[1] Division of Infection, Research Institute, Hospital for Sick Children, Toronto, Ont. M5G 1X8, Canada
[2] Department of Organic Chemistry 2, Chemical Center, P.O. Box 124, S-221-00 Lund, Sweden
[3] Department of Medical Biochemistry, University of Goteborg, Medicinaregatan 7, 405 30 Goteborg, Sweden
[4] Department of Biochemistry, University of Toronto, Toronto, Ont., Canada