Scientists at St. Jude Children's Research Hospital and Columbia University/New York State Psychiatric Institute are studying G protein-coupled receptors (GPCRs), membrane proteins that are the target of one-third of approved drugs. Using single-molecule imaging techniques, researchers gained fresh insight into the process by which cellular signals are relayed by GPCRs. The work may aid the development of novel drugs by manipulating the way they activate certain pathways. A paper on the work appeared today in Cell.