The origin of life on Earth calls for the existence of a polymeric chain capable to replicate and evolve toward more complex early forms of life. The RNA world hypothesis postulates that RNA was the first genetic polymer that led to the initiation of terrestrial life. Even if RNA world hypothesis is still considered one of the most plausible theories for the origin of life on Earth, many unresolved questions still remain. The most compelling one is that RNA polynucleotides undergo quick degradation in an aqueous solution at ambient temperature due to the ability of the deprotonated 2′-OH ribose group to attack and disrupt the phosphodiester bond between monomers. However, recent experimental findings have shown how the eutectic phase between growing ice crystals can offer a more favorable environment for the polymerization of longer RNA chains, hampering the RNA hydrolysis, and thus enabling replication and self-catalytic RNA activities. Herein, by employing multiple classical molecular dynamic simulations, we investigate the physicochemical behavior of all the essential reactants (i.e., methylisocyanide, 2- methyl-butyraldehyde, 2-Aminoimidazole, adenosine monophosphate, AMP) and intermediate pre-complexes needed for a non-enzymatic primer extension of a single strand RNA (see PNAS, 2022, 119, 17, e2116429119), at the air/ice interface and at the grain boundaries (i.e., the boundaries among growing crystals). We observed that, as the ice lattice grows, the concentration of the reactants increases in the interfacial environments. Moreover, the phosphate group of nucleotides is anchored by hydrogen bonds to the underlying crystal structures, while the other reactants, needed to activate the polymerization of the nucleotides, can diffuse more in these interfacial pre-melted and disordered environments. Finally, we also report less susceptibility of formed dibridged nucleotides to hydrolysis, which is explained by the strong hydrogen bonding of the phosphate groups with water belonging to the underlying crystalline ice substrate at the air/ice and grain boundary interfaces. In a primordial atmosphere or in periods of reduced activity of our young Sun, extreme temperature excursions were likely to occur on Earth. Our results, together with recent experimental findings, suggest that nanoconfined environments at the growing ice lattices may have provided a suitable environment for an ancient “RNA World on Ice”, as the early stage of the origin of life on Earth.

Prebiotic RNA reactivity in nanoconfined interfacial environment at growing ice crystals

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