Protein-Binding Molecular Switches via Host–Guest Stabilized DNA Hairpins

Molecular switches, with target protein-binding activity controlled by prior binding to specific input stimuli, are ubiquitously used in Nature. However, the emulation of such responsive systems, especially in a de novo fashion, remains a significant challenge. Herein, we disclose a strategy that harnesses an intramolecular β-CD/adamantane host–guest interaction to generate a stabilized DNA hairpin (ΔT_m = 17 °C) that undergoes an input oligonucleotide (ODN)-selective structural transformation from a stem-loop conformation to a duplex. This ODN-induced conformational switch allows for the transition from an inactive state (wherein the adamantane protein-binding headgroup is encapsulated) to an activated protein-binding complex, with a freely accessible adamantane moiety. Given that hairpin domains can be readily modulated to be responsive to alternative ODN triggering sequences and that encapsulating macrocycles, such as β-CD, are good hosts for a number of protein-binding small molecules, this strategy may furnish a general method to develop ODN-responsive protein-binders.