Abstract
Replication of nucleic acids in the absence of genetically encoded enzymes represents a critical process for the emergence of cellular life. Repeated separation of complementary RNA strands is required to achieve multiple cycles of chemical replication, yet thermal denaturation under plausible prebiotic conditions is impaired by the high temperatures required to separate long RNA strands and by concurrent degradation pathways, the latter accelerated by divalent metal ions. Here we show how the melting temperature of oligoribonucleotide duplexes can be tuned by changes in pH, enabling the separation of RNA strands at moderate temperatures. At the same time, the risk of phosphodiester bond cleavage is reduced under the acid denaturation conditions herein described, both in the presence and in the absence of divalent metal ions. Through a combination of ultraviolet and circular dichroism thermal studies and gel electrophoresis, we demonstrate the relevance of geological pH oscillations in the context of the RNA strand separation problem. Our results reveal new insights in the field of prebiotic chemistry, supporting plausible geochemical scenarios in which non-enzymatic RNA replication might have taken place.
Highlights
Replication of nucleic acids in the absence of genetically encoded enzymes represents a critical process for the emergence of cellular life
Recent investigations have shown how RNA mononucleotides, along with other building blocks considered necessary for life, might have chemically formed from the interplay of plausible prebiotic reaction networks in a defined geochemical setting.[1−6] the transition from the chemistry of RNA monomers to the biology of a self-replicating system has been challenged by the many problems encountered with multiple cycles of non-enzymatic RNA replication.[7]
The plausibility of thermal denaturation of RNA is hampered by the high melting temperature of oligoribonucleotides, to the point that duplexes of >30 bp are considered impossible to melt under plausible prebiotic conditions.[7]
Summary
Replication of nucleic acids in the absence of genetically encoded enzymes represents a critical process for the emergence of cellular life. Our study initially focused on outlining the effect of acidic pH values on the temperature at which 50% of a 13mer RNA duplex is denatured [melting point (Tm)].
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