RNA auto-polymerisation from 2’,3’-cyclic nucleotides at air-water interfaces

Abstract

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.

Prebiotic Foam Environments to Oligomerize and Accumulate RNA

“…As reported in Figure 6 with the grey data points, the oligomerization in the fully dry condition is yields significantly less than for the reaction in the heated foam. At this point, we can only speculate that this might be due to the length dependent accumulation at the interface [7,38,39] …”

“…The foam brings together both the dry and wet state, offering increased flexibility for prebiotic reactions. It has been established previously that the oligomerization is driven in the dry state [23–25,38] . In the foam setting, only a small fraction of the molecules are in the dry state at the air‐water interface on the warm side.…”

“…Given the fact that polymerization in the wet state is strongly reduced in its yield, we do not expect that this is the cause of the prominence of G in the polymerization product. Moreover, the polymerization of G is also enhanced in the dry state, indicating other mechanism for its preference, possibly due to the pK a of the base or its enhanced stacking interaction [38] …”

“…In recent study, 2’,3’ cyclic nucleotides were shown to self‐polymerize without catalysts under low salt conditions and elevated pH in the dry state. In case of mixed oligonucleotides polyG leads the copolymerization [38] . Therefore, the wet‐dry cycling inherent to the heated foam was tested.…”

“…In case of mixed oligonucleotides polyG leads the copolymerization. [38] Therefore, the wet-dry cycling inherent to the heated foam was tested.…”