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Mathis P, Sage E, Byrdin M. Pushing the limits of flash photolysis to unravel the secrets of biological electron and proton transfer. Photochem Photobiol Sci 2022; 21:1533-1544. [DOI: 10.1007/s43630-021-00134-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2021] [Indexed: 11/25/2022]
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Gibasiewicz K, Pajzderska M, Białek R, Jones MR. Temperature dependence of nanosecond charge recombination in mutant Rhodobacter sphaeroides reaction centers: modelling of the protein dynamics. Photochem Photobiol Sci 2021; 20:913-922. [PMID: 34213754 DOI: 10.1007/s43630-021-00069-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/18/2021] [Indexed: 10/20/2022]
Abstract
We investigated the influence of a range of factors-temperature, redox midpoint potential of an electron carrier, and protein dynamics-on nanosecond electron transfer within a protein. The model reaction was back electron transfer from a bacteriopheophytin anion, HA-, to an oxidized primary electron donor, P+, in a wild type Rhodobacter sphaeroides reaction center (RC) with a permanently reduced secondary electron acceptor (quinone, QA-). Also used were two modified RCs with single amino acid mutations near the monomeric bacteriochlorophyll, BA, located between P and HA. Both mutant RCs showed significant slowing down of this back electron transfer reaction with decreasing temperature, similar to that observed with the wild type RC, but contrasting with a number of single point mutant RCs studied previously. The observed similarities and differences are explained in the framework of a (P+BA- ↔ P+HA-) equilibrium model with an important role played by protein relaxation. The major cause of the observed temperature dependence, both in the wild type RC and in the mutant proteins, is a limitation in access to the thermally activated pathway of charge recombination via the state P+BA- at low temperatures. The data indicate that in all RCs both charge recombination pathways, the thermally activated one and a direct one without involvement of the P+BA- state, are controlled by the protein dynamics. It is concluded that the modifications of the protein environment affect the overall back electron transfer kinetics primarily by changing the redox potential of BA and not by changing the protein relaxation dynamics.
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Affiliation(s)
- Krzysztof Gibasiewicz
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland.
| | - Maria Pajzderska
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
| | - Rafał Białek
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Medical Sciences BuildingUniversity Walk, Bristol, BS8 1TD, UK
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Białek R, Thakur K, Ruff A, Jones MR, Schuhmann W, Ramanan C, Gibasiewicz K. Insight into Electron Transfer from a Redox Polymer to a Photoactive Protein. J Phys Chem B 2020; 124:11123-11132. [PMID: 33236901 PMCID: PMC7735723 DOI: 10.1021/acs.jpcb.0c08714] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/10/2020] [Indexed: 11/29/2022]
Abstract
Biohybrid photoelectrochemical systems in photovoltaic or biosensor applications have gained considerable attention in recent years. While the photoactive proteins engaged in such systems usually maintain an internal charge separation quantum yield of nearly 100%, the subsequent steps of electron and hole transfer beyond the protein often limit the overall system efficiency and their kinetics remain largely uncharacterized. To reveal the dynamics of one of such charge-transfer reactions, we report on the reduction of Rhodobacter sphaeroides reaction centers (RCs) by Os-complex-modified redox polymers (P-Os) characterized using transient absorption spectroscopy. RCs and P-Os were mixed in buffered solution in different molar ratios in the presence of a water-soluble quinone as an electron acceptor. Electron transfer from P-Os to the photoexcited RCs could be described by a three-exponential function, the fastest lifetime of which was on the order of a few microseconds, which is a few orders of magnitude faster than the internal charge recombination of RCs with fully separated charge. This was similar to the lifetime for the reduction of RCs by their natural electron donor, cytochrome c2. The rate of electron donation increased with increasing ratio of polymer to protein concentrations. It is proposed that P-Os and RCs engage in electrostatic interactions to form complexes, the sizes of which depend on the polymer-to-protein ratio. Our findings throw light on the processes within hydrogel-based biophotovoltaic devices and will inform the future design of materials optimally suited for this application.
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Affiliation(s)
- Rafał Białek
- Faculty
of Physics, Adam Mickiewicz University, Poznań, ul. Uniwersytetu
Poznańskiego 2, 61-614 Poznań, Poland
| | - Kalyani Thakur
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Adrian Ruff
- Analytical
Chemistry—Center for Electrochemical Sciences, Faculty of Biochemistry
and Chemistry, Faculty of Biochemistry and Chemistry, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Michael R. Jones
- School
of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, U.K.
| | - Wolfgang Schuhmann
- Analytical
Chemistry—Center for Electrochemical Sciences, Faculty of Biochemistry
and Chemistry, Faculty of Biochemistry and Chemistry, Ruhr-University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | - Charusheela Ramanan
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Krzysztof Gibasiewicz
- Faculty
of Physics, Adam Mickiewicz University, Poznań, ul. Uniwersytetu
Poznańskiego 2, 61-614 Poznań, Poland
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Lee SH, Blake IM, Larsen AG, McDonald JA, Ohkubo K, Fukuzumi S, Reimers JR, Crossley MJ. Synthetically tuneable biomimetic artificial photosynthetic reaction centres that closely resemble the natural system in purple bacteria. Chem Sci 2016; 7:6534-6550. [PMID: 27928494 PMCID: PMC5125414 DOI: 10.1039/c6sc01076h] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 06/16/2016] [Indexed: 12/18/2022] Open
Abstract
Porphyrin-based photosynthetic reaction centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale. The established lifetimes are long compared to other processes in organic solar cells or other organic light harvesting systems. These rigid, synthetically flexible molecules provide the closest mimics to the natural PRC so far synthesised and present a future direction for the design of light harvesters with controllable absorption, redox, and kinetics properties.
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Affiliation(s)
- Sai-Ho Lee
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia .
| | - Iain M Blake
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia .
| | - Allan G Larsen
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia .
| | - James A McDonald
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia .
| | - Kei Ohkubo
- Department of Material and Life Science , Graduate School of Engineering , Osaka University , Suita , Osaka 565-0871 , Japan .
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 120-750 , Korea ; Faculty of Science and Engineering , Meijo University , Nagoya , Aichi 468-0073 , Japan
| | - Jeffrey R Reimers
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia . ; International Centre for Quantum and Molecular Structure , Shanghai University , 200444 , Shanghai , China . ; School of Mathematical and Physical Sciences , The University of Technology Sydney , 2007 , NSW , Australia .
| | - Maxwell J Crossley
- School of Chemistry F11 , The University of Sydney , 2006 , NSW , Australia .
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Gibasiewicz K, Białek R, Pajzderska M, Karolczak J, Burdziński G, Jones MR, Brettel K. Weak temperature dependence of P (+) H A (-) recombination in mutant Rhodobacter sphaeroides reaction centers. PHOTOSYNTHESIS RESEARCH 2016; 128:243-258. [PMID: 26942583 PMCID: PMC4877430 DOI: 10.1007/s11120-016-0239-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 02/24/2016] [Indexed: 06/05/2023]
Abstract
In contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P (+) H A (-) → PH A charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron acceptors. These mutated reaction centers have diverse overall kinetics of charge recombination, spanning an average lifetime from ~2 to ~20 ns. Despite these differences a protein relaxation model applied previously to wild-type reaction centers was successfully used to relate the observed kinetics to the temporal evolution of the free energy level of the state P (+) H A (-) relative to P (+) B A (-) . We conclude that the observed variety in the kinetics of charge recombination, together with their weak temperature dependence, is caused by a combination of factors that are each affected to a different extent by the point mutations in a particular mutant complex. These are as follows: (1) the initial free energy gap between the states P (+) B A (-) and P (+) H A (-) , (2) the intrinsic rate of P (+) B A (-) → PB A charge recombination, and (3) the rate of protein relaxation in response to the appearance of the charge separated states. In the case of a mutant which displays rapid P (+) H A (-) recombination (ELL), most of this recombination occurs in an unrelaxed protein in which P (+) B A (-) and P (+) H A (-) are almost isoenergetic. In contrast, in a mutant in which P (+) H A (-) recombination is relatively slow (GML), most of the recombination occurs in a relaxed protein in which P (+) H A (-) is much lower in energy than P (+) H A (-) . The weak temperature dependence in the ELL reaction center and a YLH mutant was modeled in two ways: (1) by assuming that the initial P (+) B A (-) and P (+) H A (-) states in an unrelaxed protein are isoenergetic, whereas the final free energy gap between these states following the protein relaxation is large (~250 meV or more), independent of temperature and (2) by assuming that the initial and final free energy gaps between P (+) B A (-) and P (+) H A (-) are moderate and temperature dependent. In the case of the GML mutant, it was concluded that the free energy gap between P (+) B A (-) and P (+) H A (-) is large at all times.
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Affiliation(s)
- Krzysztof Gibasiewicz
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland.
| | - Rafał Białek
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland
| | - Maria Pajzderska
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland
| | - Jerzy Karolczak
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland
- Center for Ultrafast Laser Spectroscopy, A. Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland
| | - Gotard Burdziński
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań, Poland
| | - Michael R Jones
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Klaus Brettel
- Laboratoire Mécanismes Fondamentaux de la Bioénergétique, UMR 8221, CEA - iBiTec-S, CNRS, Université Paris Sud, 91191, Gif-Sur-Yvette, France
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