Electronic excitation transfer in the photosynthetic unit: Reflections on work of William Arnold

Knox, Robert

doi:10.1007/bf00040993

Cited by 36 publications

(25 citation statements)

References 31 publications

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“…1 Several theoretical models predict, however, that in cases where the coupling between chromophores is strong, the Förster model is inadequate. [2][3][4] Historically, the Fenna-Matthews-Olson complex (FMO) has provided a convenient model system for studies of energy transfer in photosynthesis where the classical Förster model breaks down. 4,5 Like most photosynthetic antennae, FMO consists of an array of chromophores embedded within a protein scaffold.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional electronic spectroscopy of bacteriochlorophyll a in solution: Elucidating the coherence dynamics of the Fenna-Matthews-Olson complex using its chromophore as a control

Fransted

Caram

Hayes

et al. 2012

The Journal of Chemical Physics

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Following the observation of long-lived coherences in the two-dimensional (2D) electronic spectra of the Fenna-Matthews-Olson (FMO) complex, many theoretical works suggest that coherences between excitons may play a role in the efficient energy transfer that occurs in photosynthetic antennae. This interpretation of the dynamics depends on the assignment of quantum beating signals to superpositions of excitons, which is complicated by the possibility of observing both electronic and vibrational coherences in 2D spectra. Here, we explore 2D spectra of bacteriochlorophyll a (BChla) in solution in an attempt to isolate vibrational beating signals in the absence of excitonic signals to identify the origin of the quantum beats in 2D spectra of FMO. Even at high laser power, our BChla spectra show strong beating only from the nonresonant response of the solvent. The beating signals that we can conclusively assign to vibrational modes of BChla are only slightly above the noise and at higher frequencies than those previously observed in spectra of FMO. Our results suggest that the beating observed in spectra of FMO is of a radically different character than the signals observed here and can therefore be attributed to electronic coherences or intermolecular degrees of freedom.

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Section: Introductionmentioning

confidence: 99%

Two-dimensional electronic spectroscopy of bacteriochlorophyll a in solution: Elucidating the coherence dynamics of the Fenna-Matthews-Olson complex using its chromophore as a control

Fransted

Caram

Hayes

et al. 2012

The Journal of Chemical Physics

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“…A more complete description of this connection is found in Ref. 12. On a personal note, Kenkre and I were able to tell Förster about this result in Rochester, less than a year before his untimely death in 1974.…”

Section: Strong and Weak Coupling Problemmentioning

confidence: 89%

“…Oppenheimer questioned how excitation moved from phycocyanin to Chlorophyll, came up with a version of Förster's mechanism that predicted the equivalent of "R −6 transfer." The connection has to be carefully gleaned 12 from the Arnold-Oppenheimer papers. 13,14 In 1947, Förster himself considered the photosynthesis problem, 15 but results of more intensive experimental work of the 1950s…”

Section: Excitation Transfer 1930 To 1945mentioning

confidence: 99%

Förster’s resonance excitation transfer theory: not just a formula

Knox

2012

J. Biomed. Opt.

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Abstract. After 65 years of increasing scrutiny and application, Theodor Förster's treatment of resonance excitation transfer is widely quoted and has acquired the acronym FRET, in which "F" originally and rather curiously stood for "fluorescence." In this brief and mostly qualitative survey, we review some of its history, mention its important limitations, and relate some personal encounters with Förster.

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“…[1][2][3][4] While incoherent (or hopping) dynamics has been found to be the dominant mechanism of energy transfer, it is not the only mechanism. 5 Coherent dynamics involves ballistic energy flow between sites. It has been suggested that energy transfer is characterized by interplay of the two regimes.…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that energy transfer is characterized by interplay of the two regimes. 5,6 The microscopic distinction between the regimes arises from how the bath interacts with the electronic states. While fourwave mixing experiments had been employed to understand coherent and incoherent nuclear motion and energy transfer dynamics in biological systems, 7,8 the development of twodimensional electronic spectroscopy (2DES) has facilitated detailed analysis of four-wave mixing signals by resolving absorption and emission frequencies.…”

Section: Introductionmentioning

confidence: 99%

Towards quantification of vibronic coupling in photosynthetic antenna complexes

Singh

Westberg

Wang

et al. 2015

The Journal of Chemical Physics

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Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency-by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime. C 2015 AIP Publishing LLC. [http://dx

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Electronic excitation transfer in the photosynthetic unit: Reflections on work of William Arnold

Cited by 36 publications

References 31 publications

Two-dimensional electronic spectroscopy of bacteriochlorophyll a in solution: Elucidating the coherence dynamics of the Fenna-Matthews-Olson complex using its chromophore as a control

Two-dimensional electronic spectroscopy of bacteriochlorophyll a in solution: Elucidating the coherence dynamics of the Fenna-Matthews-Olson complex using its chromophore as a control

Förster’s resonance excitation transfer theory: not just a formula

Towards quantification of vibronic coupling in photosynthetic antenna complexes

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