1 Biophysics Program, Institute for Physical Science and Technology, Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742; dave.thirumalai@gmail.com.
2 Department of Physics, Case Western Reserve University, Cleveland, OH 44106;
3 Biophysics Program, Institute for Physical Science and Technology, Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742;
4 California Institute for Quantitative Biosciences, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.