1. Department of Pharmacology, University of Texas Southwestern
Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas
75390-9050, Department of Chemistry and Biochemistry, Center for Theoretical
Biological Physics, University of California at San Diego, La Jolla,
California 92093, and College of Chemistry and Molecular Engineering,
Peking University, Beijing 100871, P.R. China