Polyesters as a Model System for Building Primitive Biologies from Non-Biological Prebiotic Chemistry

Abstract

A variety of organic chemicals were likely available on prebiotic Earth. These derived from diverse processes including atmospheric and geochemical synthesis and extraterrestrial input, and were delivered to environments including oceans, lakes, and subaerial hot springs. Prebiotic chemistry generates both molecules used by modern organisms, such as proteinaceous amino acids, as well as many molecule types not used in biochemistry. As prebiotic chemical diversity was likely high, and the core of biochemistry uses a rather small set of common building blocks, the majority of prebiotically available organic compounds may not have been those used in modern biochemistry. Chemical evolution was unlikely to have been able to discriminate which molecules would eventually be used in biology, and instead, interactions among compounds were governed simply by abundance and chemical reactivity. Previous work has shown that likely prebiotically available α-hydroxy acids can combinatorially polymerize into polyesters that self-assemble to create new phases which are able to compartmentalize other molecule types. The unexpectedly rich complexity of hydroxy acid chemistry and the likely enormous structural diversity of prebiotic organic chemistry suggests chemical evolution could have been heavily influenced by molecules not used in contemporary biochemistry, and that there is a considerable amount of prebiotic chemistry which remains unexplored.

The Future of Origin of Life Research: Bridging Decades-Old Divisions

“…If one considers that the accumulation of biomolecules is a biological invention, optimizing for certain geochemical and/or biochemical properties [119], then compounds such as aHAs may have played a role in some form of nascent biology not conserved in modern biology [142]. Considering the 'messy' nature (meaning the inherent diversity) of prebiotic chemistry [143,144], this may have been the case, and the utility of central biomolecules such as RNA and ubiquitous metabolites to elucidate the OoL may be partial, despite their omnipresence in modern life.…”

Origin of Species before Origin of Life: The Role of Speciation in Chemical Evolution

“…Such systems can be of varying structural and functional complexity and could be produced from either associative (such as in complex coacervates [ 105 , 106 , 107 ]) or segregative (such as in polyethylene glycol (PEG) and dextran aqueous two-phase systems [ 78 , 108 ]) phase separation [ 109 ]. Other prebiotically plausible compartment systems have also been proposed, such as rock pores [ 110 , 111 ], polyester microdroplets [ 112 , 113 ], supercritical carbon dioxide droplets [ 114 , 115 ], or even combinations of different membraneless and membrane-bound systems [ 116 , 117 , 118 , 119 , 120 ].…”

Prebiotic oligomerization and self-assembly of structurally diverse xenobiological monomers

“…problem in understanding the origins of life 59,60 . These systems could in principle be based on many polymer types [43][44][45][46]61 , and which types were prevalent in prebiological environments would depend on the balance of monomer synthesis, i.e., abundance as a result of robustness of prebiotic synthesis under a given set of conditions, and reactivity, including robustness of elongation mechanisms to environmental conditions, as well as the relative stability and other emergent properties of the polymer.…”

“…In the context of prebiotic chemistry, Orgel and co-workers were among the first to explore oligomerization of cyclic monomers, namely 2′,3′-adenosine monophosphate (cAMP), under drying conditions 40 – 42 . Since this study explored an oligomerization mechanism not used in contemporary biochemistry, it represents an example of the idea that there may have been “scaffolding” chemistries which helped to bootstrap the origins of life 43 . The idea of such scaffolding chemistries has been raised in other prebiotic contexts (e.g., the pre-RNA world 44 , 45 ) among others 43 .…”

“…Since this study explored an oligomerization mechanism not used in contemporary biochemistry, it represents an example of the idea that there may have been "scaffolding" chemistries which helped to bootstrap the origins of life 43 . The idea of such scaffolding chemistries has been raised in other prebiotic contexts (e.g., the pre-RNA world 44,45 ) among others 43 .…”