Yann R Chemla1, Taekjip Ha2. 1. Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61820, USA. ychemla@illinois.edu tjha@illinois.edu. 2. Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61820, USA. Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61820, USA. ychemla@illinois.edu tjha@illinois.edu.