In humans, hundreds of thousands of protein-protein interactions (PPIs) play critical roles in regulating biological functions, and their dysregulation causes a number of diseases. Compounds that control PPIs have gained much attention due to their large potential application in new therapeutics. My research focuses on design of synthetic agents that recognize large protein surfaces, and disrupt and detect PPIs that are implicated in pathogenesis. Our molecular design is based on the module assembly; small compounds are designed for local protein surfaces, and are assembled to create midsized multivalent agents. For example, the assembled chemical probe consisting of an antitumor agent was found to detect intracellular PPIs efficiently. This probe may be useful for understanding the biology underlying the unique antitumor activity.