Challenges facing an understanding of the nature of low-energy excited states in photosynthesis

Reimers, Jeffrey R.; Biczysko, Małgorzata; Bruce, Douglas; Coker, David F.; Frankcombe, Terry J.; Hashimoto, Hideki; Hauer, Jürgen; Jankowiak, Ryszard; Kramer, Tobias; Linnanto, Juha; Mamedov, Fikret; Müh, Frank; Rätsep, Margus; Renger, Thomas; Styring, Stenbjörn; Wan, Jian; Wang, Zhuan; Wang-Otomo, Zheng-Yu; Weng, Yuxiang; Yang, Chen; Zhang, Jianping; Freiberg, Arvi; Krausz, Elmars

doi:10.1016/j.bbabio.2016.06.010

Cited by 80 publications

(113 citation statements)

References 261 publications

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“…To understand the significance of PsbH in the context of light‐harvesting, we have to consider low‐energy states that have been discovered in many photosynthetic systems as reviewed by Reimers et al These states become manifest in optical absorptions energetically well below that of the RC, that is, in the case of PSII at wavelengths larger than about 680 nm (see also the discussion of the RC absorption spectrum below). A distinction has to be made between extremely red‐shifted states of yet unknown origin and more moderately red‐shifted states giving rise to absorption at 694 nm as well as corresponding emission signals . We are only concerned with the latter type of states here.…”

Section: Pigments and Lipids Of The Core Complexmentioning

confidence: 99%

Structural basis of light‐harvesting in the photosystem II core complex

Müh

Zouni

2020

Protein Science

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Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.

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Section: Pigments and Lipids Of The Core Complexmentioning

confidence: 99%

Structural basis of light‐harvesting in the photosystem II core complex

Müh

Zouni

2020

Protein Science

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“…This model does not take into account i) electrochromic shifts from the low quantum yield side-pathway of electron transfer, including ChlZ bleaching near 670 nm [36], and ii) photophysical shifts of the lowest energy states of CP47 [24] and CP43 [33] near 690 nm. The lowest excited states [40] of peripheral antennae are long-lived and prone to non-resonant hole-burning upon sustained illumination.…”

Section: Exciton Calculationsmentioning

confidence: 99%

The primary donor of far-red Photosystem II: Chl_D1 or P_D2?

Judd

Morton

Nuernberg

et al. 2020

Preprint

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Far-red light (FRL) Photosystem II (PSII) isolated from Chroococcidiopsis thermalis is studied using parallel analyses of low-temperature absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopies in conjunction with fluorescence measurements. This extends earlier studies Science 360 (2018) 1210-1213. We confirm that the chlorophyll absorbing at 726 nm is the primary electron donor. At 1.8 K efficient photochemistry occurs when exciting at 726 nm and shorter wavelengths;but not at wavelengths longer than 726 nm. The 726 nm absorption peak exhibits a 21 ± 4 cm -1 electrochromic shift due to formation of the semiquinone anion, QA •-. Modelling indicates that no other FRL pigment is located among the 6 central reaction center chlorins: PD1, PD2 ChlD1, ChlD2, PheoD1 and PheoD2. Two of these chlorins, ChlD1 and PD2, are located at a distance and orientation relative to QA •so as to account for the observed electrochromic shift. Previously, ChlD1 was taken as the most likely candidate for the primary donor based on spectroscopy, sequence analysis and mechanistic arguments. Here, a more detailed comparison of the spectroscopic data with exciton modelling of the electrochromic pattern indicates that PD2 is at least as likely as ChlD1 to be responsible for the 726 nm absorption. The correspondence in sign and magnitude of the CD observed at 726 nm with that predicted from modelling favors PD2 as the primary donor. The pros and cons of PD2 vs ChlD1 as the location of the FRL-primary donor are discussed.

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“…Identification of such dark states and their coupling to the excitonic manifold is essential to understanding the biophysics of the combined function of light-harvesting and photoprotection in LHCII. 35 Conformational (protein) dynamics is also supposed to play a crucial rule in the process of switching between light-harvesting and quenching. [36][37][38][39] Previous 2D electronic spectroscopy (2DES) experiments on LHCII have been instrumental to further developing the exciton/ energy transfer model of this system.…”

Section: Introductionmentioning

confidence: 99%

Evidence for coherent mixing of excited and charge-transfer states in the major plant light-harvesting antenna, LHCII

Ramanan

Ferretti

Roon

et al. 2017

Phys. Chem. Chem. Phys.

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LHCII, the major light harvesting antenna from plants, plays a dual role in photosynthesis. In low light it is a light-harvester, while in high light it is a quencher that protects the organism from photodamage. The switching mechanism between these two orthogonal conditions is mediated by protein dynamic disorder and photoprotective energy dissipation. The latter in particular is thought to occur in part via spectroscopically 'dark' states. We searched for such states in LHCII trimers from spinach, at both room temperature and at 77 K. Using 2D electronic spectroscopy, we explored coherent interactions between chlorophylls absorbing on the low-energy side of LHCII, which is the region that is responsible for both light-harvesting and photoprotection. 2D beating frequency maps allow us to identify four frequencies with strong excitonic character. In particular, our results show the presence of a low-lying state that is coupled to a low-energy excitonic state. We assign this to a mixed excitonic-charge transfer state involving the state with charge separation within the Chl a603-b609 heterodimer, borrowing some dipole strength from the Chl a602-a603 excited states. Such a state may play a role in photoprotection, in conjunction with specific and environmentally controlled realizations of protein dynamic disorder. Our identification and assignment of the coherences observed in the 2D frequency maps suggests that the structure of exciton states as well as a mixing of the excited and charge-transfer states is affected by coupling of these states to resonant vibrations in LHCII.

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Challenges facing an understanding of the nature of low-energy excited states in photosynthesis

Cited by 80 publications

References 261 publications

Structural basis of light‐harvesting in the photosystem II core complex

Structural basis of light‐harvesting in the photosystem II core complex

The primary donor of far-red Photosystem II: Chl_D1 or P_D2?

Evidence for coherent mixing of excited and charge-transfer states in the major plant light-harvesting antenna, LHCII

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Challenges facing an understanding of the nature of low-energy excited states in photosynthesis

Cited by 80 publications

References 261 publications

Structural basis of light‐harvesting in the photosystem II core complex

Structural basis of light‐harvesting in the photosystem II core complex

The primary donor of far-red Photosystem II: ChlD1 or PD2?

Evidence for coherent mixing of excited and charge-transfer states in the major plant light-harvesting antenna, LHCII

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The primary donor of far-red Photosystem II: Chl_D1 or P_D2?