1. Centre for Molecular Design, Institute of Biomedical and Biomolecular Science, University of Portsmouth, King Henry 1 Street, Portsmouth PO1 2DY, U.K., ICI Strategic Technology Group, Wilton Centre, Wilton, Redcar TS10 4RF, U.K., and ChemQuest, Delamere House, 1 Royal Crescent, Sandown, Isle of Wight PO36 8LZ U.K.