1. Laboratory of Biophysics, “Jožef Stefan” Institute, Jamova 39, SI-1000 Ljubljana, Slovenia, Department of Intelligent Systems, “Jožef Stefan” Institute, Jamova 39, SI-1000 Ljubljana, Slovenia, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia, and Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, NL-6703 HA Wageningen, The Netherlands