Peptide Formation on Layered Mineral Surfaces: The Key Role of Brucite-like Minerals on the Enhanced Formation of Alanine Dipeptides

Abstract

Alkaline hydrothermal vent environments have gained much attention as potential sites for abiotic synthesis of a range of organic molecules. However the key process of peptide formation has generally been undertaken at lower pH, and using dissolved copper ions to enhance selectivity and reactivity. Here, we explore whether layered precipitate minerals, abundant at alkaline hydrothermal systems, can promote peptide bond formation for surface-bound alanine under cycles of wetting and drying. While we find low level activity in brucite and binary layered double hydroxide carbonate minerals (typically < 0.1% yield), the inclusion of structural copper to form a ternary layered double hydroxide mineral significantly increased the yield to > 7 %. However the performance decreased over successive wetting/drying cycles. Control experiments show that this high degree of dipeptide formation cannot be attributed to leached copper from the mineral structure. While only dipeptides are observed, the yields obtained suggest that such processes, if occurring on the early Earth, could have added to the pool of available biological building units.