Mechanism of Primary Charge Separation in Photosynthetic Reaction Centers

Savikhin, Sergei; Jankowiak, Ryszard

doi:10.1007/978-1-4939-1148-6_7

Cited by 31 publications

(45 citation statements)

References 217 publications

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“…Note that primary reactions of electron transfer cannot be distinctly separated from processes of the excitation energy transfer within the antenna because they both occur within the same time range . In the majority of studies on the fast kinetics of spectral changes in PSI, flashes with duration >100 fs and centered at ~700 nm were used . However, recently we have used an alternative approach including short (~20 fs) flashes with relatively low power (~20 nJ) centered at 720 nm with a bandwidth of 40 nm.…”

Section: Resultsmentioning

confidence: 99%

“…To date, the kinetics of the primary charge separation and the nature of the primary electron donor and acceptor in PSI remain controversial . Most of the previous studies put the primary charge separation step from P700* to A 0 in PSI reaction center in the 0.8–4 ps time range, and the subsequent electron transfer from primary electron acceptor A 0 to the secondary electron acceptor A 1 was suggested to occur in 10–50 ps range . However, Refs.…”

Section: Introductionmentioning

confidence: 99%

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Comparisons of Electron Transfer Reactions in a Cyanobacterial Tetrameric and Trimeric Photosystem I Complexes

Шелаев

Mamedov

Гостев

et al. 2018

Photochem & Photobiology

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Photosystem I (PSI) is a Type-I reaction center and is the largest photosynthetic complex to be characterized. In cyanobacteria, PSI is organized as a trimer with a three-fold axis of symmetry. Recently, a tetrameric form of PSI has been identified in cyanobacteria. Plastids in plants and algae only contain monomeric PSI, suggesting that tetrameric PSI may be key in the transition from ancestral cyanobacterial trimeric PSI to plant/algal monomeric PSI. We have investigated the kinetics of electron transfer to the initial acceptor in PSI tetramer isolated from Chroococcidiopsis TS-821. Using a pump-probe technique with 25 fs low-energy, 720 nm pump pulses, we measure the ultrafast (<100 fs) conversion of a delocalized exciton into a charge-separated state between the primary donor P and the primary acceptor A . Comparison with previous pump-probe analysis of the trimeric PSI complexes from Synechocystis sp PCC 6803 (Shelaev et al. [2010] Biochim Biophys Acta, 1797, 1410-1420) reveals that the tetrameric (PSI) complexes from Chroococcidiopsis sp TS-821 are quite similar. The transfer of an electron from the A to the following acceptor A1 (phylloquinone) takes place in a time frame of about 30 ps, which is slightly longer compared to PSI trimeric complex (~24 ps). The slight spectral differences between trimeric and tetrameric PSI complexes are discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparisons of Electron Transfer Reactions in a Cyanobacterial Tetrameric and Trimeric Photosystem I Complexes

Шелаев

Mamedov

Гостев

et al. 2018

Photochem & Photobiology

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“…1 − 4 The primary charge separation in RCs, the initial step of ET, occurs between a (bacterio)chlorophyll species, denoted P, and a nearby (bacterio)chlorin acceptor within a few picoseconds. 5 − 7 …”

Section: Introductionmentioning

confidence: 99%

Antagonistic Effects of Point Mutations on Charge Recombination and a New View of Primary Charge Separation in Photosynthetic Proteins

et al. 2021

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Light-induced electron-transfer reactions were investigated in wild-type and three mutant Rhodobacter sphaeroides reaction centers with the secondary electron acceptor (ubiquinone Q A ) either removed or permanently reduced. Under such conditions, charge separation between the primary electron donor (bacteriochlorophyll dimer, P) and the electron acceptor (bacteriopheophytin, H A ) was followed by P + H A – → PH A charge recombination. Two reaction centers were used that had different single amino-acid mutations that brought about either a 3-fold acceleration in charge recombination compared to that in the wild-type protein, or a 3-fold deceleration. In a third mutant in which the two single amino-acid mutations were combined, charge recombination was similar to that in the wild type. In all cases, data from transient absorption measurements were analyzed using similar models. The modeling included the energetic relaxation of the charge-separated states caused by protein dynamics and evidenced the appearance of an intermediate charge-separated state, P + B A – , with B A being the bacteriochlorophyll located between P and H A . In all cases, mixing of the states P + B A – and P + H A – was observed and explained in terms of electron delocalization over B A and H A . This delocalization, together with picosecond protein relaxation, underlies a new view of primary charge separation in photosynthesis.

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“…[4][5] The motivation for using these proteins is their advantage of superior charge-separation over solid-state devices, such as silicon. [8][9][10] The spatial arrangement and approximate midpoint potentials of the cofactors are shown in Figure 1A,B. [6] One of the most well-studied bacterial photosynthetic complexes for use in biophotovoltaic applications is the reaction center (RC) pigment-protein complex from Rhodobacter sphaeroides.…”

Section: Introductionmentioning

confidence: 99%

“…The RC functions to absorb a photon of light in the near-infrared and drive an electron to form a charge-separated state with a half-life on the order of 1 s. [7] Starting from the periplasmic side of the cellular inner membrane (P-side), a series of redox-active cofactors beginning with the primary donor bacteriochlorophylls P, followed by the accessory bacteriochlorophyll B A and the bacteriopheophytin H A , to the acceptor ubiquinones Q A and Q B on the cytoplasmic side (Q-side), traverse the protein matrix with increasingly positive midpoint potentials. [8][9][10] The spatial arrangement and approximate midpoint potentials of the cofactors are shown in Figure 1A,B. The difference in potential between the donor and acceptor cofactors contributes to the energetic driving force for the redox reactions to proceed in the forward direction.…”

Section: Introductionmentioning

confidence: 99%

Highly Sensitive Method to Isolate Photocurrent Signals from Large Background Redox Currents on Protein‐Modified Electrodes

2019

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The high quantum efficiency in converting light energy into a charge-separated state is a major advantage in using photosynthetic proteins in biophotovoltaic applications. Photocurrents are typically measured at open circuit potential (OCP), where the electrochemical redox or faradaic currents are minimized. However, at potentials far from the OCP, the photocurrents produced by the proteins may be impossible to measure against the large background current, owing to electrochemical redox reactions of charge-transfer mediators and/or sacrificial electron donors. Demonstrated here is a highly sensitive method using a sinusoidal-modulated intensity of an LED excitation light source to isolate the protein-based photocurrent component from the total current irrespective of electrode surface coverage. Using a genetically modified photochemical reaction center from Rhodobacter sphaeroides as a proof-of-concept, photocurrents up to 10 4 -10 5 orders of magnitude smaller than the background electrochemical redox current (due to redox reactions directly on the electrode surface) were measured at applied voltages > 0.4 V from the OCP. The phase relationship between the optical excitation and photocurrent response was also measured and shown to be analytically useful.[a] Dr.

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Mechanism of Primary Charge Separation in Photosynthetic Reaction Centers

Cited by 31 publications

References 217 publications

Comparisons of Electron Transfer Reactions in a Cyanobacterial Tetrameric and Trimeric Photosystem I Complexes

Comparisons of Electron Transfer Reactions in a Cyanobacterial Tetrameric and Trimeric Photosystem I Complexes

Antagonistic Effects of Point Mutations on Charge Recombination and a New View of Primary Charge Separation in Photosynthetic Proteins

Highly Sensitive Method to Isolate Photocurrent Signals from Large Background Redox Currents on Protein‐Modified Electrodes

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