Cryogenic Single-Molecule Spectroscopy of the Primary Electron Acceptor in the Photosynthetic Reaction Center

Kondô, Torû; Mutoh, Risa; Tabe, Hiroaki; Kurisu, Genji; Oh‐oka, Hirozo; Fujiyoshi, Satoru; Matsushita, Michio M.

doi:10.1021/acs.jpclett.0c00891

Cited by 9 publications

(10 citation statements)

References 46 publications

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“…Similar fast EET was measured in the purified hRC, which induced fast EET yielding in the higher excitation/charge separation at P800 . Single-molecule spectroscopy by selective excitation at 670 nm of the Chl- a F (A 0 ) in hRC has shown heterogenic function of A 0 …”

Section: Introductionsupporting

confidence: 66%

“…On the other hand, 28(58)th BChl- g , whose excitation probability in the lowest (second) exciton state is the largest, is located nearby Chl- a F (A 0 ). The situation might be related to the recent results from single-molecule spectroscopy on excited fluorescence of individual Chl- a F from hRC, which have shown a heterogenic function of A 0 . We assume that BChl- g s being excited under a steady state after photoexcitation of Chl- a F are located at the inner side of hRC.…”

Section: Discussionmentioning

confidence: 99%

“…Specific physical properties and arrangements of pigments on antenna/RC complexes seem to determine the efficiencies of excitation energy transfer (EET) and electron transfer (ET) . Experimental and theoretical studies on the elementary processes of RCs have been extensively performed to understand the optimization mechanisms under significantly different natural environments. − …”

Section: Introductionmentioning

confidence: 99%

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Comparison between the Light-Harvesting Mechanisms of Type-I Photosynthetic Reaction Centers of Heliobacteria and Photosystem I: Pigment Site Energy Distribution and Exciton State

et al. 2021

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The photosynthetic pigment system on the anoxygenic type-I reaction center of heliobacteria (hRC), which has a symmetrical structure, was analyzed. The excitonic coupling among all of the bacteriochlorophyll g (BChl-g) molecules and chlorophyll a (Chl-a) molecules and the site energy for each pigment were calculated using Poisson-TrESP and the charge density coupling (CDC) methods. The obtained theoretical model reproduced the optical absorption and circular dichroism spectra. It also interpreted the decay-associated spectra upon the photoselective laser excitation, which represent the ultrafast excitation energy migration process, better than the simpler hRC models that assumed constant pigment site energy shifts. Spatial movements of excitation energy on pigments on hRC upon the laser excitation were visualized. The energy dissipation by carotenoid molecules in hRC was also predicted. The hRC model was compared with the model of the reaction center of cyanobacterial photosystem I (PSI), which carries 95 Chl-a on the analogous type-I structure with significantly different amino-acid sequences, pigment species, and output redox powers. It is shown that the locations and site energy values of pigments in hRC resemble those in the core of PSI, except for the red-Chl-a sites, suggesting common functional mechanisms implicated in their evolution.

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Section: Introductionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison between the Light-Harvesting Mechanisms of Type-I Photosynthetic Reaction Centers of Heliobacteria and Photosystem I: Pigment Site Energy Distribution and Exciton State

et al. 2021

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“…As suggested by Niedringhaus et al and others (14,54) it is possible that the 2-step vs superexchange mechanism dichotomy is too simplistic (55,56). The difference in rates in the two P* populations in NO2Y, which may both involve some form of superexchange ET, also suggests that the usual formulation of the superexchange mechanism itself may be too simplistic.…”

Section: Verification Of Ncaa Incorporation and Minimal Structural Pe...mentioning

confidence: 97%

Photosynthetic reaction center variants made via genetic code expansion show Tyr at M210 tunes the initial electron transfer mechanism

Weaver

Lin

Faries

et al. 2021

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

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Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine (M210) close to an essential electron transfer component via its replacement with site-specific, genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and X-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild type (WT). Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via a ∼4-ps and a ∼20-ps population to produce the charge-separated state P+HA− in all variants. Global analysis indicates that in the ∼4-ps population, P+HA− forms through a two-step process, P*→ P+BA−→ P+HA−, while in the ∼20-ps population, it forms via a one-step P* → P+HA− superexchange mechanism. The percentage of the P* population that decays via the superexchange route varies from ∼25 to ∼45% among variants, while in WT, this percentage is ∼15%. Increases in the P* population that decays via superexchange correlate with increases in the free energy of the P+BA− intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an ∼110-meV increase in the free energy of P+BA− along with a dramatic diminution of the 1,030-nm transient absorption band indicative of P+BA– formation. Collectively, this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.

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Section: Verification Of Ncaa Incorporation and Minimal Structural Perturbationmentioning

confidence: 97%

Photosynthetic Reaction Center Variants Made via Genetic Code Expansion Show Tyr at M210 Tunes the Initial Electron Transfer Mechanism

Weaver

Lin²,

Faries³

et al. 2021

Preprint

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Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine close to an essential electron transfer component (M210) via its replacement with site-specific genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and x-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild-type. Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via an approximately 4 ps and 20 ps population to produce the charge-separated state P+HA- in all variants. Global analysis indicates that in the 4 ps population P+HA- forms through a 2-step process P* –> P+BA– –> P+HA-, while in the 20 ps population it forms via a 1-step P* –> P+HA– superexchange mechanism. The percentage of P* population that decays via the superexchange route varies from approximately 25% to 45% among variants while in wild-type this percentage is approximately 15%. Increases in the P* population which decays via superexchange correlates with increases in free energy of the P+BA– intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an approximately 110 meV increase in the free energy of P+BA– along with a dramatic diminution of the 1030 nm transient absorption band indicative of P+BA– formation. Collectively this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.<br>

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Cryogenic Single-Molecule Spectroscopy of the Primary Electron Acceptor in the Photosynthetic Reaction Center

Cited by 9 publications

References 46 publications

Comparison between the Light-Harvesting Mechanisms of Type-I Photosynthetic Reaction Centers of Heliobacteria and Photosystem I: Pigment Site Energy Distribution and Exciton State

Comparison between the Light-Harvesting Mechanisms of Type-I Photosynthetic Reaction Centers of Heliobacteria and Photosystem I: Pigment Site Energy Distribution and Exciton State

Photosynthetic reaction center variants made via genetic code expansion show Tyr at M210 tunes the initial electron transfer mechanism

Photosynthetic Reaction Center Variants Made via Genetic Code Expansion Show Tyr at M210 Tunes the Initial Electron Transfer Mechanism

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