Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

Journal Article · Tue Jul 25 00:00:00 EDT 2017 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1702261114· OSTI ID:1372716

Duan, Hong-Guang ^[1]; Prokhorenko, Valentyn I. ^[2]; Cogdell, Richard J. ^[3]; Ashraf, Khuram ^[3]; Stevens, Amy L. ^[4]; Thorwart, Michael ^[5]; Miller, R. J. Dwayne ^[4]

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1. Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany,, I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany,, The Hamburg Center for Ultrafast Imaging, 22761 Hamburg, Germany,
2. Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany,
3. Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Science, University of Glasgow, Glasgow G12 8QQ, United Kingdom,
4. Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany,, The Hamburg Center for Ultrafast Imaging, 22761 Hamburg, Germany,, Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6,, Department of Physics, University of Toronto, Toronto, ON, Canada M5S 3H6
5. I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany,, The Hamburg Center for Ultrafast Imaging, 22761 Hamburg, Germany,

During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales <100 fs. Today’s understanding of the energy transfer includes the fact that the excitons are delocalized over a few neighboring sites, but the role of quantum coherence is considered as irrelevant for the transfer dynamics because it typically decays within a few tens of femtoseconds. This orthodox picture of incoherent energy transfer between clusters of a few pigments sharing delocalized excitons has been challenged by ultrafast optical spectroscopy experiments with the Fenna–Matthews–Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

• Research Organization: Washington Univ., St. Louis, MO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0001035
• OSTI ID: 1372716
• Alternate ID(s): OSTI ID: 1465780
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Vol. 114 Journal Issue: 32; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of Sciences
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES