One Step up the Ladder of Prebiotic Complexity: Formation of Nonrandom Linear Polypeptides from Binary Systems of Amino Acids on Silica

Abstract

Evidence for the formation of linearo ligopeptides with nonrandoms equences from mixtures of amino acids coadsorbed on silica ands ubmitted to as imple thermal activation is presented. The amino acid couples (glutamic acid + leucine)a nd (aspartic acid + valine) were deposited on a fumed silica and submitted to as ingle heating step at moderate temperature. The evolution of the systemsw as characterized by X-ray diffraction, infrared spectroscopy,t hermosgravimetric analysis, HPLC, and electrospray ionizationm ass spectrometry (ESI-MS). Evidence for the formation of amide bonds was found in all systemss tudied. Whilet he products of single aminoa cids activation on silica could be consid-ered as evolutionary dead ends, (glutamic acid + leucine) and, at to somee xtent, (aspartic acid + valine) gave rise to the high yield formation of linear peptides up to the hexamers. Oligopeptides of such length have not been observed beforei ns urface polymerization scenarios (unless the amino acids had been depositedb yc hemical vapor deposition, which is not realistic in ap rebiotic environment). Furthermore,n ot all possible amino acid sequences werep resent in the activation products,w hich is indicative of polymerization selectivity.These resultsare promisingf or origins of life studies because they suggest the emergence of nonrandom biopolymers in as imple prebiotic scenario.

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

“…The analysis of complex polypeptide mixtures can hardly be accomplished in situ in the adsorbed phase, so that efficient desorption is a necessary requirement for quantitative analysis of the reaction products. In the related system Asp+Val/SiO2 system, also studied by Sakhno et al 39 as already mentioned, some of the reaction products had a very high affinity for the surface and hardly desorbed at all, so that the composition of the desorption solution did not faithfully reflect that of the condensation products. The importance of peptide desorption was underlined, from another point of view, by de Duve and Miller.…”

“…The two bands at 1667 cm -1 , assigned to amide I (mostly due to C=O stretching vibration), and 1520 cm -1 (corresponding to amide II vibration) reveal peptide bond formation. Moreover, the presence of the amide II band suggests the formation of linear peptides, 39 since this band is not apparent in cyclic dipeptides (DKPs) that are the chief polymerization products in many AA/SiO2 systems. 22 Figure 1.…”

Boron in Prebiological Evolution

“…Silicate (or its dry version, silica) has been suggested to participate in some prebiological reactions such as the polymerization of amino acids, [71] phosphoribosyl pyrophosphate synthesis, [72] the formose reaction, [73] and in stabilizing ribose furanose conformers [69] …”

A comparative study of alanine adsorption and condensation to peptides in two clay minerals

“…The modification would concern both the COOand the NH 3 + moieties; the accompanying band shifts are larger than those observed for H-bonds, but smaller than for covalent bonding. (Rosado et al, 1997;Caroline, et al, 2009;Mohsin, et al 2018 (Sakhno et al, 2019), the latter is probably an amide I band, the amide groups being formed by condensation of the ammonium and carboxylates of the original amino acids. Note that the amide II band expected in the 1500-1600 cm -1 region appears to be absent, an occurrence that has been correlated with the formation of the cyclic dimer (diketopiperazine).…”

“…Two important exceptions may be found in the work of Bujdák and Rode ((Bujdák and Rode, 1999b) and (Bujdák and Rode, 1999a), respectively). Recent work on amino acids polymerization more often uses silica or titania as a support, in part for reasons regarding the ease of characterization (Guo and Holland, 2015;Martra et al, 2014;Sakhno et al, 2019) or, if clays are used, montmorillonite is often chosen as a generic smectite (Kollár et al, 2003;Bu et al, 2019). In the present paper, we report on the comparative polymerization ability of two different clay minerals, kaolinite and hectorite, that differ in layer structure as well as in layer charge.…”