1. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, 2153 North Campus Drive, Evanston, Illinois 60208-3300, Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-7229, and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602