1. Department of Physical Chemistry, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
2. Centro de Investigacións Cientı́ficas Avanzadas and Departamento de Quı́mica, Facultade de Ciencias, Universidade da Coruña, 15071 Coruña, Galicia, Spain
3. Univ. Brest, UMR-CNRS 6521 CEMCA, 6, av. Victor le Gorgeu, 29200 Brest, France
4. MR Neuroimaging Agents, Max Planck Institute for Biological Cybernetics, 72076 Tuebingen, Germany
5. Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France