Abstract 5-Formylcytosine (5fC) is a chemically edited, naturally occurring nucleobase which appears in the context of modified DNA strands. The understanding of the impact of 5fC on dsDNA physical properties is to date limited. In this work, we applied temperature-dependent 1H Chemical Exchange Saturation Transfer (CEST) NMR experiments to non-invasively and site-specifically measure the thermodynamic and kinetic influence of formylated cytosine nucleobase on the melting process involving dsDNA. Incorporation of 5fC within symmetrically positioned CpG sites destabilizes the whole dsDNA structure—as witnessed from the ∼2°C decrease in the melting temperature and 5–10 kJ mol−1 decrease in ΔG°—and affects the kinetic rates of association and dissociation. We observed an up to ∼5-fold enhancement of the dsDNA dissociation and an up to ∼3-fold reduction in ssDNA association rate constants, over multiple temperatures and for several proton reporters. Eyring and van’t Hoff analysis proved that the destabilization is not localized, instead all base-pairs are affected and the transition states resembles the single-stranded conformation. These results advance our knowledge about the role of 5fC as a semi-permanent epigenetic modification and assist in the understanding of its interactions with reader proteins.

For the emergence of life, the abiotic synthesis of RNA from its monomers is a central step. We found that in alkaline, drying conditions in bulk and at heated air‐water interfaces, 2′,3′‐cyclic nucleotides oligomerised without additional catalyst, forming up to 10‐mers within a day. The oligomerisation proceeded at a pH range of 7–12, at temperatures between 40–80 °C and was marginally enhanced by K+ ions. Among the canonical ribonucleotides, cGMP oligomerised most efficiently. Quantification was performed using HPLC coupled to ESI‐TOF by fitting the isotope distribution to the mass spectra. Our study suggests a oligomerisation mechanism where cGMP aids the incorporation of the relatively unreactive nucleotides C, A and U. The 2′,3′‐cyclic ribonucleotides are byproducts of prebiotic phosphorylation, nucleotide syntheses and RNA hydrolysis, indicating direct recycling pathways. The simple reaction condition offers a plausible entry point for RNA to the evolution of life on early Earth.

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.

In this study, the effect of CurDAc, a water-soluble curcumin derivative, on the formation and stability of amyloid fibers is revealed. CurDAc interaction with amyloid is structurally selective, which is...