1
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Yao Z, Li P, Chen K, Yang Y, Beyer A, Westphal M, Niu QJ, Gölzhäuser A. Defect-Healed Carbon Nanomembranes for Enhanced Salt Separation: Scalable Synthesis and Performance. ACS APPLIED MATERIALS & INTERFACES 2024; 16:22614-22621. [PMID: 38641328 PMCID: PMC11073045 DOI: 10.1021/acsami.4c00252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/27/2024] [Accepted: 02/28/2024] [Indexed: 04/21/2024]
Abstract
Carbon nanomembranes (CNMs), with a high density of subnanometer channels, enable superior salt separation performance compared to conventional membranes. However, defects that occur during the synthesis and transfer processes impede their technical realization on a macroscopic scale. Here, we introduce a practical and scalable interfacial polymerization method to effectively heal defects while preserving the subnanometer pores within CNMs. The defect-healed freestanding CNMs show an exceptional performance in forward osmosis (FO), achieving a water flux of 105 L m-2 h-1 and a specific reverse salt flux of 0.1 g L-1 when measured with 1 M NaCl as draw solution. This water flux is 10 times higher than that of commercially available FO membranes, and the reverse salt flux is 70% lower. Through successful implementation of the defect-healing method and support optimization, we demonstrate the synthesis of fully functional, centimeter-scale CNM-based composite membranes showing high water permeance and a high salt rejection. Our defect-healing method presents a promising pathway to overcome limitations in CNM synthesis, advancing their potential for practical salt separation applications.
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Affiliation(s)
- Zhen Yao
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
| | - Pengfei Li
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
- College
of Chemical Engineering, China University
of Petroleum (East China), Qingdao 266580, PR China
| | - Kuo Chen
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
- College
of Chemical Engineering, China University
of Petroleum (East China), Qingdao 266580, PR China
| | - Yang Yang
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
| | - André Beyer
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
| | - Michael Westphal
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
| | - Qingshan Jason Niu
- Institute
for Advanced Study, Shenzhen University, Shenzhen 518060, PR China
| | - Armin Gölzhäuser
- Physics
of Supramolecular Systems and Surfaces, Bielefeld University, Bielefeld 33615, Germany
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2
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Doveiko D, Martin ARG, Vyshemirsky V, Stebbing S, Kubiak-Ossowska K, Rolinski O, Birch DJS, Chen Y. Nanoparticle Metrology of Silicates Using Time-Resolved Multiplexed Dye Fluorescence Anisotropy, Small Angle X-ray Scattering, and Molecular Dynamics Simulations. MATERIALS (BASEL, SWITZERLAND) 2024; 17:1686. [PMID: 38612200 PMCID: PMC11012945 DOI: 10.3390/ma17071686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 03/29/2024] [Accepted: 04/02/2024] [Indexed: 04/14/2024]
Abstract
We investigate the nanometrology of sub-nanometre particle sizes in industrially manufactured sodium silicate liquors at high pH using time-resolved fluorescence anisotropy. Rather than the previous approach of using a single dye label, we investigate and quantify the advantages and limitations of multiplexing two fluorescent dye labels. Rotational times of the non-binding rhodamine B and adsorbing rhodamine 6G dyes are used to independently determine the medium microviscosity and the silicate particle radius, respectively. The anisotropy measurements were performed on the range of samples prepared by diluting the stock solution of silicate to concentrations ranging between 0.2 M and 2 M of NaOH and on the stock solution at different temperatures. Additionally, it was shown that the particle size can also be measured using a single excitation wavelength when both dyes are present in the sample. The recovered average particle size has an upper limit of 7.0 ± 1.2 Å. The obtained results were further verified using small-angle X-ray scattering, with the recovered particle size equal to 6.50 ± 0.08 Å. To disclose the impact of the dye label on the measured complex size, we further investigated the adsorption state of rhodamine 6G on silica nanoparticles using molecular dynamics simulations, which showed that the size contribution is strongly impacted by the size of the nanoparticle of interest. In the case of the higher radius of curvature (less curved) of larger particles, the size contribution of the dye label is below 10%, while in the case of smaller and more curved particles, the contribution increases significantly, which also suggests that the particles of interest might not be perfectly spherical.
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Affiliation(s)
- Daniel Doveiko
- Photophysics Group, Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK (D.J.S.B.)
| | - Alan R. G. Martin
- EPSRC Future Continuous Manufacturing and Advanced Crystallisation National Facility, University of Strathclyde, 99 George Street, Glasgow G1 1RD, UK;
| | | | | | | | - Olaf Rolinski
- Photophysics Group, Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK (D.J.S.B.)
| | - David J. S. Birch
- Photophysics Group, Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK (D.J.S.B.)
| | - Yu Chen
- Photophysics Group, Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK (D.J.S.B.)
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3
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Shankar S, Murphy BB, Driscoll N, Shekhirev M, Valurouthu G, Shevchuk K, Anayee M, Cimino F, Gogotsi Y, Vitale F. Effect of the deposition process on the stability of Ti 3C 2T x MXene films for bioelectronics. 2D MATERIALS 2023; 10:044001. [PMID: 37521001 PMCID: PMC10373437 DOI: 10.1088/2053-1583/ace26c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Abstract
Ti3C2Tx MXene is emerging as the enabling material in a broad range of wearable and implantable medical technologies, thanks to its outstanding electrical, electrochemical, and optoelectronic properties, and its compatibility with high-throughput solution-based processing. While the prevalence of Ti3C2Tx MXene in biomedical research, and in particular bioelectronics, has steadily increased, the long-term stability and degradation of Ti3C2Tx MXene films have not yet been thoroughly investigated, limiting its use for chronic applications. Here, we investigate the stability of Ti3C2Tx films and electrodes under environmental conditions that are relevant to medical and bioelectronic technologies: storage in ambient atmosphere (shelf-life), submersion in saline (akin to the in vivo environment), and storage in a desiccator (low-humidity). Furthermore, to evaluate the effect of the MXene deposition method and thickness on the film stability in the different conditions, we compare thin (25 nm), and thick (1.0 μm) films and electrodes fabricated via spray-coating and blade-coating. Our findings indicate that film processing method and thickness play a significant role in determining the long-term performance of Ti3C2Tx films and electrodes, with highly aligned, thick films from blade coating remarkably retaining their conductivity, electrochemical impedance, and morphological integrity even after 30 days in saline. Our extensive spectroscopic analysis reveals that the degradation of Ti3C2Tx films in high-humidity environments is primarily driven by moisture intercalation, ingress, and film delamination, with evidence of only minimal to moderate oxidation.
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Affiliation(s)
- Sneha Shankar
- Department of Bioengineering, 210 S. 33rd Street, 240 Skirkanich Hall
- Center for Neuroengineering & Therapeutics, 240 S. 33rd Street, 301 Hayden Hall
- Center for Neurotrauma, Neurodegeneration, and Restoration, 3900 Woodlawn Ave., Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States 19104
| | - Brendan B. Murphy
- Center for Neuroengineering & Therapeutics, 240 S. 33rd Street, 301 Hayden Hall
- Department of Neurology, 3400 Spruce Street, University of Pennsylvania, Philadelphia, PA, United States 19104
- Center for Neurotrauma, Neurodegeneration, and Restoration, 3900 Woodlawn Ave., Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States 19104
| | - Nicolette Driscoll
- Department of Bioengineering, 210 S. 33rd Street, 240 Skirkanich Hall
- Center for Neuroengineering & Therapeutics, 240 S. 33rd Street, 301 Hayden Hall
- Center for Neurotrauma, Neurodegeneration, and Restoration, 3900 Woodlawn Ave., Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States 19104
| | - Mikhail Shekhirev
- A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, 3141 Chestnut Street, Drexel University, Philadelphia, PA, United States 19104
| | - Geetha Valurouthu
- A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, 3141 Chestnut Street, Drexel University, Philadelphia, PA, United States 19104
| | - Kateryna Shevchuk
- A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, 3141 Chestnut Street, Drexel University, Philadelphia, PA, United States 19104
| | - Mark Anayee
- A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, 3141 Chestnut Street, Drexel University, Philadelphia, PA, United States 19104
| | - Francesca Cimino
- Department of Bioengineering, 210 S. 33rd Street, 240 Skirkanich Hall
- Center for Neuroengineering & Therapeutics, 240 S. 33rd Street, 301 Hayden Hall
| | - Yury Gogotsi
- A. J. Drexel Nanomaterials Institute, Department of Materials Science and Engineering, 3141 Chestnut Street, Drexel University, Philadelphia, PA, United States 19104
| | - Flavia Vitale
- Center for Neuroengineering & Therapeutics, 240 S. 33rd Street, 301 Hayden Hall
- Department of Neurology, 3400 Spruce Street, University of Pennsylvania, Philadelphia, PA, United States 19104
- Department of Physical Medicine & Rehabilitation, 1800 Lombard Street, University of Pennsylvania, Philadelphia, PA, United States 19147
- Center for Neurotrauma, Neurodegeneration, and Restoration, 3900 Woodlawn Ave., Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States 19104
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4
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Middleton J, Scott AJ, Storey R, Marucci M, Ghadiri M. Prediction of the Effective Work Function of Aspirin and Paracetamol Crystals by Density Functional Theory-A First-Principles Study. CRYSTAL GROWTH & DESIGN 2023; 23:6308-6317. [PMID: 37692333 PMCID: PMC10485818 DOI: 10.1021/acs.cgd.3c00218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 07/10/2023] [Indexed: 09/12/2023]
Abstract
Crystals of active pharmaceutical ingredients (API) are prone to triboelectric charging due to their dielectric nature. This characteristic, coupled with their typically low density and often large aspect ratio, poses significant challenges in the manufacturing process. The pharmaceutical industry frequently encounters issues during the secondary processing of APIs, such as particle adhesion to walls, clump formation, unreliable flow, and the need for careful handling to mitigate the risk of fire and explosions. These challenges are further intensified by the limited availability of powder quantities for testing, particularly in the early stages of drug development. Therefore, it is highly desirable to develop predictive tools that can assess the triboelectric propensity of APIs. In this study, Density Functional Theory calculations are employed to predict the effective work function of different facets of aspirin and paracetamol crystals, both in a vacuum and in the presence of water molecules on their surfaces. The calculations reveal significant variations in the work function across different facets and materials. Moreover, the adsorption of water molecules induces a shift in the work function. These findings underscore the considerable impact of distinct surface terminations and the presence of molecular water on the calculated effective work function of pharmaceuticals. Consequently, this approach offers a valuable predictive tool for determining the triboelectric propensity of APIs.
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Affiliation(s)
- James
R. Middleton
- School
of Chemical and Process Engineering, University
of Leeds, Leeds LS2 9JT, United
Kingdom
| | - Andrew J. Scott
- School
of Chemical and Process Engineering, University
of Leeds, Leeds LS2 9JT, United
Kingdom
| | - Richard Storey
- New
Modalities Product Development, Pharmaceutical Technology & Development,
Operations, AstraZeneca, Macclesfield SK10 2NA, United Kingdom
| | - Mariagrazia Marucci
- Oral
Product Development, Pharmaceutical Technology & Development,
Operations, AstraZeneca, Gothenburg 413 27, Sweden
| | - Mojtaba Ghadiri
- School
of Chemical and Process Engineering, University
of Leeds, Leeds LS2 9JT, United
Kingdom
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5
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Yao Z, Meyerbröker N, Qi Y, Cremer J, Westphal M, Anselmetti D, Yang Y, Gölzhäuser A. Scalable Synthesis of Carbon Nanomembranes from Amorphous Molecular Layers. ACS APPLIED MATERIALS & INTERFACES 2023; 15:41101-41108. [PMID: 37587014 DOI: 10.1021/acsami.3c07369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
Nanoporous carbon nanomembranes (CNMs) created by self-assembled monolayers ideally combine a high water flux and precise ion selectivity for molecular separation and water desalination. However, their practical implementation is often challenged by the availability of large epitaxial substrates, limiting the membrane up-scaling. Here, we report a scalable synthesis of CNMs from poly(4-vinylbiphenyl) (PVBP) spin-coated on SiO2/Si wafers. Electron irradiation of the amorphous PVBP molecular layers induces the formation of a continuous membrane with a thickness of 15 nm and a high density of subnanometer pores, providing a water permeance as high as 530 L m-2 h-1 bar-1, while repelling ions and molecules larger than 1 nm in size. A further introduction of a reinforced porous block copolymer layer enables the fabrication of centimeter-scale CNM composites that efficiently separate organic dyes from water. These results suggest a feasible route for large-scale nanomembrane fabrication.
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Affiliation(s)
- Zhen Yao
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
| | | | - Yubo Qi
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
| | - Julian Cremer
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
| | - Michael Westphal
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
| | - Dario Anselmetti
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
| | - Yang Yang
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Haibin Road 1119, Guangzhou 511458, China
| | - Armin Gölzhäuser
- Faculty of Physics, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany
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6
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Del Mundo JT, Rongpipi S, Yang H, Ye D, Kiemle SN, Moffitt SL, Troxel CL, Toney MF, Zhu C, Kubicki JD, Cosgrove DJ, Gomez EW, Gomez ED. Grazing-incidence diffraction reveals cellulose and pectin organization in hydrated plant primary cell wall. Sci Rep 2023; 13:5421. [PMID: 37012389 PMCID: PMC10070456 DOI: 10.1038/s41598-023-32505-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 03/28/2023] [Indexed: 04/05/2023] Open
Abstract
The primary cell wall is highly hydrated in its native state, yet many structural studies have been conducted on dried samples. Here, we use grazing-incidence wide-angle X-ray scattering (GIWAXS) with a humidity chamber, which enhances scattering and the signal-to-noise ratio while keeping outer onion epidermal peels hydrated, to examine cell wall properties. GIWAXS of hydrated and dried onion reveals that the cellulose ([Formula: see text]) lattice spacing decreases slightly upon drying, while the (200) lattice parameters are unchanged. Additionally, the ([Formula: see text]) diffraction intensity increases relative to (200). Density functional theory models of hydrated and dry cellulose microfibrils corroborate changes in crystalline properties upon drying. GIWAXS also reveals a peak that we attribute to pectin chain aggregation. We speculate that dehydration perturbs the hydrogen bonding network within cellulose crystals and collapses the pectin network without affecting the lateral distribution of pectin chain aggregates.
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Affiliation(s)
- Joshua T Del Mundo
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Sintu Rongpipi
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Hui Yang
- Department of Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Dan Ye
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Sarah N Kiemle
- Department of Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | | | - Charles L Troxel
- SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Michael F Toney
- Department of Chemical and Biological Engineering and the Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - James D Kubicki
- Department of Earth, Environmental and Resource Sciences, University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Daniel J Cosgrove
- Department of Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Esther W Gomez
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
| | - Enrique D Gomez
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
- Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802, USA.
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7
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Gesztesi J, Broddrick JT, Lannin T, Lee JA. The chemical neighborhood of cells in a diffusion-limited system. Front Microbiol 2023; 14:1155726. [PMID: 37143535 PMCID: PMC10151505 DOI: 10.3389/fmicb.2023.1155726] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 03/20/2023] [Indexed: 05/06/2023] Open
Abstract
Microorganisms follow us everywhere, and they will be essential to sustaining long-term human space exploration through applications such as vitamin synthesis, biomining, and more. Establishing a sustainable presence in space therefore requires that we better understand how stress due to the altered physical conditions of spaceflight affects our companion organisms. In microgravity environments such as orbital space stations, microorganisms likely experience the change in gravity primarily through changes in fluid mixing processes. Without sedimentation and density-driven convection, diffusion becomes the primary process governing the movement of growth substrates and wastes for microbial cells in suspension culture. Non-motile cells might therefore develop a substrate-deficient "zone of depletion" and experience stress due to starvation and/or waste build-up. This would in turn impact the concentration-dependent uptake rate of growth substrates and could be the cause of the altered growth rates previously observed in microorganisms in spaceflight and in ground-simulated microgravity. To better understand the extent of these concentration differences and their potential influence on substrate uptake rates, we used both an analytical solution and finite difference method to visualize concentration fields around individual cells. We modeled diffusion, using Fick's Second Law, and nutrient uptake, using Michaelis-Menten kinetics, and assessed how that distribution varies in systems with multiple cells and varied geometries. We determined the radius of the zone of depletion, within which cells had reduced the substrate concentration by 10%, to be 5.04 mm for an individual Escherichia coli cell in the conditions we simulated. However, we saw a synergistic effect with multiple cells near each other: multiple cells in close proximity decreased the surrounding concentration by almost 95% from the initial substrate concentration. Our calculations provide researchers an inside look at suspension culture behavior in the diffusion-limited environment of microgravity at the scale of individual cells.
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Affiliation(s)
- Juliana Gesztesi
- NASA Ames Research Center, Universities Space Research Association, Moffett Field, CA, United States
- College of Engineering, Northeastern University, Boston, MA, United States
| | - Jared T. Broddrick
- NASA Ames Research Center, Space Biosciences Research Branch, Moffett Field, CA, United States
| | - Timothy Lannin
- College of Engineering, Northeastern University, Boston, MA, United States
| | - Jessica A. Lee
- NASA Ames Research Center, Space Biosciences Research Branch, Moffett Field, CA, United States
- *Correspondence: Jessica A. Lee,
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8
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Zhang Y, Oestreicher J, Binns WJ, Briggs S, Kim CS, Béland LK. A Coarse-Grained Interaction Model for Sodium Dominant Montmorillonite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13226-13237. [PMID: 36256513 DOI: 10.1021/acs.langmuir.2c02233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Montmorillonite is the main crystalline mineral present in bentonite. It is an absorbent, swelling material; the physical chemistry underlying its ability to absorb water and swell occurs at the nanoscale, governed by electrical double-layer interactions. In turn, absorption and swelling lead to important changes in the macroscopic transport properties of the clay. Mesoscale models can help us establish a link between these nanoscale processes and macroscale properties, notably by providing a detailed description of its pore network. Models on the scale of hundreds to thousands of nanometers are required, which cannot realistically be handled using traditional all-atom molecular dynamics simulations. This work presents a coarse-grained (CG) mesoscale model of sodium montmorillonite. In our model, montmorillonite platelets are represented by two types of particles: central nonhydrogen-bonded particles and edge hydrogen-bonding particles. The particle interactions are described by two-body potentials, which were optimized based on all-atom molecular dynamics simulations. Specifically, several potential mean force calculations involving dry and hydrated montmorillonite were performed, using the ClayFF potential to calculate interatomic forces. The CG model was validated by testing the scalability of the model, testing its ability to reproduce potentials of mean force reported elsewhere in the literature, and by comparing the calculated elastic properties of a system containing 1000 Na montmorillonite platelets to experimentally measured elastic properties of bentonite. The simulated elastic properties obtained using our mesoscale model agree with these experimental values.
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Affiliation(s)
- Yaoting Zhang
- Department of Mechanical & Materials Engineering, Queen's University, Nicol Hall, 60 Union Street, Kingston, K7L 3N6Ontario, Canada
- Nuclear Waste Management Organization, 22 St. Clair Avenue East Fourth Floor, Toronto, M4T 2S3Ontario, Canada
| | - Jeremy Oestreicher
- Department of Mechanical & Materials Engineering, Queen's University, Nicol Hall, 60 Union Street, Kingston, K7L 3N6Ontario, Canada
| | - W Jeffrey Binns
- Nuclear Waste Management Organization, 22 St. Clair Avenue East Fourth Floor, Toronto, M4T 2S3Ontario, Canada
| | - Scott Briggs
- Nuclear Waste Management Organization, 22 St. Clair Avenue East Fourth Floor, Toronto, M4T 2S3Ontario, Canada
| | - Chang Seok Kim
- Nuclear Waste Management Organization, 22 St. Clair Avenue East Fourth Floor, Toronto, M4T 2S3Ontario, Canada
| | - Laurent K Béland
- Department of Mechanical & Materials Engineering, Queen's University, Nicol Hall, 60 Union Street, Kingston, K7L 3N6Ontario, Canada
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9
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Breakspear S, Frueh P, Neu A, Noecker B, Popescu C, Uellner Q. Learning from hair moisture sorption and hysteresis. Int J Cosmet Sci 2022; 44:555-568. [PMID: 35892223 DOI: 10.1111/ics.12806] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure. METHODS The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered. RESULTS By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of "breaking symmetry", derived from moisture sorption-desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulfide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100 %. The analysis suggested that, aside from the glass transition event occurring at around 60-70 % relative humidity, there is another, less examined, transition occurring at around 30 % relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour. CONCLUSION The moisture sorption-desorption by hair was shown not only to allow a quantitative differentiation among various cosmetic treatments of the hair, but also to provide valuable information on the structure of the fibre.
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Affiliation(s)
| | - P Frueh
- KAO Germany GmbH, Darmstadt, Germany.,KAO Corporation, Tokyo, Japan
| | - A Neu
- KAO Germany GmbH, Darmstadt, Germany
| | - B Noecker
- KAO Germany GmbH, Darmstadt, Germany
| | - C Popescu
- KAO Germany GmbH, Darmstadt, Germany
| | - Q Uellner
- KAO Germany GmbH, Darmstadt, Germany
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10
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Guccini V, Yu S, Meng Z, Kontturi E, Demmel F, Salazar-Alvarez G. The Impact of Surface Charges of Carboxylated Cellulose Nanofibrils on the Water Motions in Hydrated Films. Biomacromolecules 2022; 23:3104-3115. [PMID: 35786867 PMCID: PMC9364319 DOI: 10.1021/acs.biomac.1c01517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cellulose nanofibrils (CNFs) with carboxylated surface ligands are a class of materials with tunable surface functionality, good mechanical properties, and bio-/environmental friendliness. They have been used in many applications as scaffold, reinforcing, or functional materials, where the interaction between adsorbed moisture and the CNF could lead to different properties and structures and become critical to the performance of the materials. In this work, we exploited multiple experimental methods to study the water movement in hydrated films made of carboxylated CNFs prepared by TEMPO oxidation with two different surface charges of 600 and 1550 μmol·g-1. A combination of quartz crystal microbalance with dissipation (QCM-D) and small-angle X-ray scattering (SAXS) shows that both the surface charge of a single fibril and the films' network structure contribute to the moisture uptake. The films with 1550 μmol·g-1 surface charges take up twice the amount of moisture per unit mass, leading to the formation of nanostructures with an average radius of gyration of 2.1 nm. Via the nondestructive quasi-elastic neutron scattering (QENS), a faster motion is explained as a localized movement of water molecules inside confined spheres, and a slow diffusive motion is found with the diffusion coefficient close to bulk water at room temperature via a random jump diffusion model and regardless of the surface charge in films made from CNFs.
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Affiliation(s)
- Valentina Guccini
- Department of Materials and Environmental Chemistry (MMK), Stockholm University, Stockholm SE-10691, Sweden.,Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, Aalto 00076, Finland
| | - Shun Yu
- Department of Materials and Environmental Chemistry (MMK), Stockholm University, Stockholm SE-10691, Sweden.,Smart Materials, Division of Bioeconomy and Health, RISE Research Institute of Sweden, Drottning Kristinas väg 61, Stockholm 114 86, Sweden
| | - Zhoujun Meng
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, Aalto 00076, Finland
| | - Eero Kontturi
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, Aalto 00076, Finland
| | - Franz Demmel
- ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QZ, UK
| | - Germán Salazar-Alvarez
- Department of Materials and Environmental Chemistry (MMK), Stockholm University, Stockholm SE-10691, Sweden.,Department of Materials Science and Engineering, Ångström Laboratory, Uppsala University, Box 35, Uppsala SE-751 03, Sweden.,Center for Neutron Scattering, Uppsala University, Box 35, Uppsala SE-751 03, Sweden
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11
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Kruk D, Masiewicz E, Budny J, Kolodziejski K, Zulewska J, Wieczorek Z. Relationship between macroscopic properties of honey and molecular dynamics – temperature effects. J FOOD ENG 2022. [DOI: 10.1016/j.jfoodeng.2021.110782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Kangas J, Bischof JC, Hogan CJ. Kinetics of nonisothermal phase change with arbitrary temperature-time history and initial transformed phase distributions. J Chem Phys 2021; 155:211101. [PMID: 34879664 DOI: 10.1063/5.0072299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
This paper describes the extension of the classic Avrami equation to nonisothermal systems with arbitrary temperature-time history and arbitrary initial distributions of transformed phase. We start by showing that through examination of phase change in Fourier space, we can decouple the nucleation rate, growth rate, and transformed fraction, leading to the derivation of a nonlinear differential equation relating these three properties. We then consider a population balance partial differential equation (PDE) on the phase size distribution and solve it analytically. Then, by relating this PDE solution to the transformed fraction of phase, we are able to derive initial conditions to the differential equation relating nucleation rate, growth rate, and transformed fraction.
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Affiliation(s)
- Joseph Kangas
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - John C Bischof
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Christopher J Hogan
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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13
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Hong TZX, You L, Dahanayaka M, Law AWK, Zhou K. Influence of Substitutional Defects in ZIF-8 Membranes on Reverse Osmosis Desalination: A Molecular Dynamics Study. Molecules 2021; 26:molecules26113392. [PMID: 34205198 PMCID: PMC8200035 DOI: 10.3390/molecules26113392] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 05/17/2021] [Accepted: 05/19/2021] [Indexed: 11/17/2022] Open
Abstract
In this study, molecular dynamics simulation is used to investigate the effects of water-based substitutional defects in zeolitic imidazolate frameworks (ZIF)-8 membranes on their reverse osmosis (RO) desalination performance. ZIF-8 unit cells containing up to three defect sites are used to construct the membranes. These substitutional defects can either be Zn defects or linker defects. The RO desalination performance of the membranes is assessed in terms of the water flux and ion rejection rate. The effects of defects on the interactions between the ZIF-8 membranes and NaCl are investigated and explained with respect to the radial distribution function (RDF) and ion density distribution. The results show that ion adsorption on the membranes occurs at either the nitrogen atoms or the defect sites. Complete NaCl rejection can be achieved by introducing defects to change the size of the pores. It has also been discovered that the presence of linker defects increases membrane hydrophilicity. Overall, molecular dynamics simulations have been used in this study to show that water-based substitutional defects in a ZIF-8 structure reduce the water flux and influence its hydrophilicity and ion adsorption performance, which is useful in predicting the type and number of defect sites per unit cell required for RO applications. Of the seven ZIF-8 structures tested, pristine ZIF-8 exhibits the best RO desalination performance.
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Affiliation(s)
- Terence Zhi Xiang Hong
- Environmental Process Modeling Centre, Nanyang Environment and Water Research Institute, 1 Cleantech Loop, Singapore 637141, Singapore; (T.Z.X.H.); (M.D.); (A.W.-K.L.)
- Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;
| | - Liming You
- Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Madhavi Dahanayaka
- Environmental Process Modeling Centre, Nanyang Environment and Water Research Institute, 1 Cleantech Loop, Singapore 637141, Singapore; (T.Z.X.H.); (M.D.); (A.W.-K.L.)
- Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;
| | - Adrian Wing-Keung Law
- Environmental Process Modeling Centre, Nanyang Environment and Water Research Institute, 1 Cleantech Loop, Singapore 637141, Singapore; (T.Z.X.H.); (M.D.); (A.W.-K.L.)
- School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Kun Zhou
- Environmental Process Modeling Centre, Nanyang Environment and Water Research Institute, 1 Cleantech Loop, Singapore 637141, Singapore; (T.Z.X.H.); (M.D.); (A.W.-K.L.)
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
- Correspondence: ; Tel.: +65-6790-5499; Fax: +65-6792-4062
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14
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Glebov EM, Plyusnin VF. On the Cause of Solvent Effect in $${\text{Pt}^{\text{IV}}}\text{Cl}_{6}^{{2 - }}$$ Photochemistry. HIGH ENERGY CHEMISTRY 2021. [DOI: 10.1134/s0018143921030036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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15
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Lin Y, Fichou Y, Longhini AP, Llanes LC, Yin P, Bazan GC, Kosik KS, Han S. Liquid-Liquid Phase Separation of Tau Driven by Hydrophobic Interaction Facilitates Fibrillization of Tau. J Mol Biol 2021; 433:166731. [PMID: 33279579 PMCID: PMC7855949 DOI: 10.1016/j.jmb.2020.166731] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/29/2020] [Accepted: 11/30/2020] [Indexed: 11/17/2022]
Abstract
Amyloid aggregation of tau protein is implicated in neurodegenerative diseases, yet its facilitating factors are poorly understood. Recently, tau has been shown to undergo liquid liquid phase separation (LLPS) both in vivo and in vitro. LLPS was shown to facilitate tau amyloid aggregation in certain cases, while being independent of aggregation in other cases. It is therefore important to understand the differentiating properties that resolve this apparent conflict. We report on a model system of hydrophobically driven LLPS induced by high salt concentration (LLPS-HS), and compare it to electrostatically driven LLPS represented by tau-RNA/heparin complex coacervation (LLPS-ED). We show that LLPS-HS promotes tau protein dehydration, undergoes maturation and directly leads to canonical tau fibrils, while LLPS-ED is reversible, remains hydrated and does not promote amyloid aggregation. We show that the nature of the interaction driving tau condensation is a differentiating factor between aggregation-prone and aggregation-independent LLPS.
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Affiliation(s)
- Yanxian Lin
- Biomolecular Science and Engineering, University of California, Santa Barbara, CA 93106, United States
| | - Yann Fichou
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States
| | - Andrew P Longhini
- Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, United States
| | - Luana C Llanes
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States; Center for Polymers and Organic Solids, University of California, Santa Barbara, CA 93106, United States
| | - Pengyi Yin
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States
| | - Guillermo C Bazan
- Departments of Chemistry and Chemical Engineering, National University of Singapore, 117543, Singapore
| | - Kenneth S Kosik
- Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, United States; Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, United States.
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16
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Mermigkis PG, Mavrantzas VG. Geometric Analysis of Clusters of Free Volume Accessible to Small Penetrants and Their Connectivity in Polymer Nanocomposites Containing Carbon Nanotubes. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Panagiotis G. Mermigkis
- Department of Chemical Engineering, University of Patras & FORTH/ICE-HT, Patras GR 26504, Greece
| | - Vlasis G. Mavrantzas
- Department of Chemical Engineering, University of Patras & FORTH/ICE-HT, Patras GR 26504, Greece
- Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland
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17
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Malfait B, Correia NT, Ciotonea C, Dhainaut J, Dacquin JP, Royer S, Tabary N, Guinet Y, Hédoux A. Manipulating the physical states of confined ibuprofen in SBA-15 based drug delivery systems obtained by solid-state loading: Impact of the loading degree. J Chem Phys 2020; 153:154506. [PMID: 33092366 DOI: 10.1063/5.0020992] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using the Milling-Assisted Loading (MAL) solid-state method for loading a poorly water-soluble drug (ibuprofen, IBP) within the SBA-15 matrix has given the opportunity to manipulate the physical state of drugs for optimizing bioavailability. The MAL method makes it easy to control and analyze the influence of the degree of loading on the physical state of IBP inside the SBA-15 matrix with an average pore diameter of 9.4 nm. It was found that the density of IBP molecules in an average pore size has a direct influence on both the glass transition and the mechanism of crystallization. Detailed analyzes of the crystallite distribution and melting by Raman mapping, x-ray diffraction, and differential scanning calorimetry have shown that the crystals are localized in the core of the channel and surrounded by a liquid monolayer. The results of these complementary investigations have been used for determining the relevant parameters (related to the SBA-15 matrix and to the IBP molecule) and the nature of the physical state of the confined matter.
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Affiliation(s)
- Benjamin Malfait
- Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
| | - Natália T Correia
- Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
| | - Carmen Ciotonea
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS -Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Jérémy Dhainaut
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS -Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Jean-Philippe Dacquin
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS -Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Sébastien Royer
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS -Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Nicolas Tabary
- Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
| | - Yannick Guinet
- Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
| | - Alain Hédoux
- Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
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18
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Kumar R, Muthukumar M. Surface Tension of Dielectric-Air Interfaces. J Phys Chem B 2020; 124:5265-5270. [PMID: 32479081 DOI: 10.1021/acs.jpcb.0c01430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Analytical and semianalytical expressions for the surface tension of dielectric-air interfaces are presented after considering local and nonlocal dielectric effects near interfaces. It is shown that the nonlocal effects of dielectrics are significant for highly polar dielectric fluids such as water. Far from the interface, nonlocal dielectric effects are shown to cause not only the oscillatory potential of the mean force but also a reversal of sign at intermediate distances.
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Affiliation(s)
- Rajeev Kumar
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.,Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Murugappan Muthukumar
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01002, United States
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19
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Matveev VV. Cell theory, intrinsically disordered proteins, and the physics of the origin of life. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 149:114-130. [PMID: 30965040 DOI: 10.1016/j.pbiomolbio.2019.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/01/2019] [Accepted: 04/05/2019] [Indexed: 12/30/2022]
Abstract
Cell theory, as formulated by Theodor Schwann in 1839, introduced the idea that the cell is the main structural unit of living nature. Later, in solving the problem of cell multiplication, Rudolf Virchow expanded the cell theory with a postulate: all cells only arise from pre-existing cells. But what did the very first cell arise from? This paper proposes extending the Virchow's law by the assumption that between the nonliving protocell and the first living cell the continuity of fundamental physical properties (the principle of invariance of physical properties) is preserved. The protocell is understood here as a cell-shaped physical system on the basis of the self-organized biologically significant prebiotic macromolecules, primarily peptides, having a potential to transform into the living cell. Biophase is considered as the physical basis of the membraneless protocell, the internal environment of which is separated from the external environment due to the phase of adsorbed water. The evidence is given that the first protocells may have been formed on the basis of intrinsically disordered peptides. Data on the similarity of the physical properties of living cells and the following model systems are given: protein and artificial polymer solutions, coacervate droplets, and ion-exchange resin granules. Available data on the similarity of the physical properties of cell models and living cells allow us to rephrase the Virchow's postulate as follows: the physical properties of a living cell could only arise from pre-existing physical properties of the protocell.
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Affiliation(s)
- Vladimir V Matveev
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave 4, St. Petersburg, 194064, Russia.
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20
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Rocha MA, Shiflett MB. Water Sorption and Diffusivity in [C2C1im][BF4], [C4C1im][OAc], and [C4C1im][Cl]. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.8b05689] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Alejandra Rocha
- Department of Chemical and Petroleum Engineering, University of Kansas, 1450 Jayhawk Boulevard, Lawrence, Kansas 66045, United States
| | - Mark B. Shiflett
- Department of Chemical and Petroleum Engineering, University of Kansas, 1450 Jayhawk Boulevard, Lawrence, Kansas 66045, United States
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21
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Fan Z, Bi LJ, Jin G, Qi Z. Electrostatic interaction in the NH2-terminus accelerates inactivation of the Kv1.4 channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2076-83. [DOI: 10.1016/j.bbamem.2010.07.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 07/21/2010] [Accepted: 07/26/2010] [Indexed: 11/27/2022]
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22
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Sugiharto S, Carland JE, Lewis TM, Moorhouse AJ, Barry PH. External divalent cations increase anion-cation permeability ratio in glycine receptor channels. Pflugers Arch 2010; 460:131-52. [PMID: 20198385 DOI: 10.1007/s00424-010-0792-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 01/15/2010] [Accepted: 01/22/2010] [Indexed: 11/24/2022]
Abstract
The functional role of ligand-gated ion channels in the central nervous system depends on their relative anion-cation permeability. Using standard whole-cell patch clamp measurements and NaCl dilution potential measurements, we explored the effect of external divalent ions on anion-cation selectivity in alpha1-homomeric wild-type glycine receptor channels. We show that increasing external Ca(2+) from 0 to 4 mM resulted in a sigmoidal increase in anion-cation permeability by 37%, reaching a maximum above about 2 mM. Our accurate quantification of this effect required rigorous correction for liquid junction potentials (LJPs) using ion activities, and allowing for an initial offset potential. Failure to do this results in a considerable overestimation of the Ca(2+)-induced increase in anion-cation permeability by almost three-fold at 4 mM external Ca(2+). Calculations of LJPs (using activities)_ were validated by precise agreement with direct experimental measurements. External SO (4) (2-) was found to decrease anion-cation permeability. Single-channel conductance measurements indicated that external Ca(2+) both decreased Na(+) permeability and increased Cl(-) permeability. There was no evidence of Ca(2+) changing channel pore diameter. Theoretical modeling indicates that the effect is not surface charge related. Rather, we propose that, under dilution conditions, the presence of an impermeant Ca(2+) ion in the channel pore region just external to the selectivity filter tends to electrostatically retard outward movement of Na(+) ions and to enhance movement of Cl(-) ions down their energy gradients.
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Affiliation(s)
- Silas Sugiharto
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
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23
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Ghai RS, Bikson M, Durand DM. Effects of applied electric fields on low-calcium epileptiform activity in the CA1 region of rat hippocampal slices. J Neurophysiol 2000; 84:274-80. [PMID: 10899202 DOI: 10.1152/jn.2000.84.1.274] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is well established that exogenous electric fields can suppress activity obtained in different models of epileptiform discharge such as penicillin and high potassium. In the low-calcium model of epilepsy, spontaneous epileptiform bursting is generated in the absence of synaptic transmission. It has been suggested that ephaptic interactions play a critical role in neuronal synchronization and burst propagation in this nonsynaptic model. We, therefore, tested the hypothesis that low-calcium bursting induced in the CA1 region of transverse and longitudinal hippocampal slices should be highly sensitive to exogenous electric fields. Uniform, low amplitude DC electric fields were applied during spontaneous low-calcium epileptiform activity. Modulation and full suppression of epileptiform activity was observed at field strengths between 1 and 5 mV/mm, a value significantly lower than in other in vitro models of epilepsy. We further investigated the hypothesis that the efficacy of electrical fields was related to changes in the extracellular space. Our results suggest that the osmolality of the perfusate can modulate the efficacy of electric fields. It was also observed that the ability of a field to suppress or modulate low-calcium activity was highly dependent on its orientation, polarity, as well as magnitude. Finally, it was observed that the extracellular potassium "waves" that normally accompany individual epileptiform events was abolished when the individual events were suppressed. These results suggest that DC fields modulate and suppress low-calcium activity by directly polarizing CA1 pyramidal cells.
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Affiliation(s)
- R S Ghai
- Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA
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24
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Warren RJ, Durand DM. Effects of applied currents on spontaneous epileptiform activity induced by low calcium in the rat hippocampus. Brain Res 1998; 806:186-95. [PMID: 9739139 DOI: 10.1016/s0006-8993(98)00723-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is known that both applied and endogenous electrical fields can modulate neuronal activity. In this study, we have demonstrated that anodic current injections can inhibit spontaneous epileptiform events in the absence of synaptic transmission. Activity was induced with low-Ca2+ (0.2 mM) artificial cerebrospinal fluid (ACSF) and detected with a voltage threshold detector. At the onset of an event, a current was injected into the stratum pyramidale via a tungsten electrode positioned within 150 micron of the recording site. Data was recorded with a glass pipette electrode. The results show that spontaneous epileptiform activity can be fully suppressed by subthreshold anodic currents with an average amplitude of 3.9 microA and a minimum amplitude of 1 microA. In addition, we observed that some events could be blocked by current pulses with shorter durations than the duration of the event itself. The possibility that increased tissue resistance could contribute to the efficacy of the currents was tested by measuring the step-potential increase evoked by anodic current injections. The data show a significant increase in the amplitude of the evoked potential after introduction of a low-Ca2+ medium, suggesting that tissue resistance is increasing. These results indicate that low-amplitude, subthreshold current pulses are sufficient to block epileptiform activity in a low-Ca2+ environment. The increased tissue resistance induced by sustained exposure to a low-Ca2+ medium could contribute to the low current amplitudes required to block the epileptiform events.
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Affiliation(s)
- R J Warren
- Departments of Biomedical Engineering and Neuroscience, Case Western Reserve University, Cleveland, OH 44106, USA
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25
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Davidson JL, Kehl SJ. Changes of activation and inactivation gating of the transient potassium current of rat pituitary melanotrophs caused by micromolar Cd2+ and Zn2+. Can J Physiol Pharmacol 1995; 73:36-42. [PMID: 7600450 DOI: 10.1139/y95-005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We studied the effects of Zn2+ and Cd2+ on the behaviour of IK(f), a transient outward potassium current in acutely dissociated melanotrophs of the pars intermedia of the rat pituitary gland. Micromolar concentrations of external Cd2+ or Zn2+ caused parallel and nearly equal rightward shifts along the voltage axis of the activation and steady-state inactivation curves for IK(f). The KD for the half-maximal shift of the activation curve was 278 microM for Cd2+ and 93 microM for Zn2+; the maximal shifts of the activation curve were 32.5 and 34 mV, for Cd2+ and Zn2+, respectively. The times to half-activation and half-inactivation were shifted rightward by 30-60 mV in both 500 microM Cd2+ and 500 microM Zn2+. We suggest that Cd2+ and Zn2+ interact specifically with a binding site on or electrically close to the IK(f) channel and in so doing modify the electric field "seen" by the voltage sensors.
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Affiliation(s)
- J L Davidson
- Department of Physiology, University of British Columbia, Vancouver, Canada
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26
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Conformational studies of peptides corresponding to the coeliac-activating regions of wheat alpha-gliadin. Biochem J 1990; 270:313-8. [PMID: 2400392 PMCID: PMC1131722 DOI: 10.1042/bj2700313] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The structures of four peptides corresponding to parts of the coeliac-activating protein A-gliadin were studied by structure prediction and c.d. spectroscopy. Three of the peptides corresponded to parts of the coeliac-activating N-terminal region (residues 3-55, 3-19 and 39-45) and contained two tetrapeptide motifs common to all coeliac-active regions (Pro-Ser-Gln-Gln and Gln-Gln-Gln-Pro). The Pro-Ser-Gln-Gln sequence was also present in the fourth peptide, on the basis of the C-terminal part of the molecule (211-217). These studies showed that beta-reverse turns were the predominant structural feature in all peptides and were predominantly of type I/III in two of the N-terminal peptides and type II in the C-terminal peptide. These turns form when the peptide is dissolved in solvents of low dielectric constant (trifluoroethanol) and high dielectric constant (water and iso-osmotic saline), although their presence in the N-terminal peptides may be masked in the latter solvents due to equilibrium with a poly-L-proline II structure favoured at lower temperatures.
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Abstract
The effect of phoratoxin B on transmembrane potentials and currents of frog skeletal muscle was studied using intracellular microelectrode recording and double sucrose gap voltage clamp techniques. Phoratoxin B irreversibly depolarized the membrane. The depolarization was insensitive to tetrodotoxin, tetraethylammonium, 4-amino-pyridine, cesium, cadmium and D-600. In voltage clamp experiments, phoratoxin B induced an inward resting current (Irest) which did not inactivate. Irest was blocked by increasing the external calcium concentration in the Ringer solution; it was not blocked when Sr2+ replaced Ca2+. Analysis of the peak sodium current indicated that while both Ca2+ and Sr2+ screen membrane surface charges, Ca2+ bound and reversed the phoratoxin B induced Irest whereas Sr2+ did not. The inward Irest induced by phoratoxin B developed in the presence of external chloride and remained unchanged in the presence of bicarbonate. The data suggest that the depolarizing action of the toxin might be attributed to an increase in the non-selective leak current and that it might act as a detergent.
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Affiliation(s)
- M P Sauviat
- Laboratoire de Physiologie Comparée, CNRS (URA 22), Université de Paris XI, France
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28
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Kell MJ, DeFelice LJ. Surface charge near the cardiac inward-rectifier channel measured from single-channel conductance. J Membr Biol 1988; 102:1-10. [PMID: 2456392 DOI: 10.1007/bf01875348] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The conductance of a channel to permeable ions depends on the number of ions near the mouth of the pore. Surface charge controls the local concentration, and impermeable cations can modify this charge. Correlating channel conductance with the concentration of impermeable cations therefore determines the local charge near the open pore. This paper presents data from cell-attached patches on embryonic chick ventricle cells, and it uses the conductance of inward-rectifier channels in the patch (in 100 mM K, with various concentrations of Na, Ca, Ba, and Mg) to estimate the local surface potential. The results indicate the presence of ionized residues near the mouth of the channel. Using the Boltzmann equation and the Gouy-Chapman relation, the surface potential due to these residues (in 100K/33Na/0Ca/0Ba/0Mg) is -40 mV, and the charge density is -0.25 e/nm2.
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Affiliation(s)
- M J Kell
- Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
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29
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Klein JW, Ware BR, Barclay G, Petty HR. Phospholipid dependence of calcium ion effects on electrophoretic mobilities of liposomes. Chem Phys Lipids 1987; 43:13-23. [PMID: 3581295 DOI: 10.1016/0009-3084(87)90013-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Electrophoretic light scattering (ELS) and depolarization of fluorescence have been used to determine the effect of membrane fluidity on the binding of Ca2+ to liposomes. ELS was used to measure the electrophoretic mobilities of the liposomes. Fluorescence depolarization was used to determine membrane fluidity. Zero to 30 mol% phosphatidylserine (PS) was incorporated into liposomes containing, as bulk phospholipids, one of the following: dimyristoyl-phosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), egg phosphatidylcholine (PC), or hydrogenated egg phosphatidylcholine (H egg PC). The binding of Ca2+ to the liposomes appears to be influenced by membrane fluidity. Liposomes containing bulk phospholipids whose phase transition temperature is higher than the experimental temperature exhibit enhanced binding of CA2+.
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Heggeness ST, Starkus JG. Saxitoxin and tetrodotoxin. Electrostatic effects on sodium channel gating current in crayfish axons. Biophys J 1986; 49:629-43. [PMID: 2421792 PMCID: PMC1329510 DOI: 10.1016/s0006-3495(86)83690-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The effects of extracellular saxitoxin (STX) and tetrodotoxin (TTX) on gating current (IgON) were studied in voltage clamped crayfish giant axons. At a holding potential (VH) of -90 mV, integrated gating charge (QON) was found to be 56% suppressed when 200 nM STX was added to the external solution, and 75% suppressed following the addition of 200 nM TTX. These concentrations of toxin are sufficiently high to block greater than 99% of sodium channels. A smaller suppression of IgON was observed when 1 nM STX was used (KD = 1-2 nM STX). The suppression of IgON by external toxin was found to be hold potential dependent, with only minimal suppression observed at the most hyperpolarized hold potentials, -140 to -120 mV. The maximal effect of these toxins on IgON was observed at hold potentials where the QON vs. VH plot was found to be steepest, -100 to -80 mV. The suppression of IgON induced by TTX is partially relieved following the removal of fast inactivation by intracellular treatment with N-bromoacetamide (NBA). The effect of STX and TTX on IgON is equivalent to a hyperpolarizing shift in the steady state inactivation curve, with 200 nM STX and 200 nM TTX inducing shifts of 4.9 +/- 1.7 mV and 10.0 +/- 2.1 mV, respectively. Our results are consistent with a model where the binding of toxin displaces a divalent cation from a negatively charged site near the external opening of the sodium channel, thereby producing a voltage offset sensed by the channel gating apparatus.
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Abstract
Experimental evidence has been published from isolated guinea pig muscle in vitro, and from direct ligand binding to receptors from T. californica, indicating that two agonist ions react with the nicotinic receptor by exchanging for one magnesium ion. It is the basis of the ion exchange receptor pair model, in which two acetylcholine ions exchange for one magnesium ion in contact with and between a pair of negatively charged receptor groups about 4 A apart. In the resting state the electrostatic attraction between the negatively charged receptor groups and the Mg2+ ion exerts a binding force. This binding force is opposed by the quantum mechanical repulsions of the electron clouds of the charged groups and ions in contact, together with the mutual repulsion of the pair of receptor oxyanions. When the Mg2+ ion is replaced by two acetylcholine ions the quaternary heads of the latter are positioned so that they form two mutually repelling ACh+ receptor group dipoles. As the Mg2+ ion leaves, its rehydration energy contributes to the sum of the electron cloud repulsions and the ACh+ receptor group dipole repulsions, causing the receptor groups to be forced apart activating the receptor macromolecule. The subsequent decrease in ACh+ concentration results in the reestablishment of the resting state. The coulombic electrostatic energy, the Born repulsion energy, the London attraction energy and the oxyanion ACh+ dipole repulsion energies have been calculated and shown to be consistent with the model. The displacement of the Mg2+ by two ACh+ ions makes several hundred kcals of energy available for receptor group separation and receptor activation.
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Aihara K, Matsumoto G, Ikegaya Y. Periodic and non-periodic responses of a periodically forced Hodgkin-Huxley oscillator. J Theor Biol 1984; 109:249-69. [PMID: 6482467 DOI: 10.1016/s0022-5193(84)80005-3] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Membrane potential responses of a Hodgkin-Huxley oscillator to an externally-applied sinusoidal current were numerically calculated with relation to bifurcation parameters of the amplitude and the frequency of the stimulating current. The Hodgkin-Huxley oscillator, or the Hodgkin-Huxley axon in the state of self-sustained oscillation of action potentials, was realized by immersing the axon in calcium-deficient sea water. The forced oscillations were analysed by the stroboscopic plots and/or the Lorenz plots. The results show that the periodically forced Hodgkin-Huxley oscillator exhibits not only periodic motions (harmonic or sub-harmonic synchronization) but also non-periodic motions (quasi-periodic or chaotic oscillation), that the motions were determined by the amplitude and the frequency of the stimulating current, and that the characteristic motions obtained in the present study were in reasonable agreement with those of our previous results, found experimentally in squid giant axons. Also, two kinds of routes to the chaotic oscillations were found; successive period-doubling bifurcations and formation of the intermittently chaotic oscillation from sub-harmonic synchronization.
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Barry PH, Gage PW. Ionic Selectivity of Channels at the End Plate. CURRENT TOPICS IN MEMBRANES AND TRANSPORT 1984. [DOI: 10.1016/s0070-2161(08)60434-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Hahin R, Campbell DT. Simple shifts in the voltage dependence of sodium channel gating caused by divalent cations. J Gen Physiol 1983; 82:785-805. [PMID: 6319538 PMCID: PMC2228720 DOI: 10.1085/jgp.82.6.785] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The effect of elevated divalent cation concentration on the kinetics of sodium ionic and gating currents was studied in voltage-clamped frog skeletal muscle fibers. Raising the Ca concentration from 2 to 40 mM resulted in nearly identical 30-mV shifts in the time courses of activation, inactivation, tail current decay, and ON and OFF gating currents, and in the steady state levels of inactivation, charge immobilization, and charge vs. voltage. Adding 38 mM Mg to the 2 mM Ca bathing a fiber produced a smaller shift of approximately 20 mV in gating current kinetics and the charge vs. voltage relationship. The results with both Ca and Mg are consistent with the hypothesis that elevated concentrations of these alkali earth cations alter Na channel gating by changing the membrane surface potential. The different shifts produced by Ca and Mg are consistent with the hypothesis that the two ions bind to fixed membrane surface charges with different affinities, in addition to possible screening.
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35
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D'Arrigo J. Biological surfactants stabilizing natural microbubbles in aqueous media. Adv Colloid Interface Sci 1983. [DOI: 10.1016/0001-8686(83)85001-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Schlieper P, Steiner R. Effect of pH and different substrates on the electrokinetic properties of (Na+, K+)-ATPase vesicles. BIOPHYSICS OF STRUCTURE AND MECHANISM 1983; 9:193-206. [PMID: 6299420 DOI: 10.1007/bf00537816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Some biophysical properties of a (Na+, K+)-ATPase preparation from guinea-pig kidney have been analysed. The recently developed technique of laser Doppler spectroscopy was applied to measure particle mobility under electrophoretic conditions. The following results were obtained: 1. magnesium ions at pH 7.3 decrease the mobility of the ATPase containing vesicles by binding to negatively charged surface groups. At pH 3.3 the competitive binding of protons causes a shift of the mobility vs. [Mg2+] curve to higher values of [Mg2+], 2. binding of ATP at pH 7.3 (Kd = 0.9 X 10(-4) M for (mM 1 NaCl, 0.2 KCl, 0.1 MgCl2, 0.1 Tris) was measured as an increase in particle mobility depending also on [Mg2+]. At pH 3.3 also unspecific ATP-binding occurred, 3. ITP and GTP had the same Kd value as ATP; ADP a slightly lower one (Kd = 1.2 X 10(-4) M). Tris-H3PO4 (Kd = 2.6 X 10(-4) M) was also able to increase particle mobility, but only at higher concentrations and not to the same extent as ATP; AMP induced only very small changes, 4. from the mobility-pH curve an isoelectric point of 4.1 is derived (buffer: 1 mM NaCl, 0.2 mM KCl, 0.1 mM MgCl2, 0.1 mM Tris). In the presence of 0.9 mM ATP the isoelectric point is shifted to 3.2. As the electrophoretic mobility is directly proportional to the net charge of the vesicles, the results may be interpreted as changes in surface charge density, originating from both a conformational change of the ATPase polypeptide and a decrease in vesicle size.
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Gilly WF, Armstrong CM. Slowing of sodium channel opening kinetics in squid axon by extracellular zinc. J Gen Physiol 1982; 79:935-64. [PMID: 6286845 PMCID: PMC2216458 DOI: 10.1085/jgp.79.6.935] [Citation(s) in RCA: 125] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The interaction of Zn ion on Na channels was studied in squid giant axons. At a concentration of 30 mM Zn2+ slows opening kinetics of Na channels with almost no alteration of closing kinetics. The effects of Zn2+ can be expressed as a "shift" of the gating parameters along the voltage axis, i.e., the amount of additional depolarization required to overcome the Zn2+ effect. In these terms the mean shifts caused by 30 mM Zn2+ were +29.5 mV for Na channel opening (on) kinetics (t1/2 on), +2 mV for closing (off) kinetics (tau off), and +8.4 mV for the gNa-V curve. Zn2+ does not change the shape of the instantaneous I-V curve for inward current, but reduces it in amplitude by a factor of or approximately 0.67. Outward current is unaffected. Effects of Zn2+ on gating current (measured in the absence of TTX) closely parallel its actions on gNa. On gating current kinetics are shifted by +27.5 mV, off kinetics by +6 mV, and the Q-V distribution by +6.5 mV. Kinetic modeling shows that Zn2+ slows the forward rate constants in activation without affecting backward rate constants. More than one of the several steps in activation must be affected. The results are not compatible with the usual simple theory of uniform fixed surface charge. They suggest instead that Zn2+ is attracted by a negatively charged element of the gating apparatus that is present at the outer membrane surface at rest, and migrates inward on activation.
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Schlieper P, Medda PK, Kaufmann R. Drug-induced zeta potential changes in liposomes studied by laser Doppler spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 644:273-83. [PMID: 6114748 DOI: 10.1016/0005-2736(81)90385-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The technique of laser Doppler spectroscopy is used to measure the electrophoretic mobility of liposomes under the influence of one beta-blocking agent and three local anesthetics. All four drugs decrease the mobility (i.e., the zeta potential) of negatively charged phospholipids (soybean lipids, phosphatidylserine and cardiolipin). The mobility of electrostatically neutral pure phosphatidylcholine (zero mobility under control conditions at pH 7 and 4) is increased linearly with the logarithm of drug concentration, indicating binding and incorporation of positively charged drug molecules. The sequence of strength of activity, measured by zeta-potential changes, corresponds to that found in biological tissues: propranolol greater than tetracaine greater than lidocaine greater than procaine. For purely negatively charged lipids (phosphatidylserine, cardiolipin) the activity of the drug is higher at acidic pH, (pH 4), while for electrostatically neutral (phosphatidylcholine) or partly neutral (soybean) lipid liposomes drug activity is about the same at pH 9, 7 and 4. A Hill plot of the data reveals noncooperative drug binding. From the line width of the scattering power spectrum the mean particle radius and the average interparticle distance in the samples are determined.
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Schlieper P, Mohan R, Kaufmann R. Electrokinetic properties of (Na+, K+)-ATPase vesicles as studied by laser Doppler spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 644:13-23. [PMID: 6266461 DOI: 10.1016/0005-2736(81)90053-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The technique of laser Doppler electrophoresis was applied for the study of the surface charge properties of (NA+, K+)-ATPase containing microsomal vesicles derived from guinea-pig kidney. The influence of pH, the screening and binding of uni- and divalent cations and the binding of ATP show: (1) one net negative charge per protein unit with a pK = 3.9; (2) deviation from the Debye relation between surface potential and ionic strength for univalent cations, with no difference in the effect of Na+ and K+; (3) Mg2+ binds with an association constant of Ka = 1.1. 10(2) M-1 while ATP binds with an apparent Ka = 1.1.10(4) M-1 for 1 mM NaCl, 0.2 mM KCI, 0.1 mM MgCl2, 0.1 mM Tris-HCl2, 0.1 mM Tris-HCl (pH 7.3). The binding is weaker at higher Mg2+ concentrations. There is no ATP binding in the absence of Mg2+. In addition, the average vesicle size derived from the linewidth of the quasielastic light scattering spectrum is 203.7 +/- 15.2 nm. In the presence of ATP a reduction in size is observed.
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Reuss L, Cheung LY, Grady TP. Mechanisms of cation permeation across apical cell membrane of Necturus gallbladder: effects of luminal pH and divalent cations on K+ and Na+ permeability. J Membr Biol 1981; 59:211-24. [PMID: 7241581 DOI: 10.1007/bf01875426] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Conventional microelectrode techniques were combined with unilateral mucosal ionic substitutions to determine the effects of luminal pH and luminal alkali-earth cation concentrations on apical membrane cation permeability in Necturus gallbladder epithelium. Acidification of the mucosal solution caused reversible depolarization of both cell membranes and increase of transepithelial resistance. Low pH media also caused: (a) reduction of the apical membrane depolarization induced by high K, and (b) increase of the apical membrane hyperpolarization produced by Na replacement with Li or N-Methyl-D-glucamine. These results, in conjunction with estimates of cell membrane conductances, indicate that acidification of the luminal solution produces a reduction of apical membrane K permeability (PK). Addition of alkali earth cations (Mg2+, Ca2+, Sr2+, or Ba2+) produced cell membrane depolarization, increase of relative resistance of the luminal membrane and reduction of the apical membrane potential change produced by a high-K mucosal medium. These results, as those produced by low pH, can be explained by a reduction of apical membrane PK. The effects of Ba2+ on membrane potential and relative apical membrane PK were larger than those of all other four cations at all concentrations tested (1-10 mM). The effect of Sr2+ was significantly larger than those of Mg2+ and Ca2+ at 10 mM, but not different at 5 mM. The reduction of PK produced by mucosal acidification appears to be mediated by: (a) nonspecific titration of membrane fixed negative charges, and (b) an effect of luminal proton activity on the apical K channel. Divalent cations reduce apical membrane PK probably by screening negative surface charges. The larger magnitude of the effects of Ba2+ and Sr2+ can be explained by binding to membrane sites, in the surface or in the K channel, in addition to their screening effect. We suggest that the action of luminal pH on K secretion in some segments of the renal tubule could be mediated in part by this pH-dependent K permeability of the luminal membrane.
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D’Arrigo JS. Structural features of the nonionic surfactants stabilizing long‐lived bubble nuclei. J Chem Phys 1980. [DOI: 10.1063/1.439746] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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D’Arrigo JS. Physical properties of the nonionic surfactants surrounding gas cavitation nuclei. J Chem Phys 1979. [DOI: 10.1063/1.438531] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kell DB. On the functional proton current pathway of electron transport phosphorylation. An electrodic view. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 549:55-99. [PMID: 38839 DOI: 10.1016/0304-4173(79)90018-1] [Citation(s) in RCA: 242] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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