1. Department of Analytical Biochemistry; University of Groningen; Antonius Deusinglaan 1 9713 AV Groningen The Netherlands
2. Department Pharmacokinetics; Toxicology and Targeting; University of Groningen; Antonius Deusinglaan 1 9713 AV Groningen The Netherlands
3. Department of Neurology; Erasmus University Medical Center; P. O. Box 1738 3000 DR Rotterdam The Netherlands
4. Department of Bio-Organic Synthesis; Leiden University; P. O. Box 9502 2300 RA Leiden The Netherlands