1. Institute of Polymers, Bulgarian Academy of Sciences, Akad. G. Bonchev St. 103A, 1113 Sofia, Bulgaria
2. Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, Zabrze, Poland
3. Department of Biochemistry, Faculty of Biology, Sofia University St. Kliment Ohridski, Dragan Tsankov Blvd. 8, 1164 Sofia, Bulgaria