1. Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, USA.
2. Department of Biostatistics, Columbia University, New York, NY 10032, USA.
3. Harvard University Center for Systems Biology, Cambridge, MA 02138, USA.
4. Department of Chemistry, University of California, Berkeley, CA 94720, USA.
5. QB3 Institute and Jason L. Choy Laboratory of Single Molecule Biophysics, Department of Molecular and Cellular Biology, Department of Physics, and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA.