Water-filled micropores in hot rock may have acted as the nurseries in which life on Earth began. A team at Ludwig-Maximilians-Universitaet (LMU) in Munich, Germany has now shown that temperature gradients in pore systems promote the cyclical replication and emergence of nucleic acids. How and in what habitats did the first life-forms arise on the young Earth? One crucial pre-condition for the origin of life is that comparatively simple biomolecules must have had opportunities to form more complex structures, which were capable of reproducing themselves and which could store genetic information in a chemically stable form. But this scenario requires some means of accumulating the precursor molecules in highly concentrated form in solution. In the early oceans, such compounds would have been present in vanishingly low concentrations. But LMU physicists, led by Professor Dieter Braun, now describe a setting that provides the necessary conditions. They show experimentally that pore systems on the seafloor that were heated by volcanic activity could have served as reaction chambers for the synthesis of RNA molecules, which serve as carriers of hereditary information in the biosphere today. “The key requirement is that the heat source be localized on one side of the elongated pore, so that the water on that side is significantly warmer than that on the other,” says Dr. Braun. Pre-formed biomolecules that are washed into the pore can then be trapped, and concentrated, by the action of the temperature gradient– thus fulfilling a major prerequisite for the formation and replication of more complex molecular structures. The molecular trapping effect is a consequence of thermophoresis: Charged molecules in a temperature gradient preferentially move from the warmer to the cooler region, allowing longer polymers in particular to be securely trapped.
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