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Paschek K, Lee M, Semenov DA, Henning TK. Prebiotic Vitamin B 3 Synthesis in Carbonaceous Planetesimals. Chempluschem 2024; 89:e202300508. [PMID: 37847591 DOI: 10.1002/cplu.202300508] [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: 09/08/2023] [Revised: 10/11/2023] [Accepted: 10/12/2023] [Indexed: 10/19/2023]
Abstract
Aqueous chemistry within carbonaceous planetesimals is promising for synthesizing prebiotic organic matter essential to all life. Meteorites derived from these planetesimals delivered these life building blocks to the early Earth, potentially facilitating the origins of life. Here, we studied the formation of vitamin B3 as it is an important precursor of the coenzyme NAD(P)(H), which is essential for the metabolism of all life as we know it. We propose a new reaction mechanism based on known experiments in the literature that explains the synthesis of vitamin B3. It combines the sugar precursors glyceraldehyde or dihydroxyacetone with the amino acids aspartic acid or asparagine in aqueous solution without oxygen or other oxidizing agents. We performed thermochemical equilibrium calculations to test the thermodynamic favorability. The predicted vitamin B3 abundances resulting from this new pathway were compared with measured values in asteroids and meteorites. We conclude that competition for reactants and decomposition by hydrolysis are necessary to explain the prebiotic content of meteorites. In sum, our model fits well into the complex network of chemical pathways active in this environment.
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Affiliation(s)
- Klaus Paschek
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany
| | - Mijin Lee
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany
| | - Dmitry A Semenov
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany
- Department of Chemistry, Ludwig Maximilian University of Munich, Butenandtstraße 5-13, House F, D-81377, Munich, Germany
| | - Thomas K Henning
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany
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2
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Hart R, Cardace D. Mineral Indicators of Geologically Recent Past Habitability on Mars. Life (Basel) 2023; 13:2349. [PMID: 38137950 PMCID: PMC10744562 DOI: 10.3390/life13122349] [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: 10/07/2023] [Revised: 11/25/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
We provide new support for habitable microenvironments in the near-subsurface of Mars, hosted in Fe- and Mg-rich rock units, and present a list of minerals that can serve as indicators of specific water-rock reactions in recent geologic paleohabitats for follow-on study. We modeled, using a thermodynamic basis without selective phase suppression, the reactions of published Martian meteorites and Jezero Crater igneous rock compositions and reasonable planetary waters (saline, alkaline waters) using Geochemist's Workbench Ver. 12.0. Solid-phase inputs were meteorite compositions for ALH 77005, Nakhla, and Chassigny, and two rock units from the Mars 2020 Perseverance rover sites, Máaz and Séítah. Six plausible Martian groundwater types [NaClO4, Mg(ClO4)2, Ca(ClO4)2, Mg-Na2(ClO4)2, Ca-Na2(ClO4)2, Mg-Ca(ClO4)2] and a unique Mars soil-water analog solution (dilute saline solution) named "Rosy Red", related to the Phoenix Lander mission, were the aqueous-phase inputs. Geophysical conditions were tuned to near-subsurface Mars (100 °C or 373.15 K, associated with residual heat from a magmatic system, impact event, or a concentration of radionuclides, and 101.3 kPa, similar to <10 m depth). Mineral products were dominated by phyllosilicates such as serpentine-group minerals in most reaction paths, but differed in some important indicator minerals. Modeled products varied in physicochemical properties (pH, Eh, conductivity), major ion activities, and related gas fugacities, with different ecological implications. The microbial habitability of pore spaces in subsurface groundwater percolation systems was interrogated at equilibrium in a thermodynamic framework, based on Gibbs Free Energy Minimization. Models run with the Chassigny meteorite produced the overall highest H2 fugacity. Models reliant on the Rosy Red soil-water analog produced the highest sustained CH4 fugacity (maximum values observed for reactant ALH 77005). In general, Chassigny meteorite protoliths produced the best yield regarding Gibbs Free Energy, from an astrobiological perspective. Occurrences of serpentine and saponite across models are key: these minerals have been observed using CRISM spectral data, and their formation via serpentinization would be consistent with geologically recent-past H2 and CH4 production and sustained energy sources for microbial life. We list index minerals to be used as diagnostic for paleo water-rock models that could have supported geologically recent-past microbial activity, and suggest their application as criteria for future astrobiology study-site selections.
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Affiliation(s)
- Roger Hart
- Department of Physics and Engineering, Community College of Rhode Island, Lincoln, RI 02865, USA
- Department of Geosciences, University of Rhode Island, Kingston, RI 02881, USA;
| | - Dawn Cardace
- Department of Geosciences, University of Rhode Island, Kingston, RI 02881, USA;
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3
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Choe JC. Mechanism of Prebiotic Uracil Synthesis from Urea and HC 3O + in Space. ASTROBIOLOGY 2022; 22:1363-1369. [PMID: 36194055 DOI: 10.1089/ast.2022.0024] [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: 06/16/2023]
Abstract
The potential energy surface for the formation of protonated uracil (UH+) from urea and HC3O+ was explored by performing quantum chemical complete basis set-QB3 calculations. A barrierless pathway was found for the formation of UH+, which was estimated to occur in the interstellar medium (ISM) much faster than the timescale of chemical revolution of typical dense interstellar clouds. Investigation of further reactions of UH+ formed through the obtained pathway led to the conclusion that uracil could be produced on icy grain surfaces but not in the gas phase of the ISM.
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Affiliation(s)
- Joong Chul Choe
- Department of Chemistry, Dongguk University-Seoul, Seoul, Korea
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4
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Paschek K, Kohler K, Pearce BKD, Lange K, Henning TK, Trapp O, Pudritz RE, Semenov DA. Possible Ribose Synthesis in Carbonaceous Planetesimals. Life (Basel) 2022; 12:404. [PMID: 35330155 PMCID: PMC8955445 DOI: 10.3390/life12030404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/02/2022] [Accepted: 03/05/2022] [Indexed: 12/03/2022] Open
Abstract
The origin of life might be sparked by the polymerization of the first RNA molecules in Darwinian ponds during wet-dry cycles. The key life-building block ribose was found in carbonaceous chondrites. Its exogenous delivery onto the Hadean Earth could be a crucial step toward the emergence of the RNA world. Here, we investigate the formation of ribose through a simplified version of the formose reaction inside carbonaceous chondrite parent bodies. Following up on our previous studies regarding nucleobases with the same coupled physico-chemical model, we calculate the abundance of ribose within planetesimals of different sizes and heating histories. We perform laboratory experiments using catalysts present in carbonaceous chondrites to infer the yield of ribose among all pentoses (5Cs) forming during the formose reaction. These laboratory yields are used to tune our theoretical model that can only predict the total abundance of 5Cs. We found that the calculated abundances of ribose were similar to the ones measured in carbonaceous chondrites. We discuss the possibilities of chemical decomposition and preservation of ribose and derived constraints on time and location in planetesimals. In conclusion, the aqueous formose reaction might produce most of the ribose in carbonaceous chondrites. Together with our previous studies on nucleobases, we found that life-building blocks of the RNA world could be synthesized inside parent bodies and later delivered onto the early Earth.
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Affiliation(s)
- Klaus Paschek
- Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; (K.K.); (T.K.H.); (O.T.); (D.A.S.)
| | - Kai Kohler
- Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; (K.K.); (T.K.H.); (O.T.); (D.A.S.)
- Department of Chemistry, Ludwig-Maximilians-University Munich, Butenandtstr. 5-13, House F, 81377 Munich, Germany
| | - Ben K. D. Pearce
- Origins Institute, McMaster University, ABB, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada; (B.K.D.P.); (R.E.P.)
- Department of Physics and Astronomy, McMaster University, ABB, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada
| | - Kevin Lange
- Institute for Theoretical Astrophysics, Center for Astronomy, Heidelberg University, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany;
| | - Thomas K. Henning
- Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; (K.K.); (T.K.H.); (O.T.); (D.A.S.)
| | - Oliver Trapp
- Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; (K.K.); (T.K.H.); (O.T.); (D.A.S.)
- Department of Chemistry, Ludwig-Maximilians-University Munich, Butenandtstr. 5-13, House F, 81377 Munich, Germany
| | - Ralph E. Pudritz
- Origins Institute, McMaster University, ABB, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada; (B.K.D.P.); (R.E.P.)
- Department of Physics and Astronomy, McMaster University, ABB, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada
| | - Dmitry A. Semenov
- Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; (K.K.); (T.K.H.); (O.T.); (D.A.S.)
- Department of Chemistry, Ludwig-Maximilians-University Munich, Butenandtstr. 5-13, House F, 81377 Munich, Germany
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5
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Factors in Protobiomonomer Selection for the Origin of the Standard Genetic Code. Acta Biotheor 2021; 69:745-767. [PMID: 34283307 DOI: 10.1007/s10441-021-09420-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 07/01/2021] [Indexed: 10/20/2022]
Abstract
Natural selection of specific protobiomonomers during abiogenic development of the prototype genetic code is hindered by the diversity of structural, spatial, and rotational isomers that have identical elemental composition and molecular mass (M), but can vary significantly in their physicochemical characteristics, such as the melting temperature Tm, the Tm:M ratio, and the solubility in water, due to different positions of atoms in the molecule. These parameters differ between cis- and trans-isomers of dicarboxylic acids, spatial monosaccharide isomers, and structural isomers of α-, β-, and γ-amino acids. The stable planar heterocyclic molecules of the major nucleobases comprise four (C, H, N, O) or three (C, H, N) elements and contain a single -C=C bond and two nitrogen atoms in each heterocycle involved in C-N and C=N bonds. They exist as isomeric resonance hybrids of single and double bonds and as a mixture of tautomer forms due to the presence of -C=O and/or -NH2 side groups. They are thermostable, insoluble in water, and exhibit solid-state stability, which is of central importance for DNA molecules as carriers of genetic information. In M-Tm diagrams, proteinogenic amino acids and the corresponding codons are distributed fairly regularly relative to the distinct clusters of purine and pyrimidine bases, reflecting the correspondence between codons and amino acids that was established in different periods of genetic code development. The body of data on the evolution of the genetic code system indicates that the elemental composition and molecular structure of protobiomonomers, and their M, Tm, photostability, and aqueous solubility determined their selection in the emergence of the standard genetic code.
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Mohammadi E, Petera L, Saeidfirozeh H, Knížek A, Kubelík P, Dudžák R, Krůs M, Juha L, Civiš S, Coulon R, Malina O, Ugolotti J, Ranc V, Otyepka M, Šponer J, Ferus M, Šponer JE. Formic Acid, a Ubiquitous but Overlooked Component of the Early Earth Atmosphere. Chemistry 2020; 26:12075-12080. [PMID: 32293757 DOI: 10.1002/chem.202000323] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 04/11/2020] [Indexed: 01/19/2023]
Abstract
Terrestrial volcanism has been one of the dominant geological forces shaping our planet since its earliest existence. Its associated phenomena, like atmospheric lightning and hydrothermal activity, provide a rich energy reservoir for chemical syntheses. Based on our laboratory simulations, we propose that on the early Earth volcanic activity inevitably led to a remarkable production of formic acid through various independent reaction channels. Large-scale availability of atmospheric formic acid supports the idea of the high-temperature accumulation of formamide in this primordial environment.
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Affiliation(s)
- Elmira Mohammadi
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Lukáš Petera
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic.,Faculty of Science, Charles University, Albertov 2030, 12843, Prague, Czech Republic
| | - Homa Saeidfirozeh
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic
| | - Antonín Knížek
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic.,Faculty of Science, Charles University, Albertov 2030, 12843, Prague, Czech Republic
| | - Petr Kubelík
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic.,Institute of Physics, Czech Academy of Sciences, Na Slovance 1999/2, 18221, Prague 8, Czech Republic
| | - Roman Dudžák
- Institute of Physics, Czech Academy of Sciences, Na Slovance 1999/2, 18221, Prague 8, Czech Republic.,Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 1782/3, 18200, Prague 8, Czech Republic
| | - Miroslav Krůs
- Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 1782/3, 18200, Prague 8, Czech Republic
| | - Libor Juha
- Institute of Physics, Czech Academy of Sciences, Na Slovance 1999/2, 18221, Prague 8, Czech Republic.,Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 1782/3, 18200, Prague 8, Czech Republic
| | - Svatopluk Civiš
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic
| | - Rémi Coulon
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Ondřej Malina
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Juri Ugolotti
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Václav Ranc
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Jiří Šponer
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic.,Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 61265, Brno, Czech Republic
| | - Martin Ferus
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223, Prague 8, Czech Republic
| | - Judit E Šponer
- Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371, Olomouc, Czech Republic.,Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 61265, Brno, Czech Republic
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7
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Choe JC. Formation of Cytosine and Uracil from Cyanoacetylaldehyde and Guanidine: A Computational Study. B KOREAN CHEM SOC 2020. [DOI: 10.1002/bkcs.11971] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Joong Chul Choe
- Department of ChemistryDongguk University‐Seoul Seoul 04620 South Korea
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8
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Tupper AS, Pudritz RE, Higgs PG. Can the RNA World Still Function without Cytidine? Mol Biol Evol 2019; 37:71-83. [DOI: 10.1093/molbev/msz200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Abstract
Most scenarios for the origin of life assume that RNA played a key role in both catalysis and information storage. The A, U, G, and C nucleobases in modern RNA all participate in secondary structure formation and replication. However, the rapid deamination of C to U and the absence of C in meteorite samples suggest that prebiotic RNA may have been deficient in cytosine. Here, we assess the ability of RNA sequences formed from a three-letter AUG alphabet to perform both structural and genetic roles in comparison to sequences formed from the AUGC alphabet. Despite forming less thermodynamically stable helices, the AUG alphabet can find a broad range of structures and thus appears sufficient for catalysis in the RNA World. However, in the AUG case, longer sequences are required to form structures with an equivalent complexity. Replication in the AUG alphabet requires GU pairing. Sequence fidelity in the AUG alphabet is low whenever G’s are present in the sequence. We find that AUG sequences evolve to AU sequences if GU pairing is rare, and to RU sequences if GU pairing is common (R denotes A or G). It is not possible to conserve a G at a specific site in either case. These problems do not rule out the possibility of an RNA World based on AUG, but they show that it wouldbe significantly more difficult than with a four-base alphabet.
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Affiliation(s)
- Andrew S Tupper
- Origins Institute and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Ralph E Pudritz
- Origins Institute and Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Paul G Higgs
- Origins Institute and Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
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9
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Pearce BKD, Ayers PW, Pudritz RE. A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients. J Phys Chem A 2019; 123:1861-1873. [DOI: 10.1021/acs.jpca.8b11323] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ben K. D. Pearce
- Origins Institute and Department of Physics and Astronomy, McMaster University, ABB 241, 1280 Main Street, Hamilton, Ontario L8S 4M1, Canada
| | - Paul W. Ayers
- Origins Institute and Department of Chemistry and Chemical Biology, McMaster University,
ABB 156, 1280 Main Street, Hamilton, Ontario L8S 4M1, Canada
| | - Ralph E. Pudritz
- Origins Institute and Department of Physics and Astronomy, McMaster University, ABB 241, 1280 Main Street, Hamilton, Ontario L8S 4M1, Canada
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10
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11
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Pearce BKD, Tupper AS, Pudritz RE, Higgs PG. Constraining the Time Interval for the Origin of Life on Earth. ASTROBIOLOGY 2018; 18:343-364. [PMID: 29570409 DOI: 10.1089/ast.2017.1674] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Estimates of the time at which life arose on Earth make use of two types of evidence. First, astrophysical and geophysical studies provide a timescale for the formation of Earth and the Moon, for large impact events on early Earth, and for the cooling of the early magma ocean. From this evidence, we can deduce a habitability boundary, which is the earliest point at which Earth became habitable. Second, biosignatures in geological samples, including microfossils, stromatolites, and chemical isotope ratios, provide evidence for when life was actually present. From these observations we can deduce a biosignature boundary, which is the earliest point at which there is clear evidence that life existed. Studies with molecular phylogenetics and records of the changing level of oxygen in the atmosphere give additional information that helps to determine the biosignature boundary. Here, we review the data from a wide range of disciplines to summarize current information on the timings of these two boundaries. The habitability boundary could be as early as 4.5 Ga, the earliest possible estimate of the time at which Earth had a stable crust and hydrosphere, or as late as 3.9 Ga, the end of the period of heavy meteorite bombardment. The lack of consensus on whether there was a late heavy meteorite bombardment that was significant enough to prevent life is the largest uncertainty in estimating the time of the habitability boundary. The biosignature boundary is more closely constrained. Evidence from carbon isotope ratios and stromatolite fossils both point to a time close to 3.7 Ga. Life must have emerged in the interval between these two boundaries. The time taken for life to appear could, therefore, be within 200 Myr or as long as 800 Myr. Key Words: Origin of life-Astrobiology-Habitability-Biosignatures-Geochemistry-Early Earth. Astrobiology 18, 343-364.
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Affiliation(s)
- Ben K D Pearce
- Origins Institute, Department of Physics and Astronomy, McMaster University , Hamilton, Canada
| | - Andrew S Tupper
- Origins Institute, Department of Physics and Astronomy, McMaster University , Hamilton, Canada
| | - Ralph E Pudritz
- Origins Institute, Department of Physics and Astronomy, McMaster University , Hamilton, Canada
| | - Paul G Higgs
- Origins Institute, Department of Physics and Astronomy, McMaster University , Hamilton, Canada
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12
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Origin of the RNA world: The fate of nucleobases in warm little ponds. Proc Natl Acad Sci U S A 2017; 114:11327-11332. [PMID: 28973920 DOI: 10.1073/pnas.1710339114] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary dust particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to warm little ponds whose wet-dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in warm little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth's early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary dust particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of "targets" for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet-dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago.
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13
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Olah GA, Mathew T, Prakash GKS. Chemical Formation of Methanol and Hydrocarbon (“Organic”) Derivatives from CO2 and H2—Carbon Sources for Subsequent Biological Cell Evolution and Life’s Origin. J Am Chem Soc 2016; 139:566-570. [DOI: 10.1021/jacs.6b10230] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- George A. Olah
- Loker Hydrocarbon Research
Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
| | - Thomas Mathew
- Loker Hydrocarbon Research
Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
| | - G. K. Surya Prakash
- Loker Hydrocarbon Research
Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
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14
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Pearce BKD, Pudritz RE. Meteorites and the RNA World: A Thermodynamic Model of Nucleobase Synthesis within Planetesimals. ASTROBIOLOGY 2016; 16:853-872. [PMID: 27827540 DOI: 10.1089/ast.2015.1451] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The possible meteorite parent body origin of Earth's pregenetic nucleobases is substantiated by the guanine (G), adenine (A), and uracil (U) measured in various meteorites. Cytosine (C) and thymine (T), however, are absent in meteorites, making the emergence of an RNA and later RNA/DNA/protein world problematic. We investigated the meteorite parent body (planetesimal) origin of all nucleobases by computationally modeling 18 reactions that potentially contribute to nucleobase formation in such environments. Out of this list, we identified the two most important reactions for each nucleobase and found that these involve small molecules such as HCN, CO, NH3, and water that ultimately arise from the protoplanetary disks in which planetesimals are built. The primary result of this study is that cytosine is unlikely to persist within meteorite parent bodies due to aqueous deamination. Thymine has a thermodynamically favorable reaction pathway from uracil, formaldehyde, and formic acid but likely did not persist within planetesimals containing H2O2 due to an oxidation reaction with this molecule. Finally, while Fischer-Tropsch (FT) synthesis is found to be the dominant source of nucleobases within our model planetesimal, non-catalytic (NC) synthesis may still be significant under certain chemical conditions (e.g., within CR2 parent bodies). We discuss several major consequences of our results for the origin of the RNA world. Key Words: Astrobiology-Cosmochemistry-Meteorites-RNA world-Abiotic organic synthesis. Astrobiology 16, 853-872.
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Affiliation(s)
- Ben K D Pearce
- Origins Institute and Department of Physics and Astronomy, McMaster University , Hamilton, Canada
| | - Ralph E Pudritz
- Origins Institute and Department of Physics and Astronomy, McMaster University , Hamilton, Canada
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