1. Department of Biosciences, Durham University, Durham DH1 3LE, U.K.
2. Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
3. School of Biosciences, University of Kent, Canterbury CT2 7NJ, U.K.
4. Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
5. Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, U.K.