Photoswitchable click amino acids: light control of conformation and bioactivity.

Click the switch: By using a photoswitchable click amino acid (PSCaa) a light-induced intramolecular thiol-ene click reaction with a neighboring cysteine under very mild conditions results in an azobenzene bridge. By expanding the genetic code for PSCaa the specific incorporation of photoswitch units into proteins in living cells can result in an exciting approach for studying light-controllable activity, in vivo.