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Mehrafrooz B, Yu L, Pandey L, Siwy ZS, Wanunu M, Aksimentiev A. Electro-osmotic Flow Generation via a Sticky Ion Action. ACS NANO 2024. [PMID: 38832758 DOI: 10.1021/acsnano.4c00829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Selective transport of ions through nanometer-sized pores is fundamental to cell biology and central to many technological processes such as water desalination and electrical energy storage. Conventional methods for generating ion selectivity include placement of fixed electrical charges at the inner surface of a nanopore through either point mutations in a protein pore or chemical treatment of a solid-state nanopore surface, with each nanopore type requiring a custom approach. Here, we describe a general method for transforming a nanoscale pore into a highly selective, anion-conducting channel capable of generating a giant electro-osmotic effect. Our molecular dynamics simulations and reverse potential measurements show that exposure of a biological nanopore to high concentrations of guanidinium chloride renders the nanopore surface positively charged due to transient binding of guanidinium cations to the protein surface. A comparison of four biological nanopores reveals the relationship between ion selectivity, nanopore shape, composition of the nanopore surface, and electro-osmotic flow. Guanidinium ions are also found to produce anion selectivity and a giant electro-osmotic flow in solid-state nanopores via the same mechanism. Our sticky-ion approach to generate electro-osmotic flow can have numerous applications in controlling molecular transport at the nanoscale and for detection, identification, and sequencing of individual proteins.
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Affiliation(s)
- Behzad Mehrafrooz
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Luning Yu
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
| | - Laxmi Pandey
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
| | - Zuzanna S Siwy
- Department of Physics, University of California at Irvine, Irvine, California 92697, United States
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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2
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Mehrafrooz B, Yu L, Siwy Z, Wanunu M, Aksimentiev A. Electro-Osmotic Flow Generation via a Sticky Ion Action. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.14.571673. [PMID: 38168277 PMCID: PMC10760089 DOI: 10.1101/2023.12.14.571673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Selective transport of ions through nanometer-sized pores is fundamental to cell biology and central to many technological processes such as water desalination and electrical energy storage. Conventional methods for generating ion selectivity include placement of fixed electrical charges at the inner surface of a nanopore through either point mutations in a protein pore or chemical treatment of a solid-state nanopore surface, with each nanopore type requiring a custom approach. Here, we describe a general method for transforming a nanoscale pore into a highly selective, anion-conducting channel capable of generating a giant electro-osmotic effect. Our molecular dynamics simulations and reverse potential measurements show that exposure of a biological nanopore to high concentrations of guanidinium chloride renders the nanopore surface positively charged due to transient binding of guanidinium cations to the protein surface. A comparison of four biological nanopores reveals the relationship between ion selectivity, nanopore shape, composition of the nanopore surface, and electro-osmotic flow. Remarkably, guanidinium ions are also found to produce anion selectivity and a giant electro-osmotic flow in solid-state nanopores via the same mechanism. Our sticky-ion approach to generate electro-osmotic flow can have numerous applications in controlling molecular transport at the nanoscale and for detection, identification, and sequencing of individual proteins.
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Affiliation(s)
- Behzad Mehrafrooz
- Center for Biophysics and Quantitative Biology
- Beckman Institute for Advanced Science and Technology
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Luning Yu
- Department of Physics, Northeastern University, Boston, MA 02115 USA
| | - Zuzanna Siwy
- Department of Physics, University of California at Irvine, Irvine, CA 92697, USA
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, MA 02115 USA
- Department of Bioengineering, Northeastern University, Boston, MA 02115, USA
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology
- Beckman Institute for Advanced Science and Technology
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois
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3
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Montes de Oca JM, Dhanasekaran J, Córdoba A, Darling SB, de Pablo JJ. Ionic Transport in Electrostatic Janus Membranes. An Explicit Solvent Molecular Dynamic Simulation. ACS NANO 2022; 16:3768-3775. [PMID: 35230815 PMCID: PMC8945361 DOI: 10.1021/acsnano.1c07706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 02/22/2022] [Indexed: 06/14/2023]
Abstract
Janus, or two-sided, charged membranes offer promise as ionic current rectifiers. In such systems, pores consisting of two regions of opposite charge can be used to generate a current from a gradient in salinity. The efficiency of nanoscale Janus pores increases dramatically as their diameter becomes smaller. However, little is known about the underlying transport processes, particularly under experimentally accessible conditions. In this work, we examine the molecular basis for rectification in Janus nanopores using an applied electric field. Molecular simulations with explicit water and ions are used to examine the structure and dynamics of all molecular species in aqueous electrolyte solutions. For several macroscopic observables, the results of such simulations are consistent with experimental observations on asymmetric membranes. Our analysis reveals a number of previously unknown features, including a pronounced local reorientation of water molecules in the pores, and a segregation of ionic species that had not been anticipated by previously reported continuum analyses of Janus pores. Using these insights, a model is proposed for ionic current rectification in which electric leakage at the pore entrance controls net transport.
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Affiliation(s)
- Joan M. Montes de Oca
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Advanced
Materials for Energy-Water Systems (AMEWS) Energy Frontier Research
Center, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Johnson Dhanasekaran
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Advanced
Materials for Energy-Water Systems (AMEWS) Energy Frontier Research
Center, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Andrés Córdoba
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Advanced
Materials for Energy-Water Systems (AMEWS) Energy Frontier Research
Center, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Seth B. Darling
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Advanced
Materials for Energy-Water Systems (AMEWS) Energy Frontier Research
Center, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
- Chemical
Sciences and Engineering Division, Argonne
National Laboratory, Lemont, Illinois 60439, United States
| | - Juan J. de Pablo
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Advanced
Materials for Energy-Water Systems (AMEWS) Energy Frontier Research
Center, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
- Materials
Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
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Pérez-Mitta G, Toimil-Molares ME, Trautmann C, Marmisollé WA, Azzaroni O. Molecular Design of Solid-State Nanopores: Fundamental Concepts and Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1901483. [PMID: 31267585 DOI: 10.1002/adma.201901483] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/16/2019] [Indexed: 06/09/2023]
Abstract
Solid-state nanopores are fascinating objects that enable the development of specific and efficient chemical and biological sensors, as well as the investigation of the physicochemical principles ruling the behavior of biological channels. The great variety of biological nanopores that nature provides regulates not only the most critical processes in the human body, including neuronal communication and sensory perception, but also the most important bioenergetic process on earth: photosynthesis. This makes them an exhaustless source of inspiration toward the development of more efficient, selective, and sophisticated nanopore-based nanofluidic devices. The key point responsible for the vibrant and exciting advance of solid nanopore research in the last decade has been the simultaneous combination of advanced fabrication nanotechnologies to tailor the size, geometry, and application of novel and creative approaches to confer the nanopore surface specific functionalities and responsiveness. Here, the state of the art is described in the following critical areas: i) theory, ii) nanofabrication techniques, iii) (bio)chemical functionalization, iv) construction of nanofluidic actuators, v) nanopore (bio)sensors, and vi) commercial aspects. The plethora of potential applications once envisioned for solid-state nanochannels is progressively and quickly materializing into new technologies that hold promise to revolutionize the everyday life.
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Affiliation(s)
- Gonzalo Pérez-Mitta
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP) - CONICET, Diagonal 113 y 64, 1900, La Plata, Argentina
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, USA
| | | | - Christina Trautmann
- GSI Helmholtzzentrum für Schwerionenforschung, 64291, Darmstadt, Germany
- Technische Universität Darmstadt, 64287, Darmstadt, Germany
| | - Waldemar A Marmisollé
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP) - CONICET, Diagonal 113 y 64, 1900, La Plata, Argentina
| | - Omar Azzaroni
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP) - CONICET, Diagonal 113 y 64, 1900, La Plata, Argentina
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5
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Zhao S, Restrepo-Pérez L, Soskine M, Maglia G, Joo C, Dekker C, Aksimentiev A. Electro-Mechanical Conductance Modulation of a Nanopore Using a Removable Gate. ACS NANO 2019; 13:2398-2409. [PMID: 30715850 PMCID: PMC6494462 DOI: 10.1021/acsnano.8b09266] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Ion channels form the basis of information processing in living cells by facilitating the exchange of electrical signals across and along cellular membranes. Applying the same principles to man-made systems requires the development of synthetic ion channels that can alter their conductance in response to a variety of external manipulations. By combining single-molecule electrical recordings with all-atom molecular dynamics simulations, we here demonstrate a hybrid nanopore system that allows for both a stepwise change of its conductance and a nonlinear current-voltage dependence. The conductance modulation is realized by using a short flexible peptide gate that carries opposite electric charge at its ends. We show that a constant transmembrane bias can position (and, in a later stage, remove) the peptide gate right at the most-sensitive sensing region of a biological nanopore FraC, thus partially blocking its channel and producing a stepwise change in the conductance. Increasing or decreasing the bias while having the peptide gate trapped in the pore stretches or compresses the peptide within the nanopore, thus modulating its conductance in a nonlinear but reproducible manner. We envision a range of applications of this removable-gate nanopore system, e.g. from an element of biological computing circuits to a test bed for probing the elasticity of intrinsically disordered proteins.
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Affiliation(s)
- Shidi Zhao
- Center for Biophysics and Quantitative Biology, Department of Physics and Beckman Institute for Advanced Science and Technology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Laura Restrepo-Pérez
- Department of Bionanoscience, Kavli Institute of Nanoscience , Delft University of Technology , van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Misha Soskine
- Groningen Biomolecular Sciences & Biotechnology Institute , University of Groningen , 9747 AG Groningen , The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute , University of Groningen , 9747 AG Groningen , The Netherlands
| | - Chirlmin Joo
- Department of Bionanoscience, Kavli Institute of Nanoscience , Delft University of Technology , van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience , Delft University of Technology , van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, Department of Physics and Beckman Institute for Advanced Science and Technology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
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6
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Wang M, Shen W, Ding S, Wang X, Wang Z, Wang Y, Liu F. A coupled effect of dehydration and electrostatic interactions on selective ion transport through charged nanochannels. NANOSCALE 2018; 10:18821-18828. [PMID: 30277244 DOI: 10.1039/c8nr04962a] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Selective ion transport is an essential feature of biological ion channels. Due to the subnanometer size and negatively charged surface of ion channels, the ion selectivity is affected by both dehydration effects and electrostatic interactions. Their coupled effect on selective ion transport, however, has been elusive. Here, using molecular dynamics simulations, we study ion (Li+ and Mg2+) transport through subnanometer carbon nanotubes (CNTs) with varying charge densities. Our results indicate that the dehydration effect governs the ionic transport at low surface charge densities, hence the nanochannel shows a selectivity for Li+ ions. In contrast, the nanochannel switches to a selectivity for Mg2+ ions as the electrostatic interaction between the cations and the negatively charged wall dominates the transport at high surface charge densities.
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Affiliation(s)
- Mao Wang
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China.
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7
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Zhang S, Yin X, Li M, Zhang X, Zhang X, Qin X, Zhu Z, Yang S, Shao Y. Ionic Current Behaviors of Dual Nano- and Micropipettes. Anal Chem 2018; 90:8592-8599. [PMID: 29939012 DOI: 10.1021/acs.analchem.8b01765] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ionic current rectification (ICR) phenomena within dual glass pipettes are investigated for the first time. We demonstrate that the ionic flow presents different behaviors in dual nano- and micropipettes when the two channels are filled with the same electrolyte KCl and hung in air. Bare dual nanopipettes cannot rectify the ionic current because of their geometric symmetry, but the ICR can be directly observed based on bare dual micropipettes. The phenomena based on dual micropipettes could be explained by the simulation of the Poisson-Nernst-Plank equation. After modification with different approaches, the dual nanopipettes have asymmetric charge patterns and show various ICR behaviors. They have been successfully employed to fabricate various nanodevices, such as ionic diodes and bipolar junction transistors. Due to the simple and fast fabrication with high reproducibility, these dual pipettes can provide a novel platform for controlling ionic flow in nano- and microfluidics, fabrication of novel nanodevices, and detection of biomolecules.
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Affiliation(s)
- Shudong Zhang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Xiaohong Yin
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Mingzhi Li
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Xianhao Zhang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Xin Zhang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Xiaoli Qin
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Zhiwei Zhu
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Shuang Yang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Yuanhua Shao
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
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8
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Li Z, Qiu Y, Li K, Sha J, Li T, Chen Y. Optimal design of graphene nanopores for seawater desalination. J Chem Phys 2018; 148:014703. [DOI: 10.1063/1.5002746] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- Zhongwu Li
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
| | - Yinghua Qiu
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
| | - Kun Li
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
| | - Jingjie Sha
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
| | - Tie Li
- Shanghai Institute of Microsystem and Information Technology, National Key Laboratory of Microsystem Technology, State Key Lab of Transducer Technology, Shanghai 200050, China
| | - Yunfei Chen
- Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China
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Abstract
Biological molecular machines perform the work of supporting life at the smallest of scales, including the work of shuttling ions across cell boundaries and against chemical gradients. Systems of artificial channels at the nanoscale can likewise control ionic concentration by way of ionic current rectification, species selectivity, and voltage gating mechanisms. Here, we theoretically show that a voltage-gated, ion species-selective, and rectifying ion channel can be built using the components of a biological water channel aquaporin. Through all-atom molecular dynamics simulations, we show that the ionic conductance of a truncated aquaporin channel nonlinearly increases with the bias magnitude, depends on the channel's orientation, and is highly cation specific but only for one polarity of the transmembrane bias. Further, we show that such an unusually complex response of the channel to transmembrane bias arises from mechanical motion of a positively charged gate that blocks cation transport. By combining two truncated aquaporins, we demonstrate a molecular system that pumps ions against their chemical gradients when subject to an alternating transmembrane bias. Our work sets the stage for future biomimicry efforts directed toward reproducing the function of biological ion pumps using synthetic components.
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10
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Restrepo-Pérez L, John S, Aksimentiev A, Joo C, Dekker C. SDS-assisted protein transport through solid-state nanopores. NANOSCALE 2017; 9:11685-11693. [PMID: 28776058 PMCID: PMC5611827 DOI: 10.1039/c7nr02450a] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Using nanopores for single-molecule sequencing of proteins - similar to nanopore-based sequencing of DNA - faces multiple challenges, including unfolding of the complex tertiary structure of the proteins and enforcing their unidirectional translocation through nanopores. Here, we combine molecular dynamics (MD) simulations with single-molecule experiments to investigate the utility of SDS (Sodium Dodecyl Sulfate) to unfold proteins for solid-state nanopore translocation, while simultaneously endowing them with a stronger electrical charge. Our simulations and experiments prove that SDS-treated proteins show a considerable loss of the protein structure during the nanopore translocation. Moreover, SDS-treated proteins translocate through the nanopore in the direction prescribed by the electrophoretic force due to the negative charge impaired by SDS. In summary, our results suggest that SDS causes protein unfolding while facilitating protein translocation in the direction of the electrophoretic force; both characteristics being advantageous for future protein sequencing applications using solid-state nanopores.
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Affiliation(s)
- Laura Restrepo-Pérez
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands.
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Yao H, Zeng J, Zhai P, Li Z, Cheng Y, Liu J, Mo D, Duan J, Wang L, Sun Y, Liu J. Large Rectification Effect of Single Graphene Nanopore Supported by PET Membrane. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11000-11008. [PMID: 28262018 DOI: 10.1021/acsami.6b16736] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Graphene is an ideal candidate for the development of solid state nanopores due to its thickness at the atomic scale and its high chemical and mechanical stabilities. A facile method was adopted to prepare single graphene nanopore supported by PET membrane (G/PET nanopore) within the three steps assisted by the swift heavy ion irradiation and asymmetric etching technology. The inversion of the ion rectification effect was confirmed in G/PET nanopore while comparing with bare PET nanopore in KCl electrolyte solution. By modifying the wall charge state of PET conical nanopore with hydrochloric acid from negative to positive, the ion rectification effect of G/PET nanopore was found to be greatly enhanced and the large rectification ratio up to 190 was obtained during this work. Moreover, the high ionic flux and high ion separation efficiency was also observed in the G/PET nanopore system. By comparing the "on" and "off" state conductance of G/PET nanopore while immersed in the solution with pH value lower than the isoelectric point of the etched PET (IEP, pH = 3.8), the voltage dependence of the off conductance was established and it was confirmed that the large rectification effect was strongly dependent on the particularly low off conductance at higher applied voltage.
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Affiliation(s)
- Huijun Yao
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Jian Zeng
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Pengfei Zhai
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Zongzhen Li
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Yaxiong Cheng
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Jiande Liu
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Dan Mo
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Jinglai Duan
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Lanxi Wang
- Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics , Feiyan Street 100, Lanzhou 730000, China
| | - Youmei Sun
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
| | - Jie Liu
- Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China
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