A single chlorophyll in each of the core antennas CP43 and CP47 transferring excitation energies to the reaction center in Photosystem II of photosynthesis

Saito, Keisuke; Kikuchi, Toshihiro; Nakayama, Miki; Mukai, Koichiro; Sumi, Hitoshi

doi:10.1016/j.jphotochem.2005.10.038

Cited by 8 publications

(12 citation statements)

References 44 publications

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“…We conclude that the kinetic model applied earlier describing energy transfer and charge separation within the D1D2-RC (16), together with two antenna compartments that transfer energy on a slow timescale, explains energy and electron transfer in the PSII core very well. The slow energy transfer from the core antennas to the D1D2-RC is in agreement with the structural data (7,9,39), but in contrast to the fast (, 1 ps) equilibration rate proposed from earlier photon counting emission data (22).…”

Section: Kinetic Model Amplitude Matrix and Target Analysissupporting

confidence: 89%

Charge Separation and Energy Transfer in the Photosystem II Core Complex Studied by Femtosecond Midinfrared Spectroscopy

Pawlowicz

Groot

Stokkum

et al. 2007

Biophysical Journal

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The core of photosystem II (PSII) of green plants contains the reaction center (RC) proteins D1D2-cytb559 and two core antennas CP43 and CP47. We have used time-resolved visible pump/midinfrared probe spectroscopy in the region between 1600 and 1800 cm(-1) to study the energy transfer and charge separation events within PSII cores. The absorption difference spectra in the region of the keto and ester chlorophyll modes show spectral evolution with time constants of 3 ps, 27 ps, 200 ps, and 2 ns. Comparison of infrared (IR) difference spectra obtained for the isolated antennas CP43 and CP47 and the D1D2-RC with those measured for the PSII core allowed us to identify the features specific for each of the PSII core components. From the presence of the CP43 and CP47 specific features in the spectra up to time delays of 20-30 ps, we conclude that the main part of the energy transfer from the antennas to the RC occurs on this timescale. Direct excitation of the pigments in the RC evolution associated difference spectra to radical pair formation of PD1+PheoD1- on the same timescale as multi-excitation annihilation and excited state equilibration within the antennas CP43 and CP47, which occur within approximately 1-3 ps. The formation of the earlier radical pair ChlD1+PheoD1-, as identified in isolated D1D2 complexes with time-resolved mid-IR spectroscopy is not observed in the current data, probably because of its relatively low concentration. Relaxation of the state PD1+PheoD1-, caused by a drop in free energy, occurs in 200 ps in closed cores. We conclude that the kinetic model proposed earlier for the energy and electron transfer dynamics within the D1D2-RC, plus two slowly energy-transferring antennas C43 and CP47 explain the complex excited state and charge separation dynamics in the PSII core very well. We further show that the time-resolved IR-difference spectrum of PD1+PheoD1- as observed in PSII cores is virtually identical to that observed in the isolated D1D2-RC complex of PSII, demonstrating that the local structure of the primary reactants has remained intact in the isolated D1D2 complex.

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Section: Kinetic Model Amplitude Matrix and Target Analysissupporting

confidence: 89%

Charge Separation and Energy Transfer in the Photosystem II Core Complex Studied by Femtosecond Midinfrared Spectroscopy

Pawlowicz

Groot

Stokkum

et al. 2007

Biophysical Journal

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“…Slow energy transfer from the antenna to the RC, occurring with an estimated intrinsic time scale of 20 ps (Figure ), plays a significant role in this equilibration time. Excitation energy equilibration between antenna and RC is thus found to occur on a larger time scale than proposed by the ERPE model (<3 ps) and consequently meets predictions from the X-ray structure. ,,,, …”

Section: Discussionsupporting

confidence: 62%

“…However, from Table it is observed that Miloslavina’s model results in an apparent energy equilibration time between antenna and RC of only 1.8 ps. Consequently, the model in Figure is favored with respect to that proposed by Miloslavina et al, because it is more consistent with the predictions from the X-ray structure. ,,,, Mutagenesis studies that perturb the radical pair free energy in a controlled way could be useful to distinguish between both models.…”

Section: Resultsmentioning

confidence: 56%

Charge Separation is Virtually Irreversible in Photosystem II Core Complexes with Oxidized Primary Quinone Acceptor

et al. 2011

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X-ray structures of the Photosystem II (PSII) core revealed relatively large interpigment distances between the CP43 and CP47 antenna complexes and the reaction center (RC) with respect to the interpigment distances in a single unit. This finding questions the possibility of fast energy equilibration among the antenna and the RC, which has been the basic explanation for the measured PSII fluorescence kinetics for more than two decades. In this study, we present time-resolved fluorescence measurements obtained with a streak-camera setup on PSII core complexes from Thermosynechococcus elongatus at room temperature (RT) and at 77 K. Kinetic modeling of the RT data obtained with oxidized quinone acceptor Q(A), reveals that the kinetics are best described by fast primary charge separation at a time scale of 1.5 ps and slow energy transfer from the antenna into the RC, which results in an energy equilibration time between the antenna and the RC of about 44 ps. This model is consistent with structure-based computations. Primary radical pair formation was found to be a virtually irreversible process. Energy equilibration within the CP43 and CP47 complexes is shown to occur at a time scale of 8 ps. Kinetic modeling of the 77 K data reveals similar energy transfer time scales in the antenna units and among the antenna and the RC as at RT, respectively, 7 and 37 ps. We conclude that the energy transfer from the CP43/CP47 antenna to the RC is the dominant factor in the total charge separation kinetics in intact PSII cores.

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“…A fit based on a kinetic model suggested that the slower trapping observed in CP47-RC is caused by a shift of the excited states distribution toward the CP47 antenna, and that the intrinsic rate for energy transfer from CP47 to RC does not limit the overall trapping kinetics in the CP47-RC complex. In contrast to these experimental studies recent resolved visible pump/mid-IR probe studies of the plant PSII core complexes (Pawlowicz et al 2007) and structure-based theoretical calculations (Saito et al 2006) are both in agreement with slow energy transfer from CP43/CP47 antenna to the RC.…”

Section: Modeling Of Excitation Transfer and Trapping In Isolated Reamentioning

confidence: 67%

“…This implies a very hydrophobic surrounding of P in the RC. As a consequence of such surroundings, the excitation energy of P* is elevated in PSII (Saito et al 2005(Saito et al , 2006.…”

Section: Optical Transition Energies Of Pigments In Photosystem IImentioning

confidence: 99%

Toward understanding molecular mechanisms of light harvesting and charge separation in photosystem II

Vassiliev

Bruce

2008

Photosynth Res

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Conversion of light energy in photosynthesis is extremely fast and efficient, and understanding the nature of this complex photophysical process is challenging. This review describes current progress in understanding molecular mechanisms of light harvesting and charge separation in photosystem II (PSII). Breakthroughs in X-ray crystallography have allowed the development and testing of more detailed kinetic models than have previously been possible. However, due to the complexity of the light conversion processes, satisfactory descriptions remain elusive. Recent advances point out the importance of variations in the photochemical properties of PSII in situ in different thylakoid membrane regions as well as the advantages of combining sophisticated time-resolved spectroscopic experiments with atomic level computational modeling which includes the effects of molecular dynamics.

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A single chlorophyll in each of the core antennas CP43 and CP47 transferring excitation energies to the reaction center in Photosystem II of photosynthesis

Cited by 8 publications

References 44 publications

Charge Separation and Energy Transfer in the Photosystem II Core Complex Studied by Femtosecond Midinfrared Spectroscopy

Charge Separation and Energy Transfer in the Photosystem II Core Complex Studied by Femtosecond Midinfrared Spectroscopy

Charge Separation is Virtually Irreversible in Photosystem II Core Complexes with Oxidized Primary Quinone Acceptor

Toward understanding molecular mechanisms of light harvesting and charge separation in photosystem II

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