1. Department of ChemistrySimon Fraser University Burnaby BC V5A 1S6 Canada
2. York Structural Biology LaboratoryDepartment of ChemistryUniversity of York York YO10 5DD UK
3. Children's Medical Research InstituteThe University of Sydney Sydney NSW 2145 Australia
4. Department of Molecular Biology and BiochemistrySimon Fraser University Burnaby BC V5A 1S6 Canada
5. Chemistry, School of Environmental and Life SciencesThe University of Newcastle University Drive Callaghan NSW 2308 Australia