Reaction centers of photosystem II with a chemically‐modified pigment composition: exchange of pheophytins with 131‐deoxo‐131‐hydroxy‐pheophytin a

Shkuropatov, A. Ya.; Khatypov, R. A.; Shkuropatova, V. A.; Zvereva, M. G.; Owens, Thomas G.; Шувалов, В.А.

doi:10.1016/s0014-5793(99)00486-x

Cited by 35 publications

(27 citation statements)

References 21 publications

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“…The main changes are related to the bleaching of Soret and Q Y bands of Chl/Pheo molecules at *430 and 682 nm, respectively, including stimulated emission from those molecules, which gives more intensive bleaching in red than in blue. In agreement with the previous measurements (Shkuropatov et al 1999) indicating that both Pheo molecules contribute to the most red absorption in the RC around 680 nm, the bleaching of the Q x band of Pheo at about 545 nm is observed at early delay times (0.1-0.2 ps) and persists up to 28.5 ps, the longest delay time employed in this work. The amplitude of the 545-nm bleaching is almost constant within this time period.…”

Section: Femtosecond Laser Photolysis Setupsupporting

confidence: 93%

Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: II. Femto- and picosecond charge separation in PSII D1/D2/Cyt b559 complex

et al. 2008

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In Part I of the article, a review of recent data on electron-transfer reactions in photosystem II (PSII) and bacterial reaction center (RC) has been presented. In Part II, transient absorption difference spectroscopy with 20-fs resolution was applied to study the primary charge separation in PSII RC (DI/DII/Cyt b 559 complex) excited at 700 nm at 278 K. It was shown that the initial electron-transfer reaction occurs within 0.9 ps with the formation of the charge-separated state P680(+)Chl(D1)(-), which relaxed within 14 ps as indicated by reversible bleaching of 670-nm band that was tentatively assigned to the Chl(D1) absorption. The subsequent electron transfer from Chl(D1)(-) within 14 ps was accompanied by a development of the radical anion band of Pheo(D1) at 445 nm, attributable to the formation of the secondary radical pair P680(+)Pheo(D1)(-). The key point of this model is that the most blue Q(y) transition of Chl(D1) in RC is allowing an effective stabilization of separated charges. Although an alternative mechanism of charge separation with Chl(D1)* as a primary electron donor and Pheo(D1) as a primary acceptor can not be ruled out, it is less consistent with the kinetics and spectra of absorbance changes induced in the PSII RC preparation by femtosecond excitation at 700 nm.

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Section: Femtosecond Laser Photolysis Setupsupporting

confidence: 93%

Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: II. Femto- and picosecond charge separation in PSII D1/D2/Cyt b559 complex

et al. 2008

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“…1 it was assumed that the electron is localized at the pheophytin of the D1-branch, Pheo D1 , and the hole resides at the special-pair chlorophyll of the same branch, P D1 . The first assumption is justified by the fact that electron transfer occurs only along the D1-branch (31,32) and the second one, suggested earlier from difference spectra measured on mutant core complexes (19), was verified by considering different possibilities of hole stabilization as discussed in detail further below. The experimental and calculated spectra show two bleachings, one at ;675 nm and one at ;685 nm.…”

Section: Resultsmentioning

confidence: 82%

Spectroscopic Properties of Reaction Center Pigments in Photosystem II Core Complexes: Revision of the Multimer Model

Raszewski

Diner

Schlodder

et al. 2008

Biophysical Journal

146

198

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Absorbance difference spectra associated with the light-induced formation of functional states in photosystem II core complexes from Thermosynechococcus elongatus and Synechocystis sp. PCC 6803 (e.g., P(+)Pheo(-),P(+)Q(A)(-),(3)P) are described quantitatively in the framework of exciton theory. In addition, effects are analyzed of site-directed mutations of D1-His(198), the axial ligand of the special-pair chlorophyll P(D1), and D1-Thr(179), an amino-acid residue nearest to the accessory chlorophyll Chl(D1), on the spectral properties of the reaction center pigments. Using pigment transition energies (site energies) determined previously from independent experiments on D1-D2-cytb559 complexes, good agreement between calculated and experimental spectra is obtained. The only difference in site energies of the reaction center pigments in D1-D2-cytb559 and photosystem II core complexes concerns Chl(D1). Compared to isolated reaction centers, the site energy of Chl(D1) is red-shifted by 4 nm and less inhomogeneously distributed in core complexes. The site energies cause primary electron transfer at cryogenic temperatures to be initiated by an excited state that is strongly localized on Chl(D1) rather than from a delocalized state as assumed in the previously described multimer model. This result is consistent with earlier experimental data on special-pair mutants and with our previous calculations on D1-D2-cytb559 complexes. The calculations show that at 5 K the lowest excited state of the reaction center is lower by approximately 10 nm than the low-energy exciton state of the two special-pair chlorophylls P(D1) and P(D2) which form an excitonic dimer. The experimental temperature dependence of the wild-type difference spectra can only be understood in this model if temperature-dependent site energies are assumed for Chl(D1) and P(D1), reducing the above energy gap from 10 to 6 nm upon increasing the temperature from 5 to 300 K. At physiological temperature, there are considerable contributions from all pigments to the equilibrated excited state P*. The contribution of Chl(D1) is twice that of P(D1) at ambient temperature, making it likely that the primary charge separation will be initiated by Chl(D1) under these conditions. The calculations of absorbance difference spectra provide independent evidence that after primary electron transfer the hole stabilizes at P(D1), and that the physiologically dangerous charge recombination triplets, which may form under light stress, equilibrate between Chl(D1) and P(D1).

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“…As in the bacterial reaction center (bRC), electron transfer in PS-II is known (Shkuropatov et al, 1997(Shkuropatov et al, , 1999 to proceed only along one of the two branches, which are related by a pseudo-twofold rotation symmetry. However, an important difference between these two types of RCs is that only the PS-II RC can create a high enough redox potential for the splitting of water and the evolution of oxygen that forms the basis for life.…”

Section: Introductionmentioning

confidence: 99%

Theory of Optical Spectra of Photosystem II Reaction Centers: Location of the Triplet State and the Identity of the Primary Electron Donor

Raszewski

Saenger

Renger

2005

Biophysical Journal

184

282

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Based on the structural analysis of photosystem II of Thermosynechococcus elongatus, a detailed calculation of optical properties of reaction-center (D1-D2) complexes is presented applying a theory developed previously. The calculations of absorption, linear dichroism, circular dichroism, fluorescence spectra, all at 6 K, and the temperature-dependence of the absorption spectrum are used to extract the local optical transition energies of the reaction-center pigments, the so-called site energies, from experimental data. The site energies are verified by calculations and comparison with seven additional independent experiments. Exciton relaxation and primary electron transfer in the reaction center are studied using the site energies. The calculations are used to interpret transient optical data. Evidence is provided for the accessory chlorophyll of the D1-branch as being the primary electron donor and the location of the triplet state at low temperatures.

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Reaction centers of photosystem II with a chemically‐modified pigment composition: exchange of pheophytins with 13¹‐deoxo‐13¹‐hydroxy‐pheophytin a

Cited by 35 publications

References 21 publications

Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: II. Femto- and picosecond charge separation in PSII D1/D2/Cyt b559 complex

Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: II. Femto- and picosecond charge separation in PSII D1/D2/Cyt b559 complex

Spectroscopic Properties of Reaction Center Pigments in Photosystem II Core Complexes: Revision of the Multimer Model

Theory of Optical Spectra of Photosystem II Reaction Centers: Location of the Triplet State and the Identity of the Primary Electron Donor

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