Can proteins perform logic? (September 2005) - News - PhysicsWeb: "The main role of many proteins is to transmit and process information in living cells. These processes involve other molecules called regulatory ligands that bind to specific sites on the surface of the protein. It has been known for almost 50 years that a typical protein can switch between an inactive and an active state as the concentration of the ligand varies. These states could be used to represent the '0's and '1's of binary logic, but proteins are not true logic gates because a large change in concentration is needed to switch them from one state to another. "