1. Department
of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
2. Protein
and Peptide Pharmaceutical Laboratory, Institute of Biophysics Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, People’s Republic of China
3. Department
of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80303, United States