1. School of Chemistry, University of Bristol Molecular Recognition Centre, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K., Department of Biochemistry, University of Bristol Molecular Recognition Centre, University of Bristol, University Walk, Bristol BS8 1TD, U.K., Department of Chemistry, Ultra High Field NMR Centre, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, U.K., and John Innes Centre, Norwich NR4 7UH, U.K.