1. Biosciences at Rice, Rice University, 6100 Main St., Houston, Texas 77005, USA
2. Biosciences Division, Midwest Center for Structural Genomics, Argonne National Laboratory, Bldg. 446/Rm. A104, 970 South Cass Avenue, Argonne, Illinois 60439, USA
3. Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
4. Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, USA