1. Department of Nuclear Medicine, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich 81675, Germany
2. Lehrstuhl für Biologische Chemie, School of Life Sciences, Technical University of Munich, Freising 85354, Germany
3. Department of Nuclear Medicine, Medical University Innsbruck, Innsbruck 6020, Austria
4. Laboratory of Structural Biology, Institute of Biotechnology, Czech Academy of Sciences, Vestec 252 50, Czech Republic