1. Department of Molecular and Cell Biology, Department of Physics, Howard Hughes Medical Institute, and Kavli Energy NanoScience Institute, University of California, Berkeley, California 94720, USA;
2. Department of Chemistry, University of California, Berkeley, California 94720, USA
3. Cell, Molecular, Developmental Biology, and Biophysics Graduate Program, Johns Hopkins University, Baltimore, Maryland 21218, USA
4. Department of Biology and Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA;