Formation and self-assembly of long prebiotic oligomers produced by the condensation of unactivated amino acids on oxide surfaces

In situ IR and mass spectrometry evidence for the catalytic formation on SiO2 and TiO2 surfaces of glycine oligomers (poly-Gly) up to 16 units long by successive feeding with monomers from the vapor phase is presented. Parallel experiments carried out on hydroxyapatite resulted in the unreactive adsorption of Gly, thus indicating that the oligomerization was specifically catalyzed by the surfaces of SiO2 and TiO2. Furthermore, the poly-Gly moved on the surface when contacted with H2O vapor and formed self-assembled aggregates containing both helical and β-sheet-like structural motifs. These results indicate that polypeptides formed by the condensation of amino acids adsorbed on a mineral surface can evolve into structured supramolecular assemblies.