Adam Cohen: Visualizing cellular voltage

W hen ion concentrations differ on either side of a membrane, this produces a difference in electrical potential, or voltage, across the membrane. Neurons utilize this voltage to transmit information in the form of electrical signals. But might cell voltage also affect processes such as embryonic development or the behavior of yeast and other microbes? These questions cannot be answered using the traditional tools of electrophysiology. Physicist Adam Cohen is interested in viewing biological problems in new ways (1, 2) and lately has been working to make it possible to study the roles of cellular voltage. Cohen recently discovered that some light-sensing proteins of the rhodopsin family can be " run in reverse " so that, instead of changing a cell's voltage in response to light, they fl uoresce in response to changes in cellular voltage (3–5). Cohen's group has since worked to optimize these new optical voltage sensors and has great plans for this new technology, as he told us when we called him at his Harvard laboratory. Did you have any role models growing up? My father is a professor at Rockefeller University, and he and my mother were very supportive of my interest in science. They gave me an oscilloscope for my bar mitz-vah because they knew I loved tinkering with electronics. I was also strongly infl uenced by one of my science teachers, the advisor to my high school's science club. He fostered my interest in science, but he and I also talked a lot about the country he came from, Liberia. He told me a lot about what was going on there and inspired me to get involved with Liberian science education. Have you been to Liberia? Yes, twice. The country's scientifi c infrastructure had been largely destroyed during a 14-year-long civil war that ended in 2003. Worse, most of the teachers had been either killed or forced to fl ee the country, so Liberia had to rebuild its scientific systems basically from scratch. My second trip to Liberia was made with a woman named Liz Wood and a friend of mine from high school, Ben Rapoport, with the aim of helping restore science education in Liberia. We worked with the faculty at the University of Liberia to develop a science curriculum. It included lectures and research projects that could be done with materials available in the Liberian marketplace so they wouldn't have to import …