1. Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, U.K., Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K., Centre for Macromolecular Hydrodynamics, University of Nottingham, Sutton Bonington, Nottingham LE12 5 RD, U.K., and Departamento de Quimica, CQFB, Universidade Nova de Lisboa, 2829-516 Monte de Caparica, Portugal