Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040 Regensburg, Germany and Faculty of Mathematics and Computer Science, University of Hagen, D-58084 Hagen, Germany.|Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040 Regensburg, Germany and Faculty of Mathematics and Computer Science, University of Hagen, D-58084 Hagen, Germany.|Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040 Regensburg, Germany and Faculty of Mathematics and Computer Science, University of Hagen, D-58084 Hagen, Germany.