Chalfie, Martin, 1947–, American biologist, b. Chicago, Ph.D. Harvard, 1977. In 1982 Chalfie joined the faculty at Columbia, where he is now the William R. Kenan, Jr., Professor of Biological Sciences. In 2008 he shared the Nobel Prize in Chemistry with Roger Tsien and Osamu Shimomura for their discovery and development of the green fluorescent protein (GFP). Chalfie demonstrated the value of GFP as a luminous genetic tag for various biological phenomena, enabling specific proteins to be located and tracked in living organisms. As a result of the work of the three, GFP has become one of the most important tools in contemporary bioscience.