1. S. X. Wang, M. Mure, and J. P. Klinman are in the Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
2. K. F. Medzihradszky and A. L. Burlingame are in the Department of Pharmaceutical Chemistry and the Liver Center, University of California, San Francisco, CA 94143, USA.
3. D. E. Brown and D. M. Dooley are in the Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
4. A. J. Smith is at the Beckman Center, Stanford University Medical Center, Stanford, CA 94305, USA.
5. H. M. Kagan is in the Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA.