Abstract
Accurate replication of encoded information would have been crucial for the formation and propagation of functional ribozymes during the early evolution of life. Studies aimed at understanding prebiotically pertinent nonenzymatic reactions have predominantly used activated nucleotides. However, the existence of concentrated pools of activated monomers on prebiotic Earth is debatable. In this study, we explored the feasibility of nonenzymatic copying reactions using the more prebiotically relevant 5′-nucleoside monophosphates (5′-NMP). These reactions, involving a 20-mer primer, were performed in the presence of amphiphiles, under volcanic geothermal conditions. Interestingly, the extended primer was not comparable to the expected full length 21-mer product. Our results suggest loss of the nitrogenous base in the extended primer. This phenomenon persisted even after lowering the temperature and when different rehydration solutions were used. We envisage that the loss of the informational moiety on the incoming 5′-NMP, might be occurring during addition of this monomer to the pre-existing oligomer. Significantly, when 5′-ribose monophosphate was used, multiple additions to the aforementioned primer were observed that resulted in hybrid polymers. Such hybrid oligomers could have been important for exploring a vast chemical space of plausible alternate nucleobases, thus having important implications for the origin of primitive informational polymers.
Highlights
A widely accepted hypothesis pertaining to the existence of a putative ‘RNA World’ presumes that RNA molecules played a central role during the emergence and evolution of early life on Earth
It becomes pertinent and important to study the feasibility of nonenzymatic information transfer and related processes, using non-activated nucleotides, which are prebiotically relevant in comparison to their activated counterparts
Few studies reported the polymerization of 5′-nucleoside monophosphates (5′-NMP) under DH-RH regimens, at low pH and in a range of high temperatures[9,11]
Summary
A widely accepted hypothesis pertaining to the existence of a putative ‘RNA World’ presumes that RNA molecules played a central role during the emergence and evolution of early life on Earth. Dehydration at high temperatures results in concentration of the reactants, it enhances the loss of water molecules, facilitating condensation and, promoting bond formation Such alternate DH-RH cycles would have been facilitated on the prebiotic Earth by diurnal cycles, seasonal variations etc. To our knowledge, no study has been reported to date wherein information transfer using RNA, and prebiotically relevant non-activated nucleotides, has been systematically evaluated especially under prebiotically relevant volcanic geothermal conditions These RNA based studies are crucial as they pertain to a molecule whose relevance to the emergence of early life has been demonstrated in multiple lines of studies. In this particular study, we aimed to discern phospholipid-assisted template-directed primer extension reactions, under DH-RH regimes and at elevated temperatures. Such hybrid polymers could have potentially been significant in sampling different bases during the emergence of primitive functional polymers on the early Earth[11]
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