Rapamycin is a small molecule originally isolated from nature. It has antibiotic and immunosuppressive properties. It also allows two proteins which do not normally interact to bind together in the cell, which causes problems in the nutrient-sensing pathway.
One technique for discovering small molecules of biological relevance is to expose cultured cells to a variety of small molecules and look for changes in the cells' appearance, behavior or other measurable qualities.
Small molecules are chemicals that can interact with proteins to affect their functions. Learn about the structure and biological functions of various small molecules like sugar and caffeine.