1. Spallation Neutron Source, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, Department of Chemistry, University of Toledo, Toledo, Ohio 53606, Bioscience Division, Mailstop M888, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, and Laboratory for Protein Crystallography, Centre for Amyloidosis and Acute Phase Proteins, Department of Medicine, University College London (Hampstead Campus), Rowland Hill Street, London NW3 2PF, U.K.