1. Department
of Physics, University of Illinois at Urbana−Champaign, 1110 W. Green Street, Urbana, Illinois 61801, United States
2. Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, 405 N. Mathews Ave, Urbana, Illinois 61801, United States
3. Department
of Biochemistry, University of Illinois at Urbana−Champaign, 600 S. Mathews Ave, Urbana, Illinois 61801, United States
4. Center
for Biophysics and Computational Biology, University of Illinois at Urbana−Champaign, 607 S. Mathews Ave, Urbana, Illinois 61801, United States
5. Department
of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
6. A. F. Ioffe Physical-Technical Institute, Politechnicheskaya 26, 194021 St. Petersburg, Russia