1. Biological Chemistry, Biomedical Sciences Division, Sir Alexander Fleming Building, Imperial College of Science, Technology and Medicine, University of London, South Kensington, London, SW7 2AZ, U.K., Department of Analytical and Pharmaceutical Chemistry, The Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100 Copenhagen, Denmark, and Division of Analytical Sciences, GlaxoSmithKline Pharmaceuticals, New Frontiers Science Park (North), Third Avenue, Harlow, Essex, CM19 5AW, U.K.