1. Department of Chemistry, Zhejiang University, Hangzhou 310027 Zhejiang, P. R. China
2. Dr. Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, P. R. China
3. College of Biology, Hunan University, Changsha 410082, Hunan, P. R. China