1. The Laboratory of Molecular Biophysics, Rex Richards Building, South Parks Road, Oxford, OX1 3QU, U.K., The Oxford Centre for Molecular Sciences, New Chemistry Building, South Parks Road, Oxford, OX1 3QT, U.K., Structural Biology Group, The Glaxo-Wellcome Research Laboratories, Langley Court, Beckenham, Kent, BR3 3BS, U.K., School of Pharmaceutical Sciences, Showa University, Hatanodai 1-5-8, Shinagawa-ku, Tokyo 142, Japan, and School of Chemistry, The University of Birmingham, Edgbaston, Birmingham, B15...