Origins of Life and Molecular Information: Selectivity in Mineral Surface-Induced Prebiotic Amino Acid Polymerization

In current living matter, biopolymers follow specific sequences that give them special properties, such as the sequence of amino acids (AAs) in proteins and peptides. A major challenge for the elucidation of the origins of life lies in understanding how, for example, nonrandom polypeptides have been selected among all the possible ones. While many investigations established plausible prebiotic polymerization pathways, surprisingly, only a few attempted to study the selectivity of these processes. We studied a mineral surface polymerization scenario based on moderate thermal activation of leucine + glutamic acid mixtures on silica. Oligopeptides up to octamers were quantitatively formed in a “clean” prebiotic reaction and analyzed by high-resolution mass spectrometry and Fourier transform ion cyclotron resonance spectrometry for unambiguous molecular assignments. Nontrivial oligomerization selectivities are evidenced in both stoichiometric compositions and AA sequences, while comparable selectivities are not observed in other polymerization scenarios. This must therefore be due to specific catalytic reaction pathways occurring on the SiO₂ surface. A statistical measure of information contained in oligopeptide distributions is proposed. It could be used to follow the evolution of potentially meaningful complexity in biopolymers from the mineral to the biochemical world.