Stack et. al. revised manuscript -JD-22-11-07

Institute for the Biotechnology of Infectious Diseases (IBID), University of Technology Sydney (UTS), Level 6, Building 4, Corner of Thomas & Harris Street, Ultimo, Sydney, NSW 2007, Australia. 2 presently at, Department of Medical Microbiology, University of Western Sydney (UWS), Narellan Road, Campbelltown, NSW, Australia.Sandler Center for Basic Research in Parasitic Diseases, Byers Hall N508, 1700 4th Street, University of California San Francisco, San Francisco, CA 94158, USA. Departamento de Genetica, Facultad de Medicina, UDELAR , Gral. Flores 2125, CP 11800, Montevideo, Uruguay 5 presently at, the School of Biotechnology, Dublin City University, Dublin 9, Republic of Ireland. Departments of Pharmaceutical Chemistry, Pharmacology, and Biochemistry & Biophysics, University of California San Francisco, San Francisco, CA 94158, USA, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA. presently at, Gene Center Munich, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universitat Munchen, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany. Running Title: F. hepatica Cathepsin L structure-activity relationships