Supporting Information Appendix to Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

The Fenna-Matthews-Olson (FMO) protein complex was prepared from cells of the thermophilic green sulfur bacterium Chlorobium tepidum. A strain of C. tepidum that had been engineered to produce a His-tagged version of its reaction center was used in order to simplify the purification strategy. This strain was a gift of Prof. Oh-Oka (1). The cells were grown anaerobically in the light in modified Pfennig’s media (2). New cultures were allowed to go fully anaerobic in the dark overnight, then they were grown at a light intensity of about 30 micromoles photons m−2s−1 at 43◦ C for 2 to 3 days. When fully grown, the cells were harvested by centrifugation at 12,000 x g for 20 min. The reaction centres (which bind FMO) were isolated from broken cells (3). At the stage of the nickel affinity column chromatography a high salt wash at 500 mM NaCl elutes the FMO complexes. This dilute solution of FMO was then purified by a combination of ion exchange chromatography on a Whatrman DE52 cellulose resin and size exclusion chromatography on a Sepharose S-200 column.