Spectral Diffusion Induced by Proton Dynamics in Pigment−Protein Complexes

Brecht, Marc; Studier, Hauke; Radics, V.; Nieder, Jana B.; Bittl, Robert

doi:10.1021/ja806216p

Cited by 53 publications

(77 citation statements)

References 30 publications

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“…PCC 6803, respectively. There, a variability of the emission wavelength of an individual state in the range of 10 nm was invoked (8,23) and corroborated by observation (17). Assuming an even larger susceptibility of the emission wavelength of an individual emitting state to changes in the environment leads to the hypothesis that the emissions in the range C708 and C719 (C706 and C714) for PSI from T. elongatus (Synechocystis sp.…”

Section: Discussionmentioning

confidence: 64%

“…The fluorescence emission maxima for C706 and C714 are expected at Ϸ710 and Ϸ720 nm, respectively (26). The effect of spectral diffusion differs for these 3 contributions (17,24). F699 shows the least effect; therefore, stable ZPLs dominate the fluorescence emission at the single-molecule level.…”

Section: Resultsmentioning

confidence: 98%

“…The low probability of observing ZPLs in the spectral range of C715/719 is due to increased spectral diffusion acting on these chromophores (9,17). As a consequence, the highly dynamic ZPLs change their position faster than the experimental time resolution and mostly only broad intensity distributions can be observed (9,17).…”

Section: Resultsmentioning

confidence: 99%

“…These changes alter the site energies of chlorophyll a (Chla) molecules in the nanometer-range. A large portion of the spectral dynamics within the low tiers is connected with exchangeable hydrogens located close to the chromophores, e.g., within hydrogen bonds between the Chla molecules and nearby amino acid residues or structural water molecules (17).…”

mentioning

confidence: 99%

“…Under these conditions, the excitation energy is partially released as fluorescence light (22) with the maximum of the fluorescence emission found at wavelengths Ͼ715 nm. The number and the spectroscopic characteristics of these traps vary remarkably between PSI from different organisms (9,17,(23)(24)(25)(26)(27)(28)(29)(30). The efficient energy transfer from high-energy antenna states to the red pools is very advantageous in SMS because the whole fluorescence emission of PSI can be observed without interference by the excitation light, and the released fluorescence light contains information on the exciton transfer within PSI.…”

mentioning

confidence: 99%

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Protein dynamics-induced variation of excitation energy transfer pathways

Brecht

Radics

Nieder

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Strong anticorrelation between the fluorescence emission of different emitters is observed by employing single-molecule fluorescence spectroscopy on photosystem I at cryogenic temperatures. This anticorrelation demonstrates a time-dependent interaction between pigments participating in the exciton transfer chain, implying that uniquely defined energy transfer pathways within the complex do not exist. Fluctuations of the chromophores themselves or their immediate protein surroundings induce changes in their site energy, and, as a consequence, these fluctuations change the coupling within the excitation transfer pathways. The time scales of the site energy fluctuations of the individual emitters do not meet the time scales of the observed correlated emission behavior. Therefore, the emitters must be fed individually by energetically higher lying states, causing the observed intensity variations. This phenomenon is shown for photosystem I pigmentprotein complexes from 2 different cyanobacteria (Thermosynechococcus elongatus and Synechocystis sp. PCC 6803) with strongly different spectral properties underlining the general character of the findings. The variability of energy transfer pathways might play a key role in the extreme robustness of light-harvesting systems in general.exciton transfer ͉ FRET ͉ light harvesting ͉ photosynthesis ͉ single-molecule T he complex structural dynamics of proteins as a result of their combination of properties resembling, in part, the crystalline, the glassy, and the liquid state of matter is a prerequisite for protein function (1, 2). The picture of transitions between hierarchically ordered minima in a multidimensional configuration energy landscape (3) has emerged from the pioneering experiments of Frauenfelder et al. (4) as well as molecular dynamics simulations (5, 6). Local minima correspond to conformational substates (CS) separated by energy barriers into distinct tiers. Protein-embedded chromophore cofactors are ideal reporters for transitions between CS because of the susceptibility of their electronic transition energies on the specific conformation of their protein environment (2). The changes of the electronic transition energies (site energies) of individual chromophores are accessible by single-molecule spectroscopy (SMS) (7) on the single-protein level (8)(9)(10)(11)(12)(13)(14).The transition rates between different CS in proteins are spread out over an extremely wide range of time scales. As a consequence, for room temperature single-molecule experiments on pigment-protein complexes only transitions between CS of higher tiers occurring slower than the presently achievable time resolution of Ϸ0.1 s Ϫ1 can be monitored directly (14, 15). There, the individual spectra approximately resemble ensembleaveraged spectra with characteristic fluctuations in their width and specific position (13). Lowering the temperature slows down the transitions between CS in high tiers beyond realistic durations of the experiment, and transitions involving lower tiers move into the exper...

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Section: Discussionmentioning

confidence: 64%