1. Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
2. Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States
3. Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics, Northwestern University, Evanston, Illinois 60208, United States
4. College of Pharmacy, Ewha Womans University, Seoul 03760, Korea
5. Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States