1. Laboratoire de Catalyse, Chimie Fine et Polymères, Institut National Polytechnique de Toulouse, Ecole Nationale Supérieure de Chimie de Toulouse, 118, Route de Narbonne, 31077 Toulouse cedex 4, France
2. Department Fisheries and Oceans, Science Branch, Environmental Sciences Division, P.O. Box 5667, St John’s, Newfoundland, Canada A1C 5X1, and Department of Biochemistry, Memorial University of Newfoundland, St John’s, Newfoundland, A1B 3X9, Canada