[1] Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, United States
[2] Department of Biochemistry, Center for Metals in Biocatalysis, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, United States
[3] Laboratory of Biochemistry, Natl. Heart, Lung/Blood Institute, National Institutes of Health, 50 South Dr., Bethesda, MD 20892, United States