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Baldaguez Medina P, Ardila Contreras V, Hartmann F, Schmitt D, Klimek A, Elbert J, Gallei M, Su X. Investigating the Electrochemically Driven Capture and Release of Long-Chain PFAS by Redox Metallopolymer Sorbents. ACS APPLIED MATERIALS & INTERFACES 2023; 15:22112-22122. [PMID: 37114898 DOI: 10.1021/acsami.3c01670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The remediation of perfluoroalkyl substances (PFAS) is an urgent challenge due to their prevalence and persistence in the environment. Electrosorption is a promising approach for wastewater treatment and water purification, especially through the use of redox polymers to control the binding and release of target contaminants without additional external chemical inputs. However, the design of efficient redox electrosorbents for PFAS faces the significant challenge of balancing a high adsorption capacity while maintaining significant electrochemical regeneration. To overcome this challenge, we investigate redox-active metallopolymers as a versatile synthetic platform to enhance both electrochemical reversibility and electrosorption uptake capacity for PFAS removal. We selected and synthesized a series of metallopolymers bearing ferrocene and cobaltocenium units spanning a range of redox potentials to evaluate their performance for the capture and release of perfluorooctanoic acid (PFOA). Our results demonstrate that PFOA uptake and regeneration efficiency increased with more negative formal potential of the redox polymers, indicating possible structural correlations with the electron density of the metallocenes. Poly(2-(methacryloyloxy)ethyl cobaltoceniumcarboxylate hexafluorophosphate) (PMAECoPF6) showed the highest affinity toward PFOA, with an uptake capacity of more than 90 mg PFOA/g adsorbent at 0.0 V vs Ag/AgCl and a regeneration efficiency of more than 85% at -0.4 V vs Ag/AgCl. Kinetics of PFOA release showed that electrochemical bias greatly enhanced the regeneration efficiency when compared to open-circuit desorption. In addition, electrosorption of PFAS from different wastewater matrices and a range of salt concentrations demonstrated the capability of PFAS remediation in complex water sources, even at ppb levels of contaminants. Our work showcases the synthetic tunability of redox metallopolymers for enhanced electrosorption capacity and regeneration of PFAS.
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Affiliation(s)
- Paola Baldaguez Medina
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Valentina Ardila Contreras
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Frank Hartmann
- Chair in Polymer Chemistry, Saarland University, Campus C4 2, 66123 Saarbrücken, Germany
| | - Deborah Schmitt
- Chair in Polymer Chemistry, Saarland University, Campus C4 2, 66123 Saarbrücken, Germany
| | - Angelique Klimek
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Johannes Elbert
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Markus Gallei
- Chair in Polymer Chemistry, Saarland University, Campus C4 2, 66123 Saarbrücken, Germany
- Saarene, Saarland Center for Energy Materials and Sustainability, Campus C4 2, 66123 Saarbrücken, Germany
| | - Xiao Su
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
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Coherent intradimer dynamics in reaction centers of photosynthetic green bacterium Chloroflexus aurantiacus. Sci Rep 2020; 10:228. [PMID: 31937882 PMCID: PMC6959224 DOI: 10.1038/s41598-019-57115-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 12/20/2019] [Indexed: 12/04/2022] Open
Abstract
Early-time dynamics of absorbance changes (light minus dark) in the long-wavelength Qy absorption band of bacteriochlorophyll dimer P of isolated reaction centers (RCs) from thermophilic green bacterium Chloroflexus (Cfx.) aurantiacus was studied by difference pump-probe spectroscopy with 18-fs resolution at cryogenic temperature. It was found that the stimulated emission spectrum gradually moves to the red on the ~100-fs time scale and subsequently oscillates with a major frequency of ~140 cm−1. By applying the non-secular Redfield theory and linear susceptibility theory, the coherent dynamics of the stimulated emission from the excited state of the primary electron donor, bacteriochlorophyll dimer P*, was modeled. The model showed the possibility of an extremely fast transition from the locally excited state P1* to the spectrally different excited state P2*. This transition is clearly seen in the kinetics of the stimulated emission at 880 and 945 nm, where mostly P1* and P2* states emit, respectively. These findings are similar to those obtained previously in RCs of the purple bacterium Rhodobacter (Rba.) sphaeroides. The assumption about the existence of the second excited state P2* helps to explain the complicated temporal behavior of the ΔA spectrum measured by pump-probe spectroscopy. It is interesting that, in spite of the strong coupling between the P1* and P2* states assumed in our model, the form of the coherent oscillations is mainly defined by pure vibrational coherence in the excited states. A possible nature of the P2* state is discussed.
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Romero JO, Fernández-Fueyo E, Avila-Salas F, Recabarren R, Alzate-Morales J, Martínez AT. Binding and Catalytic Mechanisms of Veratryl Alcohol Oxidation by Lignin Peroxidase: A Theoretical and Experimental Study. Comput Struct Biotechnol J 2019; 17:1066-1074. [PMID: 31452859 PMCID: PMC6700493 DOI: 10.1016/j.csbj.2019.07.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/03/2019] [Accepted: 07/07/2019] [Indexed: 11/30/2022] Open
Abstract
Lignin peroxidase (LiP) and its natural substrate veratryl alcohol (VA) play a crucial role in lignin degradation by white-rot fungi. Understanding the molecular determinants for the interaction of this enzyme with its substrates is essential in the rational design of engineered peroxidases for biotechnological application. Here, we combine computational and experimental approaches to analyze the interaction of Phanerochaete chrysosporium LiP (isoenzyme H8) with VA and its radical cation (VA•+, resulting from substrate oxidation by the enzyme). Interaction energy calculations at semiempirical quantum mechanical level (SQM) between LiP and VA/VA•+ enabled to identify those residues at the acidic environment of catalytic Trp171 involved in the main interactions. Then, a battery of variants, with single and multiple mutations at these residues (Glu168, Asp165, Glu250, Asp264, and Phe267), was generated by directed mutagenesis, and their kinetics parameters were estimated on VA and two additional substrates. The experimental results show that Glu168 and Glu250 are crucial for the binding of VA, with Glu250 also contributing to the turnover of the enzyme. The experimental results were further rationalized through new calculations of interaction energies between VA/VA•+ and LiP with each of the single mutations. Finally, the delocalization of spin density was determined with quantum mechanics/molecular mechanics calculations (QM/MM), further supporting the contribution of Glu250 to VA oxidation at Trp171.
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Affiliation(s)
- Jefferson O Romero
- Centro de Bioinformática, Simulacion y Modelado (CBSM), Departamento de Bioinformática, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile.,Doctorado en Ciencias Mencion Investigacion y Desarrollo de Productos Bioactivos, Instituto de Química de Recursos Naturales, Universidad de Talca, 2 Norte 685, Casilla 747, Talca, Chile
| | - Elena Fernández-Fueyo
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28006 Madrid, Spain.,Department of Bionanoscience, Delft University of Technology, van der Maasweg 9, 2629, HZ, Delft, The Netherlands
| | - Fabián Avila-Salas
- Centro de Nanotecnología Aplicada, Facultad de Ciencias, Universidad Mayor, Camino La Pirámide 5750, Huechuraba, Chile.,Escuela de Agronomía, Facultad de Ciencias, Universidad Mayor, Camino La Pirámide 5750, Huechuraba, Chile
| | - Rodrigo Recabarren
- Centro de Bioinformática, Simulacion y Modelado (CBSM), Departamento de Bioinformática, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
| | - Jans Alzate-Morales
- Centro de Bioinformática, Simulacion y Modelado (CBSM), Departamento de Bioinformática, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
| | - Angel T Martínez
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28006 Madrid, Spain
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Mandal S, Espiritu E, Akram N, Lin S, Williams JC, Allen JP, Woodbury NW. Influence of the Electrochemical Properties of the Bacteriochlorophyll Dimer on Triplet Energy-Transfer Dynamics in Bacterial Reaction Centers. J Phys Chem B 2018; 122:10097-10107. [PMID: 30351114 DOI: 10.1021/acs.jpcb.8b07985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Energetics, protein dynamics, and electronic coupling are the key factors in controlling both electron and energy transfer in photosynthetic bacterial reaction centers (RCs). Here, we examine the rates and mechanistic pathways of the P+HA- radical-pair charge recombination, triplet state formation, and subsequent triplet energy transfer from the triplet state of the bacteriochlorophyll dimer (P) to the carotenoid in a series of mutant RCs (L131LH + M160LH (D1), L131LH + M197FH (D2), and L131LH + M160LH + M197FH (T1)) of Rhodobacter sphaeroides. In these mutants, the electronic structure of P is perturbed and the P/P+ midpoint potential is systematically increased due to addition of hydrogen bonds between P and the introduced residues. High-resolution, broad-band, transient absorption spectroscopy on the femtosecond to microsecond timescale shows that the charge recombination rate increases and the triplet energy transfer rate decreases in these mutants relative to the wild type (WT). The increase of the charge recombination rate is correlated to the increase in the energy level of P+HA- and the increase in the P/P+ midpoint potential. On the other hand, the decrease in rate of triplet energy transfer in the mutants can be explained in terms of a lower energy of 3P and a shift in the electron spin density distribution in the bacteriochlorophylls of P. The triplet energy-transfer rate follows the order of WT > L131LH + M197FH > L131LH + M160LH > L131LH + M160LH + M197FH, both at room temperature and at 77 K. A pronounced temperature dependence of the rate is observed for all of the RC samples. The activation energy associated to this process is increased in the mutants relative to WT, consistent with a lower 3P energy due to the addition of hydrogen bonds between P and the introduced residues.
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Bielytskyi P, Gräsing D, Mote KR, Sai Sankar Gupta KB, Vega S, Madhu PK, Alia A, Matysik J. 13C → 1H transfer of light-induced hyperpolarization allows for selective detection of protons in frozen photosynthetic reaction center. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 293:82-91. [PMID: 29909081 DOI: 10.1016/j.jmr.2018.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 06/06/2018] [Accepted: 06/07/2018] [Indexed: 05/14/2023]
Abstract
In the present study, we exploit the light-induced hyperpolarization occurring on 13C nuclei due to the solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) effect to boost the NMR signal intensity of selected protons via inverse cross-polarization. Such hyperpolarization transfer is implemented into 1H-detected two-dimensional 13C-1H correlation magic-angle-spinning (MAS) NMR experiment to study protons in frozen photosynthetic reaction centers (RCs). As a first trial, the performance of such an experiment is tested on selectively 13C labeled RCs from the purple bacteria of Rhodobacter sphaeroides. We observed response from the protons belonging to the photochemically active cofactors in their native protein environment. Such an approach is a potential heteronuclear spin-torch experiment which could be complementary to the classical heteronuclear correlation (HETCOR) experiments for mapping proton chemical shifts of photosynthetic cofactors and to understand the role of the proton pool around the electron donors in the electron transfer process occurring during photosynthesis.
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Affiliation(s)
- Pavlo Bielytskyi
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany
| | - Daniel Gräsing
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany
| | - Kaustubh R Mote
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad 500107, India
| | | | - Shimon Vega
- Department of Chemical Physics, Weizmann Institute of Science, 76100 Rechovot, Israel
| | - P K Madhu
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad 500107, India; Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - A Alia
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2301 RA Leiden, The Netherlands; Institut für Medizinische Physik und Biophysik, Universität Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Jörg Matysik
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany.
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Garcia-Borràs M, Houk KN, Jiménez-Osés G. Computational Design of Protein Function. COMPUTATIONAL TOOLS FOR CHEMICAL BIOLOGY 2017. [DOI: 10.1039/9781788010139-00087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The computational design of enzymes is a tremendous challenge for both chemistry and biochemistry. The ability to design stable and functional biocatalysts that could operate under different conditions to perform chemical reactions without precedent in nature, allowing the large-scale production of chemicals à la carte, would revolutionise both synthetic, pharmacologic and materials chemistry. Despite the great advances achieved, this highly multidisciplinary area of research is still in its infancy. This chapter describes the ‘inside-out’ protocol for computational enzyme design and both the achievements and limitations of the current technology are highlighted. Furthermore, molecular dynamics simulations have proved to be invaluable in the enzyme design process, constituting an important tool for discovering elusive catalytically relevant conformations of the engineered or designed enzyme. As a complement to the ‘inside-out’ design protocol, different examples where hybrid QM/MM approaches have been directly applied to discover beneficial mutations in rational computational enzyme design are described.
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Affiliation(s)
- Marc Garcia-Borràs
- Department of Chemistry and Biochemistry, University of California Los Angeles California CA 90095-1569 USA
| | - Kendall N. Houk
- Department of Chemistry and Biochemistry, University of California Los Angeles California CA 90095-1569 USA
| | - Gonzalo Jiménez-Osés
- Departamento de Química, Centro de Investigación en Síntesis Química Universidad de La Rioja 26006 Logroño La Rioja Spain
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Möbius K, Lubitz W, Savitsky A. Jim Hyde and the ENDOR Connection: A Personal Account. APPLIED MAGNETIC RESONANCE 2017; 48:1149-1183. [PMID: 29151676 PMCID: PMC5668355 DOI: 10.1007/s00723-017-0959-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Indexed: 06/07/2023]
Abstract
In this minireview, we report on our year-long EPR work, such as electron-nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultra-fast electronics for signal data handling and processing have pushed the limits of EPR spectroscopy and its multi-frequency extensions to new horizons concerning sensitivity of detection, selectivity of molecular interactions and time resolution. Among the most important advances is the upgrading of EPR to high magnetic fields, very much in analogy to what happened in NMR. The ongoing progress in EPR spectroscopy is exemplified by reviewing various multi-frequency electron-nuclear double-resonance experiments on organic radicals, light-generated donor-acceptor radical pairs in photosynthesis, and site-specifically nitroxide spin-labeled bacteriorhodopsin, the light-driven proton pump, as well as EDNMR and ENDOR on nitroxides. Signal and resolution enhancements are particularly spectacular for ENDOR, EDNMR and PELDOR on frozen-solution samples at high Zeeman fields. They provide orientation selection for disordered samples approaching single-crystal resolution at canonical g-tensor orientations-even for molecules with small g-anisotropies. Dramatic improvements of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Thus, unique structural and dynamic information is revealed that can hardly be obtained by other analytical techniques. Micromolar concentrations of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems-offering exciting applications for physicists, chemists, biochemists and molecular biologists.
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Affiliation(s)
- Klaus Möbius
- Department of Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany
- Max-Planck-Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
| | - Anton Savitsky
- Max-Planck-Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
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Lucas MF, Monza E, Jørgensen LJ, Ernst HA, Piontek K, Bjerrum MJ, Martinez ÁT, Camarero S, Guallar V. Simulating Substrate Recognition and Oxidation in Laccases: From Description to Design. J Chem Theory Comput 2017; 13:1462-1467. [PMID: 28187256 DOI: 10.1021/acs.jctc.6b01158] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To meet the very specific requirements demanded by industry, proteins must be appropriately tailored. Engineering laccases, to improve the oxidation of small molecules, with applications in multiple fields, is, however, a difficult task. Most efforts have concentrated on increasing the redox potential of the enzyme, but in recent work, we have pursued an alternate strategy to engineering these biocatalysts. In particular, we have found that redesigning substrate binding at the T1 pocket, guided by in silico methodologies, to be a more consistent option. In this work, we evaluate the robustness of our computational approach to estimate activity, emphasizing the importance of the binding event in laccase reactivity. Strengths and weaknesses of the protocol are discussed along with its potential for scoring large numbers of protein sequences and thus its significance in protein engineering.
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Affiliation(s)
- Maria Fátima Lucas
- Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center , Jordi Girona 29, E-08034 Barcelona, Spain.,Anaxomics Biotech , Balmes 89, E-08008 Barcelona, Spain
| | - Emanuele Monza
- Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center , Jordi Girona 29, E-08034 Barcelona, Spain
| | - Lise J Jørgensen
- Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 Copenhagen Ø, C., Denmark
| | - Heidi A Ernst
- Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 Copenhagen Ø, C., Denmark
| | - Klaus Piontek
- University of Freiburg , Albertstraße 21, D-79104 Freiburg im Breisgau, Germany
| | - Morten J Bjerrum
- Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 Copenhagen Ø, C., Denmark
| | - Ángel T Martinez
- Centro de Investigaciones Biológicas, CSIC , Ramiro de Maeztu 9, E-28040 Madrid, Spain
| | - Susana Camarero
- Centro de Investigaciones Biológicas, CSIC , Ramiro de Maeztu 9, E-28040 Madrid, Spain
| | - Víctor Guallar
- Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center , Jordi Girona 29, E-08034 Barcelona, Spain.,ICREA , Passeig Lluís Companys 23, E-08010 Barcelona, Spain
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Santiago G, de Salas F, Lucas MF, Monza E, Acebes S, Martinez ÁT, Camarero S, Guallar V. Computer-Aided Laccase Engineering: Toward Biological Oxidation of Arylamines. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01460] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Gerard Santiago
- Joint
BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
| | - Felipe de Salas
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain
| | - M. Fátima Lucas
- Joint
BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
- Anaxomics Biotech, Balmes 89, E-08008 Barcelona, Spain
| | - Emanuele Monza
- Joint
BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
| | - Sandra Acebes
- Joint
BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
| | - Ángel T. Martinez
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain
| | - Susana Camarero
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain
| | - Víctor Guallar
- Joint
BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
- ICREA, Passeig Lluís Companys 23, E-08010 Barcelona, Spain
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Monza E, Lucas MF, Camarero S, Alejaldre LC, Martínez AT, Guallar V. Insights into Laccase Engineering from Molecular Simulations: Toward a Binding-Focused Strategy. J Phys Chem Lett 2015; 6:1447-1453. [PMID: 26263150 DOI: 10.1021/acs.jpclett.5b00225] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Understanding the molecular determinants of enzyme performance is of primary importance for the rational design of ad hoc mutants. A novel approach, which combines efficient conformational sampling and quick reactivity scoring, is used here to shed light on how substrate oxidation was improved during the directed evolution experiment of a fungal laccase (from Pycnoporus cinnabarinus), an industrially relevant class of oxidoreductases. It is found that the enhanced activity of the evolved enzyme is mainly the result of substrate arrangement in the active site, with no important change in the redox potential of the T1 copper. Mutations at the active site shift the binding mode into a more buried substrate position and provide a more favorable electrostatic environment for substrate oxidation. As a consequence, engineering the binding event seems to be a viable way to in silico evolution of oxidoreductases.
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Affiliation(s)
- Emanuele Monza
- †Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, c/Jordi Girona 29, 08034 Barcelona, Spain
| | - M Fatima Lucas
- †Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, c/Jordi Girona 29, 08034 Barcelona, Spain
| | - Susana Camarero
- ‡Centro de Investigacion Biológica, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Lorea C Alejaldre
- ‡Centro de Investigacion Biológica, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Angel T Martínez
- ‡Centro de Investigacion Biológica, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Victor Guallar
- †Joint BSC-CRG-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, c/Jordi Girona 29, 08034 Barcelona, Spain
- §Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain
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Tufts AA, Flores M, Olson TL, Williams JC, Allen JP. Electronic structure of the Mn-cofactor of modified bacterial reaction centers measured by electron paramagnetic resonance and electron spin echo envelope modulation spectroscopies. PHOTOSYNTHESIS RESEARCH 2014; 120:207-220. [PMID: 23868400 DOI: 10.1007/s11120-013-9887-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/06/2013] [Indexed: 06/02/2023]
Abstract
The electronic structure of a Mn(II) ion bound to highly oxidizing reaction centers of Rhodobacter sphaeroides was studied in a mutant modified to possess a metal binding site at a location comparable to the Mn4Ca cluster of photosystem II. The Mn-binding site of the previously described mutant, M2, contains three carboxylates and one His at the binding site (Thielges et al., Biochemistry 44:389-7394, 2005). The redox-active Mn-cofactor was characterized using electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies. In the light without bound metal, the Mn-binding mutants showed an EPR spectrum characteristic of the oxidized bacteriochlorophyll dimer and reduced quinone whose intensity was significantly reduced due to the diminished quantum yield of charge separation in the mutant compared to wild type. In the presence of the metal and in the dark, the EPR spectrum measured at the X-band frequency of 9.4 GHz showed a distinctive spin 5/2 Mn(II) signal consisting of 16 lines associated with both allowed and forbidden transitions. Upon illumination, the amplitude of the spectrum is decreased by over 80 % due to oxidation of the metal upon electron transfer to the oxidized bacteriochlorophyll dimer. The EPR spectrum of the Mn-cofactor was also measured at the Q-band frequency of 34 GHz and was better resolved as the signal was composed of the six allowed electronic transitions with only minor contributions from other transitions. A fit of the Q-band EPR spectrum shows that the Mn-cofactor is a high spin Mn(II) species (S = 5/2) that is six-coordinated with an isotropic g-value of 2.0006, a weak zero-field splitting and E/D ratio of approximately 1/3. The ESEEM experiments showed the presence of one (14)N coordinating the Mn-cofactor. The nitrogen atom is assigned to a His by comparing our ESEEM results to those previously reported for Mn(II) ions bound to other proteins and on the basis of the X-ray structure of the M2 mutant that shows the presence of only one His, residue M193, that can coordinate the Mn-cofactor. Together, the data allow the electronic structure and coordination environment of the designed Mn-cofactor in the modified reaction centers to be characterized in detail and compared to those observed in other proteins with Mn-cofactors.
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Affiliation(s)
- A A Tufts
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ, 85287-1604, USA
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Krasilnikov PM. Problems of the theory of electron transfer in biological systems. Biophysics (Nagoya-shi) 2014. [DOI: 10.1134/s0006350914010059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Möbius K, Lubitz W, Savitsky A. High-field EPR on membrane proteins - crossing the gap to NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 75:1-49. [PMID: 24160760 DOI: 10.1016/j.pnmrs.2013.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 07/15/2013] [Accepted: 07/15/2013] [Indexed: 06/02/2023]
Abstract
In this review on advanced EPR spectroscopy, which addresses both the EPR and NMR communities, considerable emphasis is put on delineating the complementarity of NMR and EPR concerning the measurement of molecular interactions in large biomolecules. From these interactions, detailed information can be revealed on structure and dynamics of macromolecules embedded in solution- or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultrafast electronics for signal data handling and processing have pushed to new horizons the limits of EPR spectroscopy and its multifrequency extensions concerning the sensitivity of detection, the selectivity with respect to interactions, and the resolution in frequency and time domains. One of the most important advances has been the extension of EPR to high magnetic fields and microwave frequencies, very much in analogy to what happens in NMR. This is exemplified by referring to ongoing efforts for signal enhancement in both NMR and EPR double-resonance techniques by exploiting dynamic nuclear or electron spin polarization via unpaired electron spins and their electron-nuclear or electron-electron interactions. Signal and resolution enhancements are particularly spectacular for double-resonance techniques such as ENDOR and PELDOR at high magnetic fields. They provide greatly improved orientational selection for disordered samples that approaches single-crystal resolution at canonical g-tensor orientations - even for molecules with small g-anisotropies. Exchange of experience between the EPR and NMR communities allows for handling polarization and resolution improvement strategies in an optimal manner. Consequently, a dramatic improvement of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Unique structural and dynamic information is thus revealed that can hardly be obtained by any other analytical techniques. Micromolar quantities of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems - offering highly interesting applications for chemists, biochemists and molecular biologists. In three case studies, representative examples of advanced EPR spectroscopy are reviewed: (I) High-field PELDOR and ENDOR structure determination of cation-anion radical pairs in reaction centers from photosynthetic purple bacteria and cyanobacteria (Photosystem I); (II) High-field ENDOR and ELDOR-detected NMR spectroscopy on the oxygen-evolving complex of Photosystem II; and (III) High-field electron dipolar spectroscopy on nitroxide spin-labelled bacteriorhodopsin for structure-function studies. An extended conclusion with an outlook to further developments and applications is also presented.
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Affiliation(s)
- Klaus Möbius
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany; Department of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin, Germany.
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Harris MA, Luehr CA, Faries KM, Wander M, Kressel L, Holten D, Hanson DK, Laible PD, Kirmaier C. Protein Influence on Charge-Asymmetry of the Primary Donor in Photosynthetic Bacterial Reaction Centers Containing a Heterodimer: Effects on Photophysical Properties and Electron Transfer. J Phys Chem B 2013; 117:4028-41. [DOI: 10.1021/jp401138h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Michelle A. Harris
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United
States
| | - Craig A. Luehr
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Kaitlyn M. Faries
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United
States
| | - Marc Wander
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Lucas Kressel
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United
States
| | - Deborah K. Hanson
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Philip D. Laible
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Christine Kirmaier
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United
States
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Zhang Y, LaFountain AM, Magdaong N, Fuciman M, Allen JP, Frank HA, Rusling JF. Thin Film Voltammetry of Wild Type and Mutant Reaction Center Proteins from Photosynthetic Bacteria. J Phys Chem B 2011; 115:3226-32. [PMID: 21384836 DOI: 10.1021/jp111680p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yun Zhang
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Amy M. LaFountain
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Nikki Magdaong
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Marcel Fuciman
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - James P. Allen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States
| | - Harry A. Frank
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - James F. Rusling
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
- Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut 06032, United States
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Electronic structure of the primary electron donor of Blastochloris viridis heterodimer mutants: High-field EPR study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1617-26. [DOI: 10.1016/j.bbabio.2010.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Revised: 05/18/2010] [Accepted: 06/04/2010] [Indexed: 11/22/2022]
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Sakamoto R, Nishikawa M, Yamamura T, Kume S, Nishihara H. A new special pair model comprising meso-di-p-anisylaminoporphyrin: enhancement of visible-light absorptivities and quantification of electronic communication in mixed-valent cation radical. Chem Commun (Camb) 2010; 46:2028-30. [DOI: 10.1039/b923854a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Daviso E, Prakash S, Alia A, Gast P, Neugebauer J, Jeschke G, Matysik J. The electronic structure of the primary electron donor of reaction centers of purple bacteria at atomic resolution as observed by photo-CIDNP 13C NMR. Proc Natl Acad Sci U S A 2009; 106:22281-6. [PMID: 20018724 PMCID: PMC2799707 DOI: 10.1073/pnas.0908608106] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Indexed: 11/18/2022] Open
Abstract
Composed of the two bacteriochlorophyll cofactors, P(L) and P(M), the special pair functions as the primary electron donor in bacterial reaction centers of purple bacteria of Rhodobacter sphaeroides. Under light absorption, an electron is transferred to a bacteriopheophytin and a radical pair is produced. The occurrence of the radical pair is linked to the production of enhanced nuclear polarization called photochemically induced dynamic nuclear polarization (photo-CIDNP). This effect can be used to study the electronic structure of the special pair at atomic resolution by detection of the strongly enhanced nuclear polarization with laser-flash photo-CIDNP magic-angle spinning NMR on the carotenoid-less mutant R26. In the electronic ground state, P(L) is strongly disturbed, carrying a slightly negative charge. In the radical cation state, the ratio of total electron spin densities between P(L) and P(M) is 2:1, although it is 2.5:1 for the pyrrole carbons, 2.2:1 for all porphyrinic carbons, and 4:1 for the pyrrole nitrogen. It is shown that the symmetry break between the electronic structures in the electronic ground state and in the radical cation state is an intrinsic property of the special pair supermolecule, which is particularly attributable to a modification of the structure of P(L). The significant difference in electron density distribution between the ground and radical cation states is explained by an electric polarization effect of the nearby histidine.
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Affiliation(s)
- Eugenio Daviso
- Leiden Institute of Chemistry, 2300 RA Leiden, The Netherlands
| | - Shipra Prakash
- Leiden Institute of Chemistry, 2300 RA Leiden, The Netherlands
| | - A. Alia
- Leiden Institute of Chemistry, 2300 RA Leiden, The Netherlands
| | - Peter Gast
- Leiden Institute of Physics, 2300 RA Leiden, The Netherlands; and
| | | | - Gunnar Jeschke
- Laboratorium für Physikalische Chemie, Eidgenössische Technische Hochschule Zürich, 8093 Zürich, Switzerland
| | - Jörg Matysik
- Leiden Institute of Chemistry, 2300 RA Leiden, The Netherlands
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Savitsky A, Möbius K. High-field EPR. PHOTOSYNTHESIS RESEARCH 2009; 102:311-333. [PMID: 19468856 DOI: 10.1007/s11120-009-9432-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 04/29/2009] [Indexed: 05/27/2023]
Abstract
Among the numerous spectroscopic techniques utilized in photosynthesis research, high-field/high-frequency EPR and its pulse extensions ESE, ENDOR, ESEEM, and PELDOR play an important role in the endeavor to understand, on the basis of structure and dynamics data, dominant factors that control specificity and efficiency of light-induced electron- and proton-transfer processes in primary photosynthesis. Short-lived transient intermediates of the photocycle can be characterized by high-field EPR techniques, and detailed structural information can be obtained even from disordered sample preparations. The chapter describes how multifrequency high-field EPR methodology, in conjunction with mutation strategies for site-specific isotope or spin labeling and with the support of modern quantum-chemical computation methods for data interpretation, is capable of providing new insights into the photosynthetic transfer processes. The information obtained is complementary to that of protein crystallography, solid-state NMR and laser spectroscopy.
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Affiliation(s)
- Anton Savitsky
- Department of Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany
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Ponomarenko NS, Li L, Marino AR, Tereshko V, Ostafin A, Popova JA, Bylina EJ, Ismagilov RF, Norris JR. Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1788:1822-31. [PMID: 19539602 PMCID: PMC2752317 DOI: 10.1016/j.bbamem.2009.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 05/06/2009] [Accepted: 06/03/2009] [Indexed: 01/07/2023]
Abstract
Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions 400 x 100 x 100 microm, belonged to space group P4(3)2(1)2, and were isomorphous to the ones reported earlier for the wild type (WT) strain. The structure was solved to a 2.5 A resolution limit. Electron-density maps confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall position. The highly conserved tyrosine L162, located between the primary donor and the highest potential heme C(380), revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides opportunities for investigating changes in light-induced electron transfer that reflect differences in redox cascades.
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Affiliation(s)
- Nina S. Ponomarenko
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Liang Li
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Antony R. Marino
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Valentina Tereshko
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Agnes Ostafin
- Department of Material Science, University of Utah, 316 CME, 122 S. Central Camous Drive, Salt Lake City, UT 84112, USA
| | - Julia A. Popova
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Edward J. Bylina
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - Rustem F. Ismagilov
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA
| | - James R. Norris
- Department of Chemistry, University of Chicago, 929 E.57th Street, GCIS, Chicago, IL 60637, USA,Corresponding author. Tel.: +1 773 702 7864. (J.R. Norris)
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21
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Replacement of chlorophyll with di-vinyl chlorophyll in the antenna and reaction center complexes of the cyanobacterium Synechocystis sp. PCC 6803: Characterization of spectral and photochemical properties. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:191-200. [DOI: 10.1016/j.bbabio.2008.12.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 12/26/2008] [Accepted: 12/30/2008] [Indexed: 01/09/2023]
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22
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Williams JC, Allen JP. Directed Modification of Reaction Centers from Purple Bacteria. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_18] [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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23
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Allen JP, Cordova JM, Jolley CC, Murray TA, Schneider JW, Woodbury NW, Williams JC, Niklas J, Klihm G, Reus M, Lubitz W. EPR, ENDOR, and special TRIPLE measurements of P(*+) in wild type and modified reaction centers from Rb. sphaeroides. PHOTOSYNTHESIS RESEARCH 2009; 99:1-10. [PMID: 18819016 DOI: 10.1007/s11120-008-9346-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 07/22/2008] [Indexed: 05/26/2023]
Abstract
The influence of the protein environment on the primary electron donor, P, a bacteriochlorophyll a dimer, of reaction centers from Rhodobacter sphaeroides, has been investigated using electron paramagnetic resonance and electron nuclear double resonance spectroscopy. These techniques were used to probe the effects on P that are due to alteration of three amino acid residues, His L168, Asn L170, and Asn M199. The introduction of Glu at L168, Asp at L170, or Asp at M199 changes the oxidation/reduction midpoint potential of P in a pH-dependent manner (Williams et al. (2001) Biochemistry 40, 15403-15407). For the double mutant His L168 to Glu and Asn at L170 to Asp, excitation results in electron transfer along the A-side branch of cofactors at pH 7.2, but at pH 9.5, a long-lived state involving B-side cofactors is produced (Haffa et al. (2004) J Phys Chem B 108, 4-7). Using electron paramagnetic resonance spectroscopy, the mutants with alterations of each of the three individual residues and a double mutant, with changes at L168 and L170, were found to have increased linewidths of 10.1-11.0 G compared to the linewidth of 9.6 G for wild type. The Special TRIPLE spectra were pH dependent, and at pH 8, the introduction of aspartate at L170 increased the spin density ratio, rho (L)/rho (M), to 6.1 while an aspartate at the symmetry related position, M199, decreased the ratio to 0.7 compared to the value of 2.1 for wild type. These results indicate that the energy of the two halves of P changes by about 100 meV due to the mutations and are consistent with the interpretation that electrostatic interactions involving these amino acid residues contribute to the switch in pathway of electron transfer.
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Affiliation(s)
- J P Allen
- Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, AZ, 85287-1604, USA.
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Kálmán L, Williams JC, Allen JP. Comparison of bacterial reaction centers and photosystem II. PHOTOSYNTHESIS RESEARCH 2008; 98:643-655. [PMID: 18853275 DOI: 10.1007/s11120-008-9369-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Accepted: 09/11/2008] [Indexed: 05/26/2023]
Abstract
In photosynthetic organisms, the utilization of solar energy to drive electron and proton transfer reactions across membranes is performed by pigment-protein complexes including bacterial reaction centers (BRCs) and photosystem II. The well-characterized BRC has served as a structural and functional model for the evolutionarily-related photosystem II for many years. Even though these complexes transfer electrons and protons across cell membranes in analogous manners, they utilize different secondary electron donors. Photosystem II has the unique ability to abstract electrons from water, while BRCs use molecules with much lower potentials as electron donors. This article compares the two complexes and reviews the factors that give rise to the functional differences. Also discussed are the modifications that have been performed on BRCs so that they perform reactions, such as amino acid and metal oxidation, which occur in photosystem II.
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Affiliation(s)
- László Kálmán
- Department of Physics, Concordia University, Montreal, QC, Canada
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25
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Ptushenko VV, Cherepanov DA, Krishtalik LI, Semenov AY. Semi-continuum electrostatic calculations of redox potentials in photosystem I. PHOTOSYNTHESIS RESEARCH 2008; 97:55-74. [PMID: 18483776 DOI: 10.1007/s11120-008-9309-y] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 04/24/2008] [Indexed: 05/19/2023]
Abstract
The midpoint redox potentials (E(m)) of all cofactors in photosystem I from Synechococcus elongatus as well as of the iron-sulfur (Fe(4)S(4)) clusters in two soluble ferredoxins from Azotobacter vinelandii and Clostridium acidiurici were calculated within the framework of a semi-continuum dielectric approach. The widely used treatment of proteins as uniform media with single dielectric permittivity is oversimplified, particularly, because permanent charges are considered both as a source for intraprotein electric field and as a part of dielectric polarizability. Our approach overcomes this inconsistency by using two dielectric constants: optical epsilon(o)=2.5 for permanent charges pre-existing in crystal structure, and static epsilon(s) for newly formed charges. We also take into account a substantial dielectric heterogeneity of photosystem I revealed by photoelectric measurements and a liquid junction potential correction for E(m) values of relevant redox cofactors measured in aprotic solvents. We show that calculations based on a single permittivity have the discrepancy with experimental data larger than 0.7 V, whereas E(m) values calculated within our approach fall in the range of experimental estimates. The electrostatic analysis combined with quantum chemistry calculations shows that (i) the energy decrease upon chlorophyll dimerization is essential for the downhill mode of primary charge separation between the special pair P(700) and the primary acceptor A(0); (ii) the primary donor is apparently P(700) but not a pair of accessory chlorophylls; (iii) the electron transfer from the A branch quinone Q(A) to the iron-sulfur cluster F(X) is most probably downhill, whereas that from the B branch quinone Q(B) to F(X) is essentially downhill.
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Affiliation(s)
- Vasily V Ptushenko
- A.N.Belozersky Institute of Physical-Chemical Biology, Moscow State University, Moscow, Russia
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High-Field/High-Frequency Electron Paramagnetic Resonance Involving Single- and Multiple-Transition Schemes. BIOPHYSICAL TECHNIQUES IN PHOTOSYNTHESIS 2008. [DOI: 10.1007/978-1-4020-8250-4_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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27
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Kanchanawong P, Dahlbom MG, Treynor TP, Reimers JR, Hush NS, Boxer SG. Charge Delocalization in the Special-Pair Radical Cation of Mutant Reaction Centers of Rhodobacter sphaeroides from Stark Spectra and Nonadiabatic Spectral Simulations. J Phys Chem B 2006; 110:18688-702. [PMID: 16970500 DOI: 10.1021/jp0623894] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Stark and absorption spectra for the hole-transfer band of the bacteriochlorophyll special pair in the wild-type and L131LH, M160LH, and L131LH/M160LH mutants of the bacterial reaction center of Rhodobacter sphaeroides are presented, along with extensive analyses based on nonadiabatic spectral simulations. Dramatic changes in the Stark spectra are induced by the mutations, changes that are readily interpreted in terms of the redox-energy asymmetry and degree of charge localization in the special-pair radical cation. The effect of mutagenesis on key properties such as the electronic coupling within the special pair and the reorganization energy associated with intervalence hole transfer are determined for the first time. Results for the L131LH and M160LH/L131LH mutants indicate that these species can be considered as influencing the special pair primarily through modulation of the redox asymmetry, as is usually conceptualized, but M160LH is shown to develop a wide range of effects that can be interpreted in terms of significant mutation-induced structural changes in and around the special pair. The nonadiabatic spectra simulations are performed using both a simple two-state 1-mode and an extensive four-state 70-mode model, which includes the descriptions of additional electronic states and explicitly treats the major vibrational modes involved. Excellent agreement between the two simulation approaches is obtained. The simple model is shown to reproduce key features of the Stark effect of the main intervalence transition, while the extensive model quantitatively reproduces most features of the observed spectra for both the electronic and the phase-phonon regions, thus giving a more comprehensive description of the effect of the mutations on the properties of the special-pair radical cation. These results for a series of closely related mixed-valence complexes show that the Stark spectra provide a sensitive indicator for the properties of the mixed-valence complexes and should serve as an instructive example on the application of nonadiabatic simulations to the study of mixed-valence complexes in general as well as other chemical systems akin to the photosynthetic special pair.
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Affiliation(s)
- Pakorn Kanchanawong
- Biophysics Program and Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA
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Yerushalmi R, Brandis A, Rosenbach-Belkin V, Baldridge KK, Scherz A. Modulation of Fragmental Charge Transfer via Hydrogen Bonds. Direct Measurement of Electronic Contributions†. J Phys Chem A 2006; 110:412-21. [PMID: 16405312 DOI: 10.1021/jp052809+] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogen bonds play an important role in an overwhelming variety of fields from biology to surface and supramolecular chemistry. The term "hydrogen bond" refers to a wide range of interactions with various covalent and polar contributions. In particular, hydrogen bonds have an important role in the folding and packing of peptides and nucleic acids. Recent studies also point to the importance of hydrogen bonding in the context of second-shell interactions, in metal binding and selectivity in metalloproteins, and in controlling the dynamics of membrane proteins. In this study, we demonstrate and quantify the modulation of fragmental charge transfer from hydrogen-bonded ligands to a metal center, by employing our recently introduced molecular potentiometer. The molecular details that affect this type of fragmental charge transfer are presented and a path for transferring chemical information is demonstrated. We found that H-bond interactions in the extended positions of axial ligands provide an effective means of modulating the amount of fragmental charge transfer to a metal center, thereby dramatically influencing the electronic properties of the ligand, the binding affinity, and the binding of additional ligands. The magnitude of fragmental charge-transfer modulation induced by a single ligand-solvent H-bond interaction is comparable to those induced by covalent substitution, although H-bond enthalpy is only on the order of several kilojoules per mole. Importantly, we find a significant change in the ligand electronic properties, even for weak C-H...O=C H-bond formation, where the bond enthalpy is substantially lower than for conventional H-bond interactions. The excess fragmental charge transferred to the metal center, deduced from the spectroscopic measurements, correlates well with the computationally determined values. Our findings underscore the importance of second-shell interactions in the active sites of enzymes, beyond the structural and electrostatic importance that is widely recognized today.
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Affiliation(s)
- Roie Yerushalmi
- Department of Plant Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Diller A, Roy E, Gast P, van Gorkom HJ, Zaanen J, de Groot HJM, Glaubitz C, Matysik J. Photo-CIDNP solid-state NMR on photosystems I and II:what makes P680 special? PHOTOSYNTHESIS RESEARCH 2005; 84:303-8. [PMID: 16049790 DOI: 10.1007/s11120-005-0411-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Accepted: 01/11/2005] [Indexed: 05/03/2023]
Abstract
The origin of the extraordinary high redox potential of P680, the primary electron donor of Photosystem II, is still unknown. Photochemically induced dynamic nuclear polarisation (photo-CIDNP) 13C magic-angle spinning (MAS) NMR is a powerful method to study primary electron donors. In order to reveal the electronic structure of P680, we compare new photo-CIDNP MAS NMR data of Photosystem II to those of Photosystem I. The comparison reveals that the electronic structure of the P680 radical cation is a Chl a cofactor with strong matrix interaction, while the radical cation of P700, the primary electron donor of Photosystem I, appears to be a Chl a cofactor which is essentially undisturbed. Possible forms of cofactor-matrix interactions are discussed.
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Affiliation(s)
- Anna Diller
- Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
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Ishikita H, Loll B, Biesiadka J, Galstyan A, Saenger W, Knapp EW. Tuning electron transfer by ester-group of chlorophylls in bacterial photosynthetic reaction center. FEBS Lett 2005; 579:712-6. [PMID: 15670833 DOI: 10.1016/j.febslet.2004.12.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 12/20/2004] [Accepted: 12/20/2004] [Indexed: 11/22/2022]
Abstract
Accessory chlorophylls (B(A/B)) in bacterial photosynthetic reaction center play a key role in charge-separation. Although light-exposed and dark-adapted bRC crystal structures are virtually identical, the calculated B(A) redox potentials for one-electron reduction differ. This can be traced back to different orientations of the B(A) ester-group. This tuning ability of chlorophyll redox potentials modulates the electron transfer from SP* to B(A).
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Affiliation(s)
- Hiroshi Ishikita
- Institute of Chemistry, Crystallography, Department of Biology, Chemistry, and Pharmacy, Free University of Berlin, Takustrasse 6, D-14195 Berlin, Germany
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Möbius K, Savitsky A, Schnegg A, Plato M, Fuchs M. High-field EPR spectroscopy applied to biological systems: characterization of molecular switches for electron and ion transfer. Phys Chem Chem Phys 2005; 7:19-42. [DOI: 10.1039/b412180e] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Reimers JR, Hush NS. A Unified Description of the Electrochemical, Charge Distribution, and Spectroscopic Properties of the Special-Pair Radical Cation in Bacterial Photosynthesis. J Am Chem Soc 2004; 126:4132-44. [PMID: 15053603 DOI: 10.1021/ja036883m] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We apply our four-state 70-vibration vibronic-coupling model for the properties of the photosynthetic special-pair radical cation to: (1) interpret the observed correlations between the midpoint potential and the distribution of spin density between the two bacteriochlorophylls for 30 mutants of Rhodobacter sphaeroides, (2) interpret the observed average intervalence hole-transfer absorption energies as a function of spin density for six mutants, and (3) simulate the recently obtained intervalence electroabsorption Stark spectrum of the wild-type reaction center. While three new parameters describing the location of the sites of mutation with respect to the special pair are required to describe the midpoint-potential data, a priori predictions are made for the transition energies and the Stark spectrum. In general, excellent predictions are made of the observed quantities, with deviations being typically of the order of twice the experimental uncertainties. A unified description of many chemical and spectroscopic properties of the bacterial reaction center is thus provided. Central to the analysis is the assumption that the perturbations made to the reaction center, either via mutations of protein residues or by application of an external electric field, act only to independently modify the oxidation potentials of the two halves of the special pair and hence the redox asymmetry E0. While this appears to be a good approximation, clear evidence is presented that effects of mutation can be more extensive than what is allowed for. A thorough set of analytical equations describing the observed properties is obtained using the Born-Oppenheimer adiabatic approximation. These equations are generally appropriate for intervalence charge-transfer problems and include, for the first time, full treatment of both symmetric and antisymmetric vibrational motions. The limits of validity of the adiabatic approach to the full nonadiabatic problem are obtained.
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Reimers JR, Bilić A, Cai ZL, Dahlbom M, Lambropoulos NA, Solomon GC, Crossley MJ, Hush NS. Molecular Electronics: From Basic Chemical Principles to Photosynthesis to Steady-State Through-Molecule Conductivity to Computer Architectures. Aust J Chem 2004. [DOI: 10.1071/ch04132] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Molecular electronics offers many possibilities for the development of electronic devices beyond the limit of silicon technology. Its basic ideas and history are reviewed, and a central aspect of the delocalization of electrons across molecules and junctions is examined. Analogies between key processes affecting steady-state through-molecule conduction and equilibrium geometric and spectroscopic properties of paradigm molecules, such as hydrogen, ammonia, benzene, and the Creutz–Taube ion are drawn, and the mechanisms by which control can be exerted over molecular-electronic processes during biological photosynthesis are examined. Ab initio molecular dynamics and simulations of conductivity are then presented for carbon nanotube flanged to gold(111), and device characteristics are calculated for a molecular shift register clocked by two gold electrodes.
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Reimers JR, Shapley WA, Hush NS. Modelling the bacterial photosynthetic reaction center. V. Assignment of the electronic transition observed at 2200 cm−1in the special-pair radical-cation as a second-highest occupied molecular orbital to highest occupied molecular orbital transition. J Chem Phys 2003. [DOI: 10.1063/1.1569909] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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35
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Reimers JR, Hush NS. Modeling the bacterial photosynthetic reaction center. VII. Full simulation of the intervalence hole–transfer absorption spectrum of the special-pair radical cation. J Chem Phys 2003. [DOI: 10.1063/1.1589742] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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36
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Johnson ET, Müh F, Nabedryk E, Williams JC, Allen JP, Lubitz W, Breton J, Parson WW. Electronic and Vibronic Coupling of the Special Pair of Bacteriochlorophylls in Photosynthetic Reaction Centers from Wild-Type and Mutant Strains of Rhodobacter Sphaeroides. J Phys Chem B 2002. [DOI: 10.1021/jp021024q] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- E. T. Johnson
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - F. Müh
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - E. Nabedryk
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - J. C. Williams
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - J. P. Allen
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - W. Lubitz
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - J. Breton
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
| | - W. W. Parson
- Department of Biochemistry, Box 357350, University of Washington, Seattle, Washington 98195-7350, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Service de Bioénergétique, CEA Saclay, Bât 532, F-91191 Gif Sur Yvette Cedex France, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34−36, D-45470 Mülheim/Ruhr, Germany
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Spiedel D, Jones MR, Robert B. Tuning of the redox potential of the primary electron donor in reaction centres of purple bacteria: effects of amino acid polarity and position. FEBS Lett 2002; 527:171-5. [PMID: 12220655 DOI: 10.1016/s0014-5793(02)03203-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mutation of residues His L168 and Phe M197 in the reaction centre from Rhodobacter sphaeroides has an unusually strong effect on the mid-point redox potential (E(m)) of the pair of bacteriochlorophylls that form the primary donor of electrons, tuning E(m) over a range of nearly 250 mV. This effect is correlated to the accompanying change in the permanent dipole of the L168 or M197 residue, suggesting it is mediated by changes in charge-dipole interactions. Comparisons with mutations made at a variety of other positions show that this correlation is particular to this residue pair, perhaps reflecting their proximity to the ring I regions of the dimer bacteriochlorophylls that form the overlap region between these molecules.
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Affiliation(s)
- Diane Spiedel
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, S10 2UH, Sheffield, UK
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38
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Poluektov OG, Utschig LM, Schlesselman SL, Lakshmi KV, Brudvig GW, Kothe G, Thurnauer MC. Electronic Structure of the P700Special Pair from High-Frequency Electron Paramagnetic Resonance Spectroscopy. J Phys Chem B 2002. [DOI: 10.1021/jp021465+] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Schenkl S, Spörlein S, Müh F, Witt H, Lubitz W, Zinth W, Wachtveitl J. Selective perturbation of the second electron transfer step in mutant bacterial reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1554:36-47. [PMID: 12034469 DOI: 10.1016/s0005-2728(02)00211-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In order to specifically perturb the primary electron acceptor B(A) -- a monomeric bacteriochlorophyll (BChl) a -- involved in bacterial photosynthetic charge separation (CS), the protein environment of B(A) in the reaction center (RC) of Rhodobacter sphaeroides was modified by site-directed mutagenesis. Isolated RCs were characterized by redox titrations, low temperature optical spectroscopy, ENDOR/TRIPLE resonance spectroscopy and femtosecond time-resolved spectroscopy. Two mutations were studied: In the GS(M203) mutant a serine is introduced near the ring E keto group of B(A), while in FY(L146) a phenylalanine near the ring A acetyl group of B(A) is replaced by tyrosine. In all mutations the oxidation potential of the primary electron donor P as well as the electronic structure of both the P(*+) radical cation and the radical anion of the secondary electron acceptor, H(A)(*-), are not significantly altered compared to the wild type (WT), while changes of the optical absorption spectra at 77 K in the BChl Q(X) and Q(Y) regions are observed. The GS(M203) mutation only leads to a minor retardation of the CS reactions at room temperature, whereas for FY(L146) significant deviations from the native electron transfer (ET) rates could be detected: In addition to a faster first (2.9 ps) and a slower second (1 ps) ET step, a new 8-ps time constant was found in the FY(L146) mutant, which can be ascribed to a fraction of RCs with slowed down secondary ET. The results allow us to address the functional role of the acetyl group of B(A) and question the role of the free energy changes as the main determining factor of ET rates in RCs. It is concluded that structural rearrangements alter the electronic coupling between the pigments and thereby influence the rate of fast CS.
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Affiliation(s)
- Selma Schenkl
- Sektion Physik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, 80538 Munich, Germany
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40
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Spiedel D, Roszak AW, McKendrick K, McAuley KE, Fyfe PK, Nabedryk E, Breton J, Robert B, Cogdell RJ, Isaacs NW, Jones MR. Tuning of the optical and electrochemical properties of the primary donor bacteriochlorophylls in the reaction centre from Rhodobacter sphaeroides: spectroscopy and structure. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1554:75-93. [PMID: 12034473 DOI: 10.1016/s0005-2728(02)00215-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A series of mutations have been introduced at residue 168 of the L-subunit of the reaction centre from Rhodobacter sphaeroides. In the wild-type reaction centre, residue His L168 donates a strong hydrogen bond to the acetyl carbonyl group of one of the pair of bacteriochlorophylls (BChl) that constitutes the primary donor of electrons. Mutation of His L168 to Phe or Leu causes a large decrease in the mid-point redox potential of the primary electron donor, consistent with removal of this strong hydrogen bond. Mutations to Lys, Asp and Arg cause smaller decreases in redox potential, indicative of the presence of weak hydrogen bond and/or an electrostatic effect of the polar residue. A spectroscopic analysis of the mutant complexes suggests that replacement of the wild-type His residue causes a decrease in the strength of the coupling between the two primary donor bacteriochlorophylls. The X-ray crystal structure of the mutant in which His L168 has been replaced by Phe (HL168F) was determined to a resolution of 2.5 A, and the structural model of the HL168F mutant was compared with that of the wild-type complex. The mutation causes a shift in the position of the primary donor bacteriochlorophyll that is adjacent to residue L168, and also affects the conformation of the acetyl carbonyl group of this bacteriochlorophyll. This conformational change constitutes an approximately 27 degrees through-plane rotation, rather than the large into-plane rotation that has been widely discussed in the context of the HL168F mutation. The possible structural basis of the altered spectroscopic properties of the HL168F mutant reaction centre is discussed, as is the relevance of the X-ray crystal structure of the HL168F mutant to the possible structures of the remaining mutant complexes.
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Affiliation(s)
- Diane Spiedel
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2UH, UK
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41
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Müh F, Lendzian F, Roy M, Williams JC, Allen JP, Lubitz W. Pigment−Protein Interactions in Bacterial Reaction Centers and Their Influence on Oxidation Potential and Spin Density Distribution of the Primary Donor. J Phys Chem B 2002. [DOI: 10.1021/jp0131119] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Frank Müh
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Friedhelm Lendzian
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Mason Roy
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - JoAnn C. Williams
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - James P. Allen
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry and Biochemistry and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, and Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
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Abstract
In plants and cyanobacteria, the primary step in oxygenic photosynthesis, the light induced charge separation, is driven by two large membrane intrinsic protein complexes, the photosystems I and II. Photosystem I catalyses the light driven electron transfer from plastocyanin/cytochrome c(6) on the lumenal side of the membrane to ferredoxin/flavodoxin at the stromal side by a chain of electron carriers. Photosystem I of Synechococcus elongatus consists of 12 protein subunits, 96 chlorophyll a molecules, 22 carotenoids, three [4Fe4S] clusters and two phylloquinones. Furthermore, it has been discovered that four lipids are intrinsic components of photosystem I. Photosystem I exists as a trimer in the native membrane with a molecular mass of 1068 kDa for the whole complex. The X-ray structure of photosystem I at a resolution of 2.5 A shows the location of the individual subunits and cofactors and provides new information on the protein-cofactor interactions. [P. Jordan, P. Fromme, H.T. Witt, O. Klukas, W. Saenger, N. Krauss, Nature 411 (2001) 909-917]. In this review, biochemical data and results of biophysical investigations are discussed with respect to the X-ray crystallographic structure in order to give an overview of the structure and function of this large membrane protein.
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Affiliation(s)
- P Fromme
- Max Volmer Laboratorium für Biophysikalische Chemie Institut für Chemie, Technische Universität Berlin, Germany.
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43
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Sumi H, Kakitani T. Unified Theory on Rates for Electron Transfer Mediated by a Midway Molecule, Bridging between Superexchange and Sequential Processes. J Phys Chem B 2001. [DOI: 10.1021/jp010018b] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hitoshi Sumi
- Institute of Materials Science, University of Tsukuba, Tsukuba, 305-8573, Japan, and Department of Physics, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Toshiaki Kakitani
- Institute of Materials Science, University of Tsukuba, Tsukuba, 305-8573, Japan, and Department of Physics, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
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44
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Hughes JM, Hutter MC, Reimers JR, Hush NS. Modeling the bacterial photosynthetic reaction center. 4. The structural, electrochemical, and hydrogen-bonding properties of 22 mutants of Rhodobacter sphaeroides. J Am Chem Soc 2001; 123:8550-63. [PMID: 11525663 DOI: 10.1021/ja0035710] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Site-directed mutagenesis has been employed by a number of groups to produce mutants of bacterial photosynthetic reaction centers, with the aim of tuning their operation by modifying hydrogen-bond patterns in the close vicinity of the "special pair" of bacteriochlorophylls P identical with P(L)P(M). Direct X-ray structural measurements of the consequences of mutation are rare. Attention has mostly focused on effects on properties such as carbonyl stretching frequencies and midpoint potentials to infer indirectly the induced structural modifications. In this work, the structures of 22 mutants of Rhodobacter sphaeroides have been calculated using a mixed quantum-mechanical molecular-mechanical method by modifying the known structure of the wild type. We determine (i) the orientation of the 2a-acetyl groups in the wild type, FY(M197), and FH(M197) series mutants of the neutral and oxidized reaction center, (ii) the structure of the FY(M197) mutant and possible water penetration near the special pair, (iii) that significant protein chain distortions are required to assemble some M160 series mutants (LS(M160), LN(M160), LQ(M160), and LH(M160) are considered), (iv) that there is competition for hydrogen-bonding between the 9-keto and 10a-ester groups for the introduced histidine in LH(L131) mutants, (v) that the observed midpoint potential of P for HL(M202) heterodimer mutants, including one involving also LH(M160), can be correlated with the change of electrostatic potential experienced at P(L), (vi) that hydrogen-bond cleavage may sometimes be induced by oxidation of the special pair, (vii) that the OH group of tyrosine M210 points away from P(M), and (viii) that competitive hydrogen-bonding effects determine the change in properties of NL(L166) and NH(L166) mutants. A new technique is introduced for the determination of ionization energies at the Koopmans level from QM/MM calculations, and protein-induced Stark effects on vibrational frequencies are considered.
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Affiliation(s)
- J M Hughes
- Department of Biochemistry, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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45
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Jordan P, Fromme P, Witt HT, Klukas O, Saenger W, Krauss N. Three-dimensional structure of cyanobacterial photosystem I at 2.5 A resolution. Nature 2001; 411:909-17. [PMID: 11418848 DOI: 10.1038/35082000] [Citation(s) in RCA: 1679] [Impact Index Per Article: 73.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Life on Earth depends on photosynthesis, the conversion of light energy from the Sun to chemical energy. In plants, green algae and cyanobacteria, this process is driven by the cooperation of two large protein-cofactor complexes, photosystems I and II, which are located in the thylakoid photosynthetic membranes. The crystal structure of photosystem I from the thermophilic cyanobacterium Synechococcus elongatus described here provides a picture at atomic detail of 12 protein subunits and 127 cofactors comprising 96 chlorophylls, 2 phylloquinones, 3 Fe4S4 clusters, 22 carotenoids, 4 lipids, a putative Ca2+ ion and 201 water molecules. The structural information on the proteins and cofactors and their interactions provides a basis for understanding how the high efficiency of photosystem I in light capturing and electron transfer is achieved.
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Affiliation(s)
- P Jordan
- Institut für Chemie/Kristallographie, Freie Universität Berlin, D-14195 Berlin, Takustrasse 6, Germany
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46
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Kropacheva TN, Hoff AJ. Electrochemical Oxidation of Bacteriochlorophyll a in Reaction Centers and Antenna Complexes of Photosynthetic Bacteria. J Phys Chem B 2001. [DOI: 10.1021/jp003381b] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tatyana N. Kropacheva
- Chemistry Department, Udmurt State University, 426037 Izhevsk, Russia, and Biophysics Department, Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Arnold J. Hoff
- Chemistry Department, Udmurt State University, 426037 Izhevsk, Russia, and Biophysics Department, Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
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47
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Chang CH, Hayashi M, Liang KK, Chang R, Lin SH. A Theoretical Analysis of Absorption Spectra of Photosynthetic Reaction Centers: Mechanism of Temperature Dependent Peak Shift. J Phys Chem B 2001. [DOI: 10.1021/jp0020438] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. H. Chang
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan R.O.C., Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan R.O.C., and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - M. Hayashi
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan R.O.C., Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan R.O.C., and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - K. K. Liang
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan R.O.C., Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan R.O.C., and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - R. Chang
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan R.O.C., Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan R.O.C., and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - S. H. Lin
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan R.O.C., Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan R.O.C., and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
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Käss H, Fromme P, Witt HT, Lubitz W. Orientation and Electronic Structure of the Primary Donor Radical Cation in Photosystem I: A Single Crystals EPR and ENDOR Study. J Phys Chem B 2001. [DOI: 10.1021/jp0032311] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hanno Käss
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Str. d. 17. Juni 135, D-10623 Berlin, Germany
| | - Petra Fromme
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Str. d. 17. Juni 135, D-10623 Berlin, Germany
| | - Horst T. Witt
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Str. d. 17. Juni 135, D-10623 Berlin, Germany
| | - Wolfgang Lubitz
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Str. d. 17. Juni 135, D-10623 Berlin, Germany
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49
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Reimers JR, Hughes JM, Hush NS. Modeling the bacterial photosynthetic reaction center 3: interpretation of effects of site-directed mutagenesis on the special-pair midpoint potential. Biochemistry 2000; 39:16185-9. [PMID: 11123947 DOI: 10.1021/bi001341s] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Interpretation of changes in midpoint potential of the "special pair" in bacterial photosynthetic reaction centers caused by site-directed mutagenesis is discussed in terms of a simple tight-binding model which relates them to concomitant variations in spin distribution between the two bacteriochlorophyll molecules of the special pair. Our analysis improves on previous similar ones by Allen and co-workers [Artz, K., Williams, J. C., Allen, J. P., Lendzian, F., Rautter, J., and Lubitz, W. (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 13582; Ivancich, A., Artz, K., Williams, J. C., Allen, J. P., and Mattioli, T. A. (1998) Biochemistry 37, 11812] in that it is both more complete, including electron-phonon coupling, and more accurate. It is applied to analyze data for a series of M160 mutants of Rhodobacter sphaeroides, yielding a value of 0.18+/-0.03 eV for the electronic coupling energy between the highest occupied levels of the two bacteriochlorophylls in the wild-type and a value of the energy offset E(o) between the highest occupied molecular orbitals of the L and M bacteriochlorophylls of 0.14+/-0.03 eV. For a mutant in which the electron hole in the special pair cation is located entirely on the reactive (L) side, a potential of 641+/-30 mV with respect to the normal hydrogen electrode is predicted. This agrees well with the average value ca. 650 mV observed for the heterodimer mutant HL(M202) in which the bacteriochlorophyll on the unreactive M side has been replaced by a bacteriopheophytin, causing extensive charge localization. However, the deduced coupling is found to be very sensitive to small changes in the assumptions used in the model, and various important chemical effects remain to be included.
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Affiliation(s)
- J R Reimers
- School of Chemistry and Department of Biochemistry, University of Sydney, NSW 2006, Australia
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50
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Matysik J, Gast P, van Gorkom HJ, Hoff AJ, de Groot HJ. Photochemically induced nuclear spin polarization in reaction centers of photosystem II observed by 13C-solid-state NMR reveals a strongly asymmetric electronic structure of the P680(.+) primary donor chlorophyll. Proc Natl Acad Sci U S A 2000; 97:9865-70. [PMID: 10944191 PMCID: PMC27608 DOI: 10.1073/pnas.170138797] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We report (13)C magic angle spinning NMR observation of photochemically induced dynamic nuclear spin polarization (photo-CIDNP) in the reaction center (RC) of photosystem II (PS2). The light-enhanced NMR signals of the natural abundance (13)C provide information on the electronic structure of the primary electron donor P(680) (chlorophyll a molecules absorbing around 680 nm) and on the p(z) spin density pattern in its oxidized form, P(680)(.+). Most centerband signals can be attributed to a single chlorophyll a (Chl a) cofactor that has little interaction with other pigments. The chemical shift anisotropy of the most intense signals is characteristic for aromatic carbon atoms. The data reveal a pronounced asymmetry of the electronic spin density distribution within the P(680)(.+). PS2 shows only a single broad and intense emissive signal, which is assigned to both the C-10 and C-15 methine carbon atoms. The spin density appears shifted toward ring III. This shift is remarkable, because, for monomeric Chl a radical cations in solution, the region of highest spin density is around ring II. It leads to a first hypothesis as to how the planet can provide itself with the chemical potential to split water and generate an oxygen atmosphere using the Chl a macroaromatic cycle. A local electrostatic field close to ring III can polarize the electronic charge and associated spin density and increase the redox potential of P(680) by stabilizing the highest occupied molecular orbital, without a major change of color. This field could be produced, e.g., by protonation of the keto group of ring V. Finally, the radical cation electronic structure in PS2 is different from that in the bacterial RC, which shows at least four emissive centerbands, indicating a symmetric spin density distribution over the entire bacteriochlorophyll macrocycle.
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Affiliation(s)
- J Matysik
- Leiden Institute of Chemistry, Gorlaeus Laboratoria, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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