1. Department of Molecular Microbiology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
2. Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
3. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK