1. Department of Molecular and Cellular Biology, University of California–Berkeley, Berkeley, CA 94720, USA.
2. Department of Bioengineering and Biophysics Group, University of California–Berkeley, Berkeley, CA 94720, USA.
3. Miller Institute for Basic Research in Science, University of California–Berkeley, Berkeley, CA 94720, USA.
4. Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.