1. a Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, P. R. China
2. b Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, P. R. China
3. c Multidisciplinary Research Center, Shantou University, Shantou 515063, Guangdong, P. R. China; Protein Science Laboratory of Ministry of Education, Department of Biological Science and Biotechnology, Tsinghua University, Beijing 100084, P. R. China