The blood-brain barrier (BBB) is a highly selective membrane system that prevents unwanted passage of molecules into the brain extracellular fluid. Consequently, the BBB also significantly hinders the effectiveness of drugs used to treat a number of neurological disorders. Roche has engineered a protein module that can greatly enhance the passage of therapeutic agents across the blood-brain barrier. This 3D medical animation depicts the mechanism by which the “Brain Shuttle” module operates.