After a 48-hour incubation, the 35S would most likely be found in the S. cerevisiae's proteins.
35S is the isotope of sulfur with the half-life of 87.6 days. It is often used isotope because it is low energy β emitter and even large amounts of 35S pose no external dose hazard to exposed organism. 35S is used for the examination of protein synthesis in the Saccharomyces cerevisiae cell cycle.