1. Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany, Laboratorium für Organische und Bioorganische Chemie, Institut für Chemie, Universität Osnabrück, Barbarastrasse 7, 49069 Osnabrück, Germany, and Institute for Nanobiomedical Technology and Membrane Biology, State Key Laboratory of Biotherapy, West-China Medical School, Sichuan University, 610041Chengdu, China