1. Bioelectronics Research Group, Department of Electronics, Glasgow University, Glasgow, G12 8LT, U.K., Department of Chemistry, University of Leicester, Leicester, LE1 7RH, U.K., Department of Chemistry, De Montfort University, Leicester, LE1 9BH, U.K, ISIS Facility, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, U.K., and Institut Laue-Langevin, 38042 Grenoble Cedex 9, France