1. Biological Chemistry, Division of Biomedical Sciences, Sir Alexander Fleming Building, Imperial College, London SW7 2AZ, United Kingdom, Preclinical Safety Sciences, GlaxoSmithKline Research & Development, Ware, Herts. SG12 0DP, United Kingdom, and Analytical Technologies, GlaxoSmithKline Research & Development, Stevenage, Herts., SG1 2NY, United Kingdom