1. Edinburgh Centre for Molecular Recognition, Department of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, U.K.
2. Department of Biochemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
3. Edinburgh Centre for Molecular Recognition, Institute of Cell and Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, Scotland, U.K.