Although experiments by Miller in the 1950’s revealed the formation of a number of amino acids, a means to the efficient formation of peptides on the early Earth has been a continuous challenge. Interestingly, hydroxy acids have been identified in the primordial soup as well, and, when considering alternative pathways to the formation of peptides, gained the interest of CCE scientists. Recent successes in the formation of peptides or proto-peptides are described below.
The spark discharge experiment performed by Stanley Miller in the 1950’s shed new light on the origin of biological building blocks such as amino acids. Using Thin Layer Chromatography (TLC), Miller was able to identify a number of biologically relevant amino acids that were likely available on the early Earth. Studies of peptide chemistry led the CCE to consider the role potential condensing agents may have played in the formation of peptides. CCE scientists analyze samples and repeat studies done by Miller to better understand the role of cyanimide, a plausibly prebiotic condensing agent. In these analyses employing techniques like liquid chromatography, ion mobility spectrometry, and mass spectrometry, a substantially greater pool of products is observed, including 12 amino acids and 10-glycine containing dipeptides. The results of this work highlight the potential importance of condensing agents in prebiotic chemistry and in the polymerization of amino acids into more complex molecules.
Previous CCE studies demonstrated the formation of polyesters through wet/dry cycles that mimic day and night or seasonal changeson the early Earth. Through cyclic iterations, CCE scientists observed the formation of longer and more complex polymer distributions. Inspired by these results, studies combining hydroxy acids and amino acids under cycling conditions were performed leading to the production of depsipeptides. Through a combination of ester-amide bond exchanged and ester bond hydrolysis, depsipeptides became enriched with amino acids over increasing cycles. These results demonstrate a plausibly prebiotic route to the formation of proto-polypeptides.