1. Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of EducationInstitute of Molecular ScienceShanxi University Taiyuan 030006 P. R. China
2. School of Basic Medical SciencesShanxi Medical University Taiyuan 030001 P. R. China
3. State Key Laboratory of Superhard MaterialsJilin University Changchun 130012 P. R. China