1. Program in Biophysics, Stanford University, Stanford, California 94305, United States
2. Department of Computer Science, Stanford University, Stanford, California 94305, United States
3. Department of Chemistry, Stanford University, Stanford, California 94305, United States
4. School of Mathematical Sciences and College of Life Sciences, Nankai University, Tianjin 300071, China
5. Department of Bioengineering, Stanford University, Stanford, California 94305, United States