1. Department of ChemistryInstitute of BiochemistryUniversity of Cologne Zülpicher Straße 47 50674 Cologne Germany
2. Medical Biochemistry and Molecular BiologySaarland University Kirrberger Str., Building 44 66421 Homburg Germany
3. Institute II of Pharmacology, Center of Pharmacology, Medical FacultyUniversity of Cologne Gleueler Str. 24 50931 Cologne Germany