On destabilization of the Fenna–Matthews–Olson complex of Chlorobaculum tepidum
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The Fenna–Matthews–Olson (FMO) complex from the green sulfur bacterium Chlorobaculum tepidum was studied with respect to its stability. We provide a critical assessment of published and recently measured optical spectra. FMO complexes were found to destabilize over time producing spectral shifts, with destabilized samples having significantly higher hole-burning efficiencies; indicating a remodeled protein energy landscape. Observed correlated peak shifts near 825 and 815 nm suggest possible correlated (protein) fluctuations. It is proposed that the value of 35 cm−1 widely used for reorganization energy (E λ ), which has important implications for the contributions to the coherence rate (Kreisbeck and Kramer 3:2828–2833, 2012), in various modeling studies of two-dimensional electronic spectra is overestimated. We demonstrate that the value of E λ is most likely about 15–22 cm−1 and suggest that spectra reported in the literature (often measured on different FMO samples) exhibit varied peak positions due to different purification/isolation procedures or destabilization effects.
KeywordsFMO Light harvesting Photosynthesis Spectral hole burning
Excitation energy transfer
This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy (Grant DE-FG02-11ER16281 to R.J). Authors are thankful to Mike Reppert (The University of Chicago) and Dr. Valter Zazubovich (Concordia University) for fruitful discussions at the early stage of this work. FMO complexes were kindly provided by Dr. Jianzhong Wen (Washington University in St. Louis).
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