Prebiotic Synthesis of Protobiopolymers Under Alkaline Ocean Conditions
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Clasically, prebiotic chemistry has focused on the production and identification of simple organic molecules, many of them forming part of “intractable polymers” named tholins. In a previous work, we demonstrated that in experiments using an external energy source and inorganic carbon the aqueous aerosols improved the formation of hydrophilic tholins. Herein, we elucidate the role of pH (from 4 to 12) in prebiotic experiments using saline aqueous aerosols, spark discharges and an atmosphere containing CH4. At all values of pH, the saline aqueous aerosols increased the production of a significant variety of carboxylic acids that could have been present in a primitive Krebs cycle. Moreover, the study for the first time of hydrophilic tholins by 2-D electrophoresis revealed that these are formed by a set of unexpected heavy polymeric species. The initial alkaline conditions significantly increased both the apparent molecular weight of polymeric species up to 80 kDa and their diversity. We propose the term of protobiopolymers to denote those polymeric species fractionated by 2-D electrophoresis since these are formed by biomolecules present in living systems and show diversity in length as well as in functional groups. Thus, aerosols formed in simulated alkaline ocean conditions could provide an optimal medium for the formation of the primeval materials that could be precursors to the emergence of life.
KeywordsPrebiotic synthesis Polymer condensation Aerosol chemistry Tholins Alkaline oceans Prebiotic environments
The authors have used the research facilities of the Centro de Astrobiología (CAB) and have been supported by the Instituto Nacional de Técnica Aeroespacial “Esteban Terradas” (INTA) and by the projects AYA2009-13920-C02-01 of the Ministerio de Ciencia e Innovación (Spain). We thank Dr. S. Veintemillas for his useful comments. We thank Profesor G. Salcedo and Dr. A. Díaz-Perales for the use of their research facilities in their laboratory in the Department of Biotechnology at the Escuela Técnica Superior de Ingenieros Agrónomos (UPM).
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