1. Departments of Biochemistry and Laboratory of Medicine and Pathology, Biomedical Engineering Center, University of Minnesota Medical School, 420 Delaware Street, S.E., Minneapolis, MN 55455, U.S.A.
2. Department of Medicinal and Natural Products Chemistry, College of Pharmacy, The University of Iowa, 115 S. Grand Ave., Iowa City, IA 52242, U.S.A