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

Woolf, Vincent M.; Wittmershaus, Bruce P.; Vermaas, Wim F. J.; Duy, Tran Trung

doi:10.1007/bf00019042

Cited by 24 publications

(17 citation statements)

References 57 publications

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“…The principal peak is at 648 nm, which is at a much shorter wavelength than the absorption maximum of Chl-a and therefore cannot be due to Chl fluorescence. This peak is probably due to the trace of phycobiliprotein noticeable in the absorption spectrum, which is consistent with a previous observation (11). Since the phycobilisomes in this strain are uncoupled from the Chl, they have a high quantum yield.…”

Section: Resultssupporting

confidence: 92%

“…In this case, steady-state fluorescence with multiple-spectral types is likely to give a single major peak as observed by Holzwarth et at (10). However, a recent study by Woolf et aL (11) gave a very different spectrum in which two emitting pools (680-and 703-nm peaks) were observed at room temperature, and the number of red pigments (703 nm) was estimated to be 8-11. This observation is reexamined here.…”

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confidence: 80%

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Energy transfer and trapping in photosystem I reaction centers from cyanobacteria.

DiMagno

Chan

Jia

et al. 1995

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

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A mutant strain of the cyanobacterium Synechocystis 6803, TolE4B, was constructed by genetic deletion of the protein that links phycobilisomes to thylakoid membranes and of the CP43 and CP47 proteins of photosystem II (PSII), leaving the photosystem I (PSI) center as the sole chromophore in the photosynthetic membranes. Both intact membrane and detergent-isolated samples of PSI were characterized by time-resolved and steady-state fluorescence methods. A decay component of -25 ps dominates (99% of the amplitude) the fluorescence of the membrane sample. This result indicates that an intermediate lifetime is not associated with the intact membrane preparation and the charge separation in PSI is irreversible. The decay time of the detergent-isolated sample is similar. The 600-nm excited steady-state fluorescence spectrum displays a red fluorescence peak at "703 nm at room temperature. The 450-nm excited steady-state fluorescence spectrum is dominated by a single peak around 700 nm without 680-nm "bulk" fluorescence. The experimental results were compared with several computer simulations. Assuming an antenna size of 130 chlorophyll molecules, an apparent charge separation time of -1 ps is estimated.Alternatively, the kinetics could be modeled on the basis of a two-domain antenna for PSI, consistent with the available structural data, each containing -65 chlorophyll a molecules. If excitation can migrate freely within each domain and communication between domains occurs only close to the reaction center, a charge separation time of3-4 ps is obtained instead.Understanding of the photochemical reaction center known as photosystem I (PSI) has been greatly increased with the publication of its 6-A x-ray structure (1). However, questions concerning the light-harvesting and trapping mechanisms of this complex remain, particularly since the positions of only half of the chlorophyll (Chl) molecules have been assigned. The PSI center is a membrane-bound, multiprotein complex that catalyzes the lightdriven transport of electrons from reduced plastocyanin or cytochrome C553 to soluble ferredoxin or flavodoxin (2, 3). The complex is known to contain 10 or 11 polypeptides, about 100 Chl molecules, and 10-15 ,B-carotenes. The major reaction center proteins are called PsaA, PsaB, and PsaC, having molecular masses of 83, 83, and 9 kDa, respectively. PsaA and PsaB are disposed symmetrically in the membrane and share bonding to segment P700 itself, the primary electron donor which may be a Chl a dimer, and to Ao, a monomeric Chl-a; A1, a phylloquinone (vitamin K); and F5, a Fe4-S4 center. The two remaining Fe4-S4 centers, FA and FB, are bound to PsaC.We are interested in how energy transfer and trapping occur in PSI. The elementary transfer time (-150-300 fs) in the PSI core antenna of a PSI-only mutant of Chlamydomonas reinhardtii has been determined in a fluorescence up-conversion experiment (4). This single-step transfer time very closely approximates a previous estimate using a simple two-color lattice model (5). Energy tr...

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Section: Resultssupporting

confidence: 92%

mentioning

confidence: 80%

Energy transfer and trapping in photosystem I reaction centers from cyanobacteria.

DiMagno

Chan

Jia

et al. 1995

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

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“…The long wavelength antenna pigments of the Photosystem I antenna (absorbing at wavelength longer than 700 nm) are still a matter of considerable interest. Their presence has clearly been demonstrated at room temperature (Wittmershaus et al, 1992;Woolf et al, 1994;Hastings et al, 1994), but evidence about their position in the antenna is still scarce. Simulations by Jia et al (1992) have shown that a "funnel" model (with longer wavelength pigments located close to the reaction center) can be ruled out and that a model in which all spectral forms are randomly distributed in the antenna with one or two long wavelength pigments close to the photoactive pigments of the reaction center best describes the fluorescence kinetics at low temperature.…”

Section: Introductionmentioning

confidence: 99%

Spectral heterogeneity and time-resolved spectroscopy of excitation energy transfer in membranes of Heliobacillus mobilis at low temperatures

Lin¹,

Kleinherenbrink²,

Chiou³

et al. 1994

Biophysical Journal

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Transient absorption difference spectra in the Qy absorption band from membranes of Heliobacillus mobilis were recorded at 140 and 20 K upon 200 fs laser pulse excitation at 590 nm. Excitation transfer from short wavelength absorbing forms of bacteriochlorophyll g to long wavelength bacteriochlorophyll g occurred within 1-2 ps at both long wavelength bacteriochlorophyll g occurred within 1-2 ps at both temperatures. In addition, a slower energy transfer process with a time constant of 15 ps was observed at 20 K within the pool of long wavelength-absorbing bacteriochlorophyll g. Energy transfer from long wavelength antenna pigments to the primary electron donor P798 was observed, yielding the primary charge-separated state P798+A0-. The time constant for this process was 30 ps at 140 K and about 70 ps at 20 K. A decay component with smaller amplitude and a lifetime of up to hundreds of picoseconds was observed that was centered around 814 nm at 20 K. Kinetic simulations using simple lattice models reproduce the observed decay kinetics at 295 and 140 K, but not at 20 K. The kinetics of energy redistribution within the spectrally heterogeneous antenna system at low temperature argue against a simple "funnel" model for the organization of the antenna of Heliobacillus mobilis and favor a more random spatial distribution of spectral forms. However, the relatively high rate of energy transfer from long wavelength antenna bacteriochlorophyll g to the primary electron donor P798 at low temperature is difficult to explain with either of these models.

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“…The role of these Chls and the molecular interaction responsible for this extreme red shift are unclear. It was suggested that the red Chls may focus the excitation to the reaction center (van der Lee et al, 1993; van Grondelle et al, 1994;Shubin et al, 1995), be an intermediate trap (Wittmershaus, 1987;Woolf et al, 1994), increase the absorption cross section (Trissl, 1993), or protect the reaction center against excess excitation (Mukerji & Sauer, 1989).…”

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confidence: 98%

Fluorescence Spectroscopy of the Longwave Chlorophylls in Trimeric and Monomeric Photosystem I Core Complexes from the Cyanobacterium Spirulina platensis

et al. 1997

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The organization and interaction of chlorophylls (Chl) and the kinetics of the energy transfer in the core antenna of photosystem I (PSI) trimeric and monomeric complexes, isolated from Spirulina platensis with Triton X-100 have been studied by stationary and time-resolved fluorescence. At 295 K both complexes show an unusually intense long-wavelength emission band with prominent peaks at 730 nm (trimers) or 715 nm (monomers), whose intensity is independent of the redox state of P700. A broad band extending from 710 to 740 nm in the absorption and fluorescence excitation spectra of trimers also indicates the existence of the longwave Chls at 295 K. The 77 K fluorescence emission of PSI trimers frozen after addition of dithionite under illumination (P700 and the PSI acceptor side reduced) shows an intense band at 760 (F760) and a smaller one at 725 nm (F725); when P700 is oxidized, the intensity of F760 decreases about 15 times. In the 77 K spectrum of monomers only F725 is present in the longwave region, and its intensity does not depend on the redox state of P700. Bands of Chls with maxima near 680, 710, and 738 nm were found in the 77 K excitation spectrum of trimers, and bands near 680 and 710 nm were seen in the spectrum of monomers. Five spectrally different red Chl forms in PSI trimers and three red Chl in monomers have been resolved by deconvolution of their 77 K absorption spectra. The difference absorption spectrum, trimers-minus-monomers, shows that the appearance of the 735 nm band in trimers is accompanied by a decrease of 708, 698, and 688 nm bands present in monomers. The reversible changes of F760 intensity of Spirulina membranes as a result of their salt treatment confirm the idea that the most longwave Chl form originates from an interaction of Chls bound to different monomeric PSI subunits forming the trimer. The time-resolved fluorescence spectra of PSI trimers and monomers, measured at 287 K in the region 680-770 nm, are substantially different, although a set of similar lifetimes (9, approximately 30, approximately 66, and 1400-2200 ps) was necessary for a good fit. No effect of P700 redox state was observed on the fluorescence kinetics of both complexes at 287 K.

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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

Cited by 24 publications

References 57 publications

Energy transfer and trapping in photosystem I reaction centers from cyanobacteria.

Energy transfer and trapping in photosystem I reaction centers from cyanobacteria.

Spectral heterogeneity and time-resolved spectroscopy of excitation energy transfer in membranes of Heliobacillus mobilis at low temperatures

Fluorescence Spectroscopy of the Longwave Chlorophylls in Trimeric and Monomeric Photosystem I Core Complexes from the Cyanobacterium Spirulina platensis

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