Stuart L. Schreiber (born 6 February 1956) is a scientist at Harvard University and co-Founder of the Broad Institute. He has been active in chemical biology, especially the use of small molecules as probes of biology and medicine. Small molecules are the molecules of life most associated with dynamic information flow; these work in concert with the macromolecules (DNA, RNA, proteins) that are the basis for inherited information flow. Education and training Schreiber obtained a Bachelor of Science degree in chemistry from the University of Virginia in 1977, after which he entered Harvard University as a graduate student in Chemistry. He joined the research group of Robert B. Woodward and after Woodward's death continued his studies under the supervision of Yoshito Kishi. In 1980, he joined the faculty of Yale University as an assistant professor in Chemistry, and in 1988 he moved to Harvard University as the Morris Loeb Professor. Work in 1980s and 1990s Schreiber started his research work in organic synthesis, focusing on concepts such as the use of [2 + 2] photocycloadditions to establish stereochemistry in complex molecules, the fragmentation of hydroperoxides to produce macrolides, ancillary stereocontrol, group selectivity and two-directional synthesis. Notable accomplishments include the total syntheses of complex natural products such as talaromycin B, asteltoxin, avenaciolide, gloeosporone, hikizimicin, mycoticin A, epoxydictymene and the immunosuppressant FK-506. Following his work on the FK506-binding protein FKBP12 in 1988, Schreiber reported that the small molecules FK506 and cyclosporin inhibit the activity of the phosphatase calcineurin by forming the ternary complexes FKBP12-FK506-calcineurin and cyclophilin-ciclosporin-calcineurin. This work, together with work by Gerald Crabtree at Stanford University concerning the NFAT proteins, led to the elucidation of the calcium-calcineurin-NFAT signaling pathway. The Ras-Raf-MAPK pathway was not elucidated for another year. In 1993, Schreiber and Crabtree developed "small-molecule dimerizers", which provide small-molecule activation over numerous signaling molecules and pathways (e.g., the Fas, insulin, TGFβ and T-cell receptors) through proximity effects. Schreiber and Crabtree demonstrated that small molecules could activate a signaling pathway in an animal with temporal and spatial control. Dimerizer kits have been distributed freely resulting in many peer-reviewed publications. Its promise in gene therapy has been highlighted by the ability of a small molecule to activate a small-molecule regulated EPO receptor and to induce erythropoiesis (Ariad Pharmaceuticals, Inc.), and more recently in human clinical trials for treatment of graft-vs-host disease. In 1994, Schreiber and co-workers investigated (independently with David Sabitini) the master