1. Department
of Chemistry, University of Oxford, Oxford OX1 3TA, U.K.
2. Groningen
Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
3. Department
of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, United States
4. Department
of Pharmacology, University of Alberta, Edmonton, AB T6G 2R3, Canada