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Long distance electron transfer through the aqueous solution between redox partner proteins. Nat Commun 2018; 9:5157. [PMID: 30514833 PMCID: PMC6279779 DOI: 10.1038/s41467-018-07499-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Accepted: 11/06/2018] [Indexed: 11/25/2022] Open
Abstract
Despite the importance of electron transfer between redox proteins in photosynthesis and respiration, the inter-protein electron transfer rate between redox partner proteins has never been measured as a function of their separation in aqueous solution. Here, we use electrochemical tunneling spectroscopy to show that the current between two protein partners decays along more than 10 nm in the solution. Molecular dynamics simulations reveal a reduced ionic density and extended electric field in the volume confined between the proteins. The distance-decay factor and the calculated local barrier for electron transfer are regulated by the electrochemical potential applied to the proteins. Redox partners could use electrochemically gated, long distance electron transfer through the solution in order to conciliate high specificity with weak binding, thus keeping high turnover rates in the crowded environment of cells. Electron transport chains rely on interactions between redox proteins, but the distance-dependence of the electron transfer rate through the solution is unknown. Here, the authors show that the current between two redox protein partners occurs at long distances and is electrochemically gated.
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López-Martínez M, Artés JM, Sarasso V, Carminati M, Díez-Pérez I, Sanz F, Gorostiza P. Differential Electrochemical Conductance Imaging at the Nanoscale. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1700958. [PMID: 28722303 DOI: 10.1002/smll.201700958] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/23/2017] [Indexed: 06/07/2023]
Abstract
Electron transfer in proteins is essential in crucial biological processes. Although the fundamental aspects of biological electron transfer are well characterized, currently there are no experimental tools to determine the atomic-scale electronic pathways in redox proteins, and thus to fully understand their outstanding efficiency and environmental adaptability. This knowledge is also required to design and optimize biomolecular electronic devices. In order to measure the local conductance of an electrode surface immersed in an electrolyte, this study builds upon the current-potential spectroscopic capacity of electrochemical scanning tunneling microscopy, by adding an alternating current modulation technique. With this setup, spatially resolved, differential electrochemical conductance images under bipotentiostatic control are recorded. Differential electrochemical conductance imaging allows visualizing the reversible oxidation of an iron electrode in borate buffer and individual azurin proteins immobilized on atomically flat gold surfaces. In particular, this method reveals submolecular regions with high conductance within the protein. The direct observation of nanoscale conduction pathways in redox proteins and complexes enables important advances in biochemistry and bionanotechnology.
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Affiliation(s)
- Montserrat López-Martínez
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Department of Material Science and Physical Chemistry, University of Barcelona, 08028, Barcelona, Catalonia, Spain
- Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Poeta Mariano Esquillor s/n, 50018, Zaragoza, Spain
| | - Juan Manuel Artés
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Department of Material Science and Physical Chemistry, University of Barcelona, 08028, Barcelona, Catalonia, Spain
| | - Veronica Sarasso
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
| | - Marco Carminati
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Via Ponzio, 34/5, 20133, Milan, Italy
| | - Ismael Díez-Pérez
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Department of Material Science and Physical Chemistry, University of Barcelona, 08028, Barcelona, Catalonia, Spain
- Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Poeta Mariano Esquillor s/n, 50018, Zaragoza, Spain
| | - Fausto Sanz
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Department of Material Science and Physical Chemistry, University of Barcelona, 08028, Barcelona, Catalonia, Spain
- Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Poeta Mariano Esquillor s/n, 50018, Zaragoza, Spain
| | - Pau Gorostiza
- Institute for Bioengineering of Catalonia (IBEC) The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, 08028, Barcelona, Spain
- Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Poeta Mariano Esquillor s/n, 50018, Zaragoza, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08010, Barcelona, Spain
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Artés JM, Díez-Pérez I, Sanz F, Gorostiza P. Direct measurement of electron transfer distance decay constants of single redox proteins by electrochemical tunneling spectroscopy. ACS NANO 2011; 5:2060-2066. [PMID: 21539019 DOI: 10.1021/nn103236e] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a method to measure directly and at the single-molecule level the distance decay constant that characterizes the rate of electron transfer (ET) in redox proteins. Using an electrochemical tunneling microscope under bipotentiostatic control, we obtained current−distance spectroscopic recordings of individual redox proteins confined within a nanometric tunneling gap at a well-defined molecular orientation. The tunneling current decays exponentially, and the corresponding decay constant (β) strongly supports a two-step tunneling ET mechanism. Statistical analysis of decay constant measurements reveals differences between the reduced and oxidized states that may be relevant to the control of ET rates in enzymes and biological electron transport chains.
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Affiliation(s)
- Juan M Artés
- Institute for Bioengineering of Catalonia, Barcelona, Spain
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