Investigating Metal Oxide - Catalysed Thermal Reaction for Prebiotic Peptides Synthesis: A Comparative Study

We conducted an experimental study on the spontaneous formation of peptides from two parallel reactions gly-asp acid/val mixtures in aqueous media and in the presence and absence of metal oxide catalysts, specifically alumina and silica, at 85 ± 5°C under simulated early Earth drying-wetting cycles. Analytical techniques revealed the synthesis of homogeneous and heterogeneous peptides, including cyclic glycine structures, resulting from intra- and intermolecular condensation reactions. Peptide yield was influenced by thermal treatment duration and, to a lesser extent, the presence of metal oxide catalysts. Notably, the gly-val system preferred to form glycine homo-oligomers up to tetrameric levels and heteropeptides including diketopiperazine. Conversely, the gly-asp acid system displayed limited oligomerization, reaching only trimeric levels, and yielded glycyl-aspartic acid. These findings offer valuable insights into the potential mechanisms underlying protein evolution on primitive Earth.