Potassium-lead-switched G-quadruplexes: a new class of DNA logic gates.

A cation-driven allosteric G-quadruplex DNAzyme (PW17) was utilized to devise a conceptually new class of DNA logic gate based on cation-tuned ligand binding and release. K(+) favors the binding of hemin to parallel-stranded PW17, thereby promoting the DNAzyme activity, whereas Pb(2+) induces PW17 to undergo a parallel-to-antiparallel conformation transition and thus drives hemin to release from the G-quadruplex, deactivating the DNAzyme. Such a K(+)-Pb(2+) switched G-quadruplex, in fact, functions as a two-input INHIBIT logic gate. With the introduction of another input EDTA, this G-quadruplex can be further utilized to construct a reversibly operated IMPLICATION gate.