1. Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, U.K.
2. Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, U.K.
3. Medicine Design, GlaxoSmithKline R&D Ltd, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, U.K.