Applications of spectral hole burning spectroscopies to antenna and reaction center complexes

Reddy, N. R. S.; Lyle, Paul A.; Small, Gerald J.

doi:10.1007/bf00035536

Cited by 138 publications

(133 citation statements)

References 96 publications

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“…25 This product was estimated by Gillie et al 28 to be ~ 200 cm -1 , which is about twice as large as estimated from our site-selected fluorescence data. We do not have an appropriate explanation for this discrepancy.…”

Section: Comparison With Results From Spectral Hole-burningsupporting

confidence: 48%

“…27) and attributed to the dimeric nature of the Bchls. Also for the primary electron donor of the reaction centre of purple bacteria a large separation between zero-phonon line and peak wavelength of the phonon side band (~120 cm -1 ) was observed, 25 which predicts a Stokes'…”

Section: The Homogeneous Bandwidth Of the Long-wavelength Pigments Inmentioning

confidence: 99%

“…[24][25][26] Inhomogeneous broadening of the absorption bands (Γ i ) reflects variations in the energies of the electronic transitions of the pigments. These variations arise from slightly different conformations of the protein environment of the pigment.…”

Section: Inhomogeneous Broadeningmentioning

confidence: 99%

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Polarized site-selected fluorescence spectroscopy of isolated Photosystem I particles

Gobets

Amerongen

Monshouwer

et al. 1994

Biochimica et Biophysica Acta (BBA) - Bioenergetics

125

186

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Polarized site-selected fluorescence spectroscopy of isolated Photosystem I particles P ol ari zed site-sel ected fluo resc ence sp ec tro sco py of iso lat ed P hot osy stem I pa rtic les Bas Gobets, Herbert van Amerongen, René Monshouwer, Jochen Kruip, Matthias Rögner, Rienk van Grondelle and Jan P. Dekker Polarized steady-state fluorescence spectra have been obtained from Photosystem I core complexes of the cyanobacterium Synechocystis PCC 6803 and from LHCI containing Photosystem I (PSI-200) complexes of spinach by selective laser excitation at 4 K. Excitation above 702 nm in Synechocystis and 720 nm in PSI-200 results in highly polarized emission, suggesting that pigments absorbing at these and longer wavelengths are not able to transfer excitation energy at 4 K. In both systems the peak wavelength of the emission (λ em ) depends strongly on the excitation wavelength (λ ex ). This indicates that in both systems the long-wavelength bands responsible for the steady-state emission are inhomogeneously broadened. The width of the inhomogeneous distribution is estimated to be about 215 cm -1 in Synechocystis and 400 cm -1 in PSI-200. We conclude that the peaks of the total absorption spectra of the long-wavelength pigments of Synechocystis and PSI-200 are at 708 and 716 nm, respectively, and therefore designate these pigments as C708 and C716. The results further show that C708 and C716 are strongly homogeneously broadened, i.e. carry broad phonon side-bands. The width of these bands is estimated to be about 170 and 200 cm -1 for C708 and C716, respectively. The Stokes' shifts appear to be large: about 200 cm -1 (10 nm) for C708 and about 325 cm -1 (17 nm) for C716. These values are much higher than usually observed for 'normal' antenna pigments, but are in the same order as found previously for a number of dimeric systems. Therefore, we propose that the long-wavelength pigments in Photosystem I are excitonically coupled dimers. Based on fitting with Gaussian bands the presence of one C708 dimer per P700 is suggested in the core antenna of Synechocystis. This chapter has been published in Biochimica etBiophysica Acta 1188, 75-85, reproduced with permission.

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Section: Comparison With Results From Spectral Hole-burningsupporting

confidence: 48%

Section: The Homogeneous Bandwidth Of the Long-wavelength Pigments Inmentioning

confidence: 99%

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Polarized site-selected fluorescence spectroscopy of isolated Photosystem I particles

Gobets

Amerongen

Monshouwer

et al. 1994

Biochimica et Biophysica Acta (BBA) - Bioenergetics

125

186

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“…While the molecular structure of two bacterial reaction centers has been known for a number of years (1)(2)(3), the detailed molecular mechanism of the electron transfer is still the subject of intense investigations (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). There is general agreement that the first electron transfer process starts at a pair of bacteriochlorophyll (BChl) molecules-the special pair P-which acts as the primary donor.…”

mentioning

confidence: 99%

The accessory bacteriochlorophyll: a real electron carrier in primary photosynthesis.

Arlt

Schmidt

Kaiser

et al. 1993

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

224

151

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The primary electron transfer in reaction centers ofRhodobacter sphaeroides is studied by subpicosecond absorption spectroscopy with polarized light in the spectral range of 920-1040 nm. Here the bacteriochlorophyll anion radical has an absorption band while the other pigments of the reaction center have vanishing ground-state absorption. The transient absorption data exhibit a pronounced 0.9-ps kinetic component which shows a strong dichroism. Evaluation of the data yields an angle between the transition moments of the special pair and the species related with the 0.9-ps kinetic component of 26 ± 8. This angle compares favorably with the value of 29°expected for the reduced accessory bacteriochlorophyll. Extensive transient absorbance data are fufly consistent with a stepwise electron ransfer via the accessory bacteriochlorophyll.In the primary processes of bacterial photosynthesis, absorbed light energy is stored via an electron transfer within the reaction center (RC). While the molecular structure of two bacterial reaction centers has been known for a number of years (1-3), the detailed molecular mechanism of the electron transfer is still the subject of intense investigations (4-20). There is general agreement that the first electron transfer process starts at a pair of bacteriochlorophyll (BChl) molecules-the special pair P-which acts as the primary donor. The

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“…There have been several reports of energy-transfer processes in the PSII reaction center with lifetimes ranging from several tens to hundreds of picoseconds (4,18,28,(30)(31)(32). In particular, Small et al (28,32) (4).…”

mentioning

confidence: 99%

Subpicosecond equilibration of excitation energy in isolated photosystem II reaction centers.

Durrant

Hastings

Joseph

et al. 1992

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

103

128

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PhotosystemIH reaction centers have been studied by femtoend trent absorption spectroseopy. We demonstrate that it is possible to achieve good photoselectivity between the primary electron donor P680 and the majority of the accessory chlorins. Energy tanser can be observed in both directions between P680 and these accessory chlorins depending on which Is initily excited. This oxidizing potential is used to drive water splitting, which gives rise to oxygen evolution. The primary electron donor of PSII is thought to correspond to a spectral feature at 680 nm and is referred to as P680 (3), while a pheophytin (Ph) molecule functions as an electron acceptor (4-6). Studies of PSII core complexes binding 60 and 80 antenna chlorophylls have suggested that the primary radical pair P680+Ph-is formed at a rate of 4100 psfollowing the absorption ofa photon by antenna pigments (7).A similar conclusion was reached from photovoltage studies of larger PSII complexes (8). A kinetic model, in which there is a rapid (--1 ps) equilibration of excitation energy between the antenna pigments and P680, followed by the observed trapping of the excitation energy by radical pair formation in ""100 ps, has been proposed for this process (refs. 9 and 10; reviewed in ref. 2). This so-called trapping limited model (11) is valid when the rate of electron transfer from the primary electron donor is slower than energy transfer back to the antenna pigments. This model has also been applied to other photosynthetic antenna/reaction center complexes (12)(13)(14).However, previous studies have not been able to time resolve the energy-transfer processes that are predicted to cause the equilibration of excitation energy between the antenna and primary electron donor pigments prior to radical pair formation.We report here a study ofexcitation energy equilibration in the isolated Dl/D2/cytochrome b559 complex, which is the reaction center of PSII. This complex is much smaller than the isolated PSII core complexes discussed above, binding only six chlorophyll a and two Ph a pigments (15, 16). While several of these pigments are presumably involved in electron-transfer processes, these pigments will also function in an energy-transferring capacity before charge separation. Time-resolved fluorescence studies have determined that at least 94% of the chlorin pigments in our PSI1 reaction center preparation are able to transfer excitation energy to P680, resulting in a near unity quantum yield of the primary radical pair (17,18). In a previous study, we determined that when P680 is directly excited, Ph reduction occurs primarily at a rate of 21 ps-1 in isolated PSII reaction centers at room temperature (4).There have been several discussions of the similarities between the PSII reaction center of higher plants and the reaction center of purple bacteria (19,20). However, these two complexes are likely to be very different in terms oftheir energy-transfer kinetics when isolated from their antenna systems. The lowest SO-S, opticil transition for the pr...

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Applications of spectral hole burning spectroscopies to antenna and reaction center complexes

Cited by 138 publications

References 96 publications

Polarized site-selected fluorescence spectroscopy of isolated Photosystem I particles

Polarized site-selected fluorescence spectroscopy of isolated Photosystem I particles

The accessory bacteriochlorophyll: a real electron carrier in primary photosynthesis.

Subpicosecond equilibration of excitation energy in isolated photosystem II reaction centers.

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