1. Institute of Biomedical Research, Yunnan University, Chenggong District, Kunming 650500, Yunnan, P. R. China
2. Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), Hunan Normal University, Changsha, Hunan 410081, P. R. China
3. Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India
4. Research Computing Center, University of North Carolina, Chapel Hill, North Carolina 27599-3420, USA
5. Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, 27599-3290, USA