Peptide chain elongation: A possible role of montmorillonite in prebiotic synthesis of protein precursors

Abstract

Several studies have proven the ability of montmorillonite to catalyse amino acid condensation under assumed prebiotic conditions, simulating wetting-drying cycles. In this work, the oligomerization of short peptides gly₂, gly₃, gly₄ and ala₂ on Ca-and Cu-montmorillonite in drying-wetting cycles at 80 °C was studied. The catalytic effect of montmorillonite was found to be much higher than in the case of glycine oligomerization. From gly₂ after 3 weeks, 10% oligomers (up to gly6, with gly₃ as main products) are formed. Gly₃ and gly₄ give higher oligomers even after 1 cycle. Ala₂ produces both ala₃ and ala₄, whereas ala does not produce any oligomers under these conditions. Heteroologomerization was observed: ala-gly-gly is formed from ala and gly₂. Much higher yields are obtained using Ca-montmorillonite, because copper (II) oxidizes organic molecules. The influence of the reaction mechanism on the preferential oligomerization of oligopeptides is discussed.