Effect of various co-solutes on the oligomerization of prebiotically relevant monomers

Abstract

RNA world hypothesis suggests that RNA was the first informational biopolymer from which DNA and proteins evolved later. However, this hypothesis has historically ignored the role of other prebiotically relevant molecules that would have played an important role in the shaping of the RNA world. According to this hypothesis, synthesis of short RNA oligomers, from a large random pool of organic molecules, is thought to have happened by chemical means. Dehydration- rehydrations (DH-RH), regimes, a common theme on the prebiotic Earth, are thought to have especially favoured such uphill oligomerization reactions on the early Earth. DH-RH cycling of ribonucleotides has shown to result in RNA-like oligomers in the presence of lipids. In the current project, we set out to characterize the combined role of prebiotically relevant co-solutes, such as lipids and amino acids (for e.g. glycine, alanine, aspartate and valine), on the oligomerization of non-activated nucleotides under DH-RH cycling conditions. The aforementioned moieties are important, prebiotically relevant co-solutes that would have co-existed with the RNA monomers in the prebiotic soup. We also characterized the role of these co-solutes on depurination; an important side-reaction that has implications for the origin of informational polymers on the early Earth. In addition to this, we also wanted to understand the role of these co-solutes on the oligomerization reactions of activated nucleotides as most studies of nonenzymatic oligomerization involved the use of these activated monomers. In all, our results suggest that there is no additive role resulting from combining lipids and amino acids on, both, the oligomerization and depurination of non-activated nucleotides. Activated nucleotides also did not oligomerize efficiently in the presence of the lipids and/or amino acids under our reaction conditions. Importantly, the presence of lipids did confer some protection from depurination towards nucleotides in all the reactions that we studied.