1. Department of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland
2. Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
3. Department of Parasitology and Laboratory Practices, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27514, USA
4. Department of Biochemistry, University of Edinburgh, Edinburgh EH8 9XD, Scotland