Roderick MacKinnon, 1956–, American biochemist, b. Burlington, Mass., M.D. Tufts Univ., 1982. MacKinnon was on the faculty at Harvard Medical School from 1989–96 and has been a professor at the Howard Hughes Medical Institute of Rockefeller Univ. in New York since 1996. MacKinnon was awarded the 2003 Nobel Prize in Chemistry with Peter Agre for discoveries relating to channels in cell membranes. MacKinnon's contribution concerned ion channels, which are responsible for electrical signaling in living cells; in 1998 he determined the spatial structure of a potassium channel. Electrical signals play a number of roles in the body, including controlling the pace of the heart, regulating the secretion of hormones, and transferring information between cells in the nervous system.