Samuel Ruben's Contributions to Research on Photosynthesis and Bacterial Metabolism with Radioactive Carbon

The earliest experiments on the pathways of carbon in photosynthetic and heterotrophic metabolism using radioactive carbon, (11)C, as a tracer were performed by Samuel (Sam) Ruben, Martin Kamen, and their colleagues. The short half-life of (11)C (20 min), however, posed severe limitations on identification of metabolic intermediates, and this was a major stimulus to search for a radioactive carbon isotope of longer half-life. (14)C was discovered by Ruben and Kamen in 1940, but circumstances prevented continuation of their research using the long-lived isotope. Because of the untimely accidental death of Ruben in 1943, there are very few published accounts on the life and work of this extraordinary scientist. This paper summarizes highlights of Ruben's outstanding accomplishments.