1. Department of Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, U.K., National Research Council of Canada, Steacie Institute for Molecular Sciences, Neutron Program for Materials Research, Chalk River Laboratories, Ontario K0J 1J0, Canada, and Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ontario L8N 3Z5, Canada