1 University of Regensburg, Institute of Biophysics and Physical Biochemistry, Centre of Magnetic Resonance in Chemistry and Biomedicine, Universitätsstraße 31, 93053 Regensburg, Germany.
2 TU Dortmund University, Physical Chemistry III, Otto-Hahn-Straße 4a, 44227 Dortmund, Germany.
3 University of Regensburg, Institute of Biophysics and Physical Biochemistry, Centre of Magnetic Resonance in Chemistry and Biomedicine, Universitätsstraße 31, 93053 Regensburg, Germany. Electronic address: hans-robert.kalbitzer@ur.de.