1. University of Sofia, Faculty of Chemistry and Pharmacy,
Department of Physical Chemistry, 1 James Bourchier Avenue, 1164 Sofia, Bulgaria
2. Goethe University Frankfurt, Institute for Organic
Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max von Laue Strasse 7, 60438 Frankfurt am Main, Germany
3. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany