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

Duan, H.-G., Prokhorenko, V. I., Cogdell, R. J. , Ashraf, K., Stevens, A. L., Thorwart, M. and Miller, R.J. D. (2017) Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer. Proceedings of the National Academy of Sciences of the United States of America, 114(32), pp. 8493-8498. (doi:10.1073/pnas.1702261114) (PMID:28743751)

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Abstract

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 [Formula: see text]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.

Item Type:Articles
Keywords:2D spectroscopy, Fenna–Matthews–Olson protein, exciton, photosynthesis, quantum coherence.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard and Ashraf, Mr Khuram
Authors: Duan, H.-G., Prokhorenko, V. I., Cogdell, R. J., Ashraf, K., Stevens, A. L., Thorwart, M., and Miller, R.J. D.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Proceedings of the National Academy of Sciences of the United States of America
Publisher:National Academy of Sciences
ISSN:1091-6490
ISSN (Online):1091-6490
Published Online:25 July 2017
Copyright Holders:Copyright © 2017 National Academy of Sciences
First Published:First published in Proceedings of the National Academy of Sciences of the United States of America 114(32): 8493-8498
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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