Local pH variability scenario: Prebiotic synthesis of cyclic dipeptides via prolinamide on the Hadean Earth

Small pools near early volcanoes are recognized as optimal field for the origin of life. However, the significance of pH variability in the polymerization of biomolecules has been undervalued. Within a simulated "warm little pond," our study illustrates that a pH variability scenario provides an effective and innovative route for the generation of cyclic dipeptides from prolinamide and free amino acids, obviating the necessity for a catalyst. Subsequent investigations reveal the influential roles of activator (trimetaphosphate, abbreviated as P3m), clay minerals such as montmorillonite, calcite, magnetite, and metal ions including Ca2+, Mg2+, Mn2+, which might have been prevalent in the early Earth's environmental conditions, in facilitating this prebiotic synthetic process. In conclusion, this research provides valuable insights into the possible mechanisms of prebiotic cyclic peptide synthesis, which is a crucial step in understanding the origin of life. The proposed pH variability model offers a plausible explanation for how these peptides could have formed under early Earth conditions.