1. Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada
2. Institut für Biochemie und Molekulare Medizin, Universität Bern, Bühlstr. 28, CH-3012 Bern, Switzerland
3. Department of Molecular Genetics, University of Toronto, 1 King’s College Circle, Toronto, ON M5S 1A8, Canada