On the Role of α-Alumina in the Origin of Life: Surface Driven Assembly of Amino Acids

We investigate the hypothesis that mineral/water interfaces played a crucial catalytic role in peptide formation by promoting the self-assembly of amino acids. Using force-field-based molecular dynamics simulations, we demonstrate that the $\alpha$-alumina (0001) surface exhibits an affinity of 4 kBT for individual glycine or GG dipeptide molecules, due to hydrogen bonds formed at both the C- and N-termini. In simulations with multiple glycine molecules, surface-bound glycine enhances further adsorption, leading to the formation of long chains connected by hydrogen bonds between the carboxyl and amine groups of glycine molecules. The probability of forming long amino acid chains is examined using metadynamics enhanced sampling and a modified Flory theory. We find that the likelihood of observing chains longer than 10 glycine units increases by at least 5 orders of magnitude at the surface compared to the bulk. This surface-driven assembly is primarily due to local high density and alignment with the alumina surface pattern, resulting in a competition between enthalpy and entropy effects on adsorption. The formation of these chains necessitates the removal of coordinated water molecules. Importantly, our findings reveal that when dipeptides are present, only the N-terminus forms hydrogen bonds with the surface, suggesting that the surface may disfavor the backward hydrolysis of newly formed peptides. Together, these results propose a model for how mineral surfaces can induce configuration-specific assembly of amino acids, thereby promoting condensation reactions.