On the Unusual Temperature-Dependent Emission of the CP47 Antenna Protein Complex of Photosystem II (original) (raw)
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The Journal of Physical Chemistry B, 2008
The CP43 core antenna complex of Photosystem II is known to possess two quasi-degenerate "red"-trap states [R. Jankowiak et al. J. Phys. Chem. B 2000, 104, 11805]. It has been suggested recently [V. Zazubovich and R. Jankowiak, J. Lum. 2007, 127, 245] that the site distribution functions (SDFs) of the red states (A and B) are uncorrelated and that narrow holes are burned in the subpopulations of chlorophylls (Chls) from states A and B that are the lowestenergy Chl in their complex and previously thought not to transfer energy. This model of uncorrelated excitation energy transfer (EET) between the quasi-degenerate bands is expanded by taking into account both electron-phonon and vibrational coupling. The model is applied to fit simultaneously absorption, emission, zero-phonon action, and transient hole burned (HB) spectra obtained for the CP43 complex with minimized contribution from aggregation. It is demonstrated that the above listed spectra can be well fitted using the uncorrelated EET model, providing strong evidence for the existence of efficient energy transfer between the two lowest energy states A and B (either from A to B or from B to A) in CP43. Possible candidate Chls for the low-energy A and B states are discussed, providing a link between CP43 structure and spectroscopy. Finally, we propose that persistent holes originate from regular NPHB accompanied by the redistribution of oscillator strength due to excitonic interactions, rather than photoconversion involving Chl-protein hydrogen bonding as suggested before [J.L. Hughes et al., Biochemistry 45, 12345, 2006]. In the accompanying paper (II) it is demonstrated that the model discussed in this manuscript is consistent with excitonic calculations, which also provide very good fits to both transient and persistent HB spectra obtained under non-line narrowing conditions. Abbreviations: Chlorophyll (Chl), energy (E); capillary electrophoresis (CE); excitation energy transfer (EET); fluorescence line-narrowing (FLN); full width at half maximum (FWHM), Huang-Rhys factor (S); inhomogeneous broadening (Γ inh ); laser induced fluorescence (LIF); nonphotochemical hole burning (NPHB); photosynthetic complexes (PC); photochemical hole burning (PHB); phonon side band (PSB); Photosystem I (PSI); Photosystem II (PSII); reaction center (RC); site distribution functions (SDF); spectral hole-burning (SHB); temperature (T); zero-phonon line (ZPL).
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2001
The Photosystem II (PSII) core antenna complexes, CP43 and CP47, were prepared from spinach (Spinacia oleracea L.). The absorption spectra in the red region at room temperature were recorded for the PSII core antenna samples after increased temperature treatment (up to 80³C). Derivative and difference spectra revealed the existence of two groups of chlorophyll a (Chl a) molecules in both CP43 and CP47. The one with the absorption peak in the shorter wavelength region was designated as CP43-669 and CP47-669, while the other with the absorption peak in the longer wavelength region was designated as CP43-682 and CP47-680. The results of the thermal treatment experiment demonstrated that CP43-669 and CP47-669 may exist as monomers of Chl a and that their binding sites on the polypeptides are insensitive to thermal treatment, whereas CP43-682 and CP47-680 may exist as dimers or multimers of Chl a and their binding regions in the polypeptide chains are more sensitive to heat treatment. The excitation energy transfer mechanism between these two different groups of Chl a molecules is also analyzed.
Biophysical Journal, 1995
Fluorescence emission and triplet-minus-singlet (T-S) absorption difference spectra of the CP47 core antenna complex of photosystem II were measured as a function of temperature and compared to those of chlorophyll a in Triton X-1 00. Two spectral species were found in the chlorophyll T-S spectra of CP47, which may arise from a difference in ligation of the pigments or from an additional hydrogen bond, similar to what has been found for Chi molecules in a variety of solvents. The T-S spectra show that the lowest lying state in CP47 is at -685 nm and gives rise to fluorescence at 690 nm at 4 K. The fluorescence quantum yield is 0.11 ± 0.03 at 4 K, the chlorophyll triplet yield is 0.16 ± 0.03. Carotenoid triplets are formed efficiently at 4 K through triplet transfer from chlorophyll with a yield of 0.15 ± 0.02. The major decay channel of the lowest excited state in CP47 is internal conversion, with a quantum yield of about 0.58. Increase of the temperature results in a broadening and blue shift of the spectra due to the equilibration of the excitation over the antenna pigments. Upon increasing the temperature, a decrease of the fluorescence and triplet yields is observed to, at 270 K, a value of about 55% of the low temperature value. This decrease is significantly larger than of chlorophyll a in Triton X-100. Although the coupling to low-frequency phonon or vibration modes of the pigments is probably intermediate in CP47, the temperature dependence of the triplet and fluorescence quantum yield can be modeled using the energy gap law in the strong coupling limit of Englman and Jortner (1970. J. Mol. Phys. 18:145-164) for non-radiative decays. This yields for CP47 an average frequency of the promoting/accepting modes of 350 cm-' with an activation energy of 650 cm-1 for internal conversion and activationless intersystem crossing to the triplet state through a promoting mode with a frequency of 180 cm-'. For chlorophyll a in Triton X-1 00 the average frequency of the promoting modes for non-radiative decay is very similar, but the activation energy (300 cm-1) is significantly smaller.
Biochimica et biophysica acta, 2016
The identification of low-energy chlorophyll pigments in photosystem II (PSII) is critical to our understanding of the kinetics and mechanism of this important enzyme. We report parallel circular dichroism (CD) and circularly polarized luminescence (CPL) measurements at liquid helium temperatures of the proximal antenna protein CP47. This assembly hosts the lowest-energy chlorophylls in PSII, responsible for the well-known "F695" fluorescence band of thylakoids and PSII core complexes. Our new spectra enable a clear identification of the lowest-energy exciton state of CP47. This state exhibits a small but measurable excitonic delocalization, as predicated by its CD and CPL. Using structure-based simulations incorporating the new spectra, we propose a revised set of site energies for the 16 chlorophylls of CP47. The significant difference from previous analyses is that the lowest-energy pigment is assigned as Chl 612 (alternately numbered Chl 11). The new assignment is read...
Spectroscopic Properties of the CP43 Core Antenna Protein of Photosystem II
Biophysical Journal, 1999
CP43 is a chlorophyll-protein complex that funnels excitation energy from the main light-harvesting system of photosystem II to the photochemical reaction center. We purified CP43 from spinach photosystem II membranes in the presence of the nonionic detergent n-dodecyl-,D-maltoside and recorded its spectroscopic properties at various temperatures between 4 and 293 K by a number of polarized absorption and fluorescence techniques, fluorescence line narrowing, and Stark spectroscopy. The results indicate two "red" states in the Q y absorption region of the chlorophylls. The first peaks at 682.5 nm at 4 K, has an extremely narrow bandwidth with a full width at half-maximum of ϳ2.7 nm (58 cm Ϫ1 ) at 4 K, and has the oscillator strength of a single chlorophyll. The second peaks at ϳ679 nm, has a much broader bandshape, is caused by several excitonically interacting chlorophylls, and is responsible for all 4 K absorption at wavelengths longer than 685 nm. The Stark spectrum of CP43 resembles the first derivative of the absorption spectrum and has an exceptionally small overall size, which we attribute to opposing orientations of the monomer dipole moments of the excitonically coupled pigments.
Journal of the Chemical Society, Faraday Transactions 2, 1988
CP1, the isolated reaction centre (RC) chlorophyll(ch1)-protein of plant photosystem I(PSI) containing P700 and ca. 40 antenna Chi has been isolated using sodium dodecyl sulphate and gel electrophoresis. It retained the triplet e.s.r. polarisation pattern characteristic of active charge separation and recombination. Low-temperature and time-resolved fluorescence emission spectra showed that at least two discrete antenna chl forms were present, and excitation energy transfer between them and P700 was studied by measuring chl sub-nanosecond fluorescence decay kinetics over a range of temperatures and emission wavelengths, using ca. 100 ps Ar-ion laser excitation pulses and single-photon detection, resulting in ca. 10 ps time resolution. The two forms are F720, emitting at 720nm (low-energy sites within the antenna) and F690, emitting at 690-695 nm. The latter form was only observed at short times (<200 ps) and at low temperatures. Decay kinetics were fitted to the sum of three exponentials. The two longer (> 1 ns) components were of small amplitude and have no significance for energy transfer. The lifetime of the shortest resolved component varied in a complex way with temperature between 30 and 150ps, also dependent on emission wavelength. At T > 200 K the lifetime was 40 f 10 ps, independent of wavelength, but on lowering the temperature it developed a strong wavelength dependence with a distinct minimum at 690-695 nm. A model is presented for energy transfer between the discrete chl antenna forms which accounts for the change of the observed lifetimes with temperature. In this model F690 forms a core antenna close to the RC and can transfer energy to P700 even at 10 K. Endothermic energy transfer out of F720, which is inhibited by low temperatures, gives rise to the observed temperature dependence of the F690 and F720 fluorescence lifetimes. The initial ultrafast events in plant photosynthesis [energy transfer within an antenna pigment bed and subsequent primary charge separation in a reaction centre(RC)] have been the subject of numerous picosecond fluorescence studies.' Progress in the study of bacterial photosynthesis has depended on the biochemical extraction of relatively simple and well defined complexes from the photosynthetic apparatus. However, for plant systems these methods have not been successful and the isolated chlorophyll(ch1)protein complexes are relatively large, containing many chl molecules, which are heterogeneous and can be distinguished spectroscopically.2 This inhomogeneity is inherent for the native complex and is not a result of isolation.2
Journal of the American Chemical Society, 2010
We report low temperature (T) optical spectra of the isolated CP47 antenna complex from Photosystem II (PSII) with a low-T fluorescence emission maximum near 695 nm and not, as previously reported, at 690-693 nm. The latter emission is suggested to result from three distinct bands: a loweststate emission band near 695 nm (labeled F1) originating from the lowest-energy excitonic state A1 of intact complexes (located near 693 nm and characterized by very weak oscillator strength) as well as emission peaks near 691 nm (FT1) and 685 nm (FT2) originating from subpopulations of partly destabilized complexes. The observation of the F1 emission is in excellent agreement with the 695 nm emission observed in intact PSII cores and thylakoid membranes. We argue that the band near 684 nm previously observed in singlet-minus-triplet spectra originates from a subpopulation of partially destabilized complexes with lowestenergy traps located near 684 nm in absorption (referred to as AT2) giving rise to FT2 emission. It is demonstrated that varying contributions from the F1, FT1, and FT2 emission bands led to different maxima of fluorescence spectra reported in the literature. The fluorescence spectra are consistent with the zerophonon hole action spectra obtained in absorption mode, the profiles of the nonresonantly burned holes as a function of fluence, as well as the fluorescence line-narrowed spectra obtained for the Q y band. The lowest Q y state in absorption band (A1) is characterized by an electron-phonon coupling with the Huang-Rhys factor S of ∼1 and an inhomogeneous width of ∼180 cm -1 . The mean phonon frequency of the A1 band is 20 cm -1 . In contrast to previous observations, intact isolated CP47 reveals negligible contribution from the triplet-bottleneck hole, i.e., the AT2 trap. It has been shown that Chls in intact CP47 are connected via efficient excitation energy transfer to the A1 trap near 693 nm and that the position of the fluorescence maximum depends on the burn fluence. That is, the 695 nm fluorescence maximum shifts blue with increasing fluence, in agreement with nonresonant hole burned spectra. The above findings provide important constraints and parameters for future excitonic calculations, which in turn should offer new insight into the excitonic structure and composition of low-energy absorption traps. † Abbreviations: Chlorophyll (Chl); energy (E); electron-phonon coupling (el-ph); excitation energy transfer (EET); excitation wavelength, λ ex ; fluence (f); fluorescence line-narrowing (FLN); full width at half-maximum (fwhm); hole burning (HB); Huang-Rhys factor (S); inhomogeneous broadening (Γ inh ); laser induced fluorescence (LIF); nonline narrowed (NLN); nonphotochemical hole burning (NPHB); photosynthetic complexes (PC); photochemical hole burning (PHB); phonon sideband (PSB); Photosystem I (PSI); Photosystem II (PSII); reaction center (RC); room temperature (RT); single site absorption (SSA); site distribution functions (SDF); spectral hole-burning (SHB); species-associated difference spectra (SADS); temperature (T); mean phonon frequency (ω m ); zero-phonon line (ZPL).
Biochemistry, 1994
We report the fluorescence decay kinetics and the vibrational properties of chlorophyll a bound to the 47-kDa antenna protein (CP47) of spinach photosystem 11. The chlorophyll fluorescence of CP47 samples decays with four lifetimes ( 7 = 75.8 ps, 1.05 ns, 3.22 ns, and 5.41 ns). The 75.8-ps and 3.22-ns components are associated with chlorophyll a bound to relatively intact centers, the 1.05-11s component corresponds to chlorophyll bound to centers that are slightly perturbed, and the the 5.41-ns phase probably originates from centers that are severely denatured. The resonance Raman spectrum of CP47 a t 441.6 nm (this work) and at 406.7 nm [de Paula, I Abbreviations: ATP, adenosine triphosphate; Chl, chlorophyll; CP47, chlorophyll a binding protein associated with energy transfer in photosystem I1 and having an apparent molecular mass of 47 kDa; D1 and D2, polypeptides that make up the reaction center of photosystem 11; Mes, 2-(N-morpholino)ethanesulfonic acid; NADP+, oxidized form of nicotinamide adenine dinucleotide phosphate; P680, primary electron donor of PSII; Pheo, pheophytin; PSII, photosystem 11; XQ, wavelength of the lowest energy ?T--?T* electronic transition [Qv(O-O) transition] of chlorophylls; VC+, frequency of the stretching mode associated with the C9 keto group of chlorophyll a.