1. School of Pharmacy, Jiangsu University, Zhenjiang 212013, P. R. China
2. Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
3. Department of Materials Science, Northwestern University, Evanston, Illinois 60208, United States
4. Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, Illinois 60611, United States
5. Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, United States
6. Departments of Chemistry and Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States