51
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Willems K, Ruić D, L R Lucas F, Barman U, Verellen N, Hofkens J, Maglia G, Van Dorpe P. Accurate modeling of a biological nanopore with an extended continuum framework. NANOSCALE 2020; 12:16775-16795. [PMID: 32780087 DOI: 10.1039/d0nr03114c] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Despite the broad success of biological nanopores as powerful instruments for the analysis of proteins and nucleic acids at the single-molecule level, a fast simulation methodology to accurately model their nanofluidic properties is currently unavailable. This limits the rational engineering of nanopore traits and makes the unambiguous interpretation of experimental results challenging. Here, we present a continuum approach that can faithfully reproduce the experimentally measured ionic conductance of the biological nanopore Cytolysin A (ClyA) over a wide range of ionic strengths and bias potentials. Our model consists of the extended Poisson-Nernst-Planck and Navier-Stokes (ePNP-NS) equations and a computationally efficient 2D-axisymmetric representation for the geometry and charge distribution of the nanopore. Importantly, the ePNP-NS equations achieve this accuracy by self-consistently considering the finite size of the ions and the influence of both the ionic strength and the nanoscopic scale of the pore on the local properties of the electrolyte. These comprise the mobility and diffusivity of the ions, and the density, viscosity and relative permittivity of the solvent. Crucially, by applying our methodology to ClyA, a biological nanopore used for single-molecule enzymology studies, we could directly quantify several nanofluidic characteristics difficult to determine experimentally. These include the ion selectivity, the ion concentration distributions, the electrostatic potential landscape, the magnitude of the electro-osmotic flow field, and the internal pressure distribution. Hence, this work provides a means to obtain fundamental new insights into the nanofluidic properties of biological nanopores and paves the way towards their rational engineering.
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Affiliation(s)
- Kherim Willems
- KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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52
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Xu L, Chen LY. Identification of a New Allosteric Binding Site for Cocaine in Dopamine Transporter. J Chem Inf Model 2020; 60:3958-3968. [PMID: 32649824 PMCID: PMC7484383 DOI: 10.1021/acs.jcim.0c00346] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Dopamine (DA) transporter (DAT) is a major target for psychostimulant drugs of abuse such as cocaine that competitively binds to DAT, inhibits DA reuptake, and consequently increases synaptic DA levels. In addition to the central binding site inside DAT, the available experimental evidence suggests the existence of alternative binding sites on DAT, but detection and characterization of these sites are challenging by experiments alone. Here, we integrate multiple computational approaches to probe the potential binding sites on the wild-type Drosophila melanogaster DAT and identify a new allosteric site that displays high affinity for cocaine. This site is located on the surface of DAT, and binding of cocaine is primarily dominated by interactions with hydrophobic residues surrounding the site. We show that cocaine binding to this new site allosterically reduces the binding of DA/cocaine to the central binding pocket, and simultaneous binding of two cocaine molecules to a single DAT seems infeasible. Furthermore, we find that binding of cocaine to this site stabilizes the conformation of DAT but alters the conformational population and thereby reduces the accessibility by DA, providing molecular insights into the inhibitory mechanism of cocaine. In addition, our results indicate that the conformations induced by cocaine binding to this site may be relevant to the oligomerization of DAT, highlighting a potential role of this new site in modulating the function of DAT.
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Affiliation(s)
- Liang Xu
- Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
| | - Liao Y Chen
- Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
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53
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Botet-Carreras A, Montero MT, Sot J, Domènech Ò, Borrell JH. Characterization of monolayers and liposomes that mimic lipid composition of HeLa cells. Colloids Surf B Biointerfaces 2020; 196:111288. [PMID: 32759004 DOI: 10.1016/j.colsurfb.2020.111288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/20/2020] [Accepted: 07/27/2020] [Indexed: 10/23/2022]
Abstract
In this work, based on several studies, we develop an artificial lipid membrane to mimic the HeLa cell membrane using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS) and cholesterol (CHOL). This is then a means to further study the fusion process of specific engineered liposomes. To characterize the mimicked HeLa cell membrane, we determined a series of surface pressure-area (π-A) isotherms and the isothermal compression modulus was calculated together with the dipole moment normal to the plane of the monolayer. The existence of laterally segregated domains was assessed using a fluorescence technique (Laurdan) and two microscopy techniques: Brewster angle microscopy (BAM) and atomic force microscopy (AFM) of Langmuir-Blodgett films (LBs) extracted at 30 mN m-1. To examine the nature and composition of the observed domains, force spectroscopy (FS) based on AFM was applied to the LBs. Finally, two engineered liposome formulations were tested in a fusion assay against mimicked HeLa cell membrane LBs, showing good results and thereby opening the door to further assays and uses.
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Affiliation(s)
- Adrià Botet-Carreras
- Secció de Fisicoquímica, Facultat de Farmàcia i Ciències de l'Alimentació, Spain; Institute of Nanoscience and Nanotechnology (IN(2)UB), Universitat de Barcelona (UB), 08028, Barcelona, Catalonia, Spain
| | - M Teresa Montero
- Secció de Fisicoquímica, Facultat de Farmàcia i Ciències de l'Alimentació, Spain; Institute of Nanoscience and Nanotechnology (IN(2)UB), Universitat de Barcelona (UB), 08028, Barcelona, Catalonia, Spain
| | - Jesús Sot
- Instituto Biofisika (CSIC-UPV/HEU, Campus Universitario, 48940, Leioa, Basque Country, Spain
| | - Òscar Domènech
- Secció de Fisicoquímica, Facultat de Farmàcia i Ciències de l'Alimentació, Spain; Institute of Nanoscience and Nanotechnology (IN(2)UB), Universitat de Barcelona (UB), 08028, Barcelona, Catalonia, Spain
| | - Jordi H Borrell
- Secció de Fisicoquímica, Facultat de Farmàcia i Ciències de l'Alimentació, Spain; Institute of Nanoscience and Nanotechnology (IN(2)UB), Universitat de Barcelona (UB), 08028, Barcelona, Catalonia, Spain.
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54
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Leronni A, Bardella L, Dorfmann L, Pietak A, Levin M. On the coupling of mechanics with bioelectricity and its role in morphogenesis. J R Soc Interface 2020; 17:20200177. [PMID: 32486953 DOI: 10.1098/rsif.2020.0177] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The role of endogenous bioelectricity in morphogenesis has recently been explored through the finite volume-based code BioElectric Tissue Simulation Engine. We extend this platform to electrostatic and osmotic forces due to bioelectrical ion fluxes, causing cell cluster deformation. We further account for mechanosensitive ion channels, which, gated by membrane tension, modulate ion fluxes and, ultimately, bioelectrical forces. We illustrate the potentialities of this combined model of actuation and sensing with reference to cancer progression, osmoregulation, symmetry breaking and long-range signalling. This suggests control strategies for the manipulation of cell networks in vivo.
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Affiliation(s)
- A Leronni
- Department of Civil, Environmental, Architectural Engineering and Mathematics, University of Brescia, 25123 Brescia, Italy
| | - L Bardella
- Department of Civil, Environmental, Architectural Engineering and Mathematics, University of Brescia, 25123 Brescia, Italy
| | - L Dorfmann
- Department of Civil and Environmental Engineering, Tufts University, Medford, MA 02155, USA.,Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA
| | - A Pietak
- Allen Discovery Center, Tufts University, Medford, MA 02155, USA
| | - M Levin
- Allen Discovery Center, Tufts University, Medford, MA 02155, USA
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55
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Danelius E, Poongavanam V, Peintner S, Wieske LHE, Erdélyi M, Kihlberg J. Solution Conformations Explain the Chameleonic Behaviour of Macrocyclic Drugs. Chemistry 2020; 26:5231-5244. [DOI: 10.1002/chem.201905599] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Indexed: 02/02/2023]
Affiliation(s)
- Emma Danelius
- Department of Chemistry-BMCUppsala University 75123 Uppsala Sweden
| | | | - Stefan Peintner
- Department of Chemistry-BMCUppsala University 75123 Uppsala Sweden
| | | | - Máté Erdélyi
- Department of Chemistry-BMCUppsala University 75123 Uppsala Sweden
| | - Jan Kihlberg
- Department of Chemistry-BMCUppsala University 75123 Uppsala Sweden
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56
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Peng C, Atilaw Y, Wang J, Xu Z, Poongavanam V, Shi J, Kihlberg J, Zhu W, Erdélyi M. Conformation of the Macrocyclic Drug Lorlatinib in Polar and Nonpolar Environments: A MD Simulation and NMR Study. ACS OMEGA 2019; 4:22245-22250. [PMID: 31891108 PMCID: PMC6933765 DOI: 10.1021/acsomega.9b03797] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 11/26/2019] [Indexed: 05/02/2023]
Abstract
The replica exchange molecular dynamics (REMD) simulation is demonstrated to readily predict the conformations of the macrocyclic drug lorlatinib, as validated by solution NMR studies. In aqueous solution, lorlatinib adopts a conformer identical to its target bound structure. This conformer is stabilized by an extensive hydrogen bond network to the solvents. In chloroform, lorlatinib populates two conformers with the second one being less polar, which may contribute to lorlatinib's ability to cross cell membranes.
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Affiliation(s)
- Cheng Peng
- Drug
Discovery and Design Center; CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy
of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
- University
of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China
| | - Yoseph Atilaw
- Department
of Chemistry-BMC, Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
| | - Jinan Wang
- Drug
Discovery and Design Center; CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy
of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Zhijian Xu
- Drug
Discovery and Design Center; CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy
of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
- University
of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China
| | | | - Jiye Shi
- Drug
Discovery and Design Center; CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy
of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Jan Kihlberg
- Department
of Chemistry-BMC, Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
| | - Weiliang Zhu
- Drug
Discovery and Design Center; CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy
of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
- University
of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China
- E-mail: (W.Z.)
| | - Máté Erdélyi
- Department
of Chemistry-BMC, Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
- E-mail: (M.E.)
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57
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Osella S, Knippenberg S. Laurdan as a Molecular Rotor in Biological Environments. ACS APPLIED BIO MATERIALS 2019; 2:5769-5778. [DOI: 10.1021/acsabm.9b00789] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Silvio Osella
- Chemical and Biological Systems Simulation Lab, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
| | - Stefan Knippenberg
- RCPTM, Department of Physical Chemistry, Fac. Sciences, Palacký University, 771 46 Olomouc, Czech Republic
- Theoretical Physics, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
- Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden
- Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
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58
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Checa M, Millan-Solsona R, Blanco N, Torrents E, Fabregas R, Gomila G. Mapping the dielectric constant of a single bacterial cell at the nanoscale with scanning dielectric force volume microscopy. NANOSCALE 2019; 11:20809-20819. [PMID: 31657419 DOI: 10.1039/c9nr07659j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mapping the dielectric constant at the nanoscale of samples showing a complex topography, such as non-planar nanocomposite materials or single cells, poses formidable challenges to existing nanoscale dielectric microscopy techniques. Here we overcome these limitations by introducing Scanning Dielectric Force Volume Microscopy. This scanning probe microscopy technique is based on the acquisition of electrostatic force approach curves at every point of a sample and its post-processing and quantification by using a computational model that incorporates the actual measured sample topography. The technique provides quantitative nanoscale images of the local dielectric constant of the sample with unparalleled accuracy, spatial resolution and statistical significance, irrespectively of the complexity of its topography. We illustrate the potential of the technique by presenting a nanoscale dielectric constant map of a single bacterial cell, including its small-scale appendages. The bacterial cell shows three characteristic equivalent dielectric constant values, namely, εr,bac1 = 2.6 ± 0.2, εr,bac2 = 3.6 ± 0.4 and εr,bac3 = 4.9 ± 0.5, which enable identifying different dielectric properties of the cell wall and of the cytoplasmatic region, as well as, the existence of variations in the dielectric constant along the bacterial cell wall itself. Scanning Dielectric Force Volume Microscopy is expected to have an important impact in Materials and Life Sciences where the mapping of the dielectric properties of samples showing complex nanoscale topographies is often needed.
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Affiliation(s)
- Martí Checa
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology, c/Baldiri i Reixac 11-15, 08028, Barcelona, Spain. and Departament d'Enginyeria Electrònica i Biomèdica, Universitat de Barcelona, c/Martí i Franquès 1, 08028, Barcelona, Spain
| | - Ruben Millan-Solsona
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology, c/Baldiri i Reixac 11-15, 08028, Barcelona, Spain. and Departament d'Enginyeria Electrònica i Biomèdica, Universitat de Barcelona, c/Martí i Franquès 1, 08028, Barcelona, Spain
| | - Nuria Blanco
- Bacterial Infections: Antimicrobial Therapies, Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology, c/Baldiri i Reixac 11-15, 08028, Barcelona
| | - Eduard Torrents
- Bacterial Infections: Antimicrobial Therapies, Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology, c/Baldiri i Reixac 11-15, 08028, Barcelona
| | - Rene Fabregas
- Departament d'Enginyeria Electrònica i Biomèdica, Universitat de Barcelona, c/Martí i Franquès 1, 08028, Barcelona, Spain
| | - Gabriel Gomila
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology, c/Baldiri i Reixac 11-15, 08028, Barcelona, Spain. and Departament d'Enginyeria Electrònica i Biomèdica, Universitat de Barcelona, c/Martí i Franquès 1, 08028, Barcelona, Spain
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59
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Cheong LZ, Zhao W, Song S, Shen C. Lab on a tip: Applications of functional atomic force microscopy for the study of electrical properties in biology. Acta Biomater 2019; 99:33-52. [PMID: 31425893 DOI: 10.1016/j.actbio.2019.08.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/17/2019] [Accepted: 08/13/2019] [Indexed: 12/11/2022]
Abstract
Electrical properties, such as charge propagation, dielectrics, surface potentials, conductivity, and piezoelectricity, play crucial roles in biomolecules, biomembranes, cells, tissues, and other biological samples. However, characterizing these electrical properties in delicate biosamples is challenging. Atomic Force Microscopy (AFM), the so called "Lab on a Tip" is a powerful and multifunctional approach to quantitatively study the electrical properties of biological samples at the nanometer level. Herein, the principles, theories, and achievements of various modes of AFM in this area have been reviewed and summarized. STATEMENT OF SIGNIFICANCE: Electrical properties such as dielectric and piezoelectric forces, charge propagation behaviors play important structural and functional roles in biosystems from the single molecule level, to cells and tissues. Atomic force microscopy (AFM) has emerged as an ideal toolkit to study electrical property of biology. Herein, the basic principles of AFM are described. We then discuss the multiple modes of AFM to study the electrical properties of biological samples, including Electrostatic Force Microscopy (EFM), Kelvin Probe Force Microscopy (KPFM), Conductive Atomic Force Microscopy (CAFM), Piezoresponse Force Microscopy (PFM) and Scanning ElectroChemical Microscopy (SECM). Finally, the outlook, prospects, and challenges of the various AFM modes when studying the electrical behaviour of the samples are discussed.
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60
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Godoy-Hernandez A, Tate DJ, McMillan DGG. Revealing the Membrane-Bound Catalytic Oxidation of NADH by the Drug Target Type-II NADH Dehydrogenase. Biochemistry 2019; 58:4272-4275. [PMID: 31592658 PMCID: PMC6812066 DOI: 10.1021/acs.biochem.9b00752] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
Type-II NADH:quinone
oxidoreductases (NDH-2s) are an important
element of microbial pathogen electron transport chains and an attractive
drug target. Despite being widely studied, its mechanism and catalysis
are still poorly understood in a hydrophobic membrane environment.
A recent report for the Escherichia coli NDH-2 showed
NADH oxidation in a solution-based assay but apparently showed the
reverse reaction in electrochemical studies, calling into question
the validity of the electrochemical approach. Here we report electrochemical
catalysis in the well-studied NDH-2 from Caldalkalibacillus
thermarum (CthNDH-2). In agreement with
previous reports, we demonstrated CthNDH-2 NADH oxidation
in a solution assay and electrochemical assays revealed a system artifact
in the absence of quinone that was absent in a membrane system. However,
in the presence of either immobilized quinone or mobile quinone in
a membrane, NADH oxidation was observed as in solution-phase assays.
This conclusively establishes surface-based electrochemistry as a
viable approach for interrogating electron transfer chain drug targets.
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Affiliation(s)
- Albert Godoy-Hernandez
- Department of Biotechnology , Delft University of Technology , Van der Maasweg 9 , Delft 2629 HZ , The Netherlands
| | - Daniel J Tate
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
| | - Duncan G G McMillan
- Department of Biotechnology , Delft University of Technology , Van der Maasweg 9 , Delft 2629 HZ , The Netherlands.,Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , Tokyo 113-8656 , Japan
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61
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Zandi A, Gilani A, Abbasvandi F, Katebi P, Tafti SR, Assadi S, Moghtaderi H, Parizi MS, Saghafi M, Khayamian MA, Davari sh Z, Hoseinpour P, Gity M, Sanati H, Abdolahad M. Carbon nanotube based dielectric spectroscopy of tumor secretion; electrochemical lipidomics for cancer diagnosis. Biosens Bioelectron 2019; 142:111566. [DOI: 10.1016/j.bios.2019.111566] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 01/08/2023]
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62
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Double layer electrostatics of heterogeneous surfaces with circle phase contours. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.123606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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63
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Dols-Perez A, Marin V, Amador GJ, Kieffer R, Tam D, Aubin-Tam ME. Artificial Cell Membranes Interfaced with Optical Tweezers: A Versatile Microfluidics Platform for Nanomanipulation and Mechanical Characterization. ACS APPLIED MATERIALS & INTERFACES 2019; 11:33620-33627. [PMID: 31448892 PMCID: PMC6753654 DOI: 10.1021/acsami.9b09983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Cell lipid membranes are the site of vital biological processes, such as motility, trafficking, and sensing, many of which involve mechanical forces. Elucidating the interplay between such bioprocesses and mechanical forces requires the use of tools that apply and measure piconewton-level forces, e.g., optical tweezers. Here, we introduce the combination of optical tweezers with free-standing lipid bilayers, which are fully accessible on both sides of the membrane. In the vicinity of the lipid bilayer, optical trapping would normally be impossible due to optical distortions caused by pockets of the solvent trapped within the membrane. We solve this by drastically reducing the size of these pockets via tuning of the solvent and flow cell material. In the resulting flow cells, lipid nanotubes are straightforwardly pushed or pulled and reach lengths above half a millimeter. Moreover, the controlled pushing of a lipid nanotube with an optically trapped bead provides an accurate and direct measurement of important mechanical properties. In particular, we measure the membrane tension of a free-standing membrane composed of a mixture of dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) to be 4.6 × 10-6 N/m. We demonstrate the potential of the platform for biophysical studies by inserting the cell-penetrating trans-activator of transcription (TAT) peptide in the lipid membrane. The interactions between the TAT peptide and the membrane are found to decrease the value of the membrane tension to 2.1 × 10-6 N/m. This method is also fully compatible with electrophysiological measurements and presents new possibilities for the study of membrane mechanics and the creation of artificial lipid tube networks of great importance in intra- and intercellular communication.
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Affiliation(s)
- Aurora Dols-Perez
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Victor Marin
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Guillermo J. Amador
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
- Laboratory
for Aero and Hydrodynamics, Delft University
of Technology, Delft 2628 CD, The Netherlands
| | - Roland Kieffer
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Daniel Tam
- Laboratory
for Aero and Hydrodynamics, Delft University
of Technology, Delft 2628 CD, The Netherlands
| | - Marie-Eve Aubin-Tam
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
- E-mail: (M.A.)
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64
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Das S, Carmona A, Khatua K, Porcaro F, Somogyi A, Ortega R, Datta A. Manganese Mapping Using a Fluorescent Mn 2+ Sensor and Nanosynchrotron X-ray Fluorescence Reveals the Role of the Golgi Apparatus as a Manganese Storage Site. Inorg Chem 2019; 58:13724-13732. [PMID: 31503472 DOI: 10.1021/acs.inorgchem.9b01389] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Elucidating dynamics in transition-metal distribution and localization under physiological and pathophysiological conditions is central to our understanding of metal-ion regulation. In this Forum Article, we focus on manganese and specifically recent developments that point to the relevance of the Golgi apparatus in manganese detoxification when this essential metal ion is overaccumulated because of either environmental exposure or mutations in manganese efflux transporters. In order to further evaluate the role of the Golgi apparatus as a manganese-ion storage compartment under subcytotoxic manganese levels, we use a combination of confocal microscopy using a sensitive "turn-on" fluorescent manganese sensor, M1, and nanosynchrotron X-ray fluorescence imaging to show that manganese ions are stored in the Golgi apparatus under micromolar manganese exposure concentrations. Our results, along with previous reports on manganese accumulation, now indicate a central role of the Golgi apparatus in manganese storage and trafficking under subcytotoxic manganese levels and hint toward a possible role of the Golgi apparatus in manganese storage even under physiological conditions.
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Affiliation(s)
- Sayani Das
- Department of Chemical Sciences , Tata Institute of Fundamental Research , 1 Homi Bhabha Road , Colaba, Mumbai 400005 , India
| | - Asuncion Carmona
- Chemical Imaging and Speciation , CENBG, University of Bordeaux, UMR 5797 , 33175 Gradignan , France.,CNRS, IN2P3, CENBG, UMR 5797 , 33175 Gradignan , France
| | - Kaustav Khatua
- Department of Chemical Sciences , Tata Institute of Fundamental Research , 1 Homi Bhabha Road , Colaba, Mumbai 400005 , India
| | - Francesco Porcaro
- Chemical Imaging and Speciation , CENBG, University of Bordeaux, UMR 5797 , 33175 Gradignan , France.,CNRS, IN2P3, CENBG, UMR 5797 , 33175 Gradignan , France
| | - Andrea Somogyi
- Nanoscopium Synchrotron SOLEIL Saint-Aubin , 91192 Gif-sur-Yvette Cedex , France
| | - Richard Ortega
- Chemical Imaging and Speciation , CENBG, University of Bordeaux, UMR 5797 , 33175 Gradignan , France.,CNRS, IN2P3, CENBG, UMR 5797 , 33175 Gradignan , France
| | - Ankona Datta
- Department of Chemical Sciences , Tata Institute of Fundamental Research , 1 Homi Bhabha Road , Colaba, Mumbai 400005 , India
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65
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Gnandt D, Koslowski T. Long-range electron-electron interaction and charge transfer in protein complexes: a numerical approach. Phys Chem Chem Phys 2019; 21:18595-18604. [PMID: 31414082 DOI: 10.1039/c9cp03141c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
With application to the nitrite reductase hexameric protein complex of Desulfovibrio vulgaris, NrfH2A4, we suggest a strategy to compute the energy landscape of electron transfer in large systems of biochemical interest. For small complexes, the energy of all electronic configurations can be scanned completely on the level of a numerical solution of the Poisson-Boltzmann equation. In contrast, larger systems have to be treated using a pair approximation, which is verified here. Effective Coulomb interactions between neighbouring sites of excess electron localization may become as large as 200 meV, and they depend in a nontrivial manner on the intersite distance. We discuss the implications of strong Coulomb interactions on the thermodynamics and kinetics of charging and decharging a protein complex. Finally, we turn to the effect of embedding the system into a biomembrane.
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Affiliation(s)
- David Gnandt
- Institut für Physikalische Chemie, Universität Freiburg, Albertstraße 23a, 79104 Freiburg im Breisgau, Germany.
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66
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Borden MA. Intermolecular Forces Model for Lipid Microbubble Shells. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:10042-10051. [PMID: 30543753 DOI: 10.1021/acs.langmuir.8b03641] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Lipid-coated microbubbles are currently used clinically as ultrasound contrast agents for echocardiography and radiology and are being developed for many new diagnostic and therapeutic applications. Accordingly, there is a growing need to engineer specific formulations by employing rational design to guide lipid selection and processing. This approach requires a quantitative relationship between lipid chemistry and interfacial properties of the microbubble shell. Just such a model is proposed here on the basis of lateral Coulomb and van der Waals interactions between lipid head- and tailgroups, using previous coarse graining and force fields developed for molecular dynamics simulations. The model predicts with sufficient accuracy the monolayer permeability, the elasticity as a function of either lipid composition or temperature, and the equilibrium spreading surface tension of the lipid onto an air/water interface. In the future, the intermolecular forces model could be employed to elucidate more complex phenomena and to engineer novel microbubble formulations.
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Affiliation(s)
- Mark Andrew Borden
- Mechanical Engineering , University of Colorado , Boulder , Colorado 80309-0427 , United States
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67
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Faizi HA, Frey SL, Steinkühler J, Dimova R, Vlahovska PM. Bending rigidity of charged lipid bilayer membranes. SOFT MATTER 2019; 15:6006-6013. [PMID: 31298256 DOI: 10.1039/c9sm00772e] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We experimentally investigate the effect of lipid charge on the stiffness of bilayer membranes. The bending rigidity of membranes with composition 0-100 mol% of charged lipids, in the absence and presence of salt at different concentrations, is measured with the flicker spectroscopy method, using the shape fluctuations of giant unilamellar vesicles. The analysis considers both the mean squared amplitudes and the time autocorrelations of the shape modes. Our results show that membrane charge increases the bending rigidity relative to the charge-free membrane. The effect is diminished by the addition of monovalent salt to the suspending solutions. The trend shown by the membrane bending rigidity correlates with zeta potential measurements, confirming charge screening at different salt concentrations. The experimental results in the presence of salt are in good agreement with existing theories of membrane stiffening by surface charge.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA
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68
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Heo P, Ramakrishnan S, Coleman J, Rothman JE, Fleury JB, Pincet F. Highly Reproducible Physiological Asymmetric Membrane with Freely Diffusing Embedded Proteins in a 3D-Printed Microfluidic Setup. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1900725. [PMID: 30977975 DOI: 10.1002/smll.201900725] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/28/2019] [Indexed: 06/09/2023]
Abstract
Experimental setups to produce and to monitor model membranes have been successfully used for decades and brought invaluable insights into many areas of biology. However, they all have limitations that prevent the full in vitro mimicking and monitoring of most biological processes. Here, a suspended physiological bilayer-forming chip is designed from 3D-printing techniques. This chip can be simultaneously integrated to a confocal microscope and a path-clamp amplifier. It is composed of poly(dimethylsiloxane) and consists of a ≈100 µm hole, where the horizontal planar bilayer is formed, connecting two open crossed-channels, which allows for altering of each lipid monolayer separately. The bilayer, formed by the zipping of two lipid leaflets, is free-standing, horizontal, stable, fluid, solvent-free, and flat with the 14 types of physiologically relevant lipids, and the bilayer formation process is highly reproducible. Because of the two channels, asymmetric bilayers can be formed by making the two lipid leaflets of different composition. Furthermore, proteins, such as transmembrane, peripheral, and pore-forming proteins, can be added to the bilayer in controlled orientation and keep their native mobility and activity. These features allow in vitro recapitulation of membrane process close to physiological conditions.
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Affiliation(s)
- Paul Heo
- Laboratoire de Physique de l'Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Université Sorbonne Paris Cité, Paris, 75005, France
| | - Sathish Ramakrishnan
- Laboratoire de Physique de l'Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Université Sorbonne Paris Cité, Paris, 75005, France
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, 06510, USA
| | - Jeff Coleman
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, 06510, USA
| | - James E Rothman
- Ecole Normale Supérieure, PSL University, Paris, 75005, France
| | - Jean-Baptiste Fleury
- Department of Experimental Physics and Center for Biophysics, Saarland University, Saarbruecken, D-66123, Germany
| | - Frederic Pincet
- Laboratoire de Physique de l'Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Université Sorbonne Paris Cité, Paris, 75005, France
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69
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Hu SK, Lo FY, Hsieh CC, Chao L. Sensing Ability and Formation Criterion of Fluid Supported Lipid Bilayer Coated Graphene Field-Effect Transistors. ACS Sens 2019; 4:892-899. [PMID: 30817891 DOI: 10.1021/acssensors.8b01623] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Supported lipid bilayers (SLBs) have been widely used to provide native environments for membrane protein studies. In this study, we utilized graphene field-effect transistors (GFETs) coated with a fluid SLB to perform label-free detection of membrane-associated ligand-receptor interactions in their native lipid bilayer environment. It is known that the analyte-binding event needs to occur within the Debye length for it to be significantly sensed by an FET sensor. However, the thickness of a lipid bilayer is around 4-5-nm-thick, which is larger than the Debye length of a solution with physiologically relevant ionic strength. There is thus a question of whether an FET sensor can detect the binding event above the bilayer. In this study, we show how the existence of an SLB can influence the effective detection distance and the formation criterion of a fluid and continuous SLB on a graphene surface. We discovered that the water intercalation between the graphene and the underlying silica substrate hinders the SLB formation but is required for the stable electrical recording by a GFET. To verify the existence of a fluid SLB on graphene, which was previously complicated by the graphene fluorescence quenching effect, we developed a modified fluorescence recovery after photobleaching method. In addition, our results showed that SLB coated GFETs can quantitatively detect ligand binding onto the receptors embedded in the SLBs. The comparison of our experimental data with a theoretical model shows that the contribution of the SLB acyl chain hydrophobic region to the screening effect can be negligible and, therefore, that the effective detection region can extend beyond the SLB.
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Affiliation(s)
- Shu-Kai Hu
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
| | - Fang-Yen Lo
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
| | - Chih-Chen Hsieh
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
| | - Ling Chao
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
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70
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AFM-Based Characterization of Electrical Properties of Materials. Methods Mol Biol 2019. [PMID: 29956229 DOI: 10.1007/978-1-4939-8591-3_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Capabilities of atomic force microscopy (AFM) for characterization of local electrical properties of materials are presented in this chapter. At the beginning the probe-sample force interactions, which are employed for detection of surface topography and materials properties, are described theoretically in their application in different AFM modes and electrical techniques. The electrical techniques, which are based on detection of electrostatic probe-sample forces, are outlined in AFM contact and oscillatory resonant modes. The basic features of the detection of surface potential and capacitance gradients are explained. The applications of these techniques are illustrated on metals, surfactant compounds, semiconductors, and different polymers. Practical recommendations on use of the AFM-based electrical methods and the related challenges are given in the last section.
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71
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Gramse G, Schönhals A, Kienberger F. Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy. NANOSCALE 2019; 11:4303-4309. [PMID: 30778459 PMCID: PMC6457197 DOI: 10.1039/c8nr05880f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 02/02/2019] [Indexed: 06/09/2023]
Abstract
We investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz. The results of our nanoscale dielectric images and spectra of bacteriorhodopsin (bR) reveal Debye relaxations with time constants of τ ∼ 2 ns and τ ∼ 100 ns being characteristic of the dipole moments of the bR retinal and α-helices, respectively. However, the dipole mobility and therefore the protein biophysical function depend critically on the amount of surface water surrounding the protein, and the characteristic mobility in the secondary structure is only observed for humidity levels <30%. Our results have been achieved by adding the frequency as a second fundamental dimension to quantitative dielectric microscopy. The key elements for the success of this advanced technique are the employed heterodyne detection scheme, the broadband electrical signal source, a high frequency optimized cabling, development of calibration procedures and precise finite element modelling. Our study demonstrates the exciting possibilities of broadband dielectric microscopy for the investigation of dynamic processes in cell bioelectricity at the individual molecular level. Furthermore, the technique may shed light on local dynamic processes in related materials science applications like semiconductor research or nano-electronics.
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Affiliation(s)
- Georg Gramse
- Johannes Kepler University, Biophysics Institute, Gruberstr. 40, 4020 Linz, Austria.
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72
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Effect of cholesterol on monolayer structure of different acyl chained phospholipids. Colloids Surf B Biointerfaces 2019; 174:374-383. [DOI: 10.1016/j.colsurfb.2018.11.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 11/01/2018] [Accepted: 11/19/2018] [Indexed: 02/02/2023]
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73
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Watanabe N, Goto Y, Suga K, Nyholm TKM, Slotte JP, Umakoshi H. Solvatochromic Modeling of Laurdan for Multiple Polarity Analysis of Dihydrosphingomyelin Bilayer. Biophys J 2019; 116:874-883. [PMID: 30819567 DOI: 10.1016/j.bpj.2019.01.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 01/17/2019] [Accepted: 01/28/2019] [Indexed: 01/28/2023] Open
Abstract
The hydration properties of the interface between lipid bilayers and bulk water are important for determining membrane characteristics. Here, the emission properties of a solvent-sensitive fluorescence probe, 6-lauroyl-2-dimethylamino naphthalene (Laurdan), were evaluated in lipid bilayer systems composed of the sphingolipids D-erythro-N-palmitoyl-sphingosylphosphorylcholine (PSM) and D-erythro-N-palmitoyl-dihydrosphingomyelin (DHPSM). The glycerophospholipids 1-palmitoyl-2-palmitoyl-sn-glycero-3-phosphocholine and 1-oleoyl-2-oleoyl-sn-glycero-3-phosphocholine were used as controls. The fluorescence properties of Laurdan in sphingolipid bilayers indicated multiple excited states according to the results obtained from the emission spectra, fluorescence anisotropy, and the center-of-mass spectra during the decay time. Deconvolution of the Laurdan emission spectra into four components based on the solvent model enabled us to identify the varieties of hydration and the configurational states derived from intermolecular hydrogen bonding in sphingolipids. Sphingolipids showed specific, interfacial hydration properties stemming from their intra- and intermolecular hydrogen bonds. Particularly, the Laurdan in DHPSM revealed more hydrated properties compared to PSM, even though DHPSM has a higher Tm than PSM. Because DHPSM forms hydrogen bonds with water molecules (in 2NH configurational functional groups), the interfacial region of the DHPSM bilayer was expected to be in a highly polar environment. The careful analysis of Laurdan emission spectra through the four-component deconvolution in this study provides important insights for understanding the multiple polarity in the lipid membrane.
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Affiliation(s)
- Nozomi Watanabe
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Yuka Goto
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Keishi Suga
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Thomas K M Nyholm
- Department of Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - J Peter Slotte
- Department of Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Hiroshi Umakoshi
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
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74
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Caron G, Kihlberg J, Ermondi G. Intramolecular hydrogen bonding: An opportunity for improved design in medicinal chemistry. Med Res Rev 2019; 39:1707-1729. [PMID: 30659634 DOI: 10.1002/med.21562] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 12/18/2018] [Accepted: 12/19/2019] [Indexed: 12/14/2022]
Abstract
Recent literature shows that intramolecular hydrogen bond (IMHB) formation can positively impact upon the triad of permeability, solubility, and potency of drugs and candidates. IMHB modulation can be applied to compounds in any chemical space as a means for discovering drug candidates with both acceptable potency and absorption, distribution, metabolism, and excretion-Tox profiles. Integrating IMHB formation in design of drugs is, therefore, an exciting and timely challenge for modern medicinal chemistry. In this review, we first provide some background about IMHBs from the medicinal chemist's point of view and highlight some IMHB-associated misconceptions. Second, we propose a classification of IMHBs for drug discovery purposes, review the most common in silico tactics to include IMHBs in lead optimization and list some experimental physicochemical descriptors, which quantify the propensity of compounds to form IMHBs. By focusing on the compounds size and the number of IMHBs that can potentially be formed, we also outline the major difficulties encountered when designing compounds based on the inclusion of IMHBs. Finally, we discuss recent case studies illustrating the application of IMHB to optimize cell permeability and physicochemical properties of small molecules, cyclic peptides and macrocycles.
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Affiliation(s)
- Giulia Caron
- Molecular Biotechnology and Health Sciences Department, University of Torino, Torino, Italy
| | - Jan Kihlberg
- Department of Chemistry - BMC, Uppsala University, Uppsala, Sweden
| | - Giuseppe Ermondi
- Molecular Biotechnology and Health Sciences Department, University of Torino, Torino, Italy
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75
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Osella S, Di Meo F, Murugan NA, Fabre G, Ameloot M, Trouillas P, Knippenberg S. Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition. J Chem Theory Comput 2018; 14:5350-5359. [DOI: 10.1021/acs.jctc.8b00553] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Silvio Osella
- Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Florent Di Meo
- Faculty of Pharmacy, UMR 1248 INSERM, Limoges University, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France
| | - N. Arul Murugan
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Gabin Fabre
- LCSN-EA1069, Faculty of Pharmacy, Limoges University, 2, rue du Dr. Marcland, 87025 Limoges Cedex, France
| | - Marcel Ameloot
- Biomedical Research Institute, Hasselt University, B-3590, Diepenbeek, Belgium
| | - Patrick Trouillas
- Faculty of Pharmacy, UMR 1248 INSERM, Limoges University, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France
- Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University, tř. 17 listopadu 12, 771 46 Olomouc, Czech Republic
| | - Stefan Knippenberg
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
- Biomedical Research Institute, Hasselt University, B-3590, Diepenbeek, Belgium
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76
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Sensitivity analysis of the Poisson Nernst-Planck equations: a finite element approximation for the sensitive analysis of an electrodiffusion model. J Math Biol 2018; 78:21-56. [PMID: 30187223 DOI: 10.1007/s00285-018-1266-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 04/07/2018] [Indexed: 11/27/2022]
Abstract
Biological structures exhibiting electric potential fluctuations such as neuron and neural structures with complex geometries are modelled using an electrodiffusion or Poisson Nernst-Planck system of equations. These structures typically depend upon several parameters displaying a large degree of variation or that cannot be precisely inferred experimentally. It is crucial to understand how the mathematical model (and resulting simulations) depend on specific values of these parameters. Here we develop a rigorous approach based on the sensitivity equation for the electrodiffusion model. To illustrate the proposed methodology, we investigate the sensitivity of the electrical response of a node of Ranvier with respect to ionic diffusion coefficients and the membrane dielectric permittivity.
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77
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Choi TS, Han JY, Heo CE, Lee SW, Kim HI. Electrostatic and hydrophobic interactions of lipid-associated α-synuclein: The role of a water-limited interfaces in amyloid fibrillation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1854-1862. [DOI: 10.1016/j.bbamem.2018.02.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/05/2018] [Accepted: 02/05/2018] [Indexed: 12/22/2022]
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78
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Collins L, Kilpatrick JI, Kalinin SV, Rodriguez BJ. Towards nanoscale electrical measurements in liquid by advanced KPFM techniques: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:086101. [PMID: 29990308 DOI: 10.1088/1361-6633/aab560] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fundamental mechanisms of energy storage, corrosion, sensing, and multiple biological functionalities are directly coupled to electrical processes and ionic dynamics at solid-liquid interfaces. In many cases, these processes are spatially inhomogeneous taking place at grain boundaries, step edges, point defects, ion channels, etc and possess complex time and voltage dependent dynamics. This necessitates time-resolved and real-space probing of these phenomena. In this review, we discuss the applications of force-sensitive voltage modulated scanning probe microscopy (SPM) for probing electrical phenomena at solid-liquid interfaces. We first describe the working principles behind electrostatic and Kelvin probe force microscopies (EFM & KPFM) at the gas-solid interface, review the state of the art in advanced KPFM methods and developments to (i) overcome limitations of classical KPFM, (ii) expand the information accessible from KPFM, and (iii) extend KPFM operation to liquid environments. We briefly discuss the theoretical framework of electrical double layer (EDL) forces and dynamics, the implications and breakdown of classical EDL models for highly charged interfaces or under high ion concentrations, and describe recent modifications of the classical EDL theory relevant for understanding nanoscale electrical measurements at the solid-liquid interface. We further review the latest achievements in mapping surface charge, dielectric constants, and electrodynamic and electrochemical processes in liquids. Finally, we outline the key challenges and opportunities that exist in the field of nanoscale electrical measurements in liquid as well as providing a roadmap for the future development of liquid KPFM.
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Affiliation(s)
- Liam Collins
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America. Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
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80
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Ebtehaj Z, Hatef A, Malekmohammad M, Soltanolkotabi M. Computational Modeling and Validation of Thermally Induced Electrical Capacitance Changes for Lipid Bilayer Membranes Irradiated by Pulsed Lasers. J Phys Chem B 2018; 122:7319-7331. [PMID: 29912560 DOI: 10.1021/acs.jpcb.8b02616] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neural stimulation has widespread applications in investigating brain functions, restoring impaired neural functions, and treating numerous neurological/psychiatric diseases. Use of infrared pulses to stimulate neurons (infrared neural stimulation) offers a direct and non-invasive technique. Recent research has demonstrated that transient heating associated with the absorption of infrared light by the local aqueous medium around the cell membrane can stimulate nerves. One mechanism for this stimulation is due to a thermally induced increase in the membrane electrical capacitance, which causes cell depolarization as well as action potential production under certain physiological conditions. A theoretical and computational model helps better understand the mechanism of thermally induced electrical capacitance changes and optimize the stimulus parameters. In this article, we develop the existing theoretical models for membrane electrical capacitance and its thermally induced changes. We improve the formulation of Gouy-Chapman-Stern theory by Genet et al. and Shapiro et al. with the addition of a diffuse layer to the electrical double layer and by modifying the relation of Stern layer capacitance, to calculate the membrane capacitive charge and capacitive current. We also present a new method to calculate the membrane electrical capacitance and the rate of its thermally induced changes. In our calculations, two new factors are considered including the temperature dependence of the surface charge density and the hydrophobic core dielectric constant of the lipid bilayer. Our developed model predicts rates of 0.3 and 0.26%/°C for the thermally induced capacitance changes of the artificial lipid bilayer under two different sets of conditions previously reported by Shapiro et al. and Carvalho-de-Souza et al., respectively. Our model is in very good agreement with the corresponding experimental values given by these groups. The presented model is also able to calculate the membrane capacitive currents and investigate the voltage dependence of this current.
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Affiliation(s)
- Z Ebtehaj
- Department of Physics, Faculty of science , University of Isfahan , Isfahan 81746-73441 , Iran
| | - A Hatef
- Nipissing Computational Physics Laboratory, Department of Computer Science and Mathematics , Nipissing University , North Bay , Ontario P1B 8L7 , Canada
| | - M Malekmohammad
- Department of Physics, Faculty of science , University of Isfahan , Isfahan 81746-73441 , Iran
| | - M Soltanolkotabi
- Department of Physics, Faculty of science , University of Isfahan , Isfahan 81746-73441 , Iran
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81
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Nguyen J, Underwood JG, Llorente García I. Orienting lipid-coated graphitic micro-particles in solution using AC electric fields: A new theoretical dual-ellipsoid Laplace model for electro-orientation. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.02.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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82
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Effect of ion concentration, solution and membrane permittivity on electric energy storage and capacitance. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2385-2403. [PMID: 29885295 DOI: 10.1016/j.bbamem.2018.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 05/28/2018] [Accepted: 06/04/2018] [Indexed: 11/21/2022]
Abstract
Bio-membranes as capacitors store electric energy, but their permittivity is low whereas the permittivity of surrounding solution is high. To evaluate the effective capacitance of the membrane/solution system and determine the electric energy stored within the membrane and in the solution, we estimated their electric variables using Poisson-Nernst-Planck simulations. We calculated membrane and solution capacitances from stored electric energy. The effective capacitance was calculated by fitting a six-capacitance model to charges (fixed and ion) and associated potentials, because it cannot be considered as a result of membrane and solution capacitance in series. The electric energy stored within the membrane (typically much smaller than that in the solution), depends on the membrane permittivity, but also on the external electric field, surface charge density, water permittivity and ion concentration. The effect on capacitances is more specific. Solution capacitance rises with greater solution permittivity or ion concentration, but the membrane capacitance (much smaller than solution capacitance) is only influenced by its permittivity. Interestingly, the effective capacitance is independent of membrane or solution permittivity, but rises as the ion concentration increases and surface charge becomes positive. Experimental estimates of membrane capacitance are thus not necessarily a reliable index of its surface area.
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83
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Chinappi M, Cecconi F. Protein sequencing via nanopore based devices: a nanofluidics perspective. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:204002. [PMID: 29595524 DOI: 10.1088/1361-648x/aababe] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Proteins perform a huge number of central functions in living organisms, thus all the new techniques allowing their precise, fast and accurate characterization at single-molecule level certainly represent a burst in proteomics with important biomedical impact. In this review, we describe the recent progresses in the developing of nanopore based devices for protein sequencing. We start with a critical analysis of the main technical requirements for nanopore protein sequencing, summarizing some ideas and methodologies that have recently appeared in the literature. In the last sections, we focus on the physical modelling of the transport phenomena occurring in nanopore based devices. The multiscale nature of the problem is discussed and, in this respect, some of the main possible computational approaches are illustrated.
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Affiliation(s)
- Mauro Chinappi
- Dipartimento di Ingegneria Industriale, Università di Roma Tor Vergata, via del Politecnico 1, 00133 Roma, Italy
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84
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Beltramo PJ, Scheidegger L, Vermant J. Toward Realistic Large-Area Cell Membrane Mimics: Excluding Oil, Controlling Composition, and Including Ion Channels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:5880-5888. [PMID: 29715042 DOI: 10.1021/acs.langmuir.8b00837] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Capacitance measurements provide unique insights into the thickness, compressibility, and composition of large-area membrane bilayers and are used here in addition to demonstrate the successful incorporation of model ion channels. The simultaneous ability to control the bilayer size, manipulate tension, and optically monitor and electrically stimulate freestanding membranes enables precise determination of their specific capacitance and thickness across a wide range of areas. We confirm that membranes formed by this recently developed technique have capacitive properties similar to those formed by existing protocols, including solvent-free approaches, and discuss the effect using either hexadecane or squalene as the oil solvent. The results obtained here are relevant for other methods where lipid membranes are reconstituted from a bulk oil solvent. Because biological membranes have a diverse phospholipid profile, we show that the technique can successfully reconstitute membranes with binary composition mixtures. As an outlook, we show the capability of model membrane proteins, specifically α-hemolysin and alamethicin, to be incorporated into the formed bilayers and measure ion transport.
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Affiliation(s)
- Peter J Beltramo
- Department of Chemical Engineering , University of Massachusetts Amherst , Amherst , Massachusetts 01003 , United States
| | - Laura Scheidegger
- Department of Materials , ETH Zürich , Vladimir-Prelog-Weg 5 , 8093 Zürich , Switzerland
| | - Jan Vermant
- Department of Materials , ETH Zürich , Vladimir-Prelog-Weg 5 , 8093 Zürich , Switzerland
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85
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Meneses-Juárez E, Rivas-Silva JF, González-Melchor M. Static dielectric constant of water within a bilayer using recent water models: a molecular dynamics study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:195001. [PMID: 29583130 DOI: 10.1088/1361-648x/aab9ee] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The water confined within a surfactant bilayer is studied using different water models via molecular dynamics simulations. We considered four representative rigid models of water: the SPC/E and the TIP4P/2005, which are commonly used in numerical calculations and the more recent TIP4Q and SPC/ε models, developed to reproduce the dielectric behaviour of pure water. The static dielectric constant of the confined water was analyzed as a function of the temperature for the four models. In all cases it decreases as the temperature increases. Additionally, the static dielectric constant of the bilayer-water system was estimated through its expression in terms of the fluctuations in the total dipole moment, usually applied for isotropic systems. The estimated dielectric was compared with the available experimental data. We found that the TIP4Q and the SPC/ε produce closer values to the experimental data than the other models, particularly at room temperature. It was found that the probability of finding the sodium ion close to the head of the surfactant decreases as the temperature increases, thus the head of the surfactant is more exposed to the interaction with water when the temperature is higher.
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Affiliation(s)
- Efrain Meneses-Juárez
- Instituto de Física 'Luis Rivera Terrazas', Benemérita Universidad Autónoma de Puebla, Apartado Postal J-48, Puebla, 72570, Mexico. Facultad de Ciencias Básicas, Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Calzada Apizaquito S/N, Apizaco, Tlaxcala 90300, Mexico
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86
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Formulation, Development, and In Vitro Evaluation of a CD22 Targeted Liposomal System Containing a Non-Cardiotoxic Anthracycline for B Cell Malignancies. Pharmaceutics 2018; 10:pharmaceutics10020050. [PMID: 29662041 PMCID: PMC6027244 DOI: 10.3390/pharmaceutics10020050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 04/09/2018] [Accepted: 04/11/2018] [Indexed: 11/25/2022] Open
Abstract
Doxorubicin cardiotoxicity has led to the development of superior chemotherapeutic agents such as AD 198. However, depletion of healthy neutrophils and thrombocytes from AD 198 therapy must be limited. This can be done by the development of a targeted drug delivery system that delivers AD 198 to the malignant cells. The current research highlights the development and in vitro analysis of targeted liposomes containing AD 198. The best lipids were identified and optimized for physicochemical effects on the liposomal system. Physiochemical characteristics such as size, ζ-potential, and dissolution were also studied. Active targeting to CD22 positive cells was achieved by conjugating anti-CD22 Fab’ to the liposomal surface. Size and ζ-potential of the liposomes was between 115 and 145 nm, and −8 to−15 mV. 30% drug was released over 72 h. Higher cytotoxicity was observed in CD22+ve Daudi cells compared to CD22−ve Jurkat cells. The route of uptake was a clathrin- and caveolin-independent pathway. Intracellular localization of the liposomes was in the endolysosomes. Upon drug release, apoptotic pathways were activated partly by the regulation of apoptotic and oncoproteins such as caspase-3 and c-myc. It was observed that the CD22 targeted drug delivery system was more potent and specific compared to other untargeted formulations.
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87
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Wang Y, Shen Y, Wang X, Shen Z, Li B, Hu J, Zhang Y. Nanoscale mapping of dielectric properties based on surface adhesion force measurements. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:900-906. [PMID: 29600151 PMCID: PMC5870145 DOI: 10.3762/bjnano.9.84] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/16/2018] [Indexed: 06/08/2023]
Abstract
The detection of local dielectric properties is of great importance in a wide variety of scientific studies and applications. Here, we report a novel method for the characterization of local dielectric distributions based on surface adhesion mapping by atomic force microscopy (AFM). The two-dimensional (2D) materials graphene oxide (GO), and partially reduced graphene oxide (RGO), which have similar thicknesses but large differences in their dielectric properties, were studied as model systems. Through direct imaging of the samples with a biased AFM tip in PeakForce Quantitative Nano-Mechanics (PF-QNM) mode, the local dielectric properties of GO and RGO were revealed by mapping their surface adhesion forces. Thus, GO and RGO could be conveniently differentiated. This method provides a simple and general approach for the fast characterization of the local dielectric properties of graphene-based materials and will further facilitate their applications in energy generation and storage devices.
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Affiliation(s)
- Ying Wang
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Yue Shen
- Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008, China
| | - Xingya Wang
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhiwei Shen
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bin Li
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Jun Hu
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Yi Zhang
- Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
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88
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Ghosh Moulick R, Panaitov G, Du L, Mayer D, Offenhäusser A. Neuronal adhesion and growth on nanopatterned EA5-POPC synthetic membranes. NANOSCALE 2018; 10:5295-5301. [PMID: 29498734 DOI: 10.1039/c7nr08520f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Biomimetic membranes create opportunities for various applications, including the possibility of replacing interacting cells in a cell-cell contact. Here we have fractionated synthetic membranes using metal nano-grid structures where EphrinA5 (EA5), a neuronal adhesion promoter, was anchored via its Fc domain (immunoglobulin G (IgG)-domain). FRAP experiments were performed to check the confinement of the synthetic membrane within these nano-structures. Rat cortical primary neurons were cultured and live cell imaging techniques were used to monitor the neuronal interaction with these fractionated synthetic membranes. Computational imaging analysis of the corresponding images elucidated interesting details of the cellular behavior. The phenotypic cellular response on these nano-membrane fractions was found to be similar to that on non-fractionated synthetic membranes indicating that although the number of focal adhesion points was low (due to the reduced EA5 number) in the nano-sized membrane patches perhaps some other factors like metal grid boundaries might be playing a role in rendering the similarity.
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Affiliation(s)
- Ranjita Ghosh Moulick
- Institute of Complex Systems ICS-8, Bioelectronics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
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89
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Microwave measurement of giant unilamellar vesicles in aqueous solution. Sci Rep 2018; 8:497. [PMID: 29323157 PMCID: PMC5764977 DOI: 10.1038/s41598-017-18806-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 12/18/2017] [Indexed: 11/26/2022] Open
Abstract
A microwave technique is demonstrated to measure floating giant unilamellar vesicle (GUV) membranes in a 25 μm wide and 18.8 μm high microfluidic channel. The measurement is conducted at 2.7 and 7.9 GHz, at which a split-ring resonator (SRR) operates at odd modes. A 500 nm wide and 100 μm long SRR split gap is used to scan GUVs that are slightly larger than 25 μm in diameter. The smaller fluidic channel induces flattened GUV membrane sections, which make close contact with the SRR gap surface. The used GUVs are synthesized with POPC (16:0–18:1 PC 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), SM (16:0 Egg Sphingomyelin) and cholesterol at different molecular compositions. It is shown that SM and POPC bilayers have different dielectric permittivity values, which also change with measurement frequencies. The obtained membrane permittivity values, e.g. 73.64-j6.13 for POPC at 2.7 GHz, are more than 10 times larger than previously reported results. The discrepancy is likely due to the measurement of dielectric polarization parallel with, other than perpendicular to, the membrane surface. POPC and SM-rich GUV surface sections are also clearly identified. Further work is needed to verify the obtained large permittivity values and enable accurate analysis of membrane composition.
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90
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Jing H, Das S. Electric double layer electrostatics of lipid-bilayer-encapsulated nanoparticles: Toward a better understanding of protocell electrostatics. Electrophoresis 2017; 39:752-759. [PMID: 29235657 DOI: 10.1002/elps.201700286] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/08/2017] [Accepted: 11/08/2017] [Indexed: 11/09/2022]
Abstract
Lipid-bilayer-encapsulated nanoparticles (LBLENPs) or NP-supported LBL systems, such as protocells (which are lipid bilayer encapsulated mesoporous silica nanoparticles or MSNPs) have received extensive attention for applications like targeted drug and gene deliveries, multimodal diagnostics, characterization of membrane-geometry sensitive molecules, etc. Very often electrostatic-mediated interactions have been hypothesized to play key roles in the functioning of these LBLENPs. Despite that, very little has been done to theoretically quantify the fundamental electric double layer (EDL) electrostatics of such LBLENPs. In this study, we develop an EDL theory to describe the electrostatics of such LBLENPs. We show that the electrostatics is a manifestation of the charged/dielectric nature of the NP, LBL structure and charging, and the ionic environment in which the LBLENPs are present. We also establish that for certain conditions of charging of the NP one witnesses a most remarkable charge inversion like electrostatics within the LBL membrane or the NP itself. We anticipate that our findings will provide an extremely useful platform for better understanding the fabrication and functioning of such LBLENPs and discuss examples where our theory can be useful.
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Affiliation(s)
- Haoyuan Jing
- Department of Mechanical Engineering, University of Maryland, College Park, MD, 20742, USA
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, MD, 20742, USA
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91
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Li H, Chowdhary J, Huang L, He X, MacKerell AD, Roux B. Drude Polarizable Force Field for Molecular Dynamics Simulations of Saturated and Unsaturated Zwitterionic Lipids. J Chem Theory Comput 2017; 13:4535-4552. [PMID: 28731702 DOI: 10.1021/acs.jctc.7b00262] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Additive force fields are designed to account for induced electronic polarization in a mean-field average way, using effective empirical fixed charges. The limitation of this approximation is cause for serious concerns, particularly in the case of lipid membranes, where the molecular environment undergoes dramatic variations over microscopic length scales. A polarizable force field based on the classical Drude oscillator offers a practical and computationally efficient framework for an improved representation of electrostatic interactions in molecular simulations. Building on the first-generation Drude polarizable force field for the dipalmitoylphosphatidylcholine 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) molecule, the present effort was undertaken to improve this initial model and expand the force field to a wider range of phospholipid molecules. New lipids parametrized include dimyristoylphosphatidylcholine (DMPC), dilauroylphosphatidylcholine (DLPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), dipalmitoylphosphatidylethanolamine (DPPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). The iterative optimization protocol employed in this effort led to lipid models that achieve a good balance between reproducing quantum mechanical data on model compound representative of phospholipids and reproducing a range of experimental condensed phase properties of bilayers. A parametrization strategy based on a restrained ensemble-maximum entropy methodology was used to help accurately match the experimental NMR order parameters in the polar headgroup region. All the parameters were developed to be compatible with the remainder of the Drude polarizable force field, which includes water, ions, proteins, DNA, and selected carbohydrates.
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Affiliation(s)
- Hui Li
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, University of Chicago , Chicago, Illinois 60637, United States
| | - Janamejaya Chowdhary
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, University of Chicago , Chicago, Illinois 60637, United States
| | - Lei Huang
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, University of Chicago , Chicago, Illinois 60637, United States
| | - Xibing He
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore , Baltimore, Maryland 21201, United States
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore , Baltimore, Maryland 21201, United States
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, University of Chicago , Chicago, Illinois 60637, United States
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92
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Caron G, Vallaro M, Ermondi G. High throughput methods to measure the propensity of compounds to form intramolecular hydrogen bonding. MEDCHEMCOMM 2017; 8:1143-1151. [PMID: 30108824 PMCID: PMC6071820 DOI: 10.1039/c7md00101k] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 04/25/2017] [Indexed: 12/18/2022]
Abstract
Implementation of IMHB considerations in drug discovery needs robust and validated descriptors to experimentally verify the propensity of compounds to exhibit IMHBs. The first part of the paper presents an overview of the most common techniques to measure the propensity of compounds to form IMHBs. Then we review and discuss recently proposed high throughput (HT) physicochemical descriptors (i.e. Δlog Poct-tol, EPSA and log k'80 PLRP-S) which provide the same information. Analysis of the available data enabled us to extract guidelines for the application of these descriptors in drug discovery programs.
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Affiliation(s)
- Giulia Caron
- Molecular Biotechnology and Health Sciences Dept. , University of Torino , Quarello, 15 , 10135 Torino , Italy . ; Tel: +39 011 6708337
| | - Maura Vallaro
- Molecular Biotechnology and Health Sciences Dept. , University of Torino , Quarello, 15 , 10135 Torino , Italy . ; Tel: +39 011 6708337
| | - Giuseppe Ermondi
- Molecular Biotechnology and Health Sciences Dept. , University of Torino , Quarello, 15 , 10135 Torino , Italy . ; Tel: +39 011 6708337
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93
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Osella S, Knippenberg S. Triggering On/Off States of Photoswitchable Probes in Biological Environments. J Am Chem Soc 2017; 139:4418-4428. [DOI: 10.1021/jacs.6b13024] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Silvio Osella
- Division of Theoretical Chemistry
and Biology, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Stefan Knippenberg
- Division of Theoretical Chemistry
and Biology, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden
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94
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Kirchhofer ND, Rengert ZD, Dahlquist FW, Nguyen TQ, Bazan GC. A Ferrocene-Based Conjugated Oligoelectrolyte Catalyzes Bacterial Electrode Respiration. Chem 2017. [DOI: 10.1016/j.chempr.2017.01.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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95
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Papp E, Vancsik T, Kiss E, Szasz O. Energy Absorption by the Membrane Rafts in the Modulated Electro-Hyperthermia (mEHT). ACTA ACUST UNITED AC 2017. [DOI: 10.4236/ojbiphy.2017.74016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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96
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Bu B, Tian Z, Li D, Ji B. High Transmembrane Voltage Raised by Close Contact Initiates Fusion Pore. Front Mol Neurosci 2016; 9:136. [PMID: 28018169 PMCID: PMC5145871 DOI: 10.3389/fnmol.2016.00136] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/22/2016] [Indexed: 12/21/2022] Open
Abstract
Membrane fusion lies at the heart of neuronal communication but the detailed mechanism of a critical step, fusion pore initiation, remains poorly understood. Here, through atomistic molecular dynamics simulations, a transient pore formation induced by a close contact of two apposed bilayers is firstly reported. Such a close contact gives rise to a high local transmembrane voltage that induces the transient pore formation. Through simulations on two apposed bilayers fixed at a series of given distances, the process in which two bilayers approaching to each other under the pulling force from fusion proteins for membrane fusion was mimicked. Of note, this close contact induced fusion pore formation is contrasted with previous reported electroporation under ad hoc applied external electric field or ionic charge in-balance. We show that the transmembrane voltage increases with the decrease of the distance between the bilayers. Below a critical distance, depending on the lipid composition, the local transmembrane voltage can be sufficiently high to induce the transient pores. The size of these pores is approximately 1~2 nm in diameter, which is large enough to allow passing of neurotransmitters. A resealing of the membrane pores resulting from the neutralization of the transmembrane voltage by ions through the pores was then observed. We also found that the membrane tension can either prolong the lifetime of transient pores or cause them to dilate for full collapse. This result provides a possible mechanism for fusion pore formation and regulation of pathway of fusion process.
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Affiliation(s)
- Bing Bu
- Biomechanics and Biomaterials Laboratory, Department of Applied Mechanics, Beijing Institute of Technology Beijing, China
| | - Zhiqi Tian
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, Center for Mitochondrial Biology and Medicine, School of Life Science and Technology, Xi'an Jiaotong University Xi'an, China
| | - Dechang Li
- Biomechanics and Biomaterials Laboratory, Department of Applied Mechanics, Beijing Institute of Technology Beijing, China
| | - Baohua Ji
- Biomechanics and Biomaterials Laboratory, Department of Applied Mechanics, Beijing Institute of Technology Beijing, China
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97
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Madsen JJ, Fristrup P, Peters GH. Theoretical Assessment of Fluorinated Phospholipids in the Design of Liposomal Drug-Delivery Systems. J Phys Chem B 2016; 120:9661-71. [DOI: 10.1021/acs.jpcb.6b07206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Jesper J. Madsen
- Department of Chemistry, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Peter Fristrup
- Department of Chemistry, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Günther H. Peters
- Department of Chemistry, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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98
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Dione I, Deteix J, Briffard T, Chamberland E, Doyon N. Improved Simulation of Electrodiffusion in the Node of Ranvier by Mesh Adaptation. PLoS One 2016; 11:e0161318. [PMID: 27548674 PMCID: PMC4993505 DOI: 10.1371/journal.pone.0161318] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/03/2016] [Indexed: 01/19/2023] Open
Abstract
In neural structures with complex geometries, numerical resolution of the Poisson-Nernst-Planck (PNP) equations is necessary to accurately model electrodiffusion. This formalism allows one to describe ionic concentrations and the electric field (even away from the membrane) with arbitrary spatial and temporal resolution which is impossible to achieve with models relying on cable theory. However, solving the PNP equations on complex geometries involves handling intricate numerical difficulties related either to the spatial discretization, temporal discretization or the resolution of the linearized systems, often requiring large computational resources which have limited the use of this approach. In the present paper, we investigate the best ways to use the finite elements method (FEM) to solve the PNP equations on domains with discontinuous properties (such as occur at the membrane-cytoplasm interface). 1) Using a simple 2D geometry to allow comparison with analytical solution, we show that mesh adaptation is a very (if not the most) efficient way to obtain accurate solutions while limiting the computational efforts, 2) We use mesh adaptation in a 3D model of a node of Ranvier to reveal details of the solution which are nearly impossible to resolve with other modelling techniques. For instance, we exhibit a non linear distribution of the electric potential within the membrane due to the non uniform width of the myelin and investigate its impact on the spatial profile of the electric field in the Debye layer.
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Affiliation(s)
- Ibrahima Dione
- Département de mathématiques et de statistique/Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Université Laval, Québec, Québec, Canada
- Neurosciences cellulaires et moléculaires/Institut universitaire en santé mentale de Québec (CRIUSMQ), Université Laval, Québec, Québec, Canada
| | - Jean Deteix
- Département de mathématiques et de statistique/Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Université Laval, Québec, Québec, Canada
| | - Thomas Briffard
- Département de mathématiques et de statistique/Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Université Laval, Québec, Québec, Canada
| | - Eric Chamberland
- Département de mathématiques et de statistique/Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Université Laval, Québec, Québec, Canada
| | - Nicolas Doyon
- Département de mathématiques et de statistique/Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Université Laval, Québec, Québec, Canada
- Neurosciences cellulaires et moléculaires/Institut universitaire en santé mentale de Québec (CRIUSMQ), Université Laval, Québec, Québec, Canada
- * E-mail:
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99
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Collins L, Belianinov A, Somnath S, Balke N, Kalinin SV, Jesse S. Full data acquisition in Kelvin Probe Force Microscopy: Mapping dynamic electric phenomena in real space. Sci Rep 2016; 6:30557. [PMID: 27514987 PMCID: PMC4981877 DOI: 10.1038/srep30557] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/22/2016] [Indexed: 12/17/2022] Open
Abstract
Kelvin probe force microscopy (KPFM) has provided deep insights into the local electronic, ionic and electrochemical functionalities in a broad range of materials and devices. In classical KPFM, which utilizes heterodyne detection and closed loop bias feedback, the cantilever response is down-sampled to a single measurement of the contact potential difference (CPD) per pixel. This level of detail, however, is insufficient for materials and devices involving bias and time dependent electrochemical events; or at solid-liquid interfaces, where non-linear or lossy dielectrics are present. Here, we demonstrate direct recovery of the bias dependence of the electrostatic force at high temporal resolution using General acquisition Mode (G-Mode) KPFM. G-Mode KPFM utilizes high speed detection, compression, and storage of the raw cantilever deflection signal in its entirety at high sampling rates. We show how G-Mode KPFM can be used to capture nanoscale CPD and capacitance information with a temporal resolution much faster than the cantilever bandwidth, determined by the modulation frequency of the AC voltage. In this way, G-Mode KPFM offers a new paradigm to study dynamic electric phenomena in electroactive interfaces as well as a promising route to extend KPFM to the solid-liquid interface.
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Affiliation(s)
- Liam Collins
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Alex Belianinov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Suhas Somnath
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Nina Balke
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Sergei V Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Stephen Jesse
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.,Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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100
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Tomoike F, Tonooka T, Osaki T, Takeuchi S. Repetitive formation of optically-observable planar lipid bilayers by rotating chambers on a microaperture. LAB ON A CHIP 2016; 16:2423-2426. [PMID: 27256329 DOI: 10.1039/c6lc00363j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Optical observation of a planar lipid bilayer is an effective method of lipid bilayer characterization. However, previous methods for optically observable lipid bilayer formation are unsuitable for repetitive formation of lipid bilayers. In this paper, we propose a system that facilitates repetitive formation of horizontal lipid bilayers via mechanical rotation of the rotating part. We show that multiple bilayers can be observed within a short period, and that the electrical and optical characteristics of a bilayer can be analyzed simultaneously.
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Affiliation(s)
- Fumiaki Tomoike
- Center for International Research on Integrative Biomedical Systems (CIBiS), Institute of Industrial Science (IIS), The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan.
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