1. Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, China
2. Institute of Quantitative Biology and Department of Physics, Zhejiang University, Hangzhou 310027, China
3. Computational Biological Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
4. Department of Chemistry, Columbia University, New York, New York 10027, United States