1. Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.
2. Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, U.K.
3. ENSCO Inc., Melbourne, Florida 32940, United States
4. School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K.
5. School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, U.K.
6. Foundation for Applied Molecular Evolution, Alachua, Florida 32615, United States