1. Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195Berlin, Germany
2. Genetic Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195Berlin, Germany
3. Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden