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      Carbamoyl phosphate and its substitutes for the uracil synthesis in origins of life scenarios

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          Abstract

          The first step of pyrimidine synthesis along the orotate pathway is studied to test the hypothesis of geochemical continuity of protometabolic pathways at the origins of life. Carbamoyl phosphate (CP) is the first high-energy building block that intervenes in the in vivo synthesis of the uracil ring of UMP. Thus, the likelihood of its occurrence in prebiotic conditions is investigated herein. The evolution of carbamoyl phosphate in water and in ammonia aqueous solutions without enzymes was characterised using ATR-IR, 31P and 13C spectroscopies. Carbamoyl phosphate initially appears stable in water at ambient conditions before transforming to cyanate and carbamate/hydrogenocarbonate species within a matter of hours. Cyanate, less labile than CP, remains a potential carbamoylating agent. In the presence of ammonia, CP decomposition occurs more rapidly and generates urea. We conclude that CP is not a likely prebiotic reagent by itself. Alternatively, cyanate and urea may be more promising substitutes for CP, because they are both “energy-rich” (high free enthalpy molecules in aqueous solutions) and kinetically inert regarding hydrolysis. Energy-rich inorganic molecules such as trimetaphosphate or phosphoramidates were also explored for their suitability as sources of carbamoyl phosphate. Although these species did not generate CP or other carbamoylating agents, they exhibited energy transduction, specifically the formation of high-energy P–N bonds. Future efforts should aim to evaluate the role of carbamoylating agents in aspartate carbamoylation, which is the following reaction in the orotate pathway.

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          Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions.

          Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions was studied systematically. The dissolution behavior and solubility of cellulose were evaluated by using (13)C NMR, optical microscopy, wide-angle X-ray diffraction (WAXD), FT-IR spectroscopy, DSC, and viscometry. The experiment results revealed that cellulose having viscosity-average molecular weight ((overline) M eta) of 11.4 x 104 and 37.2 x 104 could be dissolved, respectively, in 7% NaOH/12% urea and 4.2% LiOH/12% urea aqueous solutions pre-cooled to -10 degrees C within 2 min, whereas all of them could not be dissolved in KOH/urea aqueous solution. The dissolution power of the solvent systems was in the order of LiOH/urea > NaOH/urea > KOH/urea aqueous solution. The results from DSC and (13)C NMR indicated that LiOH/urea and NaOH/urea aqueous solutions as non-derivatizing solvents broke the intra- and inter-molecular hydrogen bonding of cellulose and prevented the approach toward each other of the cellulose molecules, leading to the good dispersion of cellulose to form an actual solution.
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            On the Evolution of Biochemical Syntheses.

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              The Hot Spring Hypothesis for an Origin of Life

              We present a testable hypothesis related to an origin of life on land in which fluctuating volcanic hot spring pools play a central role. The hypothesis is based on experimental evidence that lipid-encapsulated polymers can be synthesized by cycles of hydration and dehydration to form protocells. Drawing on metaphors from the bootstrapping of a simple computer operating system, we show how protocells cycling through wet, dry, and moist phases will subject polymers to combinatorial selection and draw structural and catalytic functions out of initially random sequences, including structural stabilization, pore formation, and primitive metabolic activity. We propose that protocells aggregating into a hydrogel in the intermediate moist phase of wet-dry cycles represent a primitive progenote system. Progenote populations can undergo selection and distribution, construct niches in new environments, and enable a sharing network effect that can collectively evolve them into the first microbial communities. Laboratory and field experiments testing the first steps of the scenario are summarized. The scenario is then placed in a geological setting on the early Earth to suggest a plausible pathway from life's origin in chemically optimal freshwater hot spring pools to the emergence of microbial communities tolerant to more extreme conditions in dilute lakes and salty conditions in marine environments. A continuity is observed for biogenesis beginning with simple protocell aggregates, through the transitional form of the progenote, to robust microbial mats that leave the fossil imprints of stromatolites so representative in the rock record. A roadmap to future testing of the hypothesis is presented. We compare the oceanic vent with land-based pool scenarios for an origin of life and explore their implications for subsequent evolution to multicellular life such as plants. We conclude by utilizing the hypothesis to posit where life might also have emerged in habitats such as Mars or Saturn's icy moon Enceladus. “To postulate one fortuitously catalyzed reaction, perhaps catalyzed by a metal ion, might be reasonable, but to postulate a suite of them is to appeal to magic.” —Leslie Orgel
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                Author and article information

                Contributors
                jean-francois.lambert@sorbonne-universite.fr
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                29 September 2021
                29 September 2021
                2021
                : 11
                : 19356
                Affiliations
                [1 ]GRID grid.462844.8, ISNI 0000 0001 2308 1657, Laboratoire de Réactivité de Surface (LRS, UMR 7197 CNRS), Case courrier 178, , Sorbonne Université, ; 4, Place Jussieu, 75005 Paris, France
                [2 ]Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, Sorbonne Université, Ecole Pratique des Hautes Etudes, Université des Antilles, CNRS, CP 50, 57 rue Cuvier, 75005 Paris, France
                [3 ]GRID grid.462844.8, ISNI 0000 0001 2308 1657, Sorbonne Université, Institut des Matériaux de Paris Centre (FR2482), ; 4 Place Jussieu, 75005 Paris, France
                Article
                98747
                10.1038/s41598-021-98747-6
                8481487
                34588537
                5140be22-6a7f-4b5a-b702-3f0de7d9ca1c
                © The Author(s) 2021

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 27 May 2021
                : 6 September 2021
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100019125, Sorbonne Université;
                Categories
                Article
                Custom metadata
                © The Author(s) 2021

                Uncategorized
                biogeochemistry,astrobiology,origin of life
                Uncategorized
                biogeochemistry, astrobiology, origin of life

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