1. Departments of Chemistry and Biophysics, University of Illinois at Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, Laboratory of Molecular Parasitology, Department of Pathobiology, University of Illinois at Urbana−Champaign, 2001 South Lincoln Avenue, Urbana, Illinois 61802, Laboratorio de Química Biológica, Instituto Venezolano de Investigaciones Cientificas, Apartado Postal 21.627, Caracas 1020A, Venezuela, and Department of Infectious and Tropical Diseases, London School of Hygiene...