Coherent wavepackets in the Fenna–Matthews–Olson complex are robust to excitonic-structure perturbations caused by mutagenesis


Femtosecond pulsed excitation of light-harvesting complexes creates oscillatory features in their response. This phenomenon has inspired a large body of work aimed at uncovering the origin of the coherent beatings and possible implications for function. Here we exploit site-directed mutagenesis to change the excitonic level structure in Fenna–Matthews–Olson (FMO) complexes and compare the coherences using broadband pump–probe spectroscopy. Our experiments detect two oscillation frequencies with dephasing on a picosecond timescale—both at 77 K and at room temperature. By studying these coherences with selective excitation pump–probe experiments, where pump excitation is in resonance only with the lowest excitonic state, we show that the key contributions to these oscillations stem from ground-state vibrational wavepackets. These experiments explicitly show that the coherences—although in the ground electronic state—can be probed at the absorption resonances of other bacteriochlorophyll molecules because of delocalization of the electronic excitation over several chromophores.

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Figure 1: Crystal structure, stationary and transient absorption spectra of wild-type and mutated FMO complexes.
Figure 2: Coherent oscillations and corresponding Fourier spectra obtained from broadband pump–probe data of various FMO complexes.
Figure 3: Coherent oscillations and corresponding Fourier spectra obtained from selective pump–probe data of various FMO complexes.
Figure 4: Selective pump–probe data of wild-type FMO complex.


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This work was supported as part of the Photosynthetic Antenna Research Center, an Energy Frontier Research Center funded by the Basic Energy Sciences programme of the US Department of Energy Office of Science under award DE-SC0001035. M.M. acknowledges financial support by the European Community (H2020 Marie Skłodowska–Curie Actions), under project no. 655059. G.D.S. acknowledges CIFAR, the Canadian Institute for Advanced Research, for support through its Bio-Inspired Solar Energy programme.

Author information

R.E.B. and G.D.S. conceived the research. E.E.O. designed the ultrafast spectrometer. M.M. and E.E.O. performed the pump–probe experiments. M.M. analysed the experimental data. M.M., E.E.O. and R.G.S. discussed the experimental data. R.G.S. prepared the mutated FMO complexes. M.M., E.E.O. and G.D.S. wrote the paper. All authors commented on the manuscript.

Correspondence to Gregory D. Scholes.

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Maiuri, M., Ostroumov, E., Saer, R. et al. Coherent wavepackets in the Fenna–Matthews–Olson complex are robust to excitonic-structure perturbations caused by mutagenesis. Nature Chem 10, 177–183 (2018).

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