Prebiotic oligomerization and self-assembly of structurally diverse xenobiological monomers

Abstract

Prebiotic chemists often study how modern biopolymers, e.g., peptides and nucleic acids, could have originated in the primitive environment, though most contemporary biomonomers don’t spontaneously oligomerize under mild conditions without activation or catalysis. However, life may not have originated using the same monomeric components that it does presently. There may be numerous non-biological (or “xenobiological”) monomer types that were prebiotically abundant and capable of facile oligomerization and self-assembly. Many modern biopolymers degrade abiotically preferentially via processes which produce thermodynamically stable ring structures, e.g. diketopiperazines in the case of proteins and 2′, 3′-cyclic nucleotide monophosphates in the case of RNA. This weakness is overcome in modern biological systems by kinetic control, but this need not have been the case for primitive systems. We explored here the oligomerization of a structurally diverse set of prebiotically plausible xenobiological monomers, which can hydrolytically interconvert between cyclic and acyclic forms, alone or in the presence of glycine under moderate temperature drying conditions. These monomers included various lactones, lactams and a thiolactone, which varied markedly in their stability, propensity to oligomerize and apparent modes of initiation, and the oligomeric products of some of these formed self-organized microscopic structures which may be relevant to protocell formation.

‘Whole Organism’, Systems Biology, and Top-Down Criteria for Evaluating Scenarios for the Origin of Life

“…A wide range of scenarios has been proposed, with varying degrees of scope. Most begin with a specific venue for the initiation of prebiotic chemistry, although some advocate for the role of multiple environments in life’s origin [ 7 , 8 , 9 , 10 ]. Proposed beginning venues include marine alkaline hydrothermal vents, either within microchambers [ 11 , 12 , 13 , 14 , 15 , 16 ] or iron (oxy)hydroxide (green rust) mounds [ 2 , 17 ], hydrothermally/volcanically charged sediments [ 18 , 19 ], terrestrial geothermal hot springs [ 20 ] including at their edges [ 21 , 22 ], within the pores of pumice rafts [ 23 , 24 ], between layers of micas [ 25 ], on clay surfaces [ 26 ] or greenalite nanoparticles [ 27 ], and even within the atmosphere as the key venue for initial biosynthesis fueled by a major meteorite impact [ 10 ].…”

A material‐based panspermia hypothesis: The potential of polymer gels and membraneless droplets

“…Instead, we propose an alternative Panspermia hypothesis utilizing materials in the form of polymeric gels that can potentially be an experimental framework to study the Panspermia hypothesis and the OoL. We have briefly shown that polymer gels (in the form of polyesters) formed from a variety of prebiotically available hydroxy acids, [128,144] amino acids and cyclic compounds, [138] showed cell-like functionality and have the potential to lead to the emergence of life via chemical evolution. While these polymeric gels' cell-like functions [127,128,138] provide glimpses of the potential of non-biomoleculebased OoL models (e.g., [137,177,210]), its robustness as a Panspermia seed, especially during spaceflight and also impact shock upon arriving in a recipient planet is unknown, require necessary investigation.…”

Differential Oligomerization of Alpha versus Beta Amino Acids and Hydroxy Acids in Abiotic Proto-Peptide Synthesis Reactions

“…It is possible that, around four billion years ago, a creative phase of pre-Darwinian chemical evolution pared down the number of potential building blocks to form oligomers and polymers with levels of functionally required for Darwinian processes [15,[19][20][21][22][23][24]. Numerous models have been proposed to explain various chemical and physical aspects of the origins of biopolymers [15,18,22,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The chemistry of water and the condensation-dehydration of building blocks into chimeric metabolites, oligomers and polymers are important features of these models.…”