1. Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex
BN1 9QJ, U.K.
2. Terrence Donnelly Center for Cellular and Biomolecular
Research, University of Toronto, Toronto, Ontario
M5S 3E1, Canada
3. UK National
Crystallography Service, School
of Chemistry, University of Southampton, Highfield, Southampton SO171BJ,
U.K.