Using azobenzene photocontrol to set proteins in motion.

Controlling the activity of proteins with azobenzene photoswitches is a potent tool for manipulating their biological function. With the help of light, it is possible to change binding affinities, control allostery or manipulate complex biological processes, for example. Additionally, owing to their intrinsically fast photoisomerization, azobenzene photoswitches can serve as triggers that initiate out-of-equilibrium processes. Such switching of the activity initiates a cascade of conformational events that can be accessed with time-resolved methods. In this Review, we show how the potency of azobenzene photoswitching can be combined with transient spectroscopic techniques to disclose the order of events and experimentally observe biomolecular interactions in real time. This strategy will further our understanding of how a protein can accommodate, adapt and readjust its structure to answer an incoming signal, revealing more of the dynamical character of proteins.