The in vivo chemistry of photoswitched tethered ligands.

Nature's photoreceptors are typically composed of a chromophore that is covalently bound to a receptor protein at the top of a signaling cascade. The protein can function as a G-protein coupled receptor (GPCR), an ion channel, or as an enzyme. This logic can be mimicked with synthetic photoswitches, such as azobenzenes, that are linked to naturally 'blind' transmembrane proteins using in vivo-chemistry. The resulting semisynthetic receptors can be employed to optically control cellular functions, especially in neurons, and influence the behavior of animals with the exquisite temporal and spatial precision of light.