1. Protein Science Laboratory of the Ministry of Education; School of Life Sciences; Tsinghua University; Beijing 100084 China
2. Department of Biomaterials; Max Planck Institute of Colloids and Interfaces; Potsdam 14476 Germany
3. Department of Biotechnology and Biomedicine; Yangtze Delta Region Institute of Tsinghua University; Jiaxing Zhejiang Province 314006 China
4. Department of Chemistry; University of Alberta; Edmonton AB T6G2G2 Canada