1. Centre for Synthetic Biology and Innovation, South Kensington, Imperial College London, SW7 2AZ, UK
2. Department of Bioengineering, South Kensington, Imperial College London, SW7 2AZ, UK. Fax: +44 (0)20-7594-7615
3. Division of Molecular Biosciences, South Kensington, Imperial College London, SW7 2AZ, UK. Fax: +44 (0)20-7594-5288