1. Molecular Dynamics and Photosynthesis Research Groups, Centre for Photomolecular Sciences, Department of Biochemistry and Chemistry, Imperial College, London SW7 2AY, United Kingdom, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France, and Department of Biology, Darwin Building, University College, Gower Street, London WC1E 6BT, United Kingdom