1. Department of Chemistry and Biochemistry; University of California; San Diego La Jolla California 92093-0654
2. Department of Pharmacology; University of California; San Diego La Jolla California 92093-0654
3. Howard Hughes Medical Institute; University of California; San Diego La Jolla California 92093-0654
4. Berkeley Center for Structural Biology; Lawrence Berkeley National Laboratory; Berkeley California 94720
5. Department of Pharmacology; Emory University School of Medicine, Rollins Research Center; Atlanta Georgia 30322