1. Bioorganic and Medicinal Chemistry Research Center, School of Pharmaceutical Science, Wenzhou Medical College, Wenzhou 325035, P. R. China
2. Department of Microbiology and Immunology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
3. Institute of Bioengineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China
4. Norman Bethune College of Medical Science, Jilin University, Changchun 130012, P. R. China