1. Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
2. Center for Biophysics and Quantitative Biology, 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