RNA Oligomerization in Laboratory Analogues of Alkaline Hydrothermal Vent Systems

Abstract

Discovering pathways leading to long-chain RNA formation under feasible prebiotic conditions is an essential step toward demonstrating the viability of the RNA World hypothesis. Intensive research efforts have provided evidence of RNA oligomerization by using circular ribonucleotides, imidazole-activated ribonucleotides with montmorillonite catalyst, and ribonucleotides in the presence of lipids. Additionally, mineral surfaces such as borates, apatite, and calcite have been shown to catalyze the formation of small organic compounds from inorganic precursors (Cleaves, 2008 ), pointing to possible geological sites for the origins of life. Indeed, the catalytic properties of these particular minerals provide compelling evidence for alkaline hydrothermal vents as a potential site for the origins of life since, at these vents, large metal-rich chimney structures can form that have been shown to be energetically favorable to diverse forms of life. Here, we test the ability of iron- and sulfur-rich chimneys to support RNA oligomerization reactions using imidazole-activated and non-activated ribonucleotides. The chimneys were synthesized in the laboratory in aqueous "ocean" solutions under conditions consistent with current understanding of early Earth. Effects of elemental composition, pH, inclusion of catalytic montmorillonite clay, doping of chimneys with small organic compounds, and in situ ribonucleotide activation on RNA polymerization were investigated. These experiments, under certain conditions, showed successful dimerization by using unmodified ribonucleotides, with the generation of RNA oligomers up to 4 units in length when imidazole-activated ribonucleotides were used instead. Elemental analysis of the chimney precipitates and the reaction solutions showed that most of the metal cations that were determined were preferentially partitioned into the chimneys.

Redox and pH gradients drive amino acid synthesis in iron oxyhydroxide mineral systems

“…In natural vent systems, hydrothermal chimneys can form large and self-organized structures, containing networks of pores and/or redox-active minerals across which the gradients between vent fluid and seawater are focused. Previous work on simulating prebiotic hydrothermal chimneys has focused on factors such as carbon fixation reactions and incorporation and reactivity of organics in the chimney (19,20,37,44). We attempted pyruvate reactions in experiments where iron hydroxides were precipitated in a hydrothermal chimney structure instead of in simulated sediment.…”

Chemobrionic structures in tissue engineering: self-assembling calcium phosphate tubes as cellular scaffolds

“…[16][17][18][19] Injection system set-ups can also be adapted to mimic the chemistry found in the early oceans of Earth in order to help understand the origins of life on our planet. [20][21][22] Surprisingly, there is relatively little work that examines the use of such systems for biotechnological applications. Regenerative hard tissue scaffolds that offer through porosity and micro channels for cellular ingress are preferred to provide an environment for new tissue formation.…”

Conjecture and hypothesis: The importance of reality checks

“…The aim was to determine whether carbon dioxide (present as 10 mM sodium bicarbonate) can be reduced under these conditions, and they were able to detect ≈50 μM formic acid. In a similar laboratory simulation of an alkaline hydrothermal vent, Burcar et al [18] used mass spectrometry to detect a small yield of dimers produced from adenosine monophosphate circulating in the medium.…”