1. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, P. R. of China
2. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
3. Pfizer Worldwide Research and Development Medicine, Eastern Point Road, Groton, Connecticut 06340, United States
4. Department of Chemistry, Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Frontiers Science Center for Synthetic Biology (Ministry of Education), Tianjin University, Tianjin 300072, P. R. of China