1. Department of Chemistry, University of Pennsylvania, 231 S. South 34th Street, Philadelphia, Pennsylvania 19104, United States
2. Department of Chemical and Biomedical Engineering, University of Pennsylvania, 220 S. South 33rd Street, Philadelphia, Pennsylvania 19104, United States
3. Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, Pennsylvania 15260, United States
4. Department of Chemistry and Nano Science, Global Top 5 Program, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 120-750, Korea