1. Division of Molecular Structure, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
2. Biomedical NMR Centre, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
3. Division of Mycobacterial Research, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
4. Department of Infection, Immunity and Inflammation, University of Leicester, Leicester LE1 9HN, UK.
5. Department of Biochemistry, University of Leicester, Leicester LE1 9HN, UK.