1. School of Chemistry and Chemical Engineering; University of South China; Hengyang 421001 P. R. China
2. Department of Modern Physics; University of Science and Technology of China; Hefei 230026 P. R. China
3. Laboratory of Protein Structure and Function; University of South China; Hengyang 421001 P. R. China
4. Department of Chemistry; Shanghai Key Lab of Chemical Biology for Protein Research; & Institute of Biomedical Science; Fudan University; Shanghai 200433 P. R. China