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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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Olah GA, Mathew T, Prakash GKS. Relevance and Significance of Extraterrestrial Abiological Hydrocarbon Chemistry. J Am Chem Soc 2016; 138:6905-11. [PMID: 27045758 DOI: 10.1021/jacs.6b03136] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Astrophysical observations show similarity of observed abiological "organics"-i.e., hydrocarbons, their derivatives, and ions (carbocations and carbanions)-with studied terrestrial chemistry. Their formation pathways, their related extraterrestrial hydrocarbon chemistry originating from carbon and other elements after the Big Bang, their parent hydrocarbon and derivative (methane and methanol, respectively), and transportation of derived building blocks of life by meteorites or comets to planet Earth are discussed in this Perspective. Their subsequent evolution on Earth under favorable "Goldilocks" conditions led to more complex molecules and biological systems, and eventually to humans. The relevance and significance of extraterrestrial hydrocarbon chemistry to the limits of science in relation to the physical aspects of evolution on our planet Earth are also discussed.
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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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Mannige RV. Origination of the Protein Fold Repertoire from Oily Pluripotent Peptides. Proteomes 2014; 2:154-168. [PMID: 28250375 PMCID: PMC5302733 DOI: 10.3390/proteomes2020154] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 02/27/2014] [Accepted: 03/20/2014] [Indexed: 11/16/2022] Open
Abstract
While the repertoire of protein folds that exists today underlies most of life’s capabilities, our mechanistic picture of protein fold origination is incomplete. This paper discusses a hypothetical mechanism for the emergence of the protein fold repertoire from highly dynamic and collapsed peptides, exemplified by peptides with high oil content or hydrophobicity. These peptides are called pluripotent to emphasize their capacity to evolve into numerous folds transiently available to them. As evidence, the paper will discuss previous simulation work on the superior fold evolvability of oily peptides, trace (“fossil”) evidence within proteomes seen today, and a general relationship between protein dynamism and evolvability. Aside from implications on the origination of protein folds, the hypothesis implies that the vanishing utility of a random peptide in protein origination may be relatively exaggerated, as some random peptides with a certain composition (e.g., oily) may fare better than others. In later sections, the hypothesis is discussed in the context of existing discussions regarding the spontaneous origination of biomolecules.
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Affiliation(s)
- Ranjan V Mannige
- Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720,USA.
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Mannige RV. Dynamic New World: Refining Our View of Protein Structure, Function and Evolution. Proteomes 2014; 2:128-153. [PMID: 28250374 PMCID: PMC5302727 DOI: 10.3390/proteomes2010128] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 02/12/2014] [Accepted: 02/20/2014] [Indexed: 01/06/2023] Open
Abstract
Proteins are crucial to the functioning of all lifeforms. Traditional understanding posits that a single protein occupies a single structure ("fold"), which performs a single function. This view is radically challenged with the recognition that high structural dynamism-the capacity to be extra "floppy"-is more prevalent in functional proteins than previously assumed. As reviewed here, this dynamic take on proteins affects our understanding of protein "structure", function, and evolution, and even gives us a glimpse into protein origination. Specifically, this review will discuss historical developments concerning protein structure, and important new relationships between dynamism and aspects of protein sequence, structure, binding modes, binding promiscuity, evolvability, and origination. Along the way, suggestions will be provided for how key parts of textbook definitions-that so far have excluded membership to intrinsically disordered proteins (IDPs)-could be modified to accommodate our more dynamic understanding of proteins.
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Affiliation(s)
- Ranjan V Mannige
- Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road,Berkeley, CA 94720, USA.
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Brückner H, Becker D, Gams W, Degenkolb T. Aib and iva in the biosphere: neither rare nor necessarily extraterrestrial. Chem Biodivers 2009; 6:38-56. [PMID: 19180454 DOI: 10.1002/cbdv.200800331] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fourty-nine species and strains of filamentous fungi of the genera Acremonium, Bionectria, Clonostachys, Emericellopsis, Hypocrea/Trichoderma, Lecythophora, Monocillium, Nectriopsis, Niesslia, Tolypocladium, and Wardomyces, deposited with the culture collection of the Centraalbureau voor Schimmelcultures (CBS) in Utrecht, The Netherlands, were grown on nutrient agar plates. Organic extracts of mycelia were analyzed after acidic total hydrolysis and derivatization by GC/SIM-MS on Chirasil-L-Val for the presence of Aib (=alpha-aminoisobutyric acid, 2-methylalanine) and DL-Iva (=isovaline, 2-ethylalanine). In 37 of the hydrolysates, Aib was detected, and in several of them D-Iva or mixtures of D- and L-Iva. Non-proteinogenic Aib, in particular, is a highly specific marker for a distinctive group of fungal polypeptides named peptaibols or, comprehensively, peptaibiotics, i.e., peptides containing Aib and displaying (anti)biotic activities. The biotic synthesis of these amino acids by filamentous fungi contradicts the still widespread belief that alpha,alpha-dialkyl-alpha-amino acids do not or rarely occur in the biosphere and, if detected, are of extraterrestrial origin. The abundant production of peptaibiotics by cosmopolitan species of microfungi has also to be considered in the discussion on the occurrence of Aib and Iva in ancient and recent sediments. The detection of trace amounts of Aib in ice samples of Antarctica that are devoid of meteorites might also be related to the presence of Aib-producing microorganisms, being either indigenous psychrophiles, or being transported and localized by mechanisms related to bioaerosols and cryoconites. The presence of microfungi being capable of producing alpha,alpha-dialkyl alpha-amino acids in terrestrial samples, and possible contamination of extraterrestrial materials are pointed out to be of relevance for the reliable interpretation of cosmogeochemical data.
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Affiliation(s)
- Hans Brückner
- Interdisciplinary Research Centre for Biosystems, Land Use and Nutrition (IFZ), Department of Food Sciences, Institute of Nutritional Science, University of Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen.
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Pradeille N, Zerbe O, Möhle K, Linden A, Heimgartner H. The first total synthesis of the peptaibol hypomurocin A1 and its conformation analysis: an application of the 'azirine/oxazolone method'. Chem Biodivers 2007; 2:1127-52. [PMID: 17193196 DOI: 10.1002/cbdv.200590084] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The first total synthesis of Hypomurocin A1 (HM A1) in solution phase is described. As members of the peptaibol family, hypomurocins are constituted by two groups of peptides: six undecapeptides (undecamers) in the HM A group and six octadecapeptides (18-mers) in the HM B group. The synthesis presented has been successfully achieved by the 'azirine/oxazolone method' to introduce the two Aib-Pro sequences included in this undecapeptaibol in one step with methyl 2,2-dimethyl-2H-azirine-3-prolinate as the building block. The coupling reactions of the Z-protected amino acids or peptide acids involved the use of N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU) and 1-hydroxybenzotriazole (HOBt), and led to the peptides in good-to-very-good yields. The peptides were purified by reverse-phase HPLC and characterized by NMR spectroscopy (1H, 13C, COSY, TOCSY, HSQC, HMBC, ROESY), ESI-MS, IR, elemental analysis, optical rotation, and X-ray crystallography. An NMR analysis of HM A1 was also carried out in deuterated micelles to perform a structural comparison of the helix in solution and in membranes.
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Affiliation(s)
- Nicolas Pradeille
- Organisch-chemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich
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Fletcher SP, Jagt RBC, Feringa BL. An astrophysically-relevant mechanism for amino acid enantiomer enrichment. Chem Commun (Camb) 2007:2578-80. [PMID: 17579743 DOI: 10.1039/b702882b] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The sublimation of low ee amino acids was examined while exploring simple mechanisms by which high ee amino acids can be generated under conditions that exist in space; significant enantioenrichment of a variety of amino acids by sublimation was achieved.
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Affiliation(s)
- Stephen P Fletcher
- Department of Organic Chemistry and Molecular Inorganic Chemistry, Strating Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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Oró J, Mills T, Lazcano A. Comets and the formation of biochemical compounds on the primitive Earth--a review. ORIGINS LIFE EVOL B 2001; 21:267-77. [PMID: 11537542 DOI: 10.1007/bf01808302] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thirty years ago it was suggested that comets impacting on the primitive Earth may have represented a significant source of terrestrial volatiles, including some important precursors for prebiotic synthesis (Oró, 1961, Nature 190: 389). This possibility is strongly supported not only by models of the collisional history of the early Earth, but also by astronomical evidence that suggests that frequent collisions of comet-like bodies from the circumstellar disk around the star beta Pictoris are taking place. Although a significant fraction of the complex organic compounds that appear to be present in cometary nuclei were probably destroyed during impact, it is argued that cometary collisions with the primitive Earth represented an important source of both free-energy and volatiles, and may have created transient, gaseous environments in which prebiotic synthesis may have taken place.
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Affiliation(s)
- J Oró
- Department of Biochemical and Biophysical Sciences, University of Houston, TX 77204-5934
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Basiuk VA, Douda J. Survivability of biomolecules during extraterrestrial delivery: new results on pyrolysis of amino acids and poly-amino acids. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 2001; 27:231-236. [PMID: 11605637 DOI: 10.1016/s0273-1177(01)00052-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The hypothesis on exogenous origin of organic matter on the early Earth is strongly supported by the detection of a large variety of organic compounds (including amino acids and nucleobases) in carbonaceous chondrites. Whether such complex species can be successively delivered by other space bodies (comets, asteroids and interplanetary dust particles) is unclear and depends primarily on capability of the biomolecules to survive high temperatures during atmospheric deceleration and impacts to the terrestrial surface. Recent simulation experiments on amino acid and nucleic acid base pyrolysis under oxygen-free atmosphere demonstrated that simple representatives of these (considered thermally unstable) compounds can survive at 1-10% level a rapid heating at 500-600 degrees C. In the present work, we report on new data on the pyrolysis of amino acids and their homopolymers and discuss implications of their thermal behavior for extraterrestrial delivery.
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Affiliation(s)
- V A Basiuk
- Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior C.U., A. Postal 70-543, 04510 Mexico D.F., Mexico.
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Basiuk VA, Douda J, Navarro-Gonzalez R. Transport of extraterrestrial biomolecules to the Earth: problem of thermal stability. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1999; 24:505-514. [PMID: 11543338 DOI: 10.1016/s0273-1177(99)00092-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The idea of extraterrestrial delivery of organic matter to the early Earth is especially attractive at present and is strongly supported by the detection of a large variety of organic compounds, including amino acids and nucleobases, in carbonaceous chondrites. Whether these compounds can be delivered by other space bodies is unclear and depends primarily on capability of the biomolecules to survive high temperatures during atmospheric deceleration and impacts to the terrestrial surface. In the present study we estimated survivability of simple amino acids (alpha-aminoisobutyric acid, L-alanine, L-valine and L-leucine), purines (adenine and guanine) and pyrimidines (uracil and cytosine) under rapid heating to temperatures of 400 to 1000 degrees C under N2 or CO2 atmosphere. We have found that most of the compounds studied cannot survive the temperatures substantially higher than 700 degrees C; however at 500-600 degrees C, the recovery can be at a per cent level (or even 10%-level for adenine, uracil, alanine, and valine). Implications of the data for extraterrestrial delivery of the biomolecules are discussed.
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Affiliation(s)
- V A Basiuk
- Laboratorio de Quimica de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico.
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11
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Goldanskii VI. Nontraditional Pathways of Extraterrestrial Formation of Prebiotic Matter. J Phys Chem A 1997. [DOI: 10.1021/jp970042i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Vitalii I. Goldanskii
- N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Ulitsa Kosygina 4, 117334 Moscow, Russia
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12
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Non-traditional pathways of extraterrestrial formation of organic compounds. Russ Chem Bull 1997. [DOI: 10.1007/bf02495384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Glasby GP, Kunzendorf H. Multiple factors in the origin of the Cretaceous/Tertiary boundary: the role of environmental stress and Deccan Trap volcanism. GEOLOGISCHE RUNDSCHAU : ZEITSCHRIFT FUR ALLGEMEINE GEOLOGIE 1996; 85:191-210. [PMID: 11543126 DOI: 10.1007/bf02422228] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A review of the scenarios for the Cretaceous/ Tertiary (K/T) boundary event is presented and a coherent hypothesis for the origin of the event is formulated. Many scientists now accept that the event was caused by a meteorite impact at Chicxulub in the Yucatan Peninsula, Mexico. Our investigations show that the oceans were already stressed by the end of the Late Cretaceous as a result of the long-term drop in atmospheric CO2, the long-term drop in sea level and the frequent development of oceanic anoxia. Extinction of some marine species was already occurring several million years prior to the K/T boundary. The biota were therefore susceptible to change. The eruption of the Deccan Traps, which began at 66.2 Ma, coincides with the K/T boundary events. It erupted huge quantities of H2SO4, HCl, CO2, dust and soot into the atmosphere and led to a significant drop in sea level and marked changes in ocean temperature. The result was a major reduction in oceanic productivity and the creation of an almost dead ocean. The volcanism lasted almost 0.7 m.y. Extinction of biological species was graded and appeared to correlate with the main eruptive events. Elements such as Ir were incorporated into the volcanic ash, possibly on soot particles. This horizon accumulated under anoxic conditions in local depressions and became the marker horizon for the K/T boundary. An oxidation front penetrated this horizon leading to the redistribution of elements. The eruption of the Deccan Traps is the largest volcanic event since the Permian-Triassic event at 245 Ma. It followed a period of 36 m.y. in which the earth's magnetic field failed to reverse. Instabilities in the mantle are thought to be responsible for this eruption and therefore for the K/T event. We therefore believe that the K/T event can be explained in terms of the effects of the Deccan volcanism on an already stressed biosphere. The meteorite impact at Chicxulub took place after the onset of Deccan volcanism. It probably played a regional, rather than global, role in the K/T extinction.
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Affiliation(s)
- G P Glasby
- Department of Earth Sciences, University of Sheffield, England
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Abstract
The field of study that deals with the origins of life does not have a consensus for a theory of life's origin. An analysis of the range of theories offered shows that they share some common features that may be reliable predictors when considering the possible origins of life on another planet. The fundamental datum dealing with the origins of life is that life appeared early in the history of the Earth, probably before 3.5 Ga and possibly before 3.8 Ga. What might be called the standard theory (the Oparin-Haldane theory) posits the production of organic molecules on the early Earth followed by chemical reactions that produced increased organic complexity leading eventually to organic life capable of reproduction, mutation, and selection using organic material as nutrients. A distinct class of other theories (panspermia theories) suggests that life was carried to Earth from elsewhere--these theories receive some support from recent work on planetary impact processes. Other alternatives to the standard model suggest that life arose as an inorganic (clay) form and/or that the initial energy source was not organic material but chemical energy or sunlight. We find that the entire range of current theories suggests that liquid water is the quintessential environmental criterion for both the origin and sustenance of life. It is therefore of interest that during the time that life appeared on Earth we have evidence for liquid water present on the surface of Mars.
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Affiliation(s)
- W L Davis
- Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035-1000, USA
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Davies PC. The transfer of viable microorganisms between planets. CIBA FOUNDATION SYMPOSIUM 1996; 202:304-14; discussion 314-7. [PMID: 9243022 DOI: 10.1002/9780470514986.ch16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
There is increasing acceptance that catastrophic cosmic impacts have played an important role in shaping the history of terrestrial life. Large asteroid and cometary impacts are also capable of displacing substantial quantities of planetary surface material into space. The discovery of Martian rocks on Earth suggests that viable microorganisms within such ejecta could be exchanged between planets. If this conjecture is correct, it will have profound implications for the origin and evolution of life in the solar system.
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Affiliation(s)
- P C Davies
- Department of Physics and Mathematical Physics, University of Adelaide, Australia
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Oró J, Mills T, Lazcano A. Comets and life in the Universe. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1995; 15:81-90. [PMID: 11539264 DOI: 10.1016/s0273-1177(99)80067-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The notion that comets supplied the primitive Earth with the requisite chemical species for the process of chemical evolution, which is widely held to have led to the origin of life on Earth, has now gained considerable intellectual momentum since its first formulation in 1961. In fact, in the fall of 1991, the University of Wisconsin-Eau Claire hosted a well attended scientific meeting devoted solely to the discussion of this topic, entitled Comets and the Origin and Evolution of Life [see Special Issue of Origins of Life, P.J. Thomas (ed), vol. 21(5-6)]. As a result of the above meeting, the recently completed COSPAR/World Space Congress Symposium on Extraterrestrial Organic Chemistry and the Origins of Life, and numerous independent reports, the role of comets in the Earth's biogenesis has been thoroughly addressed in the literature. At this time, in light of a few recent findings, we present here a concise review of this topic together with a brief discussion of the possible role of cometary material in the origin of life elsewhere in the Universe.
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Affiliation(s)
- J Oró
- Department of Biochemical and Biophysical Sciences, The University of Houston, TX 77204, USA
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Ramadurai S, Lloyd D, Wallis M, Wickramasinghe NC. Extinction of dinosaurs: a possible novel cause. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1995; 15:139-146. [PMID: 11539216 DOI: 10.1016/s0273-1177(99)80075-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A novel cause of mass extinction of fauna close to the (K/T) Boundary is suggested. A large amount of non-protein amino acids (AIB and ISOVAL) has been observed close to this event. It is speculated that these amino acids may be toxic and are responsible for the extinction. The toxicity level is estimated for this suggestion to be true and experimentalists are encouraged to test this level of toxicity for the amino acids.
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Affiliation(s)
- S Ramadurai
- Tata Institute of Fundamental Research, Bombay, India
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Catastrophe: impact of comets and asteroids. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0168-6321(06)80027-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Emanuel KA, Speer K, Rotunno R, Srivastava R, Molina M. Hypercanes: A possible link in global extinction scenarios. ACTA ACUST UNITED AC 1995. [DOI: 10.1029/95jd01368] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chyba C, Sagan C. Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life. Nature 1992; 355:125-32. [PMID: 11538392 DOI: 10.1038/355125a0] [Citation(s) in RCA: 503] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Sources of organic molecules on the early Earth divide into three categories: delivery by extraterrestrial objects; organic synthesis driven by impact shocks; and organic synthesis by other energy sources (such as ultraviolet light or electrical discharges). Estimates of these sources for plausible end-member oxidation states of the early terrestrial atmosphere suggest that the heavy bombardment before 3.5 Gyr ago either produced or delivered quantities of organics comparable to those produced by other energy sources. Which sources of prebiotic organics were quantitatively dominant depends strongly on the composition of the early terrestrial atmosphere. In the event of an early strongly reducing atmosphere, production by atmospheric shocks seems to have dominated that due to electrical discharges. Organic synthesis by ultraviolet light may, in turn, have dominated shock production, but only if a long-wavelength absorber such as H2S were supplied to the atmosphere at a rate sufficient for synthesis to have been limited by ultraviolet flux, rather than by reactant abundance. In the apparently more likely case of an early terrestrial atmosphere of intermediate oxidation state, atmospheric shocks were probably of little importance for direct organic production. For [H2]/[CO2] ratios of approximately 0.1, net organic production was some three orders of magnitude lower than for reducing atmospheres, with delivery of intact exogenous organics in interplanetary dust particles (IDPs) and ultraviolet production being the most important sources. At still lower [H2]/[CO2] ratios, IDPs may have been the dominant source of prebiotic organics on the early Earth. Endogenous, exogenous and impact-shock sources of organics could each have made a significant contribution to the origins of life.
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Affiliation(s)
- C Chyba
- Laboratory for Planetary Studies, Cornell University, Ithaca, New York 14853, USA
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25
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Cometary supply of terrestrial organics: Lessons from the K/T and the present epoch. ORIGINS LIFE EVOL B 1991. [DOI: 10.1007/bf01808306] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Affiliation(s)
- W A Bonner
- Department of Chemistry, Stanford University, CA 94305
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30
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