1. Hengyang Medical College School of Chemistry and Chemical Engineering University of South China Hengyang 421001 P. R. China
2. Department of Pharmacy Hengyang Medicinal School University of South China Hengyang, Hunan 421001 P. R. China
3. Key Lab of Protein Structure and Function of Universities in Hunan Province University of South China Hengyang 421001 P. R. China
4. Department of Chemistry & Institute of Biomedical Science Fudan University Shanghai 200433 P. R. China