1. Z. R. Wu, M. E. Zawrotny, G. C. Perez-Alvarado, M. F. Summers, Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250.
2. S. Ebrahimian, L. D. Thornburg, P. Brothers, R. M. Pollack, Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, and Center for Advanced Research in Biotechnology (R. M. Pollack), 9600 Gudelsky Drive, Rockville, MD 20850.