1. Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, Department of Pathology and Laboratory Medicine and Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada V5Z 4H4, and Graduate Program in Biochemistry and Structural Biology and Graduate Program in Biophysics, State University of New York at Stony Brook, Stony Brook, New York 11794-3400