October
28,
2016
A pressing question in origins-of-life research is how polypeptides arose from amino acids before the ribosome. Recently, we discovered a plausible mechanism for abiotic peptide bond formation enabled by alpha-hydroxy acids, amino acid analogs also present on the early Earth, in a day-night environmental cycling setting (Angew. Chem. Int. Ed. 2015, 54, 9871). Using this approach, peptides with a mixture of amide and ester backbone linkages (depsipeptides) were formed. The amino acid content of depsipeptides was enriched over repeated wetting/drying cycles, evolving into traditional peptide sequences. Based on this chemistry, we prepared model prebiotic “soups” containing depsipeptides and analyzed their sequence and structure by ultra-performance liquid chromatography – traveling-wave ion mobility – tandem mass spectrometry (UPLC-TWIM-MS/MS), along with custom bioinformatics approaches. Results indicated that sequence space randomness varied depending on the set of amino acids and alpha hydroxy acids polymerized. To better study this chemistry and the resulting complex mixtures, we are also developing new tools to enable (a) more sensitive and controlled ionization, and (b) detection of depsipeptides and other species on the surface of reactive substrates, such as minerals. All these interdisciplinary activities are being pursued within the context of our NSF/NASA Center for Chemical Evolution, following proto-nucleic acid, proto-peptide, and polysaccharide formation thrusts, which I will further describe in this talk.
