Hydrazone Switch-Based Negative Feedback Loop.

A negative feedback loop that relies on the coordination-coupled deprotonation (CCD) of a hydrazone switch has been developed. Above a particular threshold of zinc(II), CCD releases enough protons to the environment to trigger a cascade of reactions that yield an imine. This imine sequesters the excess of zinc(II) from the hydrazone switch, hence lowering the effective amount of protons, and switching the cascade reactions "OFF", thus establishing the negative feedback loop.