1
|
He H, Hao R. Multiplexed Fluoro-electrochemical Single-Molecule Counting Enabled by SiC Semiconducting Nanofilm. NANO LETTERS 2024; 24:11051-11058. [PMID: 39196295 DOI: 10.1021/acs.nanolett.4c03199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
A major challenge for ultrasensitive analysis is the high-efficiency determination of different target single molecules in parallel with high accuracy. Herein, we developed a quantitative fluoro-electrochemical imaging approach for direct multiplexed single-molecule counting with a SiC-nanofilm-modified indium tin oxide transparent electrode. The nanofilm could control local pH through proton-coupled electron transfer in a lower potential range and further induce direct electrochemical oxidation of the dye molecules with a higher applied potential. The fluoro-electrochemical responses of immobilized single molecules with different pH values and redox behaviors could thus be distinguished within the same fluorescence channels. This method yields nonamplified direct counting of single molecules, as indicated by excellent linear responses in the picomolar range. The successful distinction of seven different randomly mixed dyes underscores the versatility and efficacy of the proposed method in the highly accurate determination of single dye molecules, paving the way for highly parallel single-molecule detection for diverse applications.
Collapse
Affiliation(s)
- Haihan He
- Department of Chemistry, Southern University of Science and Technology, 518055 Shenzhen, China
- Research Center for Chemical Biology and Omics Analysis, Southern University of Science and Technology, 518055 Shenzhen, China
| | - Rui Hao
- Department of Chemistry, Southern University of Science and Technology, 518055 Shenzhen, China
- Research Center for Chemical Biology and Omics Analysis, Southern University of Science and Technology, 518055 Shenzhen, China
| |
Collapse
|
2
|
Lu J, Lew MD. Single-molecule electrochemical imaging resolves the midpoint potentials of individual fluorophores on nanoporous antimony-doped tin oxide. Chem Sci 2024; 15:2037-2046. [PMID: 38332827 PMCID: PMC10848685 DOI: 10.1039/d3sc05293a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 12/29/2023] [Indexed: 02/10/2024] Open
Abstract
We report reversible switching of oxazine, cyanine, and rhodamine dyes by a nanoporous antimony-doped tin oxide electrode that enables single-molecule (SM) imaging of electrochemical activity. Since the emissive state of each fluorophore is modulated by electrochemical potential, the number of emitting single molecules follows a sigmoid function during a potential scan, and we thus optically determine the formal redox potential of each dye. We find that the presence of redox mediators (phenazine methosulfate and riboflavin) functions as an electrochemical switch on each dye's emissive state and observe significantly altered electrochemical potential and kinetics. We are therefore able to measure optically how redox mediators and the solid-state electrode modulate the redox state of fluorescent molecules, which follows an electrocatalytic (EC') mechanism, with SM sensitivity over a 900 μm2 field of view. Our observations indicate that redox mediator-assisted SM electrochemical imaging (SMEC) could be potentially used to sense any electroactive species. Combined with SM blinking and localization microscopy, SMEC imaging promises to resolve the nanoscale spatial distributions of redox species and their redox states, as well as the electron transfer kinetics of electroactive species in various bioelectrochemical processes.
Collapse
Affiliation(s)
- Jin Lu
- Preston M. Green Department of Electrical and Systems Engineering, McKelvey School of Engineering, Washington University in St. Louis St. Louis MO 63130 USA
- Institute of Materials Science and Engineering, Washington University in St. Louis St. Louis MO 63130 USA
| | - Matthew D Lew
- Preston M. Green Department of Electrical and Systems Engineering, McKelvey School of Engineering, Washington University in St. Louis St. Louis MO 63130 USA
- Institute of Materials Science and Engineering, Washington University in St. Louis St. Louis MO 63130 USA
| |
Collapse
|
3
|
Lee H, Kim K, Kang CM, Choo A, Han D, Kim J. In Situ Confocal Fluorescence Lifetime Imaging of Nanopore Electrode Arrays with Redox Active Fluorogenic Amplex Red. Anal Chem 2023; 95:1038-1046. [PMID: 36577440 DOI: 10.1021/acs.analchem.2c03742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Direct imaging of electrochemical processes on electrode surfaces is a central part of understanding spatially heterogeneous electrochemical processes on the surfaces. Herein, we report a strategy for the spatially resolved imaging of local faradaic processes on nanoscale electrochemical interfaces. This strategy is based on fluorescence lifetime imaging microscopy (FLIM) with the use of Amplex Red as a fluorogenic redox probe. After verifying the capability of Amplex Red for fluorescence lifetime imaging, we demonstrated the turn-on FLIM-based imaging of faradaic processes on the electrochemical interfaces of different dimensions. In particular, we achieved spatially resolved visualization of the local electrochemical processes occurring on even nanopore electrode arrays as well as conventional microelectrodes, including disk-shaped ultramicroelectrodes and interdigitated array microelectrodes.
Collapse
Affiliation(s)
- Hyein Lee
- Department of Chemistry, Research Institute for Basic Sciences, Kyung Hee University, Seoul02447, Republic of Korea
| | - Kyoungsoo Kim
- Department of Chemistry, The Catholic University of Korea, Bucheon14662, Gyeonggi-do, Republic of Korea
| | - Chung Mu Kang
- Electrochemistry Laboratory, Advanced Institutes of Convergence Technology, Suwon16229, Gyeonggi-do, Republic of Korea
| | - Aeri Choo
- Department of Chemistry, Research Institute for Basic Sciences, Kyung Hee University, Seoul02447, Republic of Korea
| | - Donghoon Han
- Department of Chemistry, The Catholic University of Korea, Bucheon14662, Gyeonggi-do, Republic of Korea
| | - Joohoon Kim
- Department of Chemistry, Research Institute for Basic Sciences, Kyung Hee University, Seoul02447, Republic of Korea.,KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul02447, Republic of Korea
| |
Collapse
|
4
|
Baek S, Han D, Kwon SR, Sundaresan V, Bohn PW. Electrochemical Zero-Mode Waveguide Potential-Dependent Fluorescence of Glutathione Reductase at Single-Molecule Occupancy. Anal Chem 2022; 94:3970-3977. [PMID: 35213143 PMCID: PMC8904319 DOI: 10.1021/acs.analchem.1c05091] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Understanding functional states of individual redox enzymes is important because electron-transfer reactions are fundamental to life, and single-enzyme molecules exhibit molecule-to-molecule heterogeneity in their properties, such as catalytic activity. Zero-mode waveguides (ZMW) constitute a powerful tool for single-molecule studies, enabling investigations of binding reactions up to the micromolar range due to the ability to trap electromagnetic radiation in zeptoliter-scale observation volumes. Here, we report the potential-dependent fluorescence dynamics of single glutathione reductase (GR) molecules using a bimodal electrochemical ZMW (E-ZMW), where a single-ring electrode embedded in each of the nanopores of an E-ZMW array simultaneously serves to control electrochemical potential and to confine optical radiation within the nanopores. Here, the redox state of GR is manipulated using an external potential control of the Au electrode in the presence of a redox mediator, methyl viologen (MV). Redox-state transitions in GR are monitored by correlating electrochemical and spectroscopic signals from freely diffusing MV/GR in 60 zL effective observation volumes at single GR molecule average pore occupancy, ⟨n⟩ ∼ 0.8. Fluorescence intensities decrease (increase) at reducing (oxidizing) potentials for MV due to the MV-mediated control of the GR redox state. The spectroelectrochemical response of GR to the enzyme substrate, i.e., glutathione disulfide (GSSG), shows that GSSG promotes GR oxidation via enzymatic reduction. The capabilities of E-ZMWs to probe spectroelectrochemical phenomena in zL-scale-confined environments show great promise for the study of single-enzyme reactions and can be extended to important technological applications, such as those in molecular diagnostics.
Collapse
Affiliation(s)
- Seol Baek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Donghoon Han
- Department of Chemistry, The Catholic University of Korea, Bucheon, Gyeonggi-do 14662, South Korea
| | - Seung-Ryong Kwon
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, South Korea
| | - Vignesh Sundaresan
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Paul W Bohn
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.,Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| |
Collapse
|
5
|
Abstract
We present the results of acid–base experiments performed at the single ion (H+ or OH−) limit in ∼6 aL volume nanopores incorporating electrochemical zero-mode waveguides (E-ZMWs). At pH 3 each E-ZMW nanopore contains ca. 3600H+ ions, and application of a negative electrochemical potential to the gold working electrode/optical cladding layer reduces H+ to H2, thereby depleting H+ and increasing the local pH within the nanopore. The change in pH was quantified by tracking the intensity of fluorescein, a pH-responsive fluorophore whose intensity increases with pH. This behavior was translated to the single ion limit by changing the initial pH of the electrolyte solution to pH 6, at which the average pore occupancy 〈n〉pore ∼3.6H+/nanopore. Application of an electrochemical potential sufficiently negative to change the local pH to pH 7 reduces the proton nanopore occupancy to 〈n〉pore ∼0.36H+/nanopore, demonstrating that the approach is sensitive to single H+ manipulations, as evidenced by clear potential-dependent changes in fluorescein emission intensity. In addition, at high overpotential, the observed fluorescence intensity exceeded the value predicted from the fluorescence intensity-pH calibration, an observation attributed to the nucleation of H2 nanobubbles as confirmed both by calculations and the behavior of non-pH responsive Alexa 488 fluorophore. Apart from enhancing fundamental understanding, the approach described here opens the door to applications requiring ultrasensitive ion sensing, based on the optical detection of H+ population at the single ion limit. Visualizing dynamic change in the number of protons during electroreduction of protons in attoliter volume zero-mode waveguides.![]()
Collapse
Affiliation(s)
- Vignesh Sundaresan
- Department of Chemical and Biomolecular Engineering, University of Notre Dame Notre Dame IN 46556 USA
| | - Paul W Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame Notre Dame IN 46556 USA .,Department of Chemistry and Biochemistry, University of Notre Dame Notre Dame IN 46556 USA
| |
Collapse
|
6
|
Tassy B, Dauphin AL, Man HM, Le Guenno H, Lojou E, Bouffier L, de Poulpiquet A. In Situ Fluorescence Tomography Enables a 3D Mapping of Enzymatic O 2 Reduction at the Electrochemical Interface. Anal Chem 2020; 92:7249-7256. [PMID: 32298094 DOI: 10.1021/acs.analchem.0c00844] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Getting information about the fate of immobilized enzymes and the evolution of their environment during turnover is a mandatory step toward bioelectrode optimization for effective use in biodevices. We demonstrate here the proof-of-principle visual characterization of the reactivity at an enzymatic electrode thanks to fluorescence confocal laser scanning microscopy (FCLSM) implemented in situ during the electrochemical experiment. The enzymatic O2 reduction involves proton-coupled electron transfers. Therefore, fluorescence variation of a pH-dependent fluorescent dye in the electrode vicinity enables reaction visualization. Simultaneous collection of electrochemical and fluorescence signals gives valuable space- and time-resolved information. Once the technical challenges of such a coupling are overcome, in situ FCLSM affords a unique way to explore reactivity at the electrode surface and in the electrolyte volume. Unexpected features are observed, especially the pH evolution of the enzyme environment, which is also indicated by a characteristic concentration profile within the diffusion layer. This coupled approach also gives access to a cartography of the electrode surface response (i.e., heterogeneity), which cannot be obtained solely by an electrochemical means.
Collapse
Affiliation(s)
- Bastien Tassy
- Aix-Marseille Univ., CNRS, UMR 7281, Bioenergetics and Protein Engineering, 13402 Marseille, France
| | - Alice L Dauphin
- Univ. Bordeaux, CNRS, Bordeaux INP, UMR 5255, Institute of Molecular Sciences, F-33400 Talence, France
| | - Hiu Mun Man
- Aix-Marseille Univ., CNRS, UMR 7281, Bioenergetics and Protein Engineering, 13402 Marseille, France
| | - Hugo Le Guenno
- Microscopy Facility, CNRS, FR 3479, Mediterranean Institute of Microbiology, 13402 Marseille, France
| | - Elisabeth Lojou
- Aix-Marseille Univ., CNRS, UMR 7281, Bioenergetics and Protein Engineering, 13402 Marseille, France
| | - Laurent Bouffier
- Univ. Bordeaux, CNRS, Bordeaux INP, UMR 5255, Institute of Molecular Sciences, F-33400 Talence, France
| | - Anne de Poulpiquet
- Aix-Marseille Univ., CNRS, UMR 7281, Bioenergetics and Protein Engineering, 13402 Marseille, France
| |
Collapse
|
7
|
Chen R, Alanis K, Welle TM, Shen M. Nanoelectrochemistry in the study of single-cell signaling. Anal Bioanal Chem 2020; 412:6121-6132. [PMID: 32424795 DOI: 10.1007/s00216-020-02655-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 04/02/2020] [Accepted: 04/08/2020] [Indexed: 12/28/2022]
Abstract
Label-free biosensing has been the dream of scientists and biotechnologists as reported by Vollmer and Arnold (Nat Methods 5:591-596, 2008). The ability of examining living cells is crucial to cell biology as noted by Fang (Int J Electrochem 2011:460850, 2011). Chemical measurement with electrodes is label-free and has demonstrated capability of studying living cells. In recent years, nanoelectrodes of different functionality have been developed. These nanometer-sized electrodes, coupled with scanning electrochemical microscopy (SECM), have further enabled nanometer spatial resolution study in aqueous environments. Developments in the field of nanoelectrochemistry have allowed measurement of signaling species at single cells, contributing to better understanding of cell biology. Leading studies using nanoelectrochemistry of a variety of cellular signaling molecules, including redox-active neurotransmitter (e.g., dopamine), non-redox-active neurotransmitter (e.g., acetylcholine), reactive oxygen species (ROS), and reactive nitrogen species (RNS), are reviewed here.
Collapse
Affiliation(s)
- Ran Chen
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL, 61801, USA
| | - Kristen Alanis
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL, 61801, USA
| | - Theresa M Welle
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL, 61801, USA
| | - Mei Shen
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL, 61801, USA.
| |
Collapse
|
8
|
Fu K, Kwon SR, Han D, Bohn PW. Single Entity Electrochemistry in Nanopore Electrode Arrays: Ion Transport Meets Electron Transfer in Confined Geometries. Acc Chem Res 2020; 53:719-728. [PMID: 31990518 PMCID: PMC8020881 DOI: 10.1021/acs.accounts.9b00543] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Electrochemical measurements conducted in confined volumes provide a powerful and direct means to address scientific questions at the nexus of nanoscience, biotechnology, and chemical analysis. How are electron transfer and ion transport coupled in confined volumes and how does understanding them require moving beyond macroscopic theories? Also, how do these coupled processes impact electrochemical detection and processing? We address these questions by studying a special type of confined-volume architecture, the nanopore electrode array, or NEA, which is designed to be commensurate in size with physical scaling lengths, such as the Debye length, a concordance that offers performance characteristics not available in larger scale structures.The experiments described here depend critically on carefully constructed nanoscale architectures that can usefully control molecular transport and electrochemical reactivity. We begin by considering the experimental constraints that guide the design and fabrication of zero-dimensional nanopore arrays with multiple embedded electrodes. These zero-dimensional structures are nearly ideal for exploring how permselectivity and unscreened ion migration can be combined to amplify signals and improve selectivity by enabling highly efficient redox cycling. Our studies also highlight the benefits of arrays, in that molecules escaping from a single nanopore are efficiently captured by neighboring pores and returned to the population of active redox species being measured, benefits that arise from coupling ion accumulation and migration. These tools for manipulating redox species are well-positioned to explore single molecule and single particle electron transfer events through spectroelectrochemistry, studies which are enabled by the electrochemical zero-mode waveguide (ZMW), a special hybrid nanophotonic/nanoelectronic architecture in which the lower ring electrode of an NEA nanopore functions both as a working electrode to initiate electron transfer reactions and as the optical cladding layer of a ZMW. While the work described here is largely exploratory and fundamental, we believe that the development of NEAs will enable important applications that emerge directly from the unique coupled transport and electron-transfer capabilities of NEAs, including in situ molecular separation and detection with external stimuli, redox-based electrochemical rectification in individually encapsulated nanopores, and coupled sorters and analyzers for nanoparticles.
Collapse
Affiliation(s)
- Kaiyu Fu
- Department of Radiology, Stanford University, Stanford, CA, 94306
- Department of Electrical Engineering, Stanford University, Stanford, CA, 94306
| | - Seung-Ryong Kwon
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Donghoon Han
- Department of Chemistry, The Catholic University of Korea, Bucheon, Gyeonggi-do, 14662 Republic of Korea
| | - Paul W. Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
| |
Collapse
|
9
|
Hao R, Peng Z, Zhang B. Single-Molecule Fluorescence Microscopy for Probing the Electrochemical Interface. ACS OMEGA 2020; 5:89-97. [PMID: 31956755 PMCID: PMC6963970 DOI: 10.1021/acsomega.9b03763] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 12/10/2019] [Indexed: 05/17/2023]
Abstract
The electrochemical interface is an ultrathin interfacial region between the electrode and solution where electrochemical reactions occur. The study of the electrochemical interface continues to be one of the most exciting directions in modern electrochemistry research. Much of our existing knowledge about the electrochemical interface comes from ensemble measurements and ex situ imaging of the electrode surface. Due to its enormous complexity and highly dynamic nature, however, new imaging tools that can probe the interface in situ with ultrahigh spatial and temporal resolution and single-molecule sensitivity are apparently needed. Single-molecule fluorescence microscopy (SMFM) has emerged as a powerful tool that is uniquely suited for studying the electrochemical interface. In this mini-review, we first give a brief overview of various existing SMFM methods for studying electrochemical problems. We then discuss several exciting research topics involving the use of SMFM methods for studying surface-immobilized molecules, single freely diffusing molecules, single molecules as catalytic reaction indicators, and single-molecule labeling and imaging of interfacial nanobubbles. We anticipate that we will continue to see a rapid increase in publications on stochastic electrochemistry of single molecules and nanoparticles. The increased use of SMFM will likely bring new information to our study of the electrochemical interface.
Collapse
|
10
|
Zigah D, Lojou E, Poulpiquet A. Micro‐ and Nanoscopic Imaging of Enzymatic Electrodes: A Review. ChemElectroChem 2019. [DOI: 10.1002/celc.201901065] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Dodzi Zigah
- Univ. Bordeaux, CNRSBordeaux INP ISM UMR 5255 33400 Talence France
| | - Elisabeth Lojou
- Aix-Marseille Univ., CNRSBIP, UMR 7281 31 Chemin Aiguier 13009 Marseille France
| | - Anne Poulpiquet
- Aix-Marseille Univ., CNRSBIP, UMR 7281 31 Chemin Aiguier 13009 Marseille France
| |
Collapse
|
11
|
Optical methods for studying local electrochemical reactions with spatial resolution: A critical review. Anal Chim Acta 2019; 1074:1-15. [DOI: 10.1016/j.aca.2019.02.053] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 02/21/2019] [Accepted: 02/22/2019] [Indexed: 11/19/2022]
|
12
|
Han C, Hao R, Fan Y, Edwards MA, Gao H, Zhang B. Observing Transient Bipolar Electrochemical Coupling on Single Nanoparticles Translocating through a Nanopore. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7180-7190. [PMID: 31074628 DOI: 10.1021/acs.langmuir.9b01255] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We report the observation of transient bipolar electrochemical coupling on freely moving 40 nm silver nanoparticles. The use of an asymmetric nanoelectrochemical environment at the nanopore orifice, for example, an acid inside the pipette and halide ions in the bulk, enabled us to observe unusually large current blockages of single Ag nanoparticles. We attribute these current blockages to the formation of H2 nanobubbles on the surface of Ag nanoparticles due to the coupled faradaic reactions, in which the reduction of protons and water is coupled to the oxidation of Ag and water under potentials higher than 1 V. The appearance of large current blockages was strongly dependent on the applied voltage and the choice of anions in the bulk solution. The correlation between large current blockages with the oxidation of Ag nanoparticles and their nanopore translocation was further supported by simultaneous fluorescence and electric recordings. This study demonstrates that transient bipolar electrochemistry can take place on small metal nanoparticles below 50 nm when they pass through nanopores where the electric field is highly localized. The use of a nanopore and the resistive-pulse sensing method to study transient bipolar electrochemistry of nanoparticles may be extended to future studies in ultrafast electrochemistry, nanocatalyst screening, and gas nucleation on nanoparticles.
Collapse
Affiliation(s)
- Chu Han
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Rui Hao
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Yunshan Fan
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Martin A Edwards
- Department of Chemistry , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Hongfang Gao
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Bo Zhang
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| |
Collapse
|
13
|
Fan Y, Hao R, Han C, Zhang B. Counting Single Redox Molecules in a Nanoscale Electrochemical Cell. Anal Chem 2018; 90:13837-13841. [DOI: 10.1021/acs.analchem.8b04659] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Yunshan Fan
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Rui Hao
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Chu Han
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Bo Zhang
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| |
Collapse
|
14
|
Singh R, Rathore D, Pandey CM, Geetanjali, Srivastava R. Electrochemical and Spectroscopic Studies of Riboflavin. ANALYTICAL CHEMISTRY LETTERS 2018; 8:653-664. [DOI: 10.1080/22297928.2018.1498018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 06/30/2018] [Indexed: 06/15/2023]
Affiliation(s)
- Ram Singh
- Department of Applied Chemistry, Delhi Technological University, Delhi - 110 042, India
| | - Deepshikha Rathore
- Department of Applied Chemistry, Delhi Technological University, Delhi - 110 042, India
| | - Chandra Mouli Pandey
- Department of Applied Chemistry, Delhi Technological University, Delhi - 110 042, India
| | - Geetanjali
- Department of Chemistry, Kirori Mal College, University of Delhi, Delhi - 110 007, India
| | - Richa Srivastava
- Department of Applied Chemistry, Delhi Technological University, Delhi - 110 042, India
| |
Collapse
|
15
|
Han D, Kwon SR, Fu K, Crouch GM, Bohn PW. Electrochemical Zero-Mode Waveguide Studies of Single Enzyme Reactions. PROCEEDINGS OF THE ... IEEE CONFERENCE ON NANOTECHNOLOGY. IEEE CONFERENCE ON NANOTECHNOLOGY 2018; 2018:10.1109/nano.2018.8626402. [PMID: 33912324 PMCID: PMC8078011 DOI: 10.1109/nano.2018.8626402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Because electron transfer reactions are fundamental to life processes, such as respiration, vision, and energy catabolism, it is critically important to understand the relationship between functional states of individual redox enzymes and the macroscopically observed phenotype, which results from averaging over all copies of the same enzyme. To address this problem, we have developed a new technology, based on a bifunctional nanoelectrochemical-nanophotonic architecture - the electrochemical zero mode waveguide (E-ZMW) - that can couple biological electron transfer reactions to luminescence, making it possible to observe single electron transfer events in redox enzymes. Here we describe E-ZMW architectures capable of supporting potential-controlled redox reactions with single copies of the oxidoreductase enzyme, glutathione reductase, GR, and extend these capabilities to electron transfer events where reactive oxygen species are synthesized within the ~100 zL volume of the nanopore.
Collapse
Affiliation(s)
- Donghoon Han
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Seung-Ryong Kwon
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Kaiyu Fu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Garrison M Crouch
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Paul W Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 USA
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 USA
| |
Collapse
|
16
|
Crouch GM, Han D, Bohn PW. Zero-Mode Waveguide Nanophotonic Structures for Single Molecule Characterization. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2018; 51:193001. [PMID: 34158676 PMCID: PMC8216246 DOI: 10.1088/1361-6463/aab8be] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Single-molecule characterization has become a crucial research tool in the chemical and life sciences, but limitations, such as limited concentration range, inability to control molecular distributions in space, and intrinsic phenomena, such as photobleaching, present significant challenges. Recent developments in non-classical optics and nanophotonics offer promising routes to mitigating these restrictions, such that even low affinity (K D ~ mM) biomolecular interactions can be studied. Here we introduce and review specific nanophotonic devices used to support single molecule studies. Optical nanostructures, such as zero-mode waveguides (ZMWs), are usually fabricated in thin gold or aluminum films and serve to confine the observation volume of optical microspectroscopy to attoliter to zeptoliter volumes. These simple nanostructures allow individual molecules to be isolated for optical and electrochemical analysis, even when the molecules of interest are present at high concentration (μM - mM) in bulk solution. Arrays of ZMWs may be combined with optical probes such as single molecule fluorescence, single molecule fluorescence resonance energy transfer (smFRET), and fluorescence correlation spectroscopy (FCS) for distributed analysis of large numbers of single-molecule reactions or binding events in parallel. Furthermore, ZMWs may be used as multifunctional devices, for example by combining optical and electrochemical functions in a single discrete architecture to achieve electrochemical ZMWs (E-ZMW). In this review, we will describe the optical properties, fabrication, and applications of ZMWs for single-molecule studies, as well as the integration of ZMWs into systems for chemical and biochemical analysis.
Collapse
Affiliation(s)
- Garrison M. Crouch
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Donghoon Han
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556
| | - Paul W. Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556
- Departmemt of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
| |
Collapse
|
17
|
Fu K, Bohn PW. Nanopore Electrochemistry: A Nexus for Molecular Control of Electron Transfer Reactions. ACS CENTRAL SCIENCE 2018; 4:20-29. [PMID: 29392173 PMCID: PMC5785767 DOI: 10.1021/acscentsci.7b00576] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Indexed: 05/12/2023]
Abstract
Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for next-generation nanopore electrode sensing platforms and the opportunities they present.
Collapse
Affiliation(s)
- Kaiyu Fu
- Department
of Chemistry and Biochemistry and Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Paul W. Bohn
- Department
of Chemistry and Biochemistry and Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- E-mail: . Tel: +1 574 631 1849. Fax: +1 574 631 8366
| |
Collapse
|
18
|
Peng S, Wang W, Chen C. Breaking the Concentration Barrier for Single-Molecule Fluorescence Measurements. Chemistry 2017; 24:1002-1009. [DOI: 10.1002/chem.201704065] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Sijia Peng
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, and Beijing Advanced Innovation Center for Structural Biology; Tsinghua University; Beijing, 100084 P.R. China
| | - Wenjuan Wang
- School of Life Sciences and Technology Center for Protein Sciences; Tsinghua University; Beijing, 100084 P.R. China
| | - Chunlai Chen
- School of Life Sciences, Tsinghua-Peking Joint Center for Life Sciences, and Beijing Advanced Innovation Center for Structural Biology; Tsinghua University; Beijing, 100084 P.R. China
| |
Collapse
|
19
|
Han D, Crouch GM, Fu K, Zaino Iii LP, Bohn PW. Single-molecule spectroelectrochemical cross-correlation during redox cycling in recessed dual ring electrode zero-mode waveguides. Chem Sci 2017; 8:5345-5355. [PMID: 28970913 PMCID: PMC5609146 DOI: 10.1039/c7sc02250f] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 06/18/2017] [Indexed: 11/21/2022] Open
Abstract
The ability of zero-mode waveguides (ZMW) to guide light into subwavelength-diameter nanoapertures has been exploited for studying electron transfer dynamics in zeptoliter-volume nanopores under single-molecule occupancy conditions. In this work, we report the spectroelectrochemical detection of individual molecules of the redox-active, fluorogenic molecule flavin mononucleotide (FMN) freely diffusing in solution. Our approach is based on an array of nanopore-confined recessed dual ring electrodes, wherein repeated reduction and oxidation of a single molecule at two closely spaced annular working electrodes yields amplified electrochemical signals. We have articulated these structures with an optically transparent bottom, so that the nanopores are bifunctional, exhibiting both nanophotonic and nanoelectrochemical behaviors allowing the coupling between electron transfer and fluorescence dynamics to be studied under redox cycling conditions. We also investigated the electric field intensity in electrochemical ZMWs (E-ZMW) through finite-element simulations, and the amplification of fluorescence by redox cycling agrees well with predictions based on optical confinement effects inside the E-ZMW. Proof-of-principle experiments are conducted showing that electrochemical and fluorescence signals may be correlated to reveal single molecule fluctuations in the array population. Cross-correlation of single molecule fluctuations in amperometric response and single photon emission provides unequivocal evidence of single molecule sensitivity.
Collapse
Affiliation(s)
- Donghoon Han
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA . ; ; Tel: +1 574 631 1849
| | - Garrison M Crouch
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA . ; ; Tel: +1 574 631 1849
| | - Kaiyu Fu
- Departmemt of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA
| | - Lawrence P Zaino Iii
- Departmemt of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA
| | - Paul W Bohn
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA . ; ; Tel: +1 574 631 1849.,Departmemt of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA
| |
Collapse
|
20
|
Goldschen-Ohm MP, White DS, Klenchin VA, Chanda B, Goldsmith RH. Observing Single-Molecule Dynamics at Millimolar Concentrations. Angew Chem Int Ed Engl 2017; 56:2399-2402. [PMID: 28116856 PMCID: PMC6166642 DOI: 10.1002/anie.201612050] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Indexed: 11/11/2022]
Abstract
Single-molecule fluorescence microscopy is a powerful tool for revealing chemical dynamics and molecular association mechanisms, but has been limited to low concentrations of fluorescent species and is only suitable for studying high affinity reactions. Here, we combine nanophotonic zero-mode waveguides (ZMWs) with fluorescence resonance energy transfer (FRET) to resolve single-molecule association dynamics at up to millimolar concentrations of fluorescent species. This approach extends the resolution of molecular dynamics to >100-fold higher concentrations, enabling observations at concentrations relevant to biological and chemical processes, and thus making single-molecule techniques applicable to a tremendous range of previously inaccessible molecular targets. We deploy this approach to show that the binding of cGMP to pacemaking ion channels is weakened by a slower internal conformational change.
Collapse
Affiliation(s)
- Marcel P Goldschen-Ohm
- Department of Neuroscience, University of Wisconsin-Madison, 1111 Highland Ave., Madison, WI, 53705, USA
| | - David S White
- Department of Neuroscience, University of Wisconsin-Madison, 1111 Highland Ave., Madison, WI, 53705, USA
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| | - Vadim A Klenchin
- Department of Neuroscience, University of Wisconsin-Madison, 1111 Highland Ave., Madison, WI, 53705, USA
| | - Baron Chanda
- Department of Neuroscience, University of Wisconsin-Madison, 1111 Highland Ave., Madison, WI, 53705, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, 420 Henry Mall, Madison, WI, 53706, USA
| | - Randall H Goldsmith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, WI, 53706, USA
| |
Collapse
|
21
|
Lu J, Fan Y, Howard MD, Vaughan JC, Zhang B. Single-Molecule Electrochemistry on a Porous Silica-Coated Electrode. J Am Chem Soc 2017; 139:2964-2971. [PMID: 28132499 DOI: 10.1021/jacs.6b10191] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Here we report the direct observation and quantitative analysis of single redox events on a modified indium-tin oxide (ITO) electrode. The key in the observation of single redox events are the use of a fluorogenic redox species and the nanoconfinement and hindered redox diffusion inside 3-nm-diameter silica nanochannels. A simple electrochemical process was used to grow an ultrathin silica film (∼100 nm) consisting of highly ordered parallel nanochannels exposing the electrode surface from the bottom. The electrode-supported 3-nm-diameter nanochannels temporally trap fluorescent resorufin molecules resulting in hindered molecular diffusion in the vicinity of the electrode surface. Adsorption, desorption, and heterogeneous redox events of individual resorufin molecules can be studied using total-internal reflection fluorescence (TIRF). The rate constants of adsorption and desorption processes of resorufin were characterized from single-molecule analysis to be (1.73 ± 0.08) × 10-4 cm·s-1 and 15.71 ± 0.76 s-1, respectively. The redox events of resorufin to the non-fluorescent dihydroresorufin were investigated by analyzing the change in surface population of single resorufin molecules with applied potential. The scan-rate-dependent molecular counting results (single-molecule fluorescence voltammetry) indicated a surface-controlled electrochemical kinetics of the resorufin reduction on the modified ITO electrode. This study demonstrates the great potential of mesoporous silica as a useful modification scheme for studying single redox events on a variety of transparent substrates such as ITO electrodes and gold or carbon film coated glass electrodes. The ability to electrochemically grow and transfer mesoporous silica films onto other substrates makes them an attractive material for future studies in spatial heterogeneity of electrocatalytic surfaces.
Collapse
Affiliation(s)
- Jin Lu
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Yunshan Fan
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Marco D Howard
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Joshua C Vaughan
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Bo Zhang
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| |
Collapse
|
22
|
Goldschen-Ohm MP, White DS, Klenchin VA, Chanda B, Goldsmith RH. Observing Single-Molecule Dynamics at Millimolar Concentrations. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201612050] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marcel P. Goldschen-Ohm
- Department of Neuroscience; University of Wisconsin-Madison; 1111 Highland Ave. Madison WI 53705 USA
| | - David S. White
- Department of Neuroscience; University of Wisconsin-Madison; 1111 Highland Ave. Madison WI 53705 USA
- Department of Chemistry; University of Wisconsin-Madison; 1101 University Ave. Madison WI 53706 USA
| | - Vadim A. Klenchin
- Department of Neuroscience; University of Wisconsin-Madison; 1111 Highland Ave. Madison WI 53705 USA
| | - Baron Chanda
- Department of Neuroscience; University of Wisconsin-Madison; 1111 Highland Ave. Madison WI 53705 USA
- Department of Biomolecular Chemistry; University of Wisconsin-Madison; 420 Henry Mall Madison WI 53706 USA
| | - Randall H. Goldsmith
- Department of Chemistry; University of Wisconsin-Madison; 1101 University Ave. Madison WI 53706 USA
| |
Collapse
|
23
|
Mattei M, Kang G, Goubert G, Chulhai DV, Schatz GC, Jensen L, Van Duyne RP. Tip-Enhanced Raman Voltammetry: Coverage Dependence and Quantitative Modeling. NANO LETTERS 2017; 17:590-596. [PMID: 27936805 DOI: 10.1021/acs.nanolett.6b04868] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Electrochemical atomic force microscopy tip-enhanced Raman spectroscopy (EC-AFM-TERS) was employed for the first time to observe nanoscale spatial variations in the formal potential, E0', of a surface-bound redox couple. TERS cyclic voltammograms (TERS CVs) of single Nile Blue (NB) molecules were acquired at different locations spaced 5-10 nm apart on an indium tin oxide (ITO) electrode. Analysis of TERS CVs at different coverages was used to verify the observation of single-molecule electrochemistry. The resulting TERS CVs were fit to the Laviron model for surface-bound electroactive species to quantitatively extract the formal potential E0' at each spatial location. Histograms of single-molecule E0' at each coverage indicate that the electrochemical behavior of the cationic oxidized species is less sensitive to local environment than the neutral reduced species. This information is not accessible using purely electrochemical methods or ensemble spectroelectrochemical measurements. We anticipate that quantitative modeling and measurement of site-specific electrochemistry with EC-AFM-TERS will have a profound impact on our understanding of the role of nanoscale electrode heterogeneity in applications such as electrocatalysis, biological electron transfer, and energy production and storage.
Collapse
Affiliation(s)
| | | | | | - Dhabih V Chulhai
- Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | | | - Lasse Jensen
- Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | | |
Collapse
|
24
|
Wu Z, Zhou CH, Pan LJ, Zeng T, Zhu L, Pang DW, Zhang ZL. Reliable Digital Single Molecule Electrochemistry for Ultrasensitive Alkaline Phosphatase Detection. Anal Chem 2016; 88:9166-72. [DOI: 10.1021/acs.analchem.6b02284] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Zhen Wu
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Chuan-Hua Zhou
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Liang-Jun Pan
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Tao Zeng
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Lian Zhu
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Dai-Wen Pang
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| | - Zhi-Ling Zhang
- Key Laboratory of Analytical Chemistry for Biology and
Medicine (Ministry of Education), College of Chemistry and Molecular
Sciences, State Key Laboratory of Virology, Wuhan University, Wuhan 430072, People’s Republic of China
| |
Collapse
|
25
|
Abstract
The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to fully reduced riboflavin, each with unique intermediates including a semi-quinone radical. By performing surface-enhanced Raman scattering (SERS) with simultaneous electrochemical detection of riboflavin at different pH values, we are able to correlate reversible changes in spectral features to the current changes observed in the cyclic voltammetry. Multivariate curve resolution analysis of the SERS spectra indicates that three distinct components were present at the SERS electrode at each pH during the potential sweep. To verify and better understand the variations in Raman bands across the voltammogram, density functional theory (DFT) calculations were performed to model the effect of pH and oxidation state on the riboflavin Raman spectrum. The calculated spectra show qualitative agreement with the species identified in the chemometric analysis. This combination of results indicates the presence of the oxidized, semi-quinone, and reduced forms of riboflavin and provides insight into the mechanism of the flavin redox system.
Collapse
Affiliation(s)
- Matthew R Bailey
- University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN 46556, USA.
| | - Zachary D Schultz
- University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN 46556, USA.
| |
Collapse
|
26
|
Goldschen-Ohm MP, Klenchin VA, White DS, Cowgill JB, Cui Q, Goldsmith RH, Chanda B. Structure and dynamics underlying elementary ligand binding events in human pacemaking channels. eLife 2016; 5:e20797. [PMID: 27858593 PMCID: PMC5115869 DOI: 10.7554/elife.20797] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/01/2016] [Indexed: 01/07/2023] Open
Abstract
Although molecular recognition is crucial for cellular signaling, mechanistic studies have relied primarily on ensemble measures that average over and thereby obscure underlying steps. Single-molecule observations that resolve these steps are lacking due to diffraction-limited resolution of single fluorophores at relevant concentrations. Here, we combined zero-mode waveguides with fluorescence resonance energy transfer (FRET) to directly observe binding at individual cyclic nucleotide-binding domains (CNBDs) from human pacemaker ion channels critical for heart and brain function. Our observations resolve the dynamics of multiple distinct steps underlying cyclic nucleotide regulation: a slow initial binding step that must select a 'receptive' conformation followed by a ligand-induced isomerization of the CNBD. X-ray structure of the apo CNBD and atomistic simulations reveal that the isomerization involves both local and global transitions. Our approach reveals fundamental mechanisms underpinning ligand regulation of pacemaker channels, and is generally applicable to weak-binding interactions governing a broad spectrum of signaling processes.
Collapse
Affiliation(s)
| | - Vadim A Klenchin
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States
| | - David S White
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States,Department of Chemistry, University of Wisconsin-Madison, Madison, United States
| | - John B Cowgill
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States
| | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, United States
| | - Randall H Goldsmith
- Department of Chemistry, University of Wisconsin-Madison, Madison, United States
| | - Baron Chanda
- Department of Neuroscience, University of Wisconsin-Madison, Madison, United States,Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, United States,
| |
Collapse
|
27
|
|
28
|
Affiliation(s)
- Stephen M. Oja
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Yunshan Fan
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Chadd M. Armstrong
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Peter Defnet
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Bo Zhang
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| |
Collapse
|
29
|
Mathwig K, Chi Q, Lemay SG, Rassaei L. Handling and Sensing of Single Enzyme Molecules: From Fluorescence Detection towards Nanoscale Electrical Measurements. Chemphyschem 2015; 17:452-7. [DOI: 10.1002/cphc.201500686] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Klaus Mathwig
- Pharmaceutical Analysis; Groningen Research Institute of Pharmacy; University of Groningen; P.O. Box 196 9700 AD Groningen The Netherlands
| | - Qijin Chi
- Department of Chemistry; Technical University of Denmark; 2800 Kongens Lyngby Denmark
| | - Serge G. Lemay
- MESA+ Institute for Nanotechnology; University of Twente; P.O. Box 217 7500 AE Enschede The Netherlands
| | - Liza Rassaei
- Laboratory of Organic Materials and Interfaces; Department of Chemical Engineering; Delft University of Technology; Julianalaan 136 2628 BL Delft The Netherlands
| |
Collapse
|
30
|
Zaino LP, Grismer DA, Han D, Crouch GM, Bohn PW. Single occupancy spectroelectrochemistry of freely diffusing flavin mononucleotide in zero-dimensional nanophotonic structures. Faraday Discuss 2015; 184:101-15. [PMID: 26406924 DOI: 10.1039/c5fd00072f] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Zero-mode waveguides (ZMW) have the potential to be powerful confinement tools for studying electron transfer dynamics at single molecule occupancy conditions. Flavin mononucleotide contains an isoalloxazine chromophore, which is fluorescent in the oxidized state (FMN) while the reduced state (FMNH2) exhibits dramatically lower light emission, i.e. a dark-state. This allows fluorescence emission to report the redox state of single FMN molecules, an observation that has been used previously to study single electron transfer events in surface-immobilized flavins and flavoenzymes, e.g. sarcosine oxidase, by direct wide-field imaging of ZMW arrays. Single molecule electron transfer dynamics have now been extended to the study of freely diffusing molecules using fluorescence measurements of Au ZMWs under single occupancy conditions. The Au in the ZMW serves both as an optical cladding layer and as the working electrode for potential control, thereby accessing single molecule electron transfer dynamics at μM concentrations. Consistent with expectations, the probability of observing single reduced molecules increases as the potential is scanned negative, E(appl) < E(eq), and the probability of observing emitting oxidized molecules increases at E(appl) > E(eq). Different single molecules exhibit different electron transfer properties as reflected in the position of E(eq) and the distribution of E(eq) among a population of FMN molecules. Two types of actively-controlled electroluminescence experiments were used: chronofluorometry experiments, in which the potential is alternately stepped between oxidizing and reducing potentials, and cyclic potential sweep fluorescence experiments, analogous to cyclic voltammetry, these latter experiments exhibiting a dramatic scan rate dependence with the slowest scan rates showing distinct intermediate states that are stable over a range of potentials. These states are assigned to flavosemiquinone species that are stabilized in the special environment of the ZMW nanopore.
Collapse
Affiliation(s)
- Lawrence P Zaino
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | | | | | | | | |
Collapse
|
31
|
Ma C, Zaino Iii LP, Bohn PW. Self-induced redox cycling coupled luminescence on nanopore recessed disk-multiscale bipolar electrodes. Chem Sci 2015; 6:3173-3179. [PMID: 28706689 PMCID: PMC5490416 DOI: 10.1039/c5sc00433k] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/19/2015] [Indexed: 11/21/2022] Open
Abstract
We present a new configuration for coupling fluorescence microscopy and voltammetry using self-induced redox cycling for ultrasensitive electrochemical measurements. An array of nanopores, each supporting a recessed disk electrode separated by 100 nm in depth from a planar multiscale bipolar top electrode, was fabricated using multilayer deposition, nanosphere lithography, and reactive-ion etching. Self-induced redox cycling was induced on the disk electrode producing ∼30× current amplification, which was independently confirmed by measuring induced electrogenerated chemiluminescence from Ru(bpy)32/3+/tri-n-propylamine on the floating bipolar electrode. In this design, redox cycling occurs between the recessed disk and the top planar portion of a macroscopic thin film bipolar electrode in each nanopore. Electron transfer also occurs on a remote (mm-distance) portion of the planar bipolar electrode to maintain electroneutrality. This couples the electrochemical reactions of the target redox pair in the nanopore array with a reporter, such as a potential-switchable fluorescent indicator, in the cell at the distal end of the bipolar electrode. Oxidation or reduction of reversible analytes on the disk electrodes were accompanied by reduction or oxidation, respectively, on the nanopore portion of the bipolar electrode and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin at the remote end of the bipolar electrode, respectively. In both cases, changes in fluorescence intensity were triggered by the reaction of the target couple on the disk electrode, while recovery was largely governed by diffusion of the fluorescent indicator. Reduction of 1 nM of Ru(NH3)63+ on the nanoelectrode array was detected by monitoring the fluorescence intensity of resorufin, demonstrating high sensitivity fluorescence-mediated electrochemical sensing coupled to self-induced redox cycling.
Collapse
Affiliation(s)
- Chaoxiong Ma
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
| | - Lawrence P Zaino Iii
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
| | - Paul W Bohn
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA
| |
Collapse
|
32
|
Mathwig K, Aartsma TJ, Canters GW, Lemay SG. Nanoscale methods for single-molecule electrochemistry. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2014; 7:383-404. [PMID: 25000819 DOI: 10.1146/annurev-anchem-062012-092557] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The development of experiments capable of probing individual molecules has led to major breakthroughs in fields ranging from molecular electronics to biophysics, allowing direct tests of knowledge derived from macroscopic measurements and enabling new assays that probe population heterogeneities and internal molecular dynamics. Although still somewhat in their infancy, such methods are also being developed for probing molecular systems in solution using electrochemical transduction mechanisms. Here we outline the present status of this emerging field, concentrating in particular on optical methods, metal-molecule-metal junctions, and electrochemical nanofluidic devices.
Collapse
Affiliation(s)
- Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; ,
| | | | | | | |
Collapse
|