1. Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, 112 Sienkiewicza Str., 90-363 Lodz, Poland, and Medical University of Lodz, Department of Structural Biology, 7/9 Zeligowskiego Str., 90-752 Lodz, Poland lwozniak@achilles.wam.lodz.pl