For the emergence of life, the abiotic synthesis of RNA from its monomers is a central challenge. We found alkaline drying conditions in bulk and at heated air-water interfaces where 2 ́,3 ́-cyclic nucleotides reacted to form copolymers up to 10-mers. The polymerisation proceeded at a pH range of 7-12, temperatures between 40-80 °C and was enhanced by K+ ions. Among the canonical nucleotides, cGMP polymerised most efficiently. Our study suggests a polymerisation mechanism where cGMP polymerises first to form a polymorphic scaffold into which the other relatively unreactive nucleotides copolymerise. The 2 ́,3 ́-cyclic monomers are often products in prebiotic phosphorylation, nucleotide syntheses and recyclable intermediates of RNA hydrolyses. The plausible abiotic availability and the simple dry polymerisation conditions, combined with hydrolytic recycling offers an appealing minimal entry point for RNA-based molecular evolution on early Earth.
RNA auto-polymerisation from 2’,3’–cyclic nucleotides at air-water interfaces