1. Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
2. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
3. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
4. Bioenergy and Defense Technologies Department, Sandia National Laboratories, Albuquerque, New Mexico 87185
5. Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, United Kingdom
6. Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801