The polymerisation of amino acids into peptides is thermodynamically unfavored. It is therefore necessary to provide energy to the system such as heat, radiation or chemical activation. In order to better understand how prebiotic amino acids condensed into mini-proteins in the primitive oceans, we polymerised amino acid thioesters in water in the presence of suspended mineral surfaces: sulfides (CdS, FeS, ZnS, extracts of submarine hydrothermal systems) and montmorillonite clay. At 25 °C, in the presence of CdS, ZnS, and montmorillonite, the polymerisation proceeded up to Leu_7-SEt. With hydration/dehydration (wet-dry) cycles and in the presence of CdS or of montmorillonite, significant amounts of Leu_6-OH and Leu_7-OH were obtained.
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