1. Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, Quebec, Canada H4P 2R2, Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6, Merck Frosst Canada & Co., 16711 Trans Canada Hwy., Kirkland, Quebec, Canada H9H 3L1, Boehringer Ingelheim (Canada) Ltd., 2100 Cunard Street, Laval, Quebec, Canada H7S 2G5