1. Institute of Chemistry, Karl Franzens University Graz, Heinrichstrasse 28, A-8010 Graz, Austria, Institute of Molecular Biology, Biochemistry and Microbiology, Karl Franzens University Graz, Universitätsplatz 2, A-8010 Graz, Austria, Bruker Analytik GMBH, Silberstreifen, Rheinstetten/Karlsruhe, Germany, and Institute of Pharmazeutical Chemistry, Karl Franzens University Graz, Schubertstrasse 6, A-8010 Graz, Austria