Unwinding DNA and RNA with Synthetic Complexes: On the Way to Artificial Helicases

Synthetic helicases can be designed on the basis of ligands that bind more strongly to single-stranded nucleic acids than to double-stranded nucleic acids. This can be achieved with ligands containing phenyl groups, which intercalate into single strands, but due to their small size not into double strands. Moreover, two phenyl rings are combined with a distance that allows bis-intercalation with only single strands and not double strands. In this respect, such ligands also mimic single-strand binding (SSB) proteins. Exploration with more than 23 ligands, mostly newly synthesised, shows that the distance between the phenyl rings and between those and the linker influence the DNA unwinding efficiency, which can reach a melting point decrease of almost ΔTm =50 °C at much lower concentrations than that with any other known artificial helicases. Conformational pre-organisation of the ligand plays a decisive role in optimal efficiency. Substituents at the phenyl rings have a large effect, and increase, for example, in the order of H