Zn²⁺-Selective Switch of Duplex to Hairpin DNA

DNA sequences that undergo large changes in secondary structure upon binding of small molecules are the basis for molecular switches. Here we report a Zn²⁺ complex that promotes the conversion of a fully complementary DNA double helix into DNA hairpins. The conformational switch is promoted by an isolated Zn²⁺ complex or by free ZnCl₂ and a macrocyclic ligand. The switch is selective for Zn²⁺ over biologically relevant transition-metal ions including Cu²⁺ and Fe²⁺. The dual ligand/DNA switch is an approach that may improve the selectivity for metal-ion-sensing applications