1. A Key Laboratory of Theoretical Organic Chemistry and Functional Molecule of Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, P. R. China
2. The National & Local Joint Engineering Laboratory of Animal Peptide Drug Development, Hunan Provincial Key Laboratory of Neurorestoratology, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410006, P. R. China