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A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide
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posted on 2016-04-26, 00:00 authored by Raffaele Saladino, Giorgia Botta, Bruno
Mattia Bizzarri, Ernesto Di Mauro, Juan Manuel Garcia
RuizThe
pathway from simple abiotically made organic compounds to the
molecular bricks of life, as we know it, is unknown. The most efficient
geological abiotic route to organic compounds results from the aqueous
dissolution of olivine, a reaction known as serpentinization (Sleep,
N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101,
12818–12822). In addition to molecular hydrogen and a reducing environment, serpentinization
reactions lead to high-pH alkaline brines that can become easily enriched
in silica. Under these chemical conditions, the formation of self-assembled
nanocrystalline mineral composites, namely silica/carbonate biomorphs
and metal silicate hydrate (MSH) tubular membranes (silica gardens),
is unavoidable (Kellermeier, M., et al. In Methods in Enzymology,
Research Methods in Biomineralization Science (De Yoreo,
J., Ed.) Vol. 532, pp 225–256, Academic Press, Burlington,
MA). The osmotically
driven membranous structures have remarkable catalytic properties
that could be operating in the reducing organic-rich chemical pot
in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic
molecules under mineral-driven catalytic conditions (Saladino, R.,
et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249–1253), proton irradiation (Saladino, R., et al.
(2015) Proc. Natl. Acad. Sci. USA, 112, 2746–2755),
and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657–662). Here, we show
that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic
acids, amino acids, and nucleobases. Membranes formed by the reaction
of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower
reactivities. The collections of compounds forming inside and outside
the tubular membrane are clearly specific, demonstrating that the
mineral self-assembled membranes at the same time create space compartmentalization
and selective catalysis of the synthesis of relevant compounds. Rather
than requiring odd local conditions, the prebiotic organic chemistry
scenario for the origin of life appears to be common at a universal
scale and, most probably, earlier than ever thought for our planet.
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serpentinization reactionsResearch Methodsmembranous structuresPrebiotic Chemistrymetal silicate hydratespace compartmentalizationN.Hchemical conditionschemistry scenarioMSH membranesDe Yoreocompounds resultsabiotic routeMAProcMgSO 4Fe 2NH 2 CHOBiomineralization ScienceZnCl 2prebiotic moleculesUSANatlcarboxylic acidsGlobal Scale ScenarioAcadMedicinal Chemistry
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