1. Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The
Netherlands
2. Groningen Biomolecular Sciences and Biotechnology Institute, 9747 AG Groningen,
The Netherlands
3. Max-Planck-Institut für Bioanorganische Chemie, D-45470 Mülheim
a. d. Ruhr, Germany
4. Department
of Biochemistry and
Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States