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Beletskaya EA, Lukina EA, Uvarov MN, Popov AA, Kulik LV. Geminate recombination in organic photovoltaic blend PCDTBT/PC 71BM studied by out-of-phase electron spin echo spectroscopy. J Chem Phys 2020; 152:044706. [PMID: 32007084 DOI: 10.1063/1.5131855] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The key process in organic solar cell operation is charge separation under light illumination. Due to the low dielectric constant of organic materials, the Coulomb attraction energy within the interfacial charge-transfer state (CTS) is larger than the thermal energy. Understanding the mechanism of charge separation at the organic donor/acceptor interface still remains a challenge and requires knowledge of the CTS temporal evolution. To address this problem, the CTS in the benchmark photovoltaic blend PCDTBT/PC71BM was studied by the out-of-phase Electron Spin Echo (ESE). The protocol for determining the CTS geminate recombination rate for certain electron-hole distances was developed. Simulating the out-of-phase ESE trace for the CTS in the PCDTBT/PC71BM blend allows precise determination of the electron-hole distance distribution function and its evolution with the increase in the delay after the laser flash. Distances of charge separation up to 6 nm were detected upon thermalization at a temperature of 20 K. Assuming the exponential decay of the recombination rate, the attenuation factor β = 0.08 Å-1 is estimated for the PCDTBT/PC71BM blend. Such a low attenuation factor is probably caused by a high degree of hole delocalization along the PCDTBT chain.
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Affiliation(s)
- E A Beletskaya
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - E A Lukina
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - M N Uvarov
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - A A Popov
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - L V Kulik
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
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Ponomarenko N, Niklas J, Pokkuluri PR, Poluektov O, Tiede DM. Electron Paramagnetic Resonance Characterization of the Triheme Cytochrome from Geobacter sulfurreducens. Biochemistry 2018; 57:1722-1732. [DOI: 10.1021/acs.biochem.7b00917] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Marais A, Sinayskiy I, Petruccione F, van Grondelle R. A quantum protective mechanism in photosynthesis. Sci Rep 2015; 5:8720. [PMID: 25732807 PMCID: PMC4346811 DOI: 10.1038/srep08720] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 01/29/2015] [Indexed: 11/28/2022] Open
Abstract
Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is observed to be reduced by weak magnetic fields. Reaction centres from plants' photosystem II share many features with bacterial reaction centres, including a high-spin iron whose function has remained obscure. To explain observations that the magnetic field effect is reduced by the iron, we propose that its fast-relaxing spin plays a protective role in photosynthesis by generating an effective magnetic field. We consider a simple model of the system, derive an analytical expression for the effective magnetic field and analyse the resulting triplet yield reduction. The protective mechanism is robust for realistic parameter ranges, constituting a clear example of a quantum effect playing a macroscopic role vital for life.
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Affiliation(s)
- Adriana Marais
- Quantum Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, 4001, South Africa and National Institute for Theoretical Physics, KwaZulu-Natal, South Africa
| | - Ilya Sinayskiy
- Quantum Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, 4001, South Africa and National Institute for Theoretical Physics, KwaZulu-Natal, South Africa
| | - Francesco Petruccione
- Quantum Research Group, School of Chemistry and Physics, University of KwaZulu-Natal, Durban, 4001, South Africa and National Institute for Theoretical Physics, KwaZulu-Natal, South Africa
| | - Rienk van Grondelle
- Institute for Lasers, Life and Biophotonics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
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Niklas J, Beaupré S, Leclerc M, Xu T, Yu L, Sperlich A, Dyakonov V, Poluektov OG. Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions. J Phys Chem B 2015; 119:7407-16. [DOI: 10.1021/jp511021v] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Jens Niklas
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Serge Beaupré
- Department
of Chemistry, Laval University, Quebec City, Quebec G1V 0A6, Canada
| | - Mario Leclerc
- Department
of Chemistry, Laval University, Quebec City, Quebec G1V 0A6, Canada
| | - Tao Xu
- Department
of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
| | - Luping Yu
- Department
of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
| | - Andreas Sperlich
- University of Würzburg and Bavarian Centre for Applied Energy
Research (ZAE Bayern), D-97074 Würzburg, Germany
| | - Vladimir Dyakonov
- University of Würzburg and Bavarian Centre for Applied Energy
Research (ZAE Bayern), D-97074 Würzburg, Germany
| | - Oleg G. Poluektov
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Bradshaw M, Gaffney BJ. Fluctuations of an exposed π-helix involved in lipoxygenase substrate recognition. Biochemistry 2014; 53:5102-10. [PMID: 25036469 PMCID: PMC4131896 DOI: 10.1021/bi500768c] [Citation(s) in RCA: 13] [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: 06/20/2014] [Revised: 07/16/2014] [Indexed: 01/14/2023]
Abstract
The second helix in lipoxygenases adapts to permit substrate access to the active site, but details of this process are varied and poorly understood. We therefore examined the dynamics of helix 2 in solutions of spin-labeled soybean lipoxygenase-1 and spin relaxation at 60 K of the spin-labels by catalytic iron. Helix 2 in soybean lipoxygenase structures is surface-exposed and contains one turn of π-helix, centrally located. A site-directed spin-label scan of 18 of the 21 helix 2 residues, and electron paramagnetic resonance, showed that the π-helical segment became unusually mobile, on a nanosecond time scale, under conditions favoring substrate binding (pH 9 and lipid addition), while segments before and after had relatively unchanged dynamics. Backbone dynamics of residues in the π-helical segment appeared to be correlated, at pH 9. Samples also were frozen to examine the polarity and proticity of the local environments, the effect of the local environment on intrinsic relaxation, and dipolar relaxation by two symmetries of catalytic iron. The average hyperfine tensor component, Azz, of four π-helix residues decreased by 1.75 G, with an increase in pH from 7 to 9, while it remained unaffected for nearby buried residues. Power saturation data suggested the change in polarity specific to the π-helix altered the intrinsic relaxation rates. Different symmetries of iron contributed to distance-dependent magnetic relaxation. We interpret these data to mean that a π-helix in the second helix of plant lipoxygenases is highly dynamic and is the site where lipid chains penetrate to inner helices that outline the substrate pocket.
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Affiliation(s)
- Miles
D. Bradshaw
- Department
of Biological
Science, Florida State University, Tallahassee, Florida 32306-4295, United States
| | - Betty J. Gaffney
- Department
of Biological
Science, Florida State University, Tallahassee, Florida 32306-4295, United States
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Leonova MM, Fufina TY, Vasilieva LG, Shuvalov VA. Structure-function investigations of bacterial photosynthetic reaction centers. BIOCHEMISTRY (MOSCOW) 2012; 76:1465-83. [DOI: 10.1134/s0006297911130074] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Jones MR. Structural Plasticity of Reaction Centers from Purple Bacteria. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_16] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Vieira ED, Casado NMC, Facchin G, Torre MH, Costa-Filho AJ, Calvo R. Weak Exchange Interaction Supported by a Biologically Relevant Long Chemical Bridge in a Cu−Peptide Model Compound. Inorg Chem 2006; 45:2942-7. [PMID: 16562949 DOI: 10.1021/ic051957b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The copper complex of the dipeptide L-alanyl-L-phenylalanine, catena-(L-alaninate-L-phenylalaninate-copper(II) monohydrate), identified as Cu(II)Ala-Phe, provides a convenient system to study a weak exchange interaction between unpaired spins transmitted through a biologically relevant long chemical bridge (18.34 A). In this complex, the copper ions are arranged in two symmetry-related anisotropic layers parallel to the ab plane at 13.17 A, separated by a double layer of water molecules. The equatorial-equatorial bridge considered as the most relevant path for exchange interactions between copper ions in neighbor layers contains 11 diamagnetic atoms (including three hydrogens), with two covalent amidate bridges plus three weak and moderate H bonds that go across the water layer. This interaction was studied using electron paramagnetic resonance in single-crystal samples, at 9.5 and 34.5 GHz. The measured magnitude of the interlayer interaction, |J3|/kB = 1.7(2) x 10(-3) K, is discussed in terms of values obtained for similar paths in other model compounds and in proteins. These results in model systems provide information that may be important in understanding biological functions at the molecular level.
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Affiliation(s)
- Ernanni D Vieira
- Grupo de Biofísica Molecular Sergio Mascarenhas, Departamento de Física e Informatica, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil
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Santana RC, Cunha RO, Carvalho JF, Vencato I, Calvo R. Single crystal EPR study of electronic structure and exchange interactions for copper(II)(L-arginine)2(SO4).(H2O)6: a model system to study exchange interactions between unpaired spins in proteins. J Inorg Biochem 2005; 99:415-23. [PMID: 15621273 DOI: 10.1016/j.jinorgbio.2004.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 10/04/2004] [Accepted: 10/13/2004] [Indexed: 11/15/2022]
Abstract
We report EPR measurements at 9.77 and 34.1 GHz in powder and single crystal samples of the ternary copper amino acid complex Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). The single crystal Electron Paramagnetic Resonance spectra display a single resonance for all magnetic field orientations in the ca and cb crystal planes. In the ab plane they display two resonances for most orientations of the magnetic field, and only one resonance for orientations close to the crystal axes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between copper ions. From the characteristics of the collapse and the angular dependences of the position and width of the resonances we evaluate the g-tensors of the copper molecules and estimate exchange interactions |J(1)/k(B)|=0.9 K and |J(2)/k(B)|=0.009 K between copper neighbors at 5.908 A and at 15.684 A, respectively. J(1) is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 7.133 A. J(2) is assigned to a long bridge of 12 atoms with a total bond length of 19.789 A, that includes two hydrogen bonds. The results are discussed in terms of the crystal and electronic structure of Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). We show that J(2) is in excellent agreement with the observed magnetic interaction between the reduced quinone acceptors in the photosynthetic reaction center protein of the bacterium Rb. sphaeroides, which is transmitted along a similar chemical path containing two hydrogen bonds. Our findings indicate that it is valid to estimate values for the exchange interactions between redox centers in proteins transmitted along long chemical paths containing sigma and H-bonds, from data obtained in model systems, and emphasize the importance of measuring exchange interactions in biologically relevant model systems.
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Affiliation(s)
- R C Santana
- Universidade Federal de Goiás, Instituto de Física, CP 131, Goiânia, Goiás 74001-970, Brazil.
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D'Amelio N, Gaggelli E, Mlynarz P, Molteni E, Valensin G, Lubitz W. NMR Structural Model of the Interaction of Herbicides with the Photosynthetic Reaction Center from Rhodobacter sphaeroides. Chembiochem 2004; 5:1237-44. [PMID: 15368575 DOI: 10.1002/cbic.200400012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The interaction of the herbicides acifluorfen and paraquat with the photosynthetic reaction center from Rhodobacter sphaeroides has been studied by NMR relaxation measurements. Interaction in aqueous solution has been demonstrated by evaluating motional features of the bound form through cross-relaxation terms of protons at fixed distances on the herbicides. Contributions to longitudinal nonselective relaxation rates different from the proton-proton dipolar relaxation were inferred, most probably due to paramagnetic effects originating from the high-spin nonheme Fe(II) ion in the reaction center. Paramagnetic contributions to proton relaxation rates were converted into distance constraints in order to build a model for the interaction. The models place paraquat in the QB site, where most herbicides interact, in agreement with docking calculations, whereas acifluorfen was placed between the metal and the QB site, as also demonstrated by the induced paramagnetic shifts. Acifluorfen could therefore act to break the electron-transfer pathway between the QA and QB sites.
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Affiliation(s)
- Nicola D'Amelio
- Department of Chemistry and the NMR Center, University of Siena, Via A. Moro, 53100 Siena, Italy
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Costa-Filho AJ, Nascimento OR, Calvo R. Electron Paramagnetic Resonance Study of Weak Exchange Interactions between Metal Ions in a Model System: CuIIGly-Trp. J Phys Chem B 2004. [DOI: 10.1021/jp037271r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonio J. Costa-Filho
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
| | - Otaciro R. Nascimento
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
| | - Rafael Calvo
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
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