Generation of ion-radical chlorophyll states in the light-harvesting antenna and the reaction center of cyanobacterial photosystem I

Cherepanov, Dmitry A.; Шелаев, И. В.; Гостев, Ф. Е.; Aybush, Arseniy V.; Mamedov, Mahir D.; Shuvalov, Vladimir V; Semenov, Alexey Yu.; Надточенко, В. А.

doi:10.1007/s11120-020-00731-0

Cited by 15 publications

(16 citation statements)

References 87 publications

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“…Furthermore, they are rather close to the values observed in PSI-LHCI isolated from different plants 9 , 12 , 27 − 31 or from green algae 32 − 35 and compatible with the PSI core of cyanobacteria. 35 − 37 …”

Section: Resultsmentioning

confidence: 99%

Direct Evidence for Excitation Energy Transfer Limitations Imposed by Low-Energy Chlorophylls in Photosystem I–Light Harvesting Complex I of Land Plants

et al. 2021

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The overall efficiency of photosynthetic energy conversion depends both on photochemical and excitation energy transfer processes from extended light-harvesting antenna networks. Understanding the trade-offs between increase in the antenna cross section and bandwidth and photochemical conversion efficiency is of central importance both from a biological perspective and for the design of biomimetic artificial photosynthetic complexes. Here, we employ two-dimensional electronic spectroscopy to spectrally resolve the excitation energy transfer dynamics and directly correlate them with the initial site of excitation in photosystem I–light harvesting complex I (PSI-LHCI) supercomplex of land plants, which has both a large antenna dimension and a wide optical bandwidth extending to energies lower than the peak of the reaction center chlorophylls. Upon preferential excitation of the low-energy chlorophylls (red forms), the average relaxation time in the bulk supercomplex increases by a factor of 2–3 with respect to unselective excitation at higher photon energies. This slowdown is interpreted in terms of an excitation energy transfer limitation from low-energy chlorophyll forms in the PSI-LHCI. These results aid in defining the optimum balance between the extension of the antenna bandwidth to the near-infrared region, which increases light-harvesting capacity, and high photoconversion quantum efficiency.

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Section: Resultsmentioning

confidence: 99%

Direct Evidence for Excitation Energy Transfer Limitations Imposed by Low-Energy Chlorophylls in Photosystem I–Light Harvesting Complex I of Land Plants

et al. 2021

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“…Because the continual distribution of relaxation processes was calculated independently at each probe wavelength, this method is not contingent on a priori assumptions about the form of the kinetic model of the system under study. The absorption changes on the time scale of 0.2-2 ps are related to the energy redistribution in the antenna [10,11,53] and the primary charge separation in the reaction center [8,14,15,44,57]. The slow components with the decay times of 10-70 ps may be related both to the A 0 → A 1 electron transfer [51,52] and to the excitation quenching observed in the "closed" reaction centers with pre-oxidized P 700 [10,14,53].…”

Section: Kinetic Effects Of Amino Acid Substitutions Near the Chl 2a And Chl 2b Monomersmentioning

confidence: 98%

“…The appearance of a bleach at 690 nm was previously attributed to an ultrafast (< 100 fs) reduction of the primary electron acceptor A 0 treated as excitonically coupled dimers Chl 2A -Chl 3A and Chl 2B -Chl 3B [20] in that fraction of PS I complexes in which the special pair P 700 was directly excited in the far-red spectral region [12,13]. However, the minimum at 690 nm observed at the shortest delay is now known to represent the reduced accessory Chl 2A and Chl 2B monomers [35], while the electron equilibration between Chl 2A /Chl 2B and Chl 3A /Chl 3B proceeds at 2-5 ps [10,16,44]. The excited-state absorption maxima in the region of 650-670 nm may belong to both the excited state of Chl a [45,46] and to the A 0 anion [5].…”

Section: Transient Absorption Changes Of Photosystem I Variantsmentioning

confidence: 99%

“…In all of the six PS I variants, the two fastest transitions (τ 1 ≈ 0.2 ps and τ 2 ≈ 2 ps) are accompanied by a notable recovery of absorption at around 700-710 nm (1-2 mOD), a smaller bleaching at ~ 685 nm (0.5-1 mOD), and negligible changes in the Soret region at 400-450 nm (Figures S1-S3, red and yellow lines). These fastest processes can be attributed to an uphill energy transfer in the course of excitation equilibration in the antenna [5,47] and to the primary charge separation processes in the reaction center [44].…”

Section: Transient Absorption Changes Of Photosystem I Variantsmentioning

confidence: 99%

“…The quantum yield of the ion-radical state P 700 + A 1 − formed in the PS I variants at the time scale of 500 ps was estimated by comparing the amplitudes of the initial S 0 (λ) and the final S f (λ) transient spectra of the WT and the PS I variants. The initial S 0 (λ) spectrum arising at 100 fs upon excitation of PS I in the far-red region represents a mixture of excited Chls of the LHA [41,42], excited Chls of the special pair P 700 [43], and various charge-transfer Chl +δ Chl −δ states generated both in the LHA and the RC [44] Figure 7a compares the final S f (λ) spectra of the PsaA-N600M/H/L PS I variants with that of the WT, and Fig. 7d shows the analogous S f (λ) spectra of the PsaB-N582M/H/L PS I variants.…”

Section: Quantum Yield Of the Charge Separation Reactionsmentioning

confidence: 99%

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Symmetry breaking in photosystem I: ultrafast optical studies of variants near the accessory chlorophylls in the A- and B-branches of electron transfer cofactors

Cherepanov

Шелаев

Гостев

et al. 2021

Photochem Photobiol Sci

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Femtosecond absorption spectroscopy of Photosystem I (PS I) complexes from the cyanobacterium Synechocystis sp. PCC 6803 was carried out on three pairs of complementary amino acid substitutions located near the second pair of chlorophyll molecules Chl 2A and Chl 2B (also termed A -1A and A -1B ). The absorption dynamics at delays of 0.1-500 ps were analyzed by decomposition into discrete decay-associated spectra and continuously distributed exponential components. The multiexponential deconvolution of the absorption changes revealed that the electron transfer reactions in the PsaA-N600M, PsaA-N600H, and PsaA-N600L variants near the B-branch of cofactors are similar to those of the wild type, while the PsaB-N582M, PsaB-N582H, and PsaB-N582L variants near the A-branch of cofactors cause significant alterations of the photochemical processes, making them heterogeneous and poorly described by a discrete exponential kinetic model. A redistribution of the unpaired electron between the second and the third monomers Chl 2A /Chl 2B and Chl 3A /Chl 3B was identified in the time range of 9-20 ps, and the subsequent reduction of A 1 was identified in the time range of 24-70 ps. In the PsaA-N600L and PsaB-N582H/L variants, the reduction of A 1 occurred with a decreased quantum yield of charge separation. The decreased quantum yield correlates with a slowing of the phylloquinone A 0 → A 1 reduction, but not with the initial transient spectra measured at the shortest time delay. The results support a branch competition model, where the electron is sheared between Chl 2A -Chl 3A and Chl 2B -Chl 3B cofactors before its transfer to phylloquinone in either A 1A or A 1B sites.

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Primary donor triplet states of Photosystem I and II studied by Q-band pulse ENDOR spectroscopy

et al. 2022

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The photoexcited triplet state of the “primary donors” in the two photosystems of oxygenic photosynthesis has been investigated by means of electron-nuclear double resonance (ENDOR) at Q-band (34 GHz). The data obtained represent the first set of 1H hyperfine coupling tensors of the 3P700 triplet state in PSI and expand the existing data set for 3P680. We achieved an extensive assignment of the observed electron-nuclear hyperfine coupling constants (hfcs) corresponding to the methine α-protons and the methyl group β-protons of the chlorophyll (Chl) macrocycle. The data clearly confirm that in both photosystems the primary donor triplet is located on one specific monomeric Chl at cryogenic temperature. In comparison to previous transient ENDOR and pulse ENDOR experiments at standard X-band (9–10 GHz), the pulse Q-band ENDOR spectra demonstrate both improved signal-to-noise ratio and increased resolution. The observed ENDOR spectra for 3P700 and 3P680 differ in terms of the intensity loss of lines from specific methyl group protons, which is explained by hindered methyl group rotation produced by binding site effects. Contact analysis of the methyl groups in the PSI crystal structure in combination with the ENDOR analysis of 3P700 suggests that the triplet is located on the Chl aʹ (PA) in PSI. The results also provide additional evidence for the localization of 3P680 on the accessory ChlD1 in PSII.

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Generation of ion-radical chlorophyll states in the light-harvesting antenna and the reaction center of cyanobacterial photosystem I

Cited by 15 publications

References 87 publications

Direct Evidence for Excitation Energy Transfer Limitations Imposed by Low-Energy Chlorophylls in Photosystem I–Light Harvesting Complex I of Land Plants

Direct Evidence for Excitation Energy Transfer Limitations Imposed by Low-Energy Chlorophylls in Photosystem I–Light Harvesting Complex I of Land Plants

Symmetry breaking in photosystem I: ultrafast optical studies of variants near the accessory chlorophylls in the A- and B-branches of electron transfer cofactors

Primary donor triplet states of Photosystem I and II studied by Q-band pulse ENDOR spectroscopy

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