1. Department of Biological Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, U.K., Department of Computer Science and Department of Mathematics, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, U.K., Biostructure Department, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Måløv, Denmark, Novartis Institute for Medical Sciences, 5 Gower Place, London, WC1E 6BN, U.K., and Novartis, Horsham Research Centre, Wimblehurst Road, Horsham, West Sussex, RH12 5AB, U.K.