1. State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yang Qiao Xi Lu, Fuzhou, Fujian 350002, People's Republic of China
2. Graduate School, Chinese Academy of Sciences, Beijing 10039, People's Republic of China
3. Laboratory for Structural Biology, Department of Chemistry, Graduate Programs of Biotechnology, Chemistry and Materials Science, University of Alabama in Huntsville, Huntsville, AL 35899, U.S.A.