Leó Szilárd
While at the University of Chicago, he worked with Aaron Novick and Leó Szilárd and later with Paul Talalay. In Colorado, he became codiscoverer of the clonogenic assay and the feeder cell system, making it possible to grow clones from single mammalian cells as in stem cells. He was the first to clone the immortalized HeLa cells. That procedure led to the first determination of human cell sensitivity to X-rays. Over fifty years later he documented that a luncheon conversation with Leó Szilárd, the nuclear physicist, led to the concept and physical setup for the first clonogenic assay. Dr. Marcus then spent nine years on the faculty of the Albert Einstein College of Medicine in NY supported by a ten-year U.S. Public Health Service Research Career Development Award. While there he showed the dynamic movement of virus molecules on the surface of infected cells, and with a pediatrician colleague, Dr. David Carver, developed a new test to detect rubella virus. During this time in New York, he was director for nine years of the post-doctoral course on quantitative animal virology and cell culture that was taught in the summer at Cold Spring Harbor Laboratory (NY).