Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer [Physics]
![Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer [Physics]](/image/eyJ1cmkiOiJodHRwOi8vc3RhY2thZGVtaWMuaGVyb2t1YXBwLmNvbS9pbWFnZT9pbWFnZV9pZD04MTEwIiwiZm9ybWF0Ijoid2VicCIsInF1YWxpdHkiOjEwMCwibm9DYWNoZSI6dHJ1ZX0=.webp)
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.
Publisher URL: http://feedproxy.google.com/~r/Pnas-RssFeedOfEarlyEditionArticles/~3/wvhK-G2l94M/1702261114.short
DOI: 10.1073/pnas.1702261114
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