Switchable DNA‐Based Peroxidases Controlled by a Chaotropic Ion

Here we demonstrate a switchable DNA electron‐transfer catalyst, enabled by selective destabilization of secondary structure by the denaturant, perchlorate. The system is comprised of two strands, one of which can be selectively switched between a G‐quadruplex and duplex or single‐stranded conformations. In the G‐quadruplex state, it binds hemin, enabling peroxidase activity. This switching ability arises from our finding that perchlorate, a chaotropic Hofmeister ion, selectively destabilizes duplex over G‐quadruplex DNA. By varying perchlorate concentration, we show that the DNA structure can be switched between states that do and do not catalyze electron‐transfer catalysis. State switching can be achieved in three ways: thermally, by dilution, or by concentration.