1. Biomedical Sciences Program, University of California San Diego, 9500 Gilman Drive, Mail Code 0365, La Jolla, California 92093-0365
2. Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K.
3. Department of Chemistry & Biochemistry, NSF Center for Theoretical Biological Physics, National Biomedical Computation Resource, University of California San Diego, La Jolla, California 92093
4. Department of Pharmacology, University of California San Diego, La Jolla, California 92093
5. Howard Hughes Medical Institute, University of California San Diego, La Jolla, California 92093