1
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Assembly of redox active metallo-enzymes and metallo-peptides on electrodes: Abiological constructs to probe natural processes. Curr Opin Chem Biol 2022; 68:102142. [DOI: 10.1016/j.cbpa.2022.102142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 02/28/2022] [Accepted: 03/04/2022] [Indexed: 11/23/2022]
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2
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Chattopadhyay S, Mukherjee M, Kandemir B, Bowman SEJ, Bren KL, Dey A. Contributions to cytochrome c inner- and outer-sphere reorganization energy. Chem Sci 2021; 12:11894-11913. [PMID: 34659730 PMCID: PMC8442690 DOI: 10.1039/d1sc02865k] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/05/2021] [Indexed: 11/21/2022] Open
Abstract
Cytochromes c are small water-soluble proteins that catalyze electron transfer in metabolism and energy conversion processes. Hydrogenobacter thermophilus cytochrome c552 presents a curious case in displaying fluxionality of its heme axial methionine ligand; this behavior is altered by single point mutation of the Q64 residue to N64 or V64, which fixes the ligand in a single configuration. The reorganization energy (λ) of these cytochrome c552 variants is experimentally determined using a combination of rotating disc electrochemistry, chronoamperometry and cyclic voltammetry. The differences between the λ determined from these complementary techniques helps to deconvolute the contribution of the active site and its immediate environment to the overall λ (λTotal). The experimentally determined λ values in conjunction with DFT calculations indicate that the differences in λ among the protein variants are mainly due to the differences in contributions from the protein environment and not just inner-sphere λ. DFT calculations indicate that the position of residue 64, responsible for the orientation of the axial methionine, determines the geometric relaxation of the redox active molecular orbital (RAMO). The orientation of the RAMO with respect to the heme is key to determining electron transfer coupling (HAB) which results in higher ET rates in the wild-type protein relative to the Q64V mutant despite a 150 mV higher λTotal in the former. Efficient delocalization of the redox-active molecular orbital (RAMO) in HtWT results in an increase in HAB value which in turn accelerates the electron transfer (ET) rate in spite of the higher reorganization energy (λ) than the HtQ64V mutant.![]()
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Affiliation(s)
- Samir Chattopadhyay
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
| | - Manjistha Mukherjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
| | - Banu Kandemir
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Sarah E J Bowman
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Kara L Bren
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Abhishek Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
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3
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Buhrke D, Hildebrandt P. Probing Structure and Reaction Dynamics of Proteins Using Time-Resolved Resonance Raman Spectroscopy. Chem Rev 2019; 120:3577-3630. [PMID: 31814387 DOI: 10.1021/acs.chemrev.9b00429] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanistic understanding of protein functions requires insight into the structural and reaction dynamics. To elucidate these processes, a variety of experimental approaches are employed. Among them, time-resolved (TR) resonance Raman (RR) is a particularly versatile tool to probe processes of proteins harboring cofactors with electronic transitions in the visible range, such as retinal or heme proteins. TR RR spectroscopy offers the advantage of simultaneously providing molecular structure and kinetic information. The various TR RR spectroscopic methods can cover a wide dynamic range down to the femtosecond time regime and have been employed in monitoring photoinduced reaction cascades, ligand binding and dissociation, electron transfer, enzymatic reactions, and protein un- and refolding. In this account, we review the achievements of TR RR spectroscopy of nearly 50 years of research in this field, which also illustrates how the role of TR RR spectroscopy in molecular life science has changed from the beginning until now. We outline the various methodological approaches and developments and point out current limitations and potential perspectives.
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Affiliation(s)
- David Buhrke
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
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4
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Espinoza-Cara A, Zitare U, Alvarez-Paggi D, Klinke S, Otero LH, Murgida DH, Vila AJ. Engineering a bifunctional copper site in the cupredoxin fold by loop-directed mutagenesis. Chem Sci 2018; 9:6692-6702. [PMID: 30310603 PMCID: PMC6115626 DOI: 10.1039/c8sc01444b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 06/27/2018] [Indexed: 12/30/2022] Open
Abstract
Copper sites in proteins are designed to perform either electron transfer or redox catalysis. Type 1 and CuA sites are electron transfer hubs bound to a rigid protein fold that prevents binding of exogenous ligands and side reactions. Here we report the engineering of two Type 1 sites by loop-directed mutagenesis within a CuA scaffold with unique electronic structures and functional features. A copper-thioether axial bond shorter than the copper-thiolate bond is responsible for the electronic structure features, in contrast to all other natural or chimeric sites where the copper thiolate bond is short. These sites display highly unusual features, such as: (1) a high reduction potential despite a strong interaction with the axial ligand, which we attribute to changes in the hydrogen bond network and (2) the ability to bind exogenous ligands such as imidazole and azide. This strategy widens the possibility of using natural protein scaffolds with functional features not present in nature.
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Affiliation(s)
- Andrés Espinoza-Cara
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR) , Rosario , Argentina .
- Área Biofísica , Departamento de Química Biológica , Facultad de Ciencias Bioquímicas y Farmacéuticas , Universidad Nacional de Rosario , Rosario , Argentina
| | - Ulises Zitare
- Departamento de Química Inorgánica , Analítica y Química Física-INQUIMAE , Facultad de Ciencias Exactas y Naturales , Universidad de Buenos Aires-CONICET , Buenos Aires , Argentina
| | - Damián Alvarez-Paggi
- Departamento de Química Inorgánica , Analítica y Química Física-INQUIMAE , Facultad de Ciencias Exactas y Naturales , Universidad de Buenos Aires-CONICET , Buenos Aires , Argentina
- Fundación Instituto Leloir , IIBBA-CONICET , Buenos Aires , Argentina
| | - Sebastián Klinke
- Fundación Instituto Leloir , IIBBA-CONICET , Buenos Aires , Argentina
- Plataforma Argentina de Biología Estructural y Metabolómica PLABEM. , Buenos Aires , Argentina
| | - Lisandro H Otero
- Fundación Instituto Leloir , IIBBA-CONICET , Buenos Aires , Argentina
- Plataforma Argentina de Biología Estructural y Metabolómica PLABEM. , Buenos Aires , Argentina
| | - Daniel H Murgida
- Departamento de Química Inorgánica , Analítica y Química Física-INQUIMAE , Facultad de Ciencias Exactas y Naturales , Universidad de Buenos Aires-CONICET , Buenos Aires , Argentina
| | - Alejandro J Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR) , Rosario , Argentina .
- Área Biofísica , Departamento de Química Biológica , Facultad de Ciencias Bioquímicas y Farmacéuticas , Universidad Nacional de Rosario , Rosario , Argentina
- Plataforma Argentina de Biología Estructural y Metabolómica PLABEM. , Buenos Aires , Argentina
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5
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Alvarez-Paggi D, Hannibal L, Castro MA, Oviedo-Rouco S, Demicheli V, Tórtora V, Tomasina F, Radi R, Murgida DH. Multifunctional Cytochrome c: Learning New Tricks from an Old Dog. Chem Rev 2017; 117:13382-13460. [DOI: 10.1021/acs.chemrev.7b00257] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Damián Alvarez-Paggi
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Luciana Hannibal
- Department
of Pediatrics, Universitätsklinikum Freiburg, Mathildenstrasse 1, Freiburg 79106, Germany
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - María A. Castro
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Santiago Oviedo-Rouco
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Veronica Demicheli
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Veronica Tórtora
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Florencia Tomasina
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Rafael Radi
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Daniel H. Murgida
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
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6
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Computational evidence support the hypothesis of neuroglobin also acting as an electron transfer species. J Biol Inorg Chem 2017; 22:615-623. [DOI: 10.1007/s00775-017-1455-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 03/28/2017] [Indexed: 12/31/2022]
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7
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Ranieri A, Di Rocco G, Millo D, Battistuzzi G, Bortolotti CA, Lancellotti L, Borsari M, Sola M. Thermodynamics and kinetics of reduction and species conversion at a hydrophobic surface for mitochondrial cytochromes c and their cardiolipin adducts. Electrochim Acta 2015. [DOI: 10.1016/j.electacta.2015.07.065] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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8
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Liu M, Liu L, Gao W, Su M, Ge Y, Shi L, Zhang H, Dong B, Li CY. Nanoparticle mediated micromotor motion. NANOSCALE 2015; 7:4949-55. [PMID: 25689965 DOI: 10.1039/c4nr07558g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In this paper, we report the utilization of nanoparticles to mediate the motion of a polymer single crystal catalytic micromotor. Micromotors have been fabricated by directly self-assembling functional nanoparticles (platinum and iron oxide nanoparticles) onto one or both sides of two-dimensional polymer single crystals. We show that the moving velocity of these micromotors in fluids can be readily tuned by controlling the nanoparticles' surface wettability and catalytic activity. A 3 times velocity increase has been achieved for a hydrophobic micromotor as opposed to the hydrophilic ones. Furthermore, we demonstrate that the catalytic activity of platinum nanoparticles inside the micromotor can be enhanced by their synergetic interactions with iron oxide nanoparticles and an electric field. Both strategies lead to dramatically increased moving velocities, with the highest value reaching ∼200 μm s(-1). By decreasing the nanoparticles' surface wettability and increasing their catalytic activity, a maximum of a ∼10-fold increase in the moving speed of the nanoparticle based micromotor can be achieved. Our results demonstrate the advantages of using nanoparticles in micromotor systems.
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Affiliation(s)
- Mei Liu
- Institute of Functional Nano & Soft Materials (FUNSOM) and Collaborative Innovation Center (CIC) of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu 215123, P. R. China.
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9
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Surface-enhanced resonance Raman scattering (SERRS) as a tool for the studies of electron transfer proteins attached to biomimetic surfaces: Case of cytochrome c. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2013.08.140] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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10
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Gorin CF, Beh ES, Bui QM, Dick GR, Kanan MW. Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins. J Am Chem Soc 2013; 135:11257-65. [DOI: 10.1021/ja404394z] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Craig F. Gorin
- Department of Chemistry, Stanford University, Stanford, California 94305, United
States
| | - Eugene S. Beh
- Department of Chemistry, Stanford University, Stanford, California 94305, United
States
| | - Quan M. Bui
- Department of Chemistry, Stanford University, Stanford, California 94305, United
States
| | - Graham R. Dick
- Department of Chemistry, Stanford University, Stanford, California 94305, United
States
| | - Matthew W. Kanan
- Department of Chemistry, Stanford University, Stanford, California 94305, United
States
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11
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Alvarez-Paggi D, Castro MA, Tórtora V, Castro L, Radi R, Murgida DH. Electrostatically Driven Second-Sphere Ligand Switch between High and Low Reorganization Energy Forms of Native Cytochrome c. J Am Chem Soc 2013; 135:4389-97. [DOI: 10.1021/ja311786b] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Damián Alvarez-Paggi
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - María A. Castro
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Verónica Tórtora
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Laura Castro
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Rafael Radi
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Daniel H. Murgida
- Departamento
de Química Inorgánica, Analítica y Química
Física and ‡INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina
- Departamento
de Bioquímica and ⊥Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
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12
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Amadei A, Daidone I, Bortolotti CA. A general statistical mechanical approach for modeling redox thermodynamics: the reaction and reorganization free energies. RSC Adv 2013. [DOI: 10.1039/c3ra42842g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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13
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Local intense cellular electric fields and their relevance in the computational modeling of biochemical reactions. Future Med Chem 2012; 4:1873-5. [DOI: 10.4155/fmc.12.143] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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14
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Sezer M, Millo D, Weidinger IM, Zebger I, Hildebrandt P. Analyzing the catalytic processes of immobilized redox enzymes by vibrational spectroscopies. IUBMB Life 2012; 64:455-64. [PMID: 22535701 DOI: 10.1002/iub.1020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 02/12/2012] [Indexed: 11/10/2022]
Abstract
Analyzing the structure and function of redox enzymes attached to electrodes is a central challenge in many fields of fundamental and applied life science. Electrochemical techniques such as cyclic voltammetry which are routinely used do not provide insight into the molecular structure and reaction mechanisms of the immobilized proteins. Surface-enhanced infrared absorption (SEIRA) and surface-enhanced resonance Raman (SERR) spectroscopy may fill this gap, if nanostructured Au or Ag are used as conductive support materials. In this account, we will first outline the principles of the methodology including a description of the most important strategies for biocompatible protein immobilization. Subsequently, we will critically review SERR and SEIRA spectroscopic approaches to characterize the protein and active site structure of the immobilized enzymes. Special emphasis is laid on the combination of surface-enhanced vibrational spectroscopies with electrochemical methods to analyze equilibria and dynamics of the interfacial redox processes. Finally, we will assess the potential of SERR and SEIRA spectroscopy for in situ investigations on the basis of the first promising studies on human sulfite oxidase and hydrogenases under turnover conditions.
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Affiliation(s)
- Murat Sezer
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
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15
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Gorin CF, Beh ES, Kanan MW. An Electric Field–Induced Change in the Selectivity of a Metal Oxide–Catalyzed Epoxide Rearrangement. J Am Chem Soc 2011; 134:186-9. [DOI: 10.1021/ja210365j] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Craig F. Gorin
- Stanford University, Department
of Chemistry, 337 Campus Drive, Stanford, California 94305, United
States
| | - Eugene S. Beh
- Stanford University, Department
of Chemistry, 337 Campus Drive, Stanford, California 94305, United
States
| | - Matthew W. Kanan
- Stanford University, Department
of Chemistry, 337 Campus Drive, Stanford, California 94305, United
States
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16
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Khoa Ly H, Wisitruangsakul N, Sezer M, Feng JJ, Kranich A, Weidinger IM, Zebger I, Murgida DH, Hildebrandt P. Electric-field effects on the interfacial electron transfer and protein dynamics of cytochrome c. J Electroanal Chem (Lausanne) 2011. [DOI: 10.1016/j.jelechem.2010.12.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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17
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Ly HK, Sezer M, Wisitruangsakul N, Feng JJ, Kranich A, Millo D, Weidinger IM, Zebger I, Murgida DH, Hildebrandt P. Surface-enhanced vibrational spectroscopy for probing transient interactions of proteins with biomimetic interfaces: electric field effects on structure, dynamics and function of cytochrome c. FEBS J 2011; 278:1382-90. [PMID: 21352495 DOI: 10.1111/j.1742-4658.2011.08064.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Most of the biochemical and biophysical processes of proteins take place at membranes, and are thus under the influence of strong local electric fields, which are likely to affect the structure as well as the reaction mechanism and dynamics. To analyse such electric field effects, biomimetic interfaces may be employed that consist of membrane models deposited on nanostructured metal electrodes. For such devices, surface-enhanced resonance Raman and IR absorption spectroscopy are powerful techniques to disentangle the complex interfacial processes of proteins in terms of rotational diffusion, electron transfer, and protein and cofactor structural changes. The present article reviews the results obtained for the haem protein cytochrome c, which is widely used as a model protein for studying the various reaction steps of interfacial redox processes in general. In addition, it is shown that electric field effects may be functional for the natural redox processes of cytochrome c in the respiratory chain, as well as for the switch from the redox to the peroxidase function, one of the key events preceding apoptosis.
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Affiliation(s)
- Hong Khoa Ly
- Technische Universität Berlin, Institut für Chemie, Berlin, Germany
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18
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Eckermann AL, Feld DJ, Shaw JA, Meade TJ. Electrochemistry of redox-active self-assembled monolayers. Coord Chem Rev 2010; 254:1769-1802. [PMID: 20563297 PMCID: PMC2885823 DOI: 10.1016/j.ccr.2009.12.023] [Citation(s) in RCA: 357] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Redox-active self-assembled monolayers (SAMs) provide an excellent platform for investigating electron transfer kinetics. Using a well-defined bridge, a redox center can be positioned at a fixed distance from the electrode and electron transfer kinetics probed using a variety of electrochemical techniques. Cyclic voltammetry, AC voltammetry, electrochemical impedance spectroscopy, and chronoamperometry are most commonly used to determine the rate of electron transfer of redox-activated SAMs. A variety of redox species have been attached to SAMs, and include transition metal complexes (e.g., ferrocene, ruthenium pentaammine, osmium bisbipyridine, metal clusters) and organic molecules (e.g., galvinol, C(60)). SAMs offer an ideal environment to study the outer-sphere interactions of redox species. The composition and integrity of the monolayer and the electrode material influence the electron transfer kinetics and can be investigated using electrochemical methods. Theoretical models have been developed for investigating SAM structure. This review discusses methods and monolayer compositions for electrochemical measurements of redox-active SAMs.
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19
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Ly HK, Marti MA, Martin DF, Alvarez-Paggi D, Meister W, Kranich A, Weidinger IM, Hildebrandt P, Murgida DH. Thermal Fluctuations Determine the Electron-Transfer Rates of Cytochrome c in Electrostatic and Covalent Complexes. Chemphyschem 2010; 11:1225-35. [DOI: 10.1002/cphc.200900966] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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20
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Alvarez-Paggi D, Martín DF, DeBiase PM, Hildebrandt P, Martí MA, Murgida DH. Molecular Basis of Coupled Protein and Electron Transfer Dynamics of Cytochrome c in Biomimetic Complexes. J Am Chem Soc 2010; 132:5769-78. [DOI: 10.1021/ja910707r] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Damián Alvarez-Paggi
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
| | - Diego F. Martín
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
| | - Pablo M. DeBiase
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
| | - Peter Hildebrandt
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
| | - Marcelo A. Martí
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
| | - Daniel H. Murgida
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina, and Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, Sekr. PC14, D-10623-Berlin, Germany
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Georg S, Kabuss J, Weidinger IM, Murgida DH, Hildebrandt P, Knorr A, Richter M. Distance-dependent electron transfer rate of immobilized redox proteins: a statistical physics approach. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:046101. [PMID: 20481780 DOI: 10.1103/physreve.81.046101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 02/18/2010] [Indexed: 05/29/2023]
Abstract
The electron transfer kinetics of redox proteins adsorbed on metal electrodes coated with self-assembled monolayers (SAMs) of mercaptanes shows an unusual distance-dependence. For thick SAMs, the experimentally measured electron transfer rate constant k{exp} obeys the behavior predicted by Marcus theory [R. A. Marcus and N. Sutin, Biochim. Biophys. Acta 811, 265 (1985)], whereas for thin SAMs, k{exp} remains virtually constant [Z. Q. Feng, J. Chem. Soc., Faraday Trans. 93, 1367 (1997)]. In this work, we present a simple theoretical model system for the redox protein cytochrome c electrostatically bound to a SAM-coated electrode. A statistical average of the electron tunneling rate is calculated by accounting for all possible orientations of the model protein. This approach, which takes into account the electric field dependent orientational distribution, allows for a satisfactory description of the "saturation" regime in the high electric field limit. It further predicts a nonexponential behavior of the average electron transfer processes that may be experimentally checked by extending kinetic experiments to shorter sampling times, i.e., 1/k{exp}. For a comprehensive description of the overall kinetics in the saturation regime at sampling times of the order of <<1/k{exp}, it is essential to consider the dynamics of protein reorientation, which is not implemented in the present model.
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Affiliation(s)
- Sören Georg
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
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22
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Chi Q, Zhang J, Arslan T, Borg L, Pedersen GW, Christensen HEM, Nazmudtinov RR, Ulstrup J. Approach to Interfacial and Intramolecular Electron Transfer of the Diheme Protein Cytochrome c4 Assembled on Au(111) Surfaces. J Phys Chem B 2010; 114:5617-24. [DOI: 10.1021/jp1007208] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qijin Chi
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Jingdong Zhang
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Taner Arslan
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Lotte Borg
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Gert W. Pedersen
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Hans E. M. Christensen
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Renat R. Nazmudtinov
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Jens Ulstrup
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
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Zhang J, Kuznetsov AM, Medvedev IG, Chi Q, Albrecht T, Jensen PS, Ulstrup J. Single-Molecule Electron Transfer in Electrochemical Environments. Chem Rev 2008; 108:2737-91. [PMID: 18620372 DOI: 10.1021/cr068073+] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Léger C, Bertrand P. Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies. Chem Rev 2008; 108:2379-438. [DOI: 10.1021/cr0680742] [Citation(s) in RCA: 594] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mazzei F, Favero G, Frasconi M, Tata A, Tuccitto N, Licciardello A, Pepi F. Soft-Landed Protein Voltammetry: A Tool for Redox Protein Characterization. Anal Chem 2008; 80:5937-44. [DOI: 10.1021/ac8005389] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Franco Mazzei
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Gabriele Favero
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Marco Frasconi
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Alessandra Tata
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Nunzio Tuccitto
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Antonino Licciardello
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
| | - Federico Pepi
- Dipartimento di Chimica e Tecnologie del Farmaco, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy, and Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy
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Murgida DH, Hildebrandt P. Disentangling interfacial redox processes of proteins by SERR spectroscopy. Chem Soc Rev 2008; 37:937-45. [DOI: 10.1039/b705976k] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yue H, Waldeck DH, Petrović J, Clark RA. The effect of ionic strength on the electron-transfer rate of surface immobilized cytochrome C. J Phys Chem B 2007; 110:5062-72. [PMID: 16526749 DOI: 10.1021/jp055768q] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Horse heart cytochrome c was immobilized on four different self-assembled monolayer (SAM) films. The electron tunneling kinetics were studied in the different assemblies as a function of the ionic strength of the buffer solution using cyclic voltammetry. When cytochrome c is electrostatically immobilized, the standard electron exchange rate constant k0 decreases with the increase of the solution's ionic strength. In contrast, the protein covalently attached or ligated has a rate constant independent of the ionic strength. The inhomogeneity of electrostatically immobilized cytochrome c increases with the increase of the solution's ionic strength whereas that of the covalently attached protein is independent of the ionic strength. A comparison of these different electron-transfer behaviors suggests that the thermodynamically stable geometry of cytochrome c in the electrostatic assemblies is also an electron transfer favorable one. It suggests that the surface charges of cytochrome c are capable of guiding it into geometries in which its front surface faces the electron-transfer partner. The inhomogeneity observed in this study indicates that a distribution of cytochrome c orientations and thus a distribution of electron transfer rate constants exists.
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Affiliation(s)
- Hongjun Yue
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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30
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De Biase PM, Doctorovich F, Murgida DH, Estrin DA. Electric field effects on the reactivity of heme model systems. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2006.11.104] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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31
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Albrecht T, Li WW, Haehnel W, Hildebrandt P, Ulstrup J. Voltammetry and in situ scanning tunnelling microscopy of de novo designed heme protein monolayers on Au(111)-electrode surfaces. Bioelectrochemistry 2006; 69:193-200. [PMID: 16580892 DOI: 10.1016/j.bioelechem.2006.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Accepted: 01/21/2006] [Indexed: 11/27/2022]
Abstract
In the present work, we report the electrochemical characterization and in situ scanning tunnelling microscopy (STM) studies of monolayers of an artificial de novo designed heme protein MOP-C, covalently immobilized on modified Au(111) surfaces. The protein forms closely packed monolayers, which remain electroactive upon immobilization. In situ STM images show circular structures indicating that MOP-C stands upright on the surface in accordance with the molecular design. Despite the large spatial extension of MOP-C, about 5 nm in height, conditions could be found where tip/sample interaction is minimal and proteins could be imaged without detectable tip interference. The results indicate further that the structural sensitivity of (in situ) STM depends to a significant extent on associated electron transfer kinetics. In the present case, the heme group does not contribute significantly to the tunnelling current, apparently due to slow electron transfer kinetics. As a consequence, STM images of heme-containing and heme-free MOP-C did not reveal any notable differences in apparent height or physical extension. The apparent height of heme-containing MOP-C did not show any dependence on the substrate potential being varied around the redox potential of the protein. The mere presence of an accessible molecular energy level is not sufficient to result in detectable tunnelling current modulation.
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Affiliation(s)
- Tim Albrecht
- Technische Universität Berlin, Institut f. Chemie, Max-Volmer Laboratorium für Biophysikalische Chemie, Strasse des 17. Juni 135, D-10623 Berlin, Germany
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32
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Yue H, Khoshtariya D, Waldeck DH, Grochol J, Hildebrandt P, Murgida DH. On the Electron Transfer Mechanism Between Cytochrome c and Metal Electrodes. Evidence for Dynamic Control at Short Distances. J Phys Chem B 2006; 110:19906-13. [PMID: 17020376 DOI: 10.1021/jp0620670] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cytochrome c was coordinatively bound to self-assembled monolayers of pyridine-terminated alkanethiols on Au and Ag electrodes. The mechanism of heterogeneous electron transfer of the immobilized protein was investigated by cyclic voltammetry and time-resolved surface-enhanced resonance Raman spectroelectrochemistry. The temperature, distance, and overpotential dependencies of the electron transfer rates indicate a change of mechanism from a tunneling controlled reaction at long distances (thicker films) to a solvent/protein friction controlled reaction at smaller distances (thinner films).
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Affiliation(s)
- Hongjun Yue
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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33
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Marcus parabola and reorganization energies associated with redox change of electron-transfer proteins, detected by V–I characteristics of STM currents. J Electroanal Chem (Lausanne) 2006. [DOI: 10.1016/j.jelechem.2006.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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34
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Jiang X, Wang Y, Qu X, Dong S. Surface-enhanced resonance Raman spectroscopy and spectroscopy study of redox-induced conformational equilibrium of cytochrome c adsorbed on DNA-modified metal electrode. Biosens Bioelectron 2006; 22:49-55. [PMID: 16414257 DOI: 10.1016/j.bios.2005.11.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2005] [Revised: 11/24/2005] [Accepted: 11/29/2005] [Indexed: 11/25/2022]
Abstract
The redox-induced conformational equilibrium of cytochrome c (cyt c) adsorbed on DNA-modified metal electrode and the interaction mechanism of DNA with cyt c have been studied by electrochemical, spectroscopic and spectroelectrochemical techniques. The results indicate that the external electric field induces potential-dependent coordination equilibrium of the adsorbed cyt c between its oxidized state (with native six-coordinate low-spin and non-native five-coordinate high-spin heme configuration) and its reduced state (with native six-coordinate low-spin heme configuration) on DNA-modified metal electrode. The strong interactions between DNA and cyt c induce the self-aggregation of cyt c adsorbed on DNA. The orientational distribution of cyt c adsorbed on DNA-modified metal electrode is potential-dependent, which results in the deviation from an ideal Nernstian behavior of the adsorbed cyt c at high electrode potentials. The electric-field-induced increase in the activation barrier of proton-transfer steps attributed to the rearrangement of the hydrogen bond network and the self-aggregation of cyt c upon adsorption on DNA-modified electrode strongly decrease the interfacial electron transfer rate. In addition, the strongly Coulombic interactions between DNA and cyt c only disturb the microenvironment of the heme, and do not affect the states of heme ligation and spin. The secondary structure of the adsorbed cyt c is retained, while the conformation of DNA is changed from the B form DNA to A form DNA.
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Affiliation(s)
- Xiue Jiang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Changchun, Jilin 130022, China
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35
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Xu J, Bowden EF. Determination of the Orientation of Adsorbed Cytochrome c on Carboxyalkanethiol Self-Assembled Monolayers by In Situ Differential Modification. J Am Chem Soc 2006; 128:6813-22. [PMID: 16719461 DOI: 10.1021/ja054219v] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The contact domain utilized by horse cytochrome c when adsorptively bound to a C(10)COOH self-assembled monolayer (SAM) was delineated using a chemical method based on differential modification of surface amino acids. Horse cytochrome c was adsorbed at low ionic strength (pH 7.0, 4.4 mM potassium phosphate) onto 10 microm diameter gold particles coated with HS(CH(2))(10)COOH SAMs. After in situ modification of lysyl groups by reductive Schiff-base methylation, the protein was desorbed, digested using trypsin, and the peptide mapped using LC/MS. Relative lysyl reactivities were ascertained by comparing the resulting peptide frequencies to control samples of solution cytochrome c modified to the same average extent. The least reactive lysines in adsorbed cytochrome c were found to be 13, 72, 73, 79, and 86-88, consistent with a contact region located up and to the left (Met-80 side) of the solvent-exposed heme edge (conventional front face view). The most reactive lysines were 39, 53, 55, and 60, located on the lower backside. The proposed orientation features a heme tilt angle of approximately 35-40 degrees with respect to the substrate surface normal. Factors that can complicate or distort data interpretation are discussed, and the generality of differential modification relative to existing in situ methods for protein orientation determination is also addressed.
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Affiliation(s)
- Jishou Xu
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
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36
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Kang SA, Hoke KR, Crane BR. Solvent Isotope Effects on Interfacial Protein Electron Transfer in Crystals and Electrode Films. J Am Chem Soc 2006; 128:2346-55. [PMID: 16478190 DOI: 10.1021/ja0557482] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
D(2)O-grown crystals of yeast zinc porphyrin substituted cytochrome c peroxidase (ZnCcP) in complex with yeast iso-1-cytochrome c (yCc) diffract to higher resolution (1.7 A) and pack differently than H(2)O-grown crystals (2.4-3.0 A). Two ZnCcP's bind the same yCc (porphyrin-to-porphyrin separations of 19 and 29 A), with one ZnCcP interacting through the same interface found in the H(2)O crystals. The triplet excited-state of at least one of the two unique ZnCcP's is quenched by electron transfer (ET) to Fe(III)yCc (k(e) = 220 s(-1)). Measurement of thermal recombination ET between Fe(II)yCc and ZnCcP+ in the D(2)O-treated crystals has both slow and fast components that differ by 2 orders of magnitude (k(eb)(1) = 2200 s(-1), k(eb)(2) = 30 s(-1)). Back ET in H(2)O-grown crystals is too fast for observation, but soaking H(2)O-grown crystals in D(2)O for hours generates slower back ET, with kinetics similar to those of the D(2)O-grown crystals (k(eb)(1) = 7000 s(-1), k(eb)(2) = 100 s(-1)). Protein-film voltammetry of yCc adsorbed to mixed alkanethiol monolayers on gold electrodes shows slower ET for D(2)O-grown yCc films than for H(2)O-grown films (k(H) = 800 s(-1); k(D) = 540 s(-1) at 20 degrees C). Soaking H(2)O- or D(2)O-grown films in the counter solvent produces an immediate inverse isotope effect that diminishes over hours until the ET rate reaches that found in the counter solvent. Thus, D(2)O substitution perturbs interactions and ET between yCc and either CcP or electrode films. The effects derive from slow exchanging protons or solvent molecules that in the crystal produce only small structural changes.
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Affiliation(s)
- Seong A Kang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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Todorovic S, Pereira MM, Bandeiras TM, Teixeira M, Hildebrandt P, Murgida DH. Midpoint potentials of hemes a and a3 in the quinol oxidase from Acidianus ambivalens are inverted. J Am Chem Soc 2006; 127:13561-6. [PMID: 16190720 DOI: 10.1021/ja052921l] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aa3 type B oxygen reductase from the thermophilic archaeon Acidianus ambivalens (QO) was immobilized on silver electrodes and studied by potential-dependent surface-enhanced resonance Raman (SERR) spectroscopy. The immobilized enzyme retains the native structure at the level of the heme pockets and exhibits reversible electrochemistry. From the potential dependence of specific spectral marker bands, the midpoint potentials of hemes a and a3 were unambiguously determined for the first time, being 320 +/- 20 mV for the former and 390 +/- 20 mV for the latter. Both hemes could be treated as independent one-electron Nernstian redox couples, indicating that the interaction potential is smaller than 50 mV. The reversed order of the midpoint potentials compared to those of type A (mitochondrial-like) oxidases, as well as the lack of substantial Coulombic interactions, suggests a different mechanism of electroprotonic energy transduction. In contrast to type A enzymes, a-a3 intraprotein electron transfer in QO is already guaranteed by the order of the midpoint potentials at the onset of enzyme reduction and, therefore, does not require a complex network of cooperativities to ensure exergonicity. In the immobilized state, conformational transitions of the QO a3-CuB active site, which are believed to be essential for proton translocation, are drastically slowed compared to those in solution. We ascribe this finding to the effect of the interfacial electric field, which is of the same order of magnitude as in biological membranes. These results suggest that the membrane potential may play an active role in the regulation of the enzymatic activity of QO.
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Affiliation(s)
- Smilja Todorovic
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal
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Hrabakova J, Ataka K, Heberle J, Hildebrandt P, Murgida DH. Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic study. Phys Chem Chem Phys 2006; 8:759-66. [PMID: 16482317 DOI: 10.1039/b513379n] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytochrome c oxidase was tethered to a functionalised Ag electrode via a histidine-tag on the C-terminus of subunit I or II and embedded in a phospholipid bilayer. The uniformly oriented membrane-bound proteins were studied by surface enhanced resonance Raman spectroscopy (SERRS) that reveals preservation of the native structures of the heme a and heme a(3) sites. On the basis of time-dependent SERRS measurements, the rate constant for the heterogeneous electron transfer to heme a was determined to be 0.002 s(-1) independent of the enzyme orientation and the overpotential. Taking into account that the electrode-to-heme a distance is larger than 50 A, these findings suggest an electron hopping mechanism in which the Cu(A) center is not involved. Electrochemical reduction is restricted to heme a whereas electron transfer from heme a to heme a(3), which in solution occurs on the nanosecond time scale, is drastically slowed down. It may be that the network of cooperativities that links intramolecular electron transfer and proton translocation is perturbed in the immobilised enzyme, possibly due to the effect of the interfacial electric field.
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Affiliation(s)
- Jana Hrabakova
- Technische Universität Berlin, Institut für Chemie, D-10623 Berlin, Germany
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39
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Weidinger IM, Murgida DH, Dong WF, Möhwald H, Hildebrandt P. Redox Processes of Cytochrome c Immobilized on Solid Supported Polyelectrolyte Multilayers. J Phys Chem B 2005; 110:522-9. [PMID: 16471564 DOI: 10.1021/jp056040c] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The heme protein cytochrome c (Cyt-c), immobilized on polyelectrolyte multilayers on a silver electrode, was studied by stationary and time-resolved surface-enhanced resonance Raman (SERR) spectroscopy to probe the redox site structure and the mechanism and dynamics of the potential-dependent interfacial processes. The layers were built up by sequential adsorption of polycations (poly[ethylene imine] (PEI); polyallylamine hydrochloride (PAH)) and polyanions (poly[styrene sulfonate] (PSS)). All multilayers terminated by PSS electrostatically bind Cyt-c. On PEI/PSS coatings, Cyt-c is peripherally bound and fully redox-active. Due to the interfacial potential drop, the apparent redox potential is lowered by 40 mV compared to that in solution. The rate constant for the heterogeneous electron transfer (ET) of ca. 0.1 s(-1) is consistent with electron tunneling through largely ordered PEI/PSS layers. ET is coupled to a reversible conformational transition of Cyt-c that involves a change of the coordination pattern of the heme. Additional (PAH/PSS) double layers cause a broadening of the redox transition and a drastic negative shift of the redox potential, which is attributed to the formation of PSS/Cyt-c complexes. It is concluded that Cyt-c can effectively compete with PAH for binding of PSS, resulting in a rearrangement of the layered structure and a penetration of the PSS-bound Cyt-c into the PAH/PSS double layers. This conclusion is consistent with SERR intensity and quartz microbalance measurements. ET was found to be overpotential-independent and faster than that for PEI/PSS coatings, which is interpreted in terms of specific PSS/Cyt-c complexes serving as gates for the heterogeneous ET.
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Affiliation(s)
- Inez M Weidinger
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Strasse des 17, Juni, D-10623 Berlin, Germany
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Todorovic S, Jung C, Hildebrandt P, Murgida DH. Conformational transitions and redox potential shifts of cytochrome P450 induced by immobilization. J Biol Inorg Chem 2005; 11:119-27. [PMID: 16328458 DOI: 10.1007/s00775-005-0054-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Accepted: 10/26/2005] [Indexed: 11/26/2022]
Abstract
Cytochrome P450 (P450) from Pseudomonas putida was immobilized on Ag electrodes coated with self-assembled monolayers (SAMs) via electrostatic and hydrophobic interactions as well as by covalent cross-linking. The redox and conformational equilibria of the immobilized protein were studied by potential-dependent surface-enhanced resonance Raman spectroscopy. All immobilization conditions lead to the formation of the cytochrome P420 (P420) form of the enzyme. The redox potential of the electrostatically adsorbed P420 is significantly more positive than in solution and shows a steady downshift upon shortening of the length of the carboxyl-terminated SAMs, i.e., upon increasing the strength of the local electric field. Thus, two opposing effects modulate the redox potential of the adsorbed enzyme. First, the increased hydrophobicity of the heme environment brought about by immobilization on the SAM tends to upshift the redox potential by stabilizing the formally neutral ferrous form. Second, increasing electric fields tend to stabilize the positively charged ferric form, producing the opposite effect. The results provide insight into the parameters that control the structure and redox properties of heme proteins and contribute to the understanding of the apparently anomalous behavior of P450 enzymes in bioelectronic devices.
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Affiliation(s)
- Smilja Todorovic
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal
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41
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Kang SA, Crane BR. Effects of interface mutations on association modes and electron-transfer rates between proteins. Proc Natl Acad Sci U S A 2005; 102:15465-70. [PMID: 16227441 PMCID: PMC1266099 DOI: 10.1073/pnas.0505176102] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 09/08/2005] [Indexed: 11/18/2022] Open
Abstract
Although bonding networks determine electron-transfer (ET) rates within proteins, the mechanism by which structure and dynamics influence ET across protein interfaces is not well understood. Measurements of photochemically induced ET and subsequent charge recombination between Zn-porphyrin-substituted cytochrome c peroxidase and cytochrome c in single crystals correlate reactivity with defined structures for different association modes of the redox partners. Structures and ET rates in crystals are consistent with tryptophan oxidation mediating charge recombination reactions. Conservative mutations at the interface can drastically affect how the proteins orient and dispose redox centers. Whereas some configurations are ET inactive, the wild-type complex exhibits the fastest recombination rate. Other association modes generate ET rates that do not correlate with predictions based on cofactor separations or simple bonding pathways. Inhibition of photoinduced ET at <273 K indicates gating by small-amplitude dynamics, even within the crystal. Thus, different associations achieve states of similar reactivity, and within those states conformational fluctuations enable interprotein ET.
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Affiliation(s)
- Seong A Kang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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42
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Imabayashi SI, Mita T, Kakiuchi T. Effect of the electrostatic interaction on the redox reaction of positively charged cytochrome C adsorbed on the negatively charged surfaces of acid-terminated alkanethiol monolayers on a Au(111) electrode. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:1470-1474. [PMID: 15697296 DOI: 10.1021/la047992x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The electrochemical properties of cytochrome c (cyt c) adsorbed on mixed self-assembled monolayers (SAMs) of 2-mercaptoethanesulfonate (MES)/2-mercaptoethanol (MEL) are compared with those on single-component SAMs of MES, MEL, and mercaptopropionic acid (MPA), using cyclic voltammetry and potential-modulated UV-vis reflectance spectroscopy. The rate constant of electron transfer (ET), k(et), of cyt c adsorbed on the SAM of MPA decreases from 1450 +/- 210 s(-1) at pH 7 to 890 +/- 100 s(-1) at pH 9. In contrast, the value of k(et) of cyt c on the SAM of MES is pH-independent at 100 +/- 15 s(-1). Those facts suggest that a large negative charge density on the SAM surface slows down the ET between cyt c and the electrode. The surface charge density of the SAM affects also the amount of electroactive cyt c, Gamma(e), which decreases from 10.0 +/- 1.0 to 5.3 +/- 1.1 pmol cm(-2) with increasing pH from 7 to 9 on the SAM of MPA. Similarly, the k(et) of cyt c adsorbed on the mixed SAMs of MES/MEL sharply decreases from 900 +/- 300 s(-1) to 110 s(-1) as the surface mole fraction of MES increases beyond 0.5, suggesting the presence of a negative surface charge threshold beyond which the rate of ET of cyt c is dramatically lowered. The decrease in the k(et) on the SAMs at high negative charge densities probably results from the confinement of adsorbed cyt c by the strong electrostatic force to an orientation that is not optimal for the ET reaction.
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Affiliation(s)
- Shin-ichiro Imabayashi
- Department of Chemistry and Biotechnology, Faculty of Engineering, Yokohama National University, Yokohama 240-8501, Japan.
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Murgida DH, Hildebrandt P. Redox and redox-coupled processes of heme proteins and enzymes at electrochemical interfaces. Phys Chem Chem Phys 2005; 7:3773-84. [PMID: 16358026 DOI: 10.1039/b507989f] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Modern bioelectrochemical methods rely upon the immobilisation of redox proteins and enzymes on electrodes coated with biocompatible materials to prevent denaturation. However, even when protein denaturation is effectively avoided, heterogeneous protein electron transfer is often coupled to non-Faradaic processes like reorientation, conformational transitions or acid-base equilibria. Disentangling these processes requires methods capable of probing simultaneously the structure and reaction dynamics of the adsorbed species. Here we provide an overview of the recent developments in Raman and infrared surface-enhanced spectroelectrochemical techniques applied to the study of soluble and membrane bound redox heme proteins and enzymes. Possible biological implications of the findings are critically discussed.
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Affiliation(s)
- Daniel H Murgida
- Technische Universität Berlin, Institut für Chemie, Max-Volmer-Laboratorium für Biophysikalische Chemie, Sekr. PC14, Strasse des 17. Juni 135, D-10623, Berlin, Germany.
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Murgida DH, Hildebrandt P. Electron-transfer processes of cytochrome C at interfaces. New insights by surface-enhanced resonance Raman spectroscopy. Acc Chem Res 2004; 37:854-61. [PMID: 15612675 DOI: 10.1021/ar0400443] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The heme protein cytochrome c acts as an electron carrier at the mitochondrial-membrane interface and thus exerts its function under the influence of strong electric fields. To assess possible consequences of electric fields on the redox processes of cytochrome c, the protein can be immobilized to self-assembled monolayers on electrodes and studied by surface-enhanced resonance Raman spectroscopy. Such model systems may mimic some essential features of biological interfaces including local electric field strengths. It is shown that physiologically relevant electric field strengths can effectively modulate the electron-transfer dynamics and induce conformational transitions.
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Affiliation(s)
- Daniel H Murgida
- Technische Universität Berlin, Institut für Chemie, Max Volmer Laboratorium für Biophysikalische Chemie, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany.
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Lecomte S, Ricoux R, Mahy JP, Korri-Youssoufi H. Microperoxidase 8 adsorbed on a roughened silver electrode as a monomeric high-spin penta-coordinated species: characterization by SERR spectroscopy and electrochemistry. J Biol Inorg Chem 2004; 9:850-8. [PMID: 15340868 DOI: 10.1007/s00775-004-0586-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Accepted: 07/26/2004] [Indexed: 10/26/2022]
Abstract
Microperoxidase 8 (MP8), a heme octapeptide obtained by hydrolytic digestion of cytochrome c, was adsorbed at the surface of a roughened silver electrode in order to provide a new supported biomimetic system for hemoproteins. A combination of two techniques was used to study its redox and coordination properties: electrochemistry and surface-enhanced resonance Raman (SERR) spectroscopy. This allowed us to show that MP8 could be adsorbed as a monolayer at the surface of the roughened silver electrode, where it could undergo a reversible electron transfer. Under those conditions, a redox potential of -0.4 V vs. SCE (-0.16 V vs. NHE) was measured for MP8, which was almost identical to that reported for N-acetyl-MP8 in aqueous solution. In addition, whereas MP8 appeared to aggregate in solution, and led to a mixture of high-spin penta-coordinated (5cHS) and low-spin hexa-coordinated (6cLS) iron(III) or iron(II) species, it was recovered almost exclusively as a monomeric high-spin penta-coordinated species at the surface of the electrode, both in the reduced and in the oxidized states. This then allowed a free coordination site on the iron, on the distal face of MP8 accessible to ligands. Accordingly, experiments performed in the presence of potassium cyanide demonstrated that MP8 adsorbed on a silver electrode could be ligated by a sixth CN(-) ligand. Thus there is the possibility of binding several kinds of ligands such as O(2) or H(2)O(2), which will open the way to biocatalysis of oxidation reactions at the surface of an electrode, or ligands such as drugs which will lead to the design of new biosensors for molecules of biological interest.
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Affiliation(s)
- Sophie Lecomte
- LADIR, CNRS/UPMC, 2 rue Henri Dunant, 94320 Thiais, France.
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46
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Bertini I, Turano P, Vasos PR, Bondon A, Chevance S, Simonneaux G. Cytochrome c and SDS: a molten globule protein with altered axial ligation. J Mol Biol 2004; 336:489-96. [PMID: 14757060 DOI: 10.1016/j.jmb.2003.12.045] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Saccharomices cerevisiae (yeast iso-1) cytochrome c has been investigated in the presence of 100 mM SDS in order to simulate the interaction of cytochrome c with membrane. Under these circumstances, a high spin species with detached methionine axial ligand is observed through NMR, in analogy to findings on the horse heart protein. However, at variance with the latter system, for the yeast protein also a low spin species is detected, which appears to be present with a concentration of about 40% with respect to that of the high spin species. The R(1), R(2), [1H]-15N NOE of backbone amides which are not affected by paramagnetism are homogeneous and allow a simultaneous analysis of the data for the two species. The result is that the rotational correlation time is larger than in water and larger than expected on the basis of viscosity of the SDS-containing solution. This finding suggests interactions of cytochrome c with SDS. Furthermore, it appears that there is subnanosecond backbone mobility, which also accounts for the decreased intensity of NOE cross-peaks and may be associated with equilibria between helical and random coil structure. The dynamic behavior appears to be a common feature of the high spin and low spin species and is consistent with the presence of a molten globule state. The molten globule nature of the protein could account for the presence of the different axial coordination of the heme iron. Such findings are meaningful with respect to the physiology of cytochrome c as electron transfer protein and as promoter of apoptosis.
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Affiliation(s)
- Ivano Bertini
- CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy.
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Murgida DH, Hildebrandt P, Wei J, He YF, Liu H, Waldeck DH. Surface-Enhanced Resonance Raman Spectroscopic and Electrochemical Study of Cytochrome c Bound on Electrodes through Coordination with Pyridinyl-Terminated Self-Assembled Monolayers. J Phys Chem B 2004. [DOI: 10.1021/jp0353800] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wackerbarth H, Hildebrandt P. Redox and conformational equilibria and dynamics of cytochrome c at high electric fields. Chemphyschem 2003; 4:714-24. [PMID: 12901303 DOI: 10.1002/cphc.200200618] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cytochrome c (Cyt-c) adsorbed in the electrical double layer of the Ag electrode/electrolyte interface has been studied by stationary and time-resolved surface-enhanced resonance Raman spectroscopy to analyse the effect of strong electric fields on structure and reaction equilibria and dynamics of the protein. In the potential range between +0.1 and -0.55 V (versus saturated calomel electrode), the adsorbed Cyt-c forms a potential-dependent reversible equilibrium between the native state B1 and a conformational state B2. The redox potentials of the bis-histidine-coordinated six-coordinated low-spin and five-coordinated high-spin substates of B2 were determined to be -0.425 and -0.385 V, respectively, whereas the additional six-coordinated aquo-histidine-coordinated high-spin substate was found to be redox-inactive. The redox potential for the conformational state B1 was found to be the same as in solution in agreement with the structural identity of the adsorbed B1 and the native Cyt-c. For all three redox-active species, the formal heterogeneous electron transfer rate constants are small and of the same order of magnitude (3-13 s-1), which implies that the rate-limiting step is largely independent of the redox-site structure. These findings, as well as the slow and potential-dependent transitions between the various conformational (sub-)states, can be rationalized in terms of an electric field-induced increase of the activation energy for proton-transfer steps linked to protein structural reorganisation. Further increasing the electric field strength by shifting the electrode potential above +0.1 V leads to irreversible structural changes that are attributed to an unfolding of the polypeptide chain.
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Affiliation(s)
- Hainer Wackerbarth
- Danmarks Tekniske Universitet Biouorganisk Kemi Bygning 207, 2800 Lyngby, Denmark
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49
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Jeuken LJC. Conformational reorganisation in interfacial protein electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1604:67-76. [PMID: 12765764 DOI: 10.1016/s0005-2728(03)00026-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Protein-protein electron transfer (ET) plays an essential role in all redox chains. Earlier studies which used cross-linking and increased solution viscosity indicated that the rate of many ET reactions is limited (i.e., gated) by conformational reorientations at the surface interface. These results are later supported by structural studies using NMR and molecular modelling. New insights into conformational gating have also come from electrochemical experiments in which proteins are noncovalently adsorbed on the electrode surface. These systems have the advantage that it is relatively easy to vary systematically the driving force and electronic coupling. In this review we summarize the current knowledge obtained from these electrochemical experiments and compare it with some of the results obtained for protein-protein ET.
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50
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Rivas L, Hippler-Mreyen S, Engelhard M, Hildebrandt P. Electric-field dependent decays of two spectroscopically different M-states of photosensory rhodopsin II from Natronobacterium pharaonis. Biophys J 2003; 84:3864-73. [PMID: 12770892 PMCID: PMC1302968 DOI: 10.1016/s0006-3495(03)75114-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2002] [Accepted: 01/22/2003] [Indexed: 10/21/2022] Open
Abstract
Sensory rhodopsin II (NpSRII) from Natronobacterium pharaonis was studied by resonance Raman (RR) spectroscopic techniques. Using gated 413-nm excitation, time-resolved RR measurements of the solubilized photoreceptor were carried out to probe the photocycle intermediates that are formed in the submillisecond time range. For the first time, two M-like intermediates were identified on the basis of their C=C stretching bands at 1568 and 1583 cm(-1), corresponding to the early M(L)(400) state with a lifetime of 30 micro s and the subsequent M(1)(400) state with a lifetime of 2 ms, respectively. The unusually high C=C stretching frequency of M(1)(400) has been attributed to an unprotonated retinal Schiff base in a largely hydrophobic environment, implying that the M(L)(400) --> M(1)(400) transition is associated with protein structural changes in the vicinity of the chromophore binding pocket. Time-resolved surface enhanced resonance Raman experiments of NpSRII electrostatically bound onto a rotating Ag electrode reveal that the photoreceptor runs through the photocycle also in the immobilized state. Surface enhanced resonance Raman spectra are very similar to the RR spectra of the solubilized protein, ruling out adsorption-induced structural changes in the retinal binding pocket. The photocycle kinetics, however, is sensitively affected by the electrode potential such that at 0.0 V (versus Ag/AgCl) the decay times of M(L)(400) and M(1)(400) are drastically slowed down. Upon decreasing the potential to -0.4 V, that corresponds to a decrease of the interfacial potential drop and thus of the electric field strength at the protein binding site, the photocycle kinetics becomes similar to that of NpSRII in solution. The electric-field dependence of the protein structural changes associated with the M-state transitions, which in the present spectroscopic work is revealed on a molecular level, appears to be related to the electric-field control of bacteriorhodopsin's photocycle, which has been shown to be of functional relevance.
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Affiliation(s)
- Laura Rivas
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, P-2781-901 Oeiras, Portugal
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