1. Center for Biophysics and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
2. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
3. Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States