Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040, Regensburg, Germany.|Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040, Regensburg, Germany.|Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040, Regensburg, Germany. Rainer.Merkl@ur.de.