James A Wells1, Anthony A Kossiakoff2. 1. Pharmaceutical Chemistry; Cellular and Molecular Pharmacology, University of California, San Francisco, 1700 4th Street, San Francisco, CA 94158, USA. jim.wells@ucsf.edu koss@bsd.uchicago.edu. 2. Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA. jim.wells@ucsf.edu koss@bsd.uchicago.edu.