of the lack of microbial phosphate sinks and enhanced chemical weathering of phosphate minerals under relatively CO2-rich atmospheres. Furthermore, the prevailing CO2 conditions would have buffered phosphate-rich brines to moderate pH (pH 6.5 to 9). The accumulation of phosphate and other prebiotic reagents at concentration and pH levels relevant to experimental prebiotic syntheses of key biomolecules is a compelling reason to consider carbonate-rich lakes as plausible settings for the origin of life.
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Affiliation(s)
- Jonathan D Toner
- Department of Earth & Space Sciences, University of Washington, Seattle, WA 98195
| | - David C Catling
- Department of Earth & Space Sciences, University of Washington, Seattle, WA 98195
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36
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Prebiotic Soup Components Trapped in Montmorillonite Nanoclay Form New Molecules: Car-Parrinello Ab Initio Simulations. Life (Basel) 2019; 9:life9020046. [PMID: 31167366 PMCID: PMC6617125 DOI: 10.3390/life9020046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/30/2019] [Accepted: 05/30/2019] [Indexed: 01/08/2023] Open
Abstract
The catalytic effects of complex minerals or meteorites are often mentioned as important factors for the origins of life. To assess the possible role of nanoconfinement within a catalyst consisting of montmorillonite (MMT) and the impact of local electric field on the formation efficiency of the simple hypothetical precursors of nucleic acid bases or amino acids, we performed ab initio Car–Parrinello molecular dynamics simulations. We prepared four condensed-phase systems corresponding to previously suggested prototypes of a primordial soup. We monitored possible chemical reactions occurring within gas-like bulk and MMT-confined four simulation boxes on a 20-ps time scale at 1 atm and 300 K, 400 K, and 600 K. Elevated temperatures did not affect the reactivity of the elementary components of the gas-like boxes considerably; however, the presence of the MMT nanoclay substantially increased the formation probability of new molecules. Approximately 20 different new compounds were found in boxes containing carbon monoxide or formaldehyde molecules. This observation and an analysis of the atom–atom radial distribution functions indicated that the presence of Ca2+ ions at the surface of the internal MMT cavities may be an important factor in the initial steps of the formation of complex molecules at the early stages of the Earth’s history.
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Rimmer PB, Shorttle O. Origin of Life's Building Blocks in Carbon- and Nitrogen-Rich Surface Hydrothermal Vents. Life (Basel) 2019; 9:E12. [PMID: 30682803 PMCID: PMC6463091 DOI: 10.3390/life9010012] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 01/15/2019] [Accepted: 01/19/2019] [Indexed: 11/16/2022] Open
Abstract
There are two dominant and contrasting classes of origin of life scenarios: those predicting that life emerged in submarine hydrothermal systems, where chemical disequilibrium can provide an energy source for nascent life; and those predicting that life emerged within subaerial environments, where UV catalysis of reactions may occur to form the building blocks of life. Here, we describe a prebiotically plausible environment that draws on the strengths of both scenarios: surface hydrothermal vents. We show how key feedstock molecules for prebiotic chemistry can be produced in abundance in shallow and surficial hydrothermal systems. We calculate the chemistry of volcanic gases feeding these vents over a range of pressures and basalt C/N/O contents. If ultra-reducing carbon-rich nitrogen-rich gases interact with subsurface water at a volcanic vent they result in 10 - 3 ⁻ 1 M concentrations of diacetylene (C₄H₂), acetylene (C₂H₂), cyanoacetylene (HC₃N), hydrogen cyanide (HCN), bisulfite (likely in the form of salts containing HSO₃-), hydrogen sulfide (HS-) and soluble iron in vent water. One key feedstock molecule, cyanamide (CH₂N₂), is not formed in significant quantities within this scenario, suggesting that it may need to be delivered exogenously, or formed from hydrogen cyanide either via organometallic compounds, or by some as yet-unknown chemical synthesis. Given the likely ubiquity of surface hydrothermal vents on young, hot, terrestrial planets, these results identify a prebiotically plausible local geochemical environment, which is also amenable to future lab-based simulation.
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Affiliation(s)
- Paul B Rimmer
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
- Cavendish Astrophysics, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, UK.
- MRC Laboratory of Molecular Biology, Francis Crick Ave, Cambridge CB2 0QH, UK.
| | - Oliver Shorttle
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
- Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK.
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Biscans A. Exploring the Emergence of RNA Nucleosides and Nucleotides on the Early Earth. Life (Basel) 2018; 8:life8040057. [PMID: 30404133 PMCID: PMC6316623 DOI: 10.3390/life8040057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 10/31/2018] [Accepted: 11/03/2018] [Indexed: 01/02/2023] Open
Abstract
Understanding how life began is one of the most fascinating problems to solve. By approaching this enigma from a chemistry perspective, the goal is to define what series of chemical reactions could lead to the synthesis of nucleotides, amino acids, lipids, and other cellular components from simple feedstocks under prebiotically plausible conditions. It is well established that evolution of life involved RNA which plays central roles in both inheritance and catalysis. In this review, we present historically important and recently published articles aimed at understanding the emergence of RNA nucleosides and nucleotides on the early Earth.
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Affiliation(s)
- Annabelle Biscans
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, 01605 MA, USA.
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39
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Exposed Areas Above Sea Level on Earth >3.5 Gyr Ago: Implications for Prebiotic and Primitive Biotic Chemistry. Life (Basel) 2018; 8:life8040055. [PMID: 30400350 PMCID: PMC6316429 DOI: 10.3390/life8040055] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 11/01/2018] [Accepted: 11/01/2018] [Indexed: 01/19/2023] Open
Abstract
How life began on Earth is still largely shrouded in mystery. One of the central ideas for various origins of life scenarios is Darwin’s “warm little pond”. In these small bodies of water, simple prebiotic compounds such as amino acids, nucleobases, and so on, were produced from reagents such as hydrogen cyanide and aldehydes/ketones. These simple prebiotic compounds underwent further reactions, producing more complex molecules. The process of chemical evolution would have produced increasingly complex molecules, eventually yielding a molecule with the properties of information storage and replication prone to random mutations, the hallmark of both the origin of life and evolution. However, there is one problematic issue with this scenario: On the Earth >3.5 Gyr ago there would have likely been no exposed continental crust above sea level. The only land areas that protruded out of the oceans would have been associated with hotspot volcanic islands, such as the Hawaiian island chain today. On these long-lived islands, in association with reduced gas-rich eruptions accompanied by intense volcanic lightning, prebiotic reagents would have been produced that accumulated in warm or cool little ponds and lakes on the volcano flanks. During seasonal wet–dry cycles, molecules with increasing complexity could have been produced. These islands would have thus been the most likely places for chemical evolution and the processes associated with the origin of life. The islands would eventually be eroded away and their chemical evolution products would have been released into the oceans where Darwinian evolution ultimately produced the biochemistry associated with all life on Earth today.
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40
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Selective prebiotic conversion of pyrimidine and purine anhydronucleosides into Watson-Crick base-pairing arabino-furanosyl nucleosides in water. Nat Commun 2018; 9:4073. [PMID: 30287815 PMCID: PMC6172253 DOI: 10.1038/s41467-018-06374-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 08/31/2018] [Indexed: 01/11/2023] Open
Abstract
Prebiotic nucleotide synthesis is crucial to understanding the origins of life on Earth. There are numerous candidates for life's first nucleic acid, however, currently no prebiotic method to selectively and concurrently synthesise the canonical Watson-Crick base-pairing pyrimidine (C, U) and purine (A, G) nucleosides exists for any genetic polymer. Here, we demonstrate the divergent prebiotic synthesis of arabinonucleic acid (ANA) nucleosides. The complete set of canonical nucleosides is delivered from one reaction sequence, with regiospecific glycosidation and complete furanosyl selectivity. We observe photochemical 8-mercaptopurine reduction is efficient for the canonical purines (A, G), but not the non-canonical purine inosine (I). Our results demonstrate that synthesis of ANA may have been facile under conditions that comply with plausible geochemical environments on early Earth and, given that ANA is capable of encoding RNA/DNA compatible information and evolving to yield catalytic ANA-zymes, ANA may have played a critical role during the origins of life.
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Clark BC, Kolb VM. Comet Pond II: Synergistic Intersection of Concentrated Extraterrestrial Materials and Planetary Environments to Form Procreative Darwinian Ponds. Life (Basel) 2018; 8:E12. [PMID: 29751593 PMCID: PMC6027224 DOI: 10.3390/life8020012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/24/2018] [Accepted: 05/02/2018] [Indexed: 12/12/2022] Open
Abstract
In the “comet pond” model, a rare combination of circumstances enables the entry and landing of pristine organic material onto a planetary surface with the creation of a pond by a soft impact and melting of entrained ices. Formation of the constituents of the comet in the cold interstellar medium and our circumstellar disk results in multiple constituents at disequilibrium which undergo rapid chemical reactions in the warmer, liquid environment. The planetary surface also provides minerals and atmospheric gases which chemically interact with the pond’s organic- and trace-element-rich constituents. Pond physical morphology and the heterogeneities imposed by gravitational forces (bottom sludge; surface scum) and weather result in a highly heterogeneous variety of macro- and microenvironments. Wet/dry, freeze/thaw, and natural chromatography processes further promote certain reaction sequences. Evaporation concentrates organics less volatile than water. Freezing concentrates all soluble organics into a residual liquid phase, including CH₃OH, HCN, etc. The pond’s evolutionary processes culminate in the creation of a Macrobiont with the metabolically equivalent capabilities of energy transduction and replication of RNA (or its progenitor informational macromolecule), from which smaller organisms can emerge. Planet-wide dispersal of microorganisms is achieved through wind transport, groundwater, and/or spillover from the pond into surface hydrologic networks.
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Affiliation(s)
- Benton C Clark
- Research Branch, Space Science Institute, Boulder, CO 80201, USA.
| | - Vera M Kolb
- Department of Chemistry, University of Wisconsin⁻Parkside, Kenosha, WI 53141, USA.
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