1. Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Department of Physiology, Medical University of Gdańsk, Dȩbinki 1, 80-211 Gdańsk, Poland, and Group of Peptide Biochemistry, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of Czech Republic, Flemingovo Sq.2, Prague 6, CZ-16610, Czech Republic