Orientation of photosystem-I pigments. Investigation by low-temperature linear dichroism and polarized fluorescence emission

Tapie, P.; Choquet, Yves; Breton, Jacques; Delepelaire, Philippe; Wollman, Françis-André

doi:10.1016/0005-2728(84)90079-3

Cited by 61 publications

(22 citation statements)

References 21 publications

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“…According to a comparison of the 682 to 708 nm absorption peaks at 77 K, less than 5 lowenergy Chls exist in the core-complex of green algae and plants (French et al 1972, Mullet et al 1980, Tapie et al 1984, Bassi and Simpson 1987. The isolated PSI core complex from green plants has been observed to have an absorption component with a maximum at 697 nm (Mullet et al 1980) at 77 K as determined from first-derivative absorption spectra analysis.…”

Section: Observations On Anisotropy Resultsmentioning

confidence: 99%

“…The spectral properties of these low-energy Chls depend on the organism. At 77 K, there is a fluorescence maximum around 720 nm from low-energy Chls found in the RC core complex common to higher plants, algae and cyanobacteria (Cho and Govindjee 1970, Mohanty et al 1972, Mullet et al 1980, Wollman and Bennoun 1982, Tapie et al 1984, Gamier et al 1986). LHCI from green plants contains additional low-energy Chls with an absorption maximum at 705 nm and fluorescence maximum at 735 nm at 77 K (Mullet et al 1980, Lam et al 1984.…”

Section: Introductionmentioning

confidence: 99%

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Resolution of low-energy chlorophylls in Photosystem I of Synechocystis sp. PCC 6803 at 77 and 295 K through fluorescence excitation anisotropy

et al. 1994

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Fluorescence excitation spectra of highly anisotropic emission from Photosystem I (PS I) were measured at 295 and 77 K on a PS II-less mutant of the cyanobacterium Synechocystis sp. PCC 6803 (S. 6803). When PS I was excited with light at wavelengths greater than 715 nm, fluorescence observed at 745 nm was highly polarized with anisotropies of 0.32 and 0.20 at 77 and 295 K, respectively. Upon excitation at shorter wavelengths, the 745-nm fluorescence had low anisotropy. The highly anisotropic emission observed at both 77 and 295 K is interpreted as evidence for low-energy chlorophylls (Chls) in cyanobacteria at room temperature. This indicates that low-energy Chls, defined as Chls with first excited singlet-state energy levels below or near that of the reaction center, P700, are not artifacts of low-temperature measurements.If the low-energy Chls are a distinct subset of Chls and a simple two-pool model describes the excitation transfer network adequately, one can take advantage of the low-energy Chls' high anisotropy to approximate their fluorescence excitation spectra. Maxima at 703 and 708 nm were calculated from 295 and 77 K data, respectively. Upper limits for the number of low-energy Chls per P700 in PS I from S. 6803 were calculated to be 8 (295 K) and 11 (77 K).

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Section: Observations On Anisotropy Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resolution of low-energy chlorophylls in Photosystem I of Synechocystis sp. PCC 6803 at 77 and 295 K through fluorescence excitation anisotropy

et al. 1994

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“…Immunochemical studies (24) have shown that the apoproteins of the PSI reaction center/core antenna complex are highly conserved throughout the plant kingdom. Tapie et al (25) have shown that the orientations of PSI pigments are very similar in thylakoid membranes and PSI-enriched preparations from C. reinhardtii, peas, and barley. Preparations of PSI reaction centers from spinach (Fig.…”

Section: Methodsmentioning

confidence: 99%

Antenna size dependence of fluorescence decay in the core antenna of photosystem I: estimates of charge separation and energy transfer rates.

Owens¹,

Webb²,

Mets³

et al. 1987

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

119

106

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We have examined the photophysics of energy migration and trapping in photosystem I by investigating the spectral and temporal properties of the fluorescence from the core antenna chlorophylls as a function of the antenna size. Time-correlated single photon counting was used to determine the fluorescence lifetimes in the isolated P700 chlorophyll a-protein complex and in a mutant of Chlamydomonas reinhardtii that lacks the photosystem II reaction center complex. The fluorescence decay in both types of sample is dominated by a fast (1545 psec) component that is attributed to the lifetime of excitations in the photosystem I core antenna. These excitations decay primarily by an efficient photochemical quenching on P700. The measured lifetimes show a linear relationship to the core antenna size. A linear dependence of the excitation lifetime on antenna size was predicted previously in a lattice model for excitation migration and trapping in arrays of photosynthetic pigments [Pearlstein, R. M. (1982) Photochem. Photobiol. 35, 83544M]. Based on this model, our data predict a time constant for photochemical charge separation in the photosystem I reaction center of 2.8 ± 0.7 or 3.4 ± 0.7 psec, assuming monomeric or dimeric P700, respectively. The predicted average single-step transfer time for excitation transfer between core antenna pigments is 0.21 ± 0.04 psec. Under these conditions, excitation migration in photosystem I is near the diffusion limit, with each excitation making an average of 2.4 visits to the reaction center before photoconversion.The primary steps in photosynthesis are absorption of light and creation of a singlet excitation, transfer of the excitation between pigment molecules, and photochemical charge separation in the reaction center. The relative kinetics of the excitation transfer and trapping reactions determine critical aspects of the overall light-harvesting process. Excitation transfer is believed to occur by an incoherent hopping mechanism (1), with the excitation following a random walk through the antenna pigments to the reaction center (2). The mechanism of charge separation depends on the unique redox properties of the reaction center pigments in the excited state and appears to be similar in bacteria and plants.The reaction center complex of purple photosynthetic bacteria contains only six pigment molecules (3), at least four of which are directly involved in the primary photochemical reactions (4). This relative simplicity has permitted measurement of the photochemical rate constant, kp, by direct excitation of the reaction center pigments (5-7). In contrast, the photosystem I and II (PSI and PSII) reaction center complexes isolated from oxygen-evolving plants contain a relatively large number (40-110) of chlorophyll a (Chl-a) molecules (8, 9). The presence of these core antenna pigments in reaction center preparations complicates spectroscopic and kinetic measurements of the primary photochemical reactions because of substantial overlap between the absorptions ofthe reaction...

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“…They seem to be independently associated to RC I, as shown by the selective removal of each of them by different treatments (Bassi et al, 1985;Bassi and Simpson, 1987). LHCI-730 has been shown to contain the spectral components which absorb visible radiation at the longest wavelength in the PSI-LHCI complex (Tapie et al, 1984;Mukerji and Sauer, 1990). It is consistently the only fluorescence emitter when RC I traps are closed (Stahl et al, 1989).…”

Section: Chlorophyll Alb Proteins Of Photosystem Imentioning

confidence: 99%

CHLOROPHYLL BINDING PROTEINS WITH ANTENNA FUNCTION IN HIGHER PLANTS and GREEN ALGAE

Bassi

Rigoni

Giacometti

1990

Photochem & Photobiology

158

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Orientation of photosystem-I pigments. Investigation by low-temperature linear dichroism and polarized fluorescence emission

Cited by 61 publications

References 21 publications

Resolution of low-energy chlorophylls in Photosystem I of Synechocystis sp. PCC 6803 at 77 and 295 K through fluorescence excitation anisotropy

Resolution of low-energy chlorophylls in Photosystem I of Synechocystis sp. PCC 6803 at 77 and 295 K through fluorescence excitation anisotropy

Antenna size dependence of fluorescence decay in the core antenna of photosystem I: estimates of charge separation and energy transfer rates.

CHLOROPHYLL BINDING PROTEINS WITH ANTENNA FUNCTION IN HIGHER PLANTS and GREEN ALGAE

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