1. School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, U.K., Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University of London, 29−39 Brunswick Square, London WC1N 1AX, U.K., and School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, Norfolk NR4 7TJ, U.K.