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Makhoul-Mansour M, Zhao W, Gay N, O'Connor C, Najem JS, Mao L, Freeman EC. Ferrofluid-Based Droplet Interface Bilayer Networks. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13000-13007. [PMID: 29043824 DOI: 10.1021/acs.langmuir.7b03055] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Droplet interface bilayer (DIB) networks allow for the construction of stimuli-responsive, membrane-based materials. Traditionally used for studying cellular transport phenomena, the DIB technique has proven its practicality when creating structured droplet networks. These structures consist of aqueous compartments capable of exchanging their contents across membranous barriers in a regulated fashion via embedded biomolecules, thus approximating the activity of natural cellular systems. However, lipid bilayer networks are often static and incapable of any reconfiguration in their architecture. In this study, we investigate the incorporation of a magnetic fluid or ferrofluid within the droplet phases for the creation of magnetically responsive DIB arrays. The impact of adding ferrofluid to the aqueous phases of the DIB networks is assessed by examining the bilayers' interfacial tensions, thickness, and channel activity. Once compatibility is established, potential applications of the ferrofluid-enabled DIBs are showcased by remotely modifying membrane qualities through magnetic fields. Ferrofluids do not significantly alter the bilayers' properties or functionality and can therefore be safely embedded within the DIB platform, allowing for remote manipulation of the interfacial bilayer properties.
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Affiliation(s)
| | | | - Nicole Gay
- Department of Genetics, Stanford University , Stanford, California 94305, United States
| | - Colleen O'Connor
- College of Engineering and UW Medicine, University of Washington , Seattle, Washington 98195, United States
| | - Joseph S Najem
- Joint Institute for Biological Sciences, Oak Ridge National Laboratory, and Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States
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52
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Lockhart C, Klimov DK. Cholesterol Changes the Mechanisms of Aβ Peptide Binding to the DMPC Bilayer. J Chem Inf Model 2017; 57:2554-2565. [PMID: 28910085 DOI: 10.1021/acs.jcim.7b00431] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using isobaric-isothermal all-atom replica-exchange molecular dynamics (REMD) simulations, we investigated the equilibrium binding of Aβ10-40 monomers to the zwitterionic dimyristoylphosphatidylcholine (DMPC) bilayer containing cholesterol. Our previous REMD simulations, which studied binding of the same peptide to the cholesterol-free DMPC bilayer, served as a control, against which we measured the impact of cholesterol. Our findings are as follows. First, addition of cholesterol to the DMPC bilayer partially expels the Aβ peptide from the hydrophobic core and promotes its binding to bilayer polar headgroups. Using thermodynamic and energetics analyses, we argued that Aβ partial expulsion is not related to cholesterol-induced changes in lateral pressure within the bilayer but is caused by binding energetics, which favors Aβ binding to the surface of the densely packed cholesterol-rich bilayer. Second, cholesterol has a protective effect on the DMPC bilayer structure against perturbations caused by Aβ binding. More specifically, cholesterol reduces bilayer thinning and overall depletion of bilayer density beneath the Aβ binding footprint. Third, we found that the Aβ peptide contains a single cholesterol binding site, which involves hydrophobic C-terminal amino acids (Ile31-Val36), Phe19, and Phe20 from the central hydrophobic cluster, and cationic Lys28 from the turn region. This binding site accounts for about 76% of all Aβ-cholesterol interactions. Because cholesterol binding site in the Aβ10-40 peptide does not contain the GXXXG motif featured in cholesterol interactions with the transmembrane domain C99 of the β-amyloid precursor protein, we argued that the binding mechanisms for Aβ and C99 are distinct reflecting their different conformations and positions in the lipid bilayer. Fourth, cholesterol sharply reduces the helical propensity in the bound Aβ peptide. As a result, cholesterol largely eliminates the emergence of helical structure observed upon Aβ transition from a water environment to the cholesterol-free DMPC bilayer. We explain this effect by the formation of hydrogen bonds between cholesterol and the Aβ backbone, which prevent helix formation. Taken together, we expect that our simulations will advance understanding of a molecular-level mechanism behind the role of cholesterol in Alzheimer's disease.
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Affiliation(s)
- Christopher Lockhart
- School of Systems Biology, George Mason University , Manassas, Virginia 20110, United States
| | - Dmitri K Klimov
- School of Systems Biology, George Mason University , Manassas, Virginia 20110, United States
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53
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Dharmadana D, Reynolds NP, Conn CE, Valéry C. Molecular interactions of amyloid nanofibrils with biological aggregation modifiers: implications for cytotoxicity mechanisms and biomaterial design. Interface Focus 2017; 7:20160160. [PMID: 28630679 PMCID: PMC5474041 DOI: 10.1098/rsfs.2016.0160] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Amyloid nanofibrils are ubiquitous biological protein fibrous aggregates, with a wide range of either toxic or beneficial activities that are relevant to human disease and normal biology. Protein amyloid fibrillization occurs via nucleated polymerization, through non-covalent interactions. As such, protein nanofibril formation is based on a complex interplay between kinetic and thermodynamic factors. The process entails metastable oligomeric species and a highly thermodynamically favoured end state. The kinetics, and the reaction pathway itself, can be influenced by third party moieties, either molecules or surfaces. Specifically, in the biological context, different classes of biomolecules are known to act as catalysts, inhibitors or modifiers of the generic protein fibrillization process. The biological aggregation modifiers reviewed here include lipid membranes of varying composition, glycosaminoglycans and metal ions, with a final word on xenobiotic compounds. The corresponding molecular interactions are critically analysed and placed in the context of the mechanisms of cytotoxicity of the amyloids involved in diverse pathologies and the non-toxicity of functional amyloids (at least towards their biological host). Finally, the utilization of this knowledge towards the design of bio-inspired and biocompatible nanomaterials is explored.
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Affiliation(s)
- Durga Dharmadana
- School of Health and Biomedical Sciences, Discipline of Pharmaceutical Sciences, RMIT University, Bundoora, Melbourne, Victoria 3083, Australia
- School of Science, College of Science, Engineering and Health, RMIT University, Melbourne, Victoria 3001, Australia
| | - Nicholas P. Reynolds
- ARC Training Centre for Biodevices, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Melbourne, Victoria 3122, Australia
| | - Charlotte E. Conn
- School of Science, College of Science, Engineering and Health, RMIT University, Melbourne, Victoria 3001, Australia
| | - Céline Valéry
- School of Health and Biomedical Sciences, Discipline of Pharmaceutical Sciences, RMIT University, Bundoora, Melbourne, Victoria 3083, Australia
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54
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Eells R, Barros M, Scott KM, Karageorgos I, Heinrich F, Lösche M. Structural characterization of membrane-bound human immunodeficiency virus-1 Gag matrix with neutron reflectometry. Biointerphases 2017; 12:02D408. [PMID: 28511544 PMCID: PMC5433906 DOI: 10.1116/1.4983155] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/22/2017] [Accepted: 04/26/2017] [Indexed: 12/29/2022] Open
Abstract
The structural characterization of peripheral membrane proteins represents a tremendous challenge in structural biology due to their transient interaction with the membrane and the potential multitude of protein conformations during this interaction. Neutron reflectometry is uniquely suited to address this problem because of its ability to structurally characterize biological model systems nondestructively and under biomimetic conditions that retain full protein functionality. Being sensitive to only the membrane-bound fraction of a water-soluble peripheral protein, neutron reflectometry obtains a low-resolution average structure of the protein-membrane complex that is further refined using integrative modeling strategies. Here, the authors review the current technological state of biological neutron reflectometry exemplified by a detailed report on the structure determination of the myristoylated human immunodeficiency virus-1 (HIV-1) Gag matrix associated with phosphoserine-containing model membranes. The authors found that the HIV-1 Gag matrix is able to adopt different configurations at the membrane in a pH-dependent manner and that the myristate group orients the protein in a way that is conducive to PIP2-binding.
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Affiliation(s)
- Rebecca Eells
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Marilia Barros
- Memorial Sloan Kettering Cancer Center, New York, New York 10065
| | - Kerry M Scott
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Ioannis Karageorgos
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 and NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
| | - Mathias Lösche
- Departments of Physics and Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 and NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
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55
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Malishev R, Shaham-Niv S, Nandi S, Kolusheva S, Gazit E, Jelinek R. Bacoside-A, an Indian Traditional-Medicine Substance, Inhibits β-Amyloid Cytotoxicity, Fibrillation, and Membrane Interactions. ACS Chem Neurosci 2017; 8:884-891. [PMID: 28094495 DOI: 10.1021/acschemneuro.6b00438] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Bacoside-A, a family of compounds extracted from the Bacopa monniera plant, is a folk-medicinal substance believed to exhibit therapeutic properties, particularly enhancing cognitive functions and improving memory. We show that bacoside-A exerted significant inhibitory effects upon cytotoxicity, fibrillation, and particularly membrane interactions of amyloid-beta (1-42) (Aβ42), the peptide playing a prominent role in Alzeheimer's disease progression and toxicity. Specifically, preincubation of bacoside-A with Aβ42 significantly reduced cell toxicity and inhibited fibril formation both in buffer solution and, more significantly, in the presence of membrane vesicles. In parallel, spectroscopic and microscopic analyses reveal that bacoside-A blocked membrane interactions of Aβ42, while formation of Aβ42 oligomers was not disrupted. These interesting phenomena suggest that inhibition of Aβ42 oligomer assembly into mature fibrils, and blocking membrane interactions of the oligomers are likely the underlying factors for ameliorating amyloid toxicity by bacoside-A and its putative physiological benefits.
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Affiliation(s)
- Ravit Malishev
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shira Shaham-Niv
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sukhendu Nandi
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sofiya Kolusheva
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ehud Gazit
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Raz Jelinek
- Department of Chemistry, and §Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
- Department of Molecular Microbiology
and Biotechnology, George S.
Wise Faculty of Life Sciences, and ∥Department of Materials Science and Engineering,
Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
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56
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Luo K, Jeong KB, Oh JM, Choi SJ, Jeon TJ, Kim YR. Investigation of membrane condensation induced by CaCO3 nanoparticles and its effect on membrane protein function. RSC Adv 2017. [DOI: 10.1039/c7ra09722k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Investigation of membrane condensation induced by calcium ions released from nano-CaCO3.
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Affiliation(s)
- Ke Luo
- Graduate School of Biotechnology
- Department of Food Science and Biotechnology
- College of Life Sciences
- Kyung Hee University
- Yongin 17104
| | - Ki-Baek Jeong
- Graduate School of Biotechnology
- Department of Food Science and Biotechnology
- College of Life Sciences
- Kyung Hee University
- Yongin 17104
| | - Jae-Min Oh
- Department of Chemistry and Medical Chemistry
- College of Science and Technology
- Yonsei University
- Wonju 26493
- Korea
| | - Soo-Jin Choi
- Department of Applied Food System
- Major of Food Science & Technology
- Seoul Women's University
- Seoul 01797
- Korea
| | - Tae-Joon Jeon
- Department of Biological Engineering
- Inha University
- Incheon 22212
- Korea
| | - Young-Rok Kim
- Graduate School of Biotechnology
- Department of Food Science and Biotechnology
- College of Life Sciences
- Kyung Hee University
- Yongin 17104
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57
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Proteins behaving badly. Substoichiometric molecular control and amplification of the initiation and nature of amyloid fibril formation: lessons from and for blood clotting. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 123:16-41. [DOI: 10.1016/j.pbiomolbio.2016.08.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 08/14/2016] [Accepted: 08/19/2016] [Indexed: 02/08/2023]
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58
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Valincius G, Mickevicius M, Penkauskas T, Jankunec M. Electrochemical Impedance Spectroscopy of Tethered Bilayer Membranes: An Effect of Heterogeneous Distribution of Defects in Membranes. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.11.056] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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59
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Cranfield CG, Berry T, Holt SA, Hossain KR, Le Brun AP, Carne S, Al Khamici H, Coster H, Valenzuela SM, Cornell B. Evidence of the Key Role of H 3O + in Phospholipid Membrane Morphology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10725-10734. [PMID: 27668940 DOI: 10.1021/acs.langmuir.6b01988] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This study explains the importance of the phosphate moiety and H3O+ in controlling the ionic flux through phospholipid membranes. We show that despite an increase in the H3O+ concentration when the pH is decreased, the level of ionic conduction through phospholipid bilayers is reduced. By modifying the lipid structure, we show the dominant determinant of membrane conduction is the hydrogen bonding between the phosphate oxygens on adjacent phospholipids. The modulation of conduction with pH is proposed to arise from the varying H3O+ concentrations altering the molecular area per lipid and modifying the geometry of conductive defects already present in the membrane. Given the geometrical constraints that control the lipid phase structure of membranes, these area changes predict that organisms evolving in environments with different pHs will select for different phospholipid chain lengths, as is found for organisms near highly acidic volcanic vents (short chains) or in highly alkaline salt lakes (long chains). The stabilizing effect of the hydration shells around phosphate groups also accounts for the prevalence of phospholipids across biology. Measurement of ion permeation through lipid bilayers was made tractable using sparsely tethered bilayer lipid membranes with swept frequency electrical impedance spectroscopy and ramped dc amperometry. Additional evidence of the effect of a change in pH on lipid packing density is obtained from neutron reflectometry data of tethered membranes containing perdeuterated lipids.
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Affiliation(s)
- Charles G Cranfield
- School of Life Sciences, University of Technology Sydney , Ultimo, NSW 2007, Australia
| | - Thomas Berry
- School of Life Sciences, University of Technology Sydney , Ultimo, NSW 2007, Australia
| | - Stephen A Holt
- Australian Nuclear Science and Technology Organisation , Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Khondker R Hossain
- School of Life Sciences, University of Technology Sydney , Ultimo, NSW 2007, Australia
- Australian Nuclear Science and Technology Organisation , Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Anton P Le Brun
- Australian Nuclear Science and Technology Organisation , Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia
| | - Sonia Carne
- SDx Tethered Membranes Pty. Ltd. , Unit 6, 30-32 Barcoo Street, Roseville, NSW 2069, Australia
| | - Heba Al Khamici
- School of Life Sciences, University of Technology Sydney , Ultimo, NSW 2007, Australia
| | - Hans Coster
- School of Chemical and Biomolecular Engineering, University of Sydney , Sydney, NSW 2006, Australia
| | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney , Ultimo, NSW 2007, Australia
| | - Bruce Cornell
- SDx Tethered Membranes Pty. Ltd. , Unit 6, 30-32 Barcoo Street, Roseville, NSW 2069, Australia
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60
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Vus K, Sood R, Gorbenko G, Kinnunen P. Fluorescence monitoring of the effect of oxidized lipids on the process of protein fibrillization. Methods Appl Fluoresc 2016; 4:034008. [PMID: 28355154 DOI: 10.1088/2050-6120/4/3/034008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The kinetics of lysozyme and insulin amyloid formation in the presence of the oxidized phospholipids (oxPLs) was investigated using Thioflavin T fluorescence assay. The kinetic parameters of fibrillization process (lag time and apparent rate constant) have been determined upon varying the following experimental parameters: the type of lipid assemblies (premicellar aggregates and lipid bilayer vesicles), pH, temperature and lipid-to-protein molar ratio. It was found that oxPLs premicellar aggregates induced the more pronounced increase of the maximum Thioflavin T fluorescence, which is proportional to the extent of fibril formation, compared to the vesicles composed of the oxidized and unoxidized lipids. In contrast, the oxPLs, used as dispersions or included into vesicles, inhibited fibril nucleation and elongation under near-physiological conditions in vitro compared to liposomes containing unoxidized lipids. The results obtained provide deeper insight into the molecular mechanisms of the oxidative stress-modulated conformational diseases, and could be employed for the anti-amyloid drug development.
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Affiliation(s)
- Kateryna Vus
- Department of Nuclear and Medical Physics, V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022, Ukraine. Department of Nuclear and Medical Physics, V.N. Karazin Kharkiv National University, 12-38 Aeroflotska Str., Kharkiv 61031, Ukraine
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61
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Tamaddoni N, Taylor G, Hepburn T, Michael Kilbey S, Sarles SA. Reversible, voltage-activated formation of biomimetic membranes between triblock copolymer-coated aqueous droplets in good solvents. SOFT MATTER 2016; 12:5096-5109. [PMID: 27174295 DOI: 10.1039/c6sm00400h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Biomimetic membranes assembled from block copolymers attract considerable interest because they exhibit greater stability and longetivity compared to lipid bilayers, and some enable the reconstitution of functional transmembrane biomolecules. Yet to-date, block copolymer membranes have not been achieved using the droplet interface bilayer (DIB) method, which uniquely allows assembling single- and multi-membrane networks between water droplets in oil. Herein, we investigate the formation of poly(ethylene oxide)-b-poly(dimethyl siloxane)-b-poly(ethylene oxide) triblock copolymer-stabilized interfaces (CSIs) between polymer-coated aqueous droplets in solutions comprising combinations of decane, hexadecane and AR20 silicone oil. We demonstrate that triblock-coated droplets do not spontaneously adhere in these oils because all are thermodynamically good solvents for the hydrophobic PDMS middle block. However, thinned planar membranes are reversibly formed at the interface between droplets upon the application of a sufficient transmembrane voltage, which removes excess solvent from between droplets through electrocompression. At applied voltages above the threshold required to initiate membrane thinning, electrowetting causes the area of the CSI between droplets to increase while thickness remains constant; the CSI electrowetting response is similar to that encountered with lipid-based DIBs. In combination, these results reveal that stable membranes can be assembled in a manner that is completely reversible when an external pressure is used to overcome a barrier to adhesion caused by solvent-chain interactions, and they demonstrate new capability for connecting and disconnecting aqueous droplets via polymer-stabilized membranes.
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Affiliation(s)
- Nima Tamaddoni
- Dept. of Mech., Aero. and Biomed. Engr., 1512 Middle Dr. 414 Dougherty Hall, University of Tennessee, Knoxville, TN 37996, USA.
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Somogyi A, Katonai Z, Alpár A, Wolf E. A Novel Form of Compensation in the Tg2576 Amyloid Mouse Model of Alzheimer's Disease. Front Cell Neurosci 2016; 10:152. [PMID: 27378850 PMCID: PMC4909742 DOI: 10.3389/fncel.2016.00152] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 05/27/2016] [Indexed: 12/02/2022] Open
Abstract
One century after its first description, pathology of Alzheimer’s disease (AD) is still poorly understood. Amyloid-related dendritic atrophy and membrane alterations of susceptible brain neurons in AD, and in animal models of AD are widely recognized. However, little effort has been made to study the potential effects of combined morphological and membrane alterations on signal transfer and synaptic integration in neurons that build up affected neural networks in AD. In this study spatial reconstructions and electrophysiological measurements of layer II/III pyramidal neurons of the somatosensory cortex from wild-type (WT) and transgenic (TG) human amyloid precursor protein (hAPP) overexpressing Tg2576 mice were used to build faithful segmental cable models of these neurons. Local synaptic activities were simulated in various points of the dendritic arbors and properties of subthreshold dendritic impulse propagation and predictors of synaptic input pattern recognition ability were quantified and compared in modeled WT and TG neurons. Despite the widespread dendritic degeneration and membrane alterations in mutant mouse neurons, surprisingly little, or no change was detected in steady-state and 50 Hz sinusoidal voltage transfers, current transfers, and local and propagation delays of PSPs traveling along dendrites of TG neurons. Synaptic input pattern recognition ability was also predicted to be unaltered in TG neurons in two different soma-dendritic membrane models investigated. Our simulations predict the way how subthreshold dendritic signaling and pattern recognition are preserved in TG neurons: amyloid-related membrane alterations compensate for the pathological effects that dendritic atrophy has on subthreshold dendritic signal transfer and integration in layer II/III somatosensory neurons of this hAPP mouse model for AD. Since neither propagation of single PSPs nor integration of multiple PSPs (pattern recognition) changes in TG neurons, we conclude that AD-related neuronal hyperexcitability cannot be accounted for by altered subthreshold dendritic signaling in these neurons but hyperexcitability is related to changes in active membrane properties and network connectivity.
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Affiliation(s)
- Attila Somogyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of DebrecenDebrecen, Hungary; Kenézy Gyula Hospital Ltd., Department of Emergency MedicineDebrecen, Hungary
| | - Zoltán Katonai
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
| | - Alán Alpár
- MTA-SE NAP B Research Group of Experimental Neuroanatomy and Developmental Biology, Hungarian Academy of SciencesBudapest, Hungary; Department of Anatomy, Semmelweis UniversityBudapest, Hungary
| | - Ervin Wolf
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen Debrecen, Hungary
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63
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Andersson J, Köper I. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function. MEMBRANES 2016; 6:E30. [PMID: 27249006 PMCID: PMC4931525 DOI: 10.3390/membranes6020030] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 05/24/2016] [Accepted: 05/25/2016] [Indexed: 11/30/2022]
Abstract
Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties.
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Affiliation(s)
- Jakob Andersson
- Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, Adelaide SA 5001, Australia.
| | - Ingo Köper
- Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, Adelaide SA 5001, Australia.
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64
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Preta G, Jankunec M, Heinrich F, Griffin S, Sheldon IM, Valincius G. Tethered bilayer membranes as a complementary tool for functional and structural studies: The pyolysin case. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2070-2080. [PMID: 27211243 DOI: 10.1016/j.bbamem.2016.05.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/27/2016] [Accepted: 05/17/2016] [Indexed: 10/21/2022]
Abstract
We demonstrate the use of tethered bilayer lipid membranes (tBLMs) as an experimental platform for functional and structural studies of membrane associated proteins by electrochemical techniques. The reconstitution of the cholesterol-dependent cytolysin (CDC) pyolysin (PLO) from Trueperella pyogenes into tBLMs was followed in real-time by electrochemical impedance spectroscopy (EIS). Changes of the EIS parameters of the tBLMs upon exposure to PLO solutions were consistent with the dielectric barrier damage occurring through the formation of water-filled pores in membranes. Parallel experiments involving a mutant version of PLO, which is able to bind to the membranes but does not form oligomer pores, strengthen the reliability of this methodology, since no change in the electrochemical impedance was observed. Complementary atomic force microscopy (AFM) and neutron reflectometry (NR) measurements revealed structural details of the membrane bound PLO, consistent with the structural transformations of the membrane bound toxins found for other cholesterol dependent cytolysins. In this work, using the tBLMs platform we also observed a protective effect of the dynamin inhibitor Dynasore against pyolysin as well as pneumolysin. An effect of Dynasore in tBLMs, which was earlier observed in experiments with live cells, confirms the biological relevance of the tBLMs models, as well as demonstrates the potential of the electrochemical impedance spectroscopy to quantify membrane damage by the pore forming toxins. In conclusion, tBLMs are a reliable and complementary method to explore the activity of CDCs in eukaryotic cells and to develop strategies to limit the toxic effects of CDCs.
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Affiliation(s)
- Giulio Preta
- Department of Bioelectrochemistry and Biospectroscopy, Institute of Biochemistry, Vilnius University, Vilnius, Lithuania
| | - Marija Jankunec
- Department of Bioelectrochemistry and Biospectroscopy, Institute of Biochemistry, Vilnius University, Vilnius, Lithuania
| | - Frank Heinrich
- NIST Center for Neutron Research, Gaithersburg, MD 20899, USA
| | - Sholeem Griffin
- Institute of Life Science, Swansea University Medical School, Swansea SA2 8PP, United Kingdom
| | - Iain Martin Sheldon
- Institute of Life Science, Swansea University Medical School, Swansea SA2 8PP, United Kingdom
| | - Gintaras Valincius
- Department of Bioelectrochemistry and Biospectroscopy, Institute of Biochemistry, Vilnius University, Vilnius, Lithuania.
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Ungureanu AA, Benilova I, Krylychkina O, Braeken D, De Strooper B, Van Haesendonck C, Dotti CG, Bartic C. Amyloid beta oligomers induce neuronal elasticity changes in age-dependent manner: a force spectroscopy study on living hippocampal neurons. Sci Rep 2016; 6:25841. [PMID: 27173984 PMCID: PMC4865860 DOI: 10.1038/srep25841] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 04/22/2016] [Indexed: 01/09/2023] Open
Abstract
Small soluble species of amyloid-beta (Aβ) formed during early peptide aggregation stages are responsible for several neurotoxic mechanisms relevant to the pathology of Alzheimer's disease (AD), although their interaction with the neuronal membrane is not completely understood. This study quantifies the changes in the neuronal membrane elasticity induced by treatment with the two most common Aβ isoforms found in AD brains: Aβ40 and Aβ42. Using quantitative atomic force microscopy (AFM), we measured for the first time the static elastic modulus of living primary hippocampal neurons treated with pre-aggregated Aβ40 and Aβ42 soluble species. Our AFM results demonstrate changes in the elasticity of young, mature and aged neurons treated for a short time with the two Aβ species pre-aggregated for 2 hours. Neurons aging under stress conditions, showing aging hallmarks, are the most susceptible to amyloid binding and show the largest decrease in membrane stiffness upon Aβ treatment. Membrane stiffness defines the way in which cells respond to mechanical forces in their environment and has been shown to be important for processes such as gene expression, ion-channel gating and neurotransmitter vesicle transport. Thus, one can expect that changes in neuronal membrane elasticity might directly induce functional changes related to neurodegeneration.
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Affiliation(s)
- Andreea-Alexandra Ungureanu
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium.,imec, Kapeldreef 75, B-3001 Leuven, Belgium
| | - Iryna Benilova
- VIB Center for the Biology of Diseases, ON 4 Campus Gasthuisberg, Herestraat 49, B-3001, Leuven, Belgium
| | | | | | - Bart De Strooper
- VIB Center for the Biology of Diseases, ON 4 Campus Gasthuisberg, Herestraat 49, B-3001, Leuven, Belgium
| | - Chris Van Haesendonck
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium
| | - Carlos G Dotti
- VIB Center for the Biology of Diseases, ON 4 Campus Gasthuisberg, Herestraat 49, B-3001, Leuven, Belgium.,CSIC, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid Campus Cantoblanco, 28049 Madrid, Spain
| | - Carmen Bartic
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium.,imec, Kapeldreef 75, B-3001 Leuven, Belgium
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66
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Structure of amyloid oligomers and their mechanisms of toxicities: Targeting amyloid oligomers using novel therapeutic approaches. Eur J Med Chem 2016; 114:41-58. [DOI: 10.1016/j.ejmech.2016.02.065] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 01/22/2023]
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67
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pH Induced Conformational Transitions in the Transforming Growth Factor β-Induced Protein (TGFβIp) Associated Corneal Dystrophy Mutants. Sci Rep 2016; 6:23836. [PMID: 27030015 PMCID: PMC4814907 DOI: 10.1038/srep23836] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 02/12/2016] [Indexed: 11/24/2022] Open
Abstract
Most stromal corneal dystrophies are associated with aggregation and deposition of the mutated transforming growth factor-β induced protein (TGFβIp). The 4th_FAS1 domain of TGFβIp harbors ~80% of the mutations that forms amyloidogenic and non-amyloidogenic aggregates. To understand the mechanism of aggregation and the differences between the amyloidogenic and non-amyloidogenic phenotypes, we expressed the 4th_FAS1 domains of TGFβIp carrying the mutations R555W (non-amyloidogenic) and H572R (amyloidogenic) along with the wild-type (WT). R555W was more susceptible to acidic pH compared to H572R and displayed varying chemical stabilities with decreasing pH. Thermal denaturation studies at acidic pH showed that while WT did not undergo any conformational transition, the mutants exhibited a clear pH-dependent irreversible conversion from αβ conformation to β-sheet oligomers. The β-oligomers of both mutants were stable at physiological temperature and pH. Electron microscopy and dynamic light scattering studies showed that β-oligomers of H572R were larger compared to R555W. The β-oligomers of both mutants were cytotoxic to primary human corneal stromal fibroblast (pHCSF) cells. The β-oligomers of both mutants exhibit variations in their morphologies, sizes, thermal and chemical stabilities, aggregation patterns and cytotoxicities.
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68
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69
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Taylor GJ, Venkatesan GA, Collier CP, Sarles SA. Direct in situ measurement of specific capacitance, monolayer tension, and bilayer tension in a droplet interface bilayer. SOFT MATTER 2015; 11:7592-605. [PMID: 26289743 DOI: 10.1039/c5sm01005e] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow for determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance.
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Affiliation(s)
- Graham J Taylor
- Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, 1512 Middle Drive, 414 Dougherty Engineering Building, Knoxville, TN 37996, USA.
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70
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Yi X, Zhang Y, Gong M, Yu X, Darabedian N, Zheng J, Zhou F. Ca2+ Interacts with Glu-22 of Aβ(1–42) and Phospholipid Bilayers to Accelerate the Aβ(1–42) Aggregation Below the Critical Micelle Concentration. Biochemistry 2015; 54:6323-32. [DOI: 10.1021/acs.biochem.5b00719] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Xinyao Yi
- Department
of Chemistry and Biochemistry, California State University, Los Angeles, California 90032, United States
- College
of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Yi Zhang
- College
of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Ming Gong
- Department
of Chemistry and Biochemistry, California State University, Los Angeles, California 90032, United States
| | - Xiang Yu
- Department
of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Narek Darabedian
- Department
of Chemistry and Biochemistry, California State University, Los Angeles, California 90032, United States
| | - Jie Zheng
- Department
of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Feimeng Zhou
- Department
of Chemistry and Biochemistry, California State University, Los Angeles, California 90032, United States
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71
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Wang X, Weber JK, Liu L, Dong M, Zhou R, Li J. A novel form of β-strand assembly observed in Aβ(33-42) adsorbed onto graphene. NANOSCALE 2015; 7:15341-15348. [PMID: 26331805 DOI: 10.1039/c5nr00555h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Peptide assembly plays a seminal role in the fabrication of structural and functional architectures in cells. Characteristically, peptide assemblies are often dominated by β-sheet structures, wherein component molecules are connected by backbone hydrogen bonds in a parallel or an antiparallel fashion. While β-rich peptide scaffolds are implicated in an array of neurodegenerative diseases, the mechanisms by which toxic peptides assemble and mediate neuropathic effects are still poorly understood. In this work, we employ molecular dynamics simulations to study the adsorption and assembly of the fragment Aβ33-42 (taken from the Aβ-42 peptide widely associated with Alzheimer's disease) on a graphene surface. We observe that such Aβ33-42 fragments, which are largely hydrophobic in character, readily adsorb onto the graphitic surface and coalesce into a well-structured, β-strand-like assembly. Strikingly, the structure of such complex is quite unique: hydrophobic side-chains extend over the graphene surface and interact with adjacent peptides, yielding a well-defined mosaic of hydrophobic interaction patches. This ordered structure is markedly depleted of backbone hydrogen bonds. Hence, our simulation results reveal a distinct type of β-strand assembly, maintained by hydrophobic side-chain interactions. Our finding suggests the backbone hydrogen bond is no longer crucial to the peptide assembly. Further studies concerning whether such β-strand assembly can be realized in other peptide systems and in biologically-relevant contexts are certainly warranted.
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Affiliation(s)
- Xiaofeng Wang
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing 100049, China.
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72
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Borutaite V, Morkuniene R, Valincius G. Beta-amyloid oligomers: recent developments. Biomol Concepts 2015; 2:211-22. [PMID: 25962030 DOI: 10.1515/bmc.2011.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 05/09/2011] [Indexed: 01/01/2023] Open
Abstract
Recent studies point to a critical role of soluble β-amyloid oligomers in the pathogenesis of one of the most common neurodegenerative diseases, Alzheimer's disease (AD). Beta-amyloid peptides are cleavage products of a ubiquitously expressed protein, the amyloid precursor protein. Early studies suggested that accumulation of extracellular β-amyloid aggregates are the most toxic species causing synaptic dysfunction and neuronal loss in particular regions of the brain (neurobiological features underlying cognitive decline of the AD patients). In recent years, a shift of pardigm occurred, and now there is accumulating evidence that soluble oligomeric forms of the peptide are the most toxic to neuronal cells. In this review, we discuss recent findings on the toxic effects of amyloid-β oligomers, their physico-chemical properties and the possible pathways of their formation in vitro and in vivo.
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73
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Levitt JA, Chung PH, Suhling K. Spectrally resolved fluorescence lifetime imaging of Nile red for measurements of intracellular polarity. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:096002. [PMID: 26334975 DOI: 10.1117/1.jbo.20.9.096002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 07/17/2015] [Indexed: 06/05/2023]
Abstract
Spectrally resolved confocal microscopy and fluorescence lifetime imaging have been used to measure the polarity of lipid-rich regions in living HeLa cells stained with Nile red. The emission peak from the solvatochromic dye in lipid droplets is at a shorter wavelength than other, more polar, stained internal membranes, and this is indicative of a low polarity environment. We estimate that the dielectric constant, ϵ , is around 5 in lipid droplets and 25<ϵ<40 in other lipid-rich regions. Our spectrally resolved fluorescence lifetime imaging microscopy (FLIM) data show that intracellular Nile red exhibits complex, multiexponential fluorescence decays due to emission from a short lifetime locally excited state and a longer lifetime intramolecular charge transfer state. We measure an increase in the average fluorescence lifetime of the dye with increasing emission wavelength, as shown using phasor plots of the FLIM data. We also show using these phasor plots that the shortest lifetime decay components arise from lipid droplets. Thus, fluorescence lifetime is a viable contrast parameter for distinguishing lipid droplets from other stained lipid-rich regions. Finally, we discuss the FLIM of Nile red as a method for simultaneously mapping both polarity and relative viscosity based on fluorescence lifetime measurements.
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74
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Mruetusatorn P, Polizos G, Datskos PG, Taylor G, Sarles SA, Boreyko JB, Hayes DG, Collier CP. Control of membrane permeability in air-stable droplet interface bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4224-4231. [PMID: 25790280 DOI: 10.1021/la504712g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Air-stable droplet interface bilayers (airDIBs) on oil-infused surfaces are versatile model membranes for synthetic biology applications, including biosensing of airborne species. However, airDIBs are subject to evaporation, which can, over time, destabilize them and reduce their useful lifetime compared to traditional DIBs that are fully submerged in oil. Here, we show that the lifetimes of airDIBs can be extended by as much as an order of magnitude by maintaining the temperature just above the dew point. We find that raising the temperature from near the dew point (which was 7 °C at 38.5% relative humidity and 22 °C air temperature) to 20 °C results in the loss of hydrated water molecules from the polar headgroups of the lipid bilayer membrane due to evaporation, resulting in a phase transition with increased disorder. This dehydration transition primarily affects the bilayer electrical resistance by increasing the permeability through an increasingly disordered polar headgroup region of the bilayer. Temperature and relative humidity are conveniently tunable parameters for controlling the stability and composition of airDIB membranes while still allowing for operation in ambient environments.
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Affiliation(s)
| | | | | | | | | | - Jonathan B Boreyko
- #Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
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75
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Interactions of Lipid Membranes with Fibrillar Protein Aggregates. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 855:135-55. [PMID: 26149929 DOI: 10.1007/978-3-319-17344-3_6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Amyloid fibrils are an intriguing class of protein aggregates with distinct physicochemical, structural and morphological properties. They display peculiar membrane-binding behavior, thus adding complexity to the problem of protein-lipid interactions. The consensus that emerged during the past decade is that amyloid cytotoxicity arises from a continuum of cross-β-sheet assemblies including mature fibrils. Based on literature survey and our own data, in this chapter we address several aspects of fibril-lipid interactions, including (i) the effects of amyloid assemblies on molecular organization of lipid bilayer; (ii) competition between fibrillar and monomeric membrane-associating proteins for binding to the lipid surface; and (iii) the effects of lipids on the structural morphology of fibrillar aggregates. To illustrate some of the processes occurring in fibril-lipid systems, we present and analyze fluorescence data reporting on lipid bilayer interactions with fibrillar lysozyme and with the N-terminal 83-residue fragment of amyloidogenic mutant apolipoprotein A-I, 1-83/G26R/W@8. The results help understand possible mechanisms of interaction and mutual remodeling of amyloid fibers and lipid membranes, which may contribute to amyloid cytotoxicity.
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76
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Lipids in Amyloid-β Processing, Aggregation, and Toxicity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 855:67-94. [PMID: 26149926 DOI: 10.1007/978-3-319-17344-3_3] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Aggregation of amyloid-beta (Aβ) peptide is the major event underlying neuronal damage in Alzheimer's disease (AD). Specific lipids and their homeostasis play important roles in this and other neurodegenerative disorders. The complex interplay between the lipids and the generation, clearance or deposition of Aβ has been intensively investigated and is reviewed in this chapter. Membrane lipids can have an important influence on the biogenesis of Aβ from its precursor protein. In particular, increased cholesterol in the plasma membrane augments Aβ generation and shows a strong positive correlation with AD progression. Furthermore, apolipoprotein E, which transports cholesterol in the cerebrospinal fluid and is known to interact with Aβ or compete with it for the lipoprotein receptor binding, significantly influences Aβ clearance in an isoform-specific manner and is the major genetic risk factor for AD. Aβ is an amphiphilic peptide that interacts with various lipids, proteins and their assemblies, which can lead to variation in Aβ aggregation in vitro and in vivo. Upon interaction with the lipid raft components, such as cholesterol, gangliosides and phospholipids, Aβ can aggregate on the cell membrane and thereby disrupt it, perhaps by forming channel-like pores. This leads to perturbed cellular calcium homeostasis, suggesting that Aβ-lipid interactions at the cell membrane probably trigger the neurotoxic cascade in AD. Here, we overview the roles of specific lipids, lipid assemblies and apolipoprotein E in Aβ processing, clearance and aggregation, and discuss the contribution of these factors to the neurotoxicity in AD.
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77
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Valincius G, Mickevicius M. Tethered Phospholipid Bilayer Membranes. ADVANCES IN PLANAR LIPID BILAYERS AND LIPOSOMES 2015. [DOI: 10.1016/bs.adplan.2015.01.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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78
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Taylor GJ, Sarles SA. Heating-enabled formation of droplet interface bilayers using Escherichia coli total lipid extract. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 31:325-37. [PMID: 25514167 DOI: 10.1021/la503471m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Droplet interface bilayers (DIBs) serve as a convenient platform to study interactions between synthetic lipid membranes and proteins. However, a majority of DIBs have been assembled using a single lipid type, diphytanoylphosphatidylcholine (DPhPC). The work described herein establishes a new method to assemble DIBs using total lipid extract from Escherichia coli (eTLE); it is found that incubating oil-submerged aqueous droplets containing eTLE liposomes at a temperature above the gel-fluid phase transition temperature (Tg) promotes monolayer self-assembly that does not occur below Tg. Once monolayers are properly assembled via heating, droplets can be directly connected or cooled below Tg and then connected to initiate bilayer formation. This outcome contrasts immediate droplet coalescence observed upon contact between nonheated eTLE-infused droplets. Specific capacitance measurements confirm that the interface between droplets containing eTLE lipids is a lipid bilayer with thickness of 29.6 Å at 25 °C in hexadecane. We observe that bilayers formed from eTLE or DPhPC survive cooling and heating between 25 and 50 °C and demonstrate gigaohm (GΩ) membrane resistances at all temperatures tested. Additionally, we study the insertion of alamethicin peptides into both eTLE and DPhPC membranes to understand how lipid composition, temperature, and membrane phase influence ion channel formation. Like in DPhPC bilayers, alamethicin peptides in eTLE exhibit discrete, voltage-dependent gating characterized by multiple open channel conductance levels, though at significantly lower applied voltages. Cyclic voltammetry measurements of macroscopic channel currents confirm that the voltage-dependent conductance of alamethicin channels in eTLE bilayers occurs at lower voltages than in DPhPC bilayers at equivalent peptide concentrations. This result suggests that eTLE membranes, via composition, fluidity, or the presence of subdomains, offer an environment that enhances alamethicin insertion. For both membrane compositions, increasing temperature reduces the lifetimes of single channel gating events and increases the voltage required to cause an exponential increase in channel current. However, the fact that alamethicin insertion in eTLE exhibits significantly greater sensitivity to temperature changes through its Tg suggests that membrane phase plays an important role in channel formation. These effects are much less severe in DPhPC, where heating from 25 to 50 °C does not induce a phase change. The described technique for heating-assisted monolayer formation permits the use of other high transition temperature lipids in aqueous droplets for DIB formation, thereby increasing the types of lipids that can be considered for assembling model membranes.
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Affiliation(s)
- Graham J Taylor
- Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States
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79
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Seghezza S, Diaspro A, Canale C, Dante S. Cholesterol drives aβ(1-42) interaction with lipid rafts in model membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:13934-13941. [PMID: 25360827 DOI: 10.1021/la502966m] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The molecular mechanism at the basis of the neurodegenerative process related to Alzheimer's disease (AD) is triggered by the local composition of the neural plasma membrane. The role of cholesterol is controversial. In this investigation the interaction of the AD peptide amyloid-beta (1-42) with model membranes containing lipid rafts has been investigated by atomic force microscopy techniques. Supported lipid membranes made of phospholipids/sphingomyelin/cholesterol have been investigated as a function of the molar content of cholesterol, in a range spanning the phase diagram of the lipid system. The administration of amyloid-beta induced a phase reorganization of the lipid domains, when the cholesterol molar fraction was below 5%. At the same time, a mechanical destabilization and an appreciable thinning of the membrane induced by the peptide were detected. The major interaction was observed in the presence of the gel phase Lβ, and was enhanced by a low cholesterol amount. With the appearance of the liquid ordered phase Lo, the effect was hindered. At high cholesterol content (20% mol), no detectable effects in the bilayer morphology or in its mechanical stability were recorded. These findings give new insights on the molecular mechanism of the amyloid/membrane interaction, highlighting the peculiar role of cholesterol.
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Affiliation(s)
- Silvia Seghezza
- Nanophysics, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy
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80
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Morkuniene R, Cizas P, Jankeviciute S, Petrolis R, Arandarcikaite O, Krisciukaitis A, Borutaite V. Small Aβ1-42 oligomer-induced membrane depolarization of neuronal and microglial cells: role of N-methyl-D-aspartate receptors. J Neurosci Res 2014; 93:475-86. [PMID: 25400096 DOI: 10.1002/jnr.23510] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 10/01/2014] [Accepted: 10/02/2014] [Indexed: 11/08/2022]
Abstract
Although it is well documented that soluble beta amyloid (Aβ) oligomers are critical factors in the pathogenesis of Alzheimer's disease (AD) by causing synaptic dysfunction and neuronal death, the primary mechanisms by which Aβ oligomers trigger neurodegeneration are not entirely understood. We sought to investigate whether toxic small Aβ(1-42) oligomers induce changes in plasma membrane potential of cultured neurons and glial cells in rat cerebellar granule cell cultures leading to neuronal death and whether these effects are sensitive to the N-methyl-D-aspartate receptor (NMDA-R) antagonist MK801. We found that small Aβ(1-42) oligomers induced rapid, protracted membrane depolarization of both neurons and microglia, whereas there was no change in membrane potential of astrocytes. MK801 did not modulate Aβ-induced neuronal depolarization. In contrast, Aβ1(-42) oligomer-induced decrease in plasma membrane potential of microglia was prevented by MK801. Small Aβ(1-42) oligomers significantly elevated extracellular glutamate and caused neuronal necrosis, and both were prevented by MK801. Also, small Aβ(1-42) oligomers decreased resistance of isolated brain mitochondria to calcium-induced opening of mitochondrial permeability transition pore. In conclusion, the results suggest that the primary effect of toxic small Aβ oligomers on neurons is rapid, NMDA-R-independent plasma membrane depolarization, which leads to neuronal death. Aβ oligomers-induced depolarization of microglial cells is NMDA-R dependent.
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Affiliation(s)
- Ramune Morkuniene
- Institute of Neurosciences, Lithuanian University of Health Sciences, Kaunas, Lithuania
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81
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Nanda H, Heinrich F, Lösche M. Membrane association of the PTEN tumor suppressor: neutron scattering and MD simulations reveal the structure of protein-membrane complexes. Methods 2014; 77-78:136-46. [PMID: 25461777 DOI: 10.1016/j.ymeth.2014.10.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 10/10/2014] [Accepted: 10/14/2014] [Indexed: 12/31/2022] Open
Abstract
Neutron reflection (NR) from planar interfaces is an emerging technology that provides unique and otherwise inaccessible structural information on disordered molecular systems such as membrane proteins associated with fluid bilayers, thus addressing one of the remaining challenges of structural biology. Although intrinsically a low-resolution technique, using structural information from crystallography or NMR allows the construction of NR models that describe the architecture of protein-membrane complexes at high resolution. In addition, a combination of these methods with molecular dynamics (MD) simulations has the potential to reveal the dynamics of protein interactions with the bilayer in atomistic detail. We review recent advances in this area by discussing the application of these techniques to the complex formed by the PTEN phosphatase with the plasma membrane. These studies provide insights in the cellular regulation of PTEN, its interaction with PI(4,5)P2 in the inner plasma membrane and the pathway by which its substrate, PI(3,4,5)P3, accesses the PTEN catalytic site.
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Affiliation(s)
- Hirsh Nanda
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
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82
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Zhang M, Zhao J, Zheng J. Molecular understanding of a potential functional link between antimicrobial and amyloid peptides. SOFT MATTER 2014; 10:7425-7451. [PMID: 25105988 DOI: 10.1039/c4sm00907j] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Antimicrobial and amyloid peptides do not share common sequences, typical secondary structures, or normal biological activity but both the classes of peptides exhibit membrane-disruption ability to induce cell toxicity. Different membrane-disruption mechanisms have been proposed for antimicrobial and amyloid peptides, individually, some of which are not exclusive to either peptide type, implying that certain common principles may govern the folding and functions of different cytolytic peptides and associated membrane disruption mechanisms. Particularly, some antimicrobial and amyloid peptides have been identified to have dual complementary amyloid and antimicrobial properties, suggesting a potential functional link between amyloid and antimicrobial peptides. Given that some similar structural and membrane-disruption characteristics exist between the two classes of peptides, this review summarizes major findings, recent advances, and future challenges related to antimicrobial and amyloid peptides and strives to illustrate the similarities, differences, and relationships in the sequences, structures, and membrane interaction modes between amyloid and antimicrobial peptides, with a special focus on direct interactions of the peptides with the membranes. We hope that this review will stimulate further research at the interface of antimicrobial and amyloid peptides - which has been studied less intensively than either type of peptides - to decipher a possible link between both amyloid pathology and antimicrobial activity, which can guide drug design and peptide engineering to influence peptide-membrane interactions important in human health and diseases.
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Affiliation(s)
- Mingzhen Zhang
- Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, USA.
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83
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Stereoselective synthesis of perdeuterated phytanic acid, its phospholipid derivatives and their formation into lipid model membranes for neutron reflectivity studies. Chem Phys Lipids 2014; 183:22-33. [DOI: 10.1016/j.chemphyslip.2014.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/01/2014] [Accepted: 04/07/2014] [Indexed: 11/23/2022]
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84
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van Maarschalkerweerd A, Vetri V, Langkilde AE, Foderà V, Vestergaard B. Protein/lipid coaggregates are formed during α-synuclein-induced disruption of lipid bilayers. Biomacromolecules 2014; 15:3643-54. [PMID: 25210839 DOI: 10.1021/bm500937p] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Amyloid formation is associated with neurodegenerative diseases such as Parkinson's disease (PD). Significant α-synuclein (αSN) deposition in lipid-rich Lewy bodies is a hallmark of PD. Nonetheless, an unraveling of the connection between neurodegeneration and amyloid fibrils, including the molecular mechanisms behind potential amyloid-mediated toxic effects, is still missing. Interaction between amyloid aggregates and the lipid cell membrane is expected to play a key role in the disease progress. Here, we present experimental data based on hybrid analysis of two-photon-microscopy, solution small-angle X-ray scattering and circular dichroism data. Data show in real time changes in liposome morphology and stability upon protein addition and reveal that membrane disruption mediated by amyloidogenic αSN is associated with dehydration of anionic lipid membranes and stimulation of protein secondary structure. As a result of membrane fragmentation, soluble αSN:-lipid coaggregates are formed, hence, suggesting a novel molecular mechanism behind PD amyloid cytotoxicity.
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Affiliation(s)
- Andreas van Maarschalkerweerd
- Department of Drug Design and Pharmacology, University of Copenhagen , Universitetsparken 2, 2100 Copenhagen, Denmark
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85
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Heinrich F, Lösche M. Zooming in on disordered systems: neutron reflection studies of proteins associated with fluid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1838:2341-9. [PMID: 24674984 PMCID: PMC4082750 DOI: 10.1016/j.bbamem.2014.03.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Revised: 03/13/2014] [Accepted: 03/17/2014] [Indexed: 11/23/2022]
Abstract
Neutron reflectometry (NR) is an emerging experimental technique for the structural characterization of proteins interacting with fluid bilayer membranes under conditions that mimic closely the cellular environment. Thus, cellular processes can be emulated in artificial systems and their molecular basis studied by adding cellular components one at a time in a well-controlled environment while the resulting structures, or structural changes in response to external cues, are monitored with neutron reflection. In recent years, sample environments, data collection strategies and data analysis were continuously refined. The combination of these improvements increases the information which can be obtained from NR to an extent that enables structural characterization of protein-membrane complexes at a length scale that exceeds the resolution of the measurement by far. Ultimately, the combination of NR with molecular dynamics (MD) simulations can be used to cross-validate the results of the two techniques and provide atomic-scale structural models. This review discusses these developments in detail and demonstrates how they provide new windows into relevant biomedical problems. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.
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Affiliation(s)
- Frank Heinrich
- Physics Department, Carnegie Mellon University, Pittsburgh, PA, U.S.A.; NIST Center for Neutron Research, Gaithersburg, MD, U.S.A
| | - Mathias Lösche
- Physics Department, Carnegie Mellon University, Pittsburgh, PA, U.S.A.; NIST Center for Neutron Research, Gaithersburg, MD, U.S.A..
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86
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Cissé M, Checler F. Eph receptors: new players in Alzheimer's disease pathogenesis. Neurobiol Dis 2014; 73:137-49. [PMID: 25193466 DOI: 10.1016/j.nbd.2014.08.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/01/2014] [Accepted: 08/22/2014] [Indexed: 12/23/2022] Open
Abstract
Alzheimer's disease (AD) is devastating and leads to permanent losses of memory and other cognitive functions. Although recent genetic evidences strongly argue for a causative role of Aβ in AD onset and progression (Jonsson et al., 2012), its role in AD etiology remains a matter of debate. However, even if not the sole culprit or pathological trigger, genetic and anatomical evidences in conjunction with numerous pharmacological studies, suggest that Aβ peptides, at least contribute to the disease. How Aβ contributes to memory loss remains largely unknown. Soluble Aβ species referred to as Aβ oligomers have been shown to be neurotoxic and induce network failure and cognitive deficits in animal models of the disease. In recent years, several proteins were described as potential Aβ oligomers receptors, amongst which are the receptor tyrosine kinases of Eph family. These receptors together with their natural ligands referred to as ephrins have been involved in a plethora of physiological and pathological processes, including embryonic neurogenesis, learning and memory, diabetes, cancers and anxiety. Here we review recent discoveries on Eph receptors-mediated protection against Aβ oligomers neurotoxicity as well as their potential as therapeutic targets in AD pathogenesis.
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Affiliation(s)
- Moustapha Cissé
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, "Labex Distalz", 660 route des Lucioles, 06560, Sophia-Antipolis, Valbonne, France..
| | - Frédéric Checler
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS/UNS, "Labex Distalz", 660 route des Lucioles, 06560, Sophia-Antipolis, Valbonne, France..
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87
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Mitochondrial dysfunctions in neurodegenerative diseases: relevance to Alzheimer's disease. BIOMED RESEARCH INTERNATIONAL 2014; 2014:175062. [PMID: 24900954 PMCID: PMC4036420 DOI: 10.1155/2014/175062] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/19/2014] [Accepted: 04/20/2014] [Indexed: 01/26/2023]
Abstract
Mitochondrial dysfunctions are supposed to be responsible for many neurodegenerative diseases dominating in Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). A growing body of evidence suggests that defects in mitochondrial metabolism and particularly of electron transport chain may play a role in pathogenesis of AD. Structurally and functionally damaged mitochondria do not produce sufficient ATP and are more prominent in producing proapoptotic factors and reactive oxygen species (ROS), and this can be an early stage of several mitochondrial disorders, including neurodegenerative diseases. Mitochondrial dysfunctions may be caused by both mutations in mitochondrial or nuclear DNA that code mitochondrial components and by environmental causes. In the following review, common aspects of mitochondrial impairment concerned about neurodegenerative diseases are summarized including ROS production, impaired mitochondrial dynamics, and apoptosis. Also, damaged function of electron transport chain complexes and interactions between pathological proteins and mitochondria are described for AD particularly and marginally for PD and HD.
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88
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Probing the interplay between amyloidogenic proteins and membranes using lipid monolayers and bilayers. Adv Colloid Interface Sci 2014; 207:81-92. [PMID: 24200086 DOI: 10.1016/j.cis.2013.10.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 10/11/2013] [Accepted: 10/13/2013] [Indexed: 11/21/2022]
Abstract
Many degenerative diseases such as Alzheimer's and Parkinson's involve proteins that have a tendency to misfold and aggregate eventually forming amyloid fibers. This review describes the use of monolayers, bilayers, supported membranes, and vesicles as model systems that have helped elucidate the mechanisms and consequences of the interactions between amyloidogenic proteins and membranes. These are twofold: membranes favor the formation of amyloid structures and these induce damage in those membranes. We describe studies that show how interfaces, especially charged ones, favor amyloidogenic protein aggregation by several means. First, surfaces increase the effective protein concentration reducing a three-dimensional system to a two-dimensional one. Second, charged surfaces allow electrostatic interactions with the protein. Anionic lipids as well as rafts, rich in cholesterol and gangliosides, prove to play an especially important role. Finally, these amphipathic systems also offer a hydrophobic environment favoring conformational changes, oligomerization, and eventual formation of mature fibers. In addition, we examine several models for membrane permeabilization: protein pores, leakage induced by extraction of lipids, chaotic pores, and membrane tension, presenting illustrative examples of experimental evidence in support of these models. The picture that emerges from recent work is one where more than one mechanism is in play. Which mechanism prevails depends on the protein, its aggregation state, and the lipid environment in which the interactions occur.
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89
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Veloso AJ, Chow AM, Ganesh HVS, Li N, Dhar D, Wu DCH, Mikhaylichenko S, Brown IR, Kerman K. Electrochemical Immunosensors for Effective Evaluation of Amyloid-Beta Modulators on Oligomeric and Fibrillar Aggregation Processes. Anal Chem 2014; 86:4901-9. [DOI: 10.1021/ac500424t] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
| | - Ari M. Chow
- Centre
for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
| | - Hashwin V. S. Ganesh
- Centre
for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
| | - Nan Li
- Department
of Physical and Environmental Sciences and
| | - Devjani Dhar
- Department
of Physical and Environmental Sciences and
| | | | | | - Ian R. Brown
- Centre
for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
| | - Kagan Kerman
- Department
of Physical and Environmental Sciences and
- Centre
for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
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90
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Notarachille G, Arnesano F, Calò V, Meleleo D. Heavy metals toxicity: effect of cadmium ions on amyloid beta protein 1-42. Possible implications for Alzheimer's disease. Biometals 2014; 27:371-88. [PMID: 24557150 DOI: 10.1007/s10534-014-9719-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 02/12/2014] [Indexed: 02/02/2023]
Abstract
Cadmium (Cd) is an environmental contaminant, highly toxic to humans. This biologically non-essential element accumulates in the body, especially in the kidney, liver, lung and brain and can induce several toxic effects, depending on the concentration and the exposure time. Cd has been linked to Alzheimer's disease (AD) as a probable risk factor, as it shows higher concentrations in brain tissues of AD patients than in healthy people, its implication in the formation of neurofibrillary tangles and in the aggregation process of amyloid beta peptides (AβPs). AβPs seem to have toxic properties, particularly in their aggregated state; insoluble AβP forms, such as small and large aggregates, protofibrils and fibrils, appear to be implicated in the pathogenesis of AD. In our study, we have evaluated the effect of Cd, at different concentrations, both on the AβP1-42 ion channel incorporated in a planar lipid membrane made up of phosphatidylcholine containing 30 % cholesterol and on the secondary structure of AβP1-42 in aqueous environment. Cadmium is able to interact with the AβP1-42 peptide by acting on the channel incorporated into the membrane as well as on the peptide in solution, both decreasing AβP1-42 channel frequency and in solution forming large and amorphous aggregates prone to precipitate. These experimental observations suggesting a toxic role for Cd strengthen the hypothesis that Cd may interact directly with AβPs and may be a risk factor in AD.
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Affiliation(s)
- Gabriella Notarachille
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", via E. Orabona 4, 70126, Bari, Italy
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91
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Cellular membrane fluidity in amyloid precursor protein processing. Mol Neurobiol 2014; 50:119-29. [PMID: 24553856 DOI: 10.1007/s12035-014-8652-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 01/23/2014] [Indexed: 12/20/2022]
Abstract
The senile plaque is a pathologic hallmark of Alzheimer's disease (AD). Amyloid-β peptide (Aβ), the main constituent of senile plaques, is neurotoxic especially in its oligomeric form. Aβ is derived from the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases in the amyloidogenic pathway. Alternatively, APP can be cleaved by α-secretases within the Aβ domain to produce neurotrophic and neuroprotective α-secretase-cleaved soluble APP (sAPPα) in the nonamyloidogenic pathway. Since APP and α-, β-, and γ-secretases are membrane proteins, APP processing should be highly dependent on the membrane composition and the biophysical properties of cellular membrane. In this review, we discuss the role of the biophysical properties of cellular membrane in APP processing, especially the effects of phospholipases A(2) (PLA(2)s), fatty acids, cholesterol, and Aβ on membrane fluidity in relation to their effects on APP processing.
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92
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Guerrero-Muñoz MJ, Castillo-Carranza DL, Kayed R. Therapeutic approaches against common structural features of toxic oligomers shared by multiple amyloidogenic proteins. Biochem Pharmacol 2014; 88:468-78. [PMID: 24406245 DOI: 10.1016/j.bcp.2013.12.023] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 02/03/2023]
Abstract
Impaired proteostasis is one of the main features of all amyloid diseases, which are associated with the formation of insoluble aggregates from amyloidogenic proteins. The aggregation process can be caused by overproduction or poor clearance of these proteins. However, numerous reports suggest that amyloid oligomers are the most toxic species, rather than insoluble fibrillar material, in Alzheimer's, Parkinson's, and Prion diseases, among others. Although the exact protein that aggregates varies between amyloid disorders, they all share common structural features that can be used as therapeutic targets. In this review, we focus on therapeutic approaches against shared features of toxic oligomeric structures and future directions.
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Affiliation(s)
- Marcos J Guerrero-Muñoz
- Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA; Departments of Neurology, Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Diana L Castillo-Carranza
- Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA; Departments of Neurology, Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Rakez Kayed
- Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA; Departments of Neurology, Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA.
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93
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Relini A, Marano N, Gliozzi A. Misfolding of amyloidogenic proteins and their interactions with membranes. Biomolecules 2013; 4:20-55. [PMID: 24970204 PMCID: PMC4030986 DOI: 10.3390/biom4010020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 12/13/2013] [Accepted: 12/17/2013] [Indexed: 01/07/2023] Open
Abstract
In this paper, we discuss amyloidogenic proteins, their misfolding, resulting structures, and interactions with membranes, which lead to membrane damage and subsequent cell death. Many of these proteins are implicated in serious illnesses such as Alzheimer’s disease and Parkinson’s disease. Misfolding of amyloidogenic proteins leads to the formation of polymorphic oligomers and fibrils. Oligomeric aggregates are widely thought to be the toxic species, however, fibrils also play a role in membrane damage. We focus on the structure of these aggregates and their interactions with model membranes. Study of interactions of amlyoidogenic proteins with model and natural membranes has shown the importance of the lipid bilayer in protein misfolding and aggregation and has led to the development of several models for membrane permeabilization by the resulting amyloid aggregates. We discuss several of these models: formation of structured pores by misfolded amyloidogenic proteins, extraction of lipids, interactions with receptors in biological membranes, and membrane destabilization by amyloid aggregates perhaps analogous to that caused by antimicrobial peptides.
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Affiliation(s)
- Annalisa Relini
- Department of Physics, University of Genoa, Genoa 16146, Italy.
| | - Nadia Marano
- Department of Physics, University of Genoa, Genoa 16146, Italy.
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94
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Budvytyte R, Pleckaityte M, Zvirbliene A, Vanderah DJ, Valincius G. Reconstitution of cholesterol-dependent vaginolysin into tethered phospholipid bilayers: implications for bioanalysis. PLoS One 2013; 8:e82536. [PMID: 24349307 PMCID: PMC3862629 DOI: 10.1371/journal.pone.0082536] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/24/2013] [Indexed: 11/18/2022] Open
Abstract
Functional reconstitution of the cholesterol-dependent cytolysin vaginolysin (VLY) from Gardnerella vaginalis into artificial tethered bilayer membranes (tBLMs) has been accomplished. The reconstitution of VLY was followed in real-time by electrochemical impedance spectroscopy (EIS). Changes of the EIS parameters of the tBLMs upon exposure to VLY solutions were consistent with the formation of water-filled pores in the membranes. It was found that reconstitution of VLY is a strictly cholesterol-dependent, irreversible process. At a constant cholesterol concentration reconstitution of VLY occurred in a concentration-dependent manner, thus allowing the monitoring of VLY concentration and activity in vitro and opening possibilities for tBLM utilization in bioanalysis. EIS methodology allowed us to detect VLY down to 0.5 nM (28 ng/mL) concentration. Inactivation of VLY by certain amino acid substitutions led to noticeably lesser tBLM damage. Pre-incubation of VLY with the neutralizing monoclonal antibody 9B4 inactivated the VLY membrane damage in a concentration-dependent manner, while the non-neutralizing antibody 21A5 exhibited no effect. These findings demonstrate the biological relevance of the interaction between VLY and the tBLM. The membrane-damaging interaction between VLY and tBLM was observed in the absence of the human CD59 receptor, known to strongly facilitate the hemolytic activity of VLY. Taken together, our study demonstrates the applicability of tBLMs as a bioanalytical platform for the detection of the activity of VLY and possibly other cholesterol-dependent cytolysins.
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Affiliation(s)
- Rima Budvytyte
- Department of Bioelectrochemistry and Biospectroscopy, Institute of Biochemistry, Vilnius University, Vilnius, Lithuania
- Bio Complexity Department, The Niels Bohr Institute, Copenhagen University, Copenhagen, Denmark
| | - Milda Pleckaityte
- Department of Immunology and Cell Biology, Institute of Biotechnology, Vilnius University, Vilnius, Lithuania
| | - Aurelija Zvirbliene
- Department of Immunology and Cell Biology, Institute of Biotechnology, Vilnius University, Vilnius, Lithuania
| | - David J. Vanderah
- Biomolecular Structure and Function Group, National Institute of Standards and Technology at Institute of Bioscience and Biotechnology Research, Rockville, Maryland, United States of America
| | - Gintaras Valincius
- Department of Bioelectrochemistry and Biospectroscopy, Institute of Biochemistry, Vilnius University, Vilnius, Lithuania
- * E-mail:
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95
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Signore G, Abbandonato G, Storti B, Stöckl M, Subramaniam V, Bizzarri R. Imaging the static dielectric constant in vitro and in living cells by a bioconjugable GFP chromophore analog. Chem Commun (Camb) 2013; 49:1723-5. [PMID: 23340669 DOI: 10.1039/c3cc38071h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the local static dielectric constant. This probe can be chemically functionalized for selective targeting at the intracellular level.
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Affiliation(s)
- Giovanni Signore
- Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Pisa, Italy
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96
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Wilson NP, Gates B, Castellanos M. Modeling the short time-scale dynamics of β-amyloid–neuron interactions. J Theor Biol 2013; 331:28-37. [DOI: 10.1016/j.jtbi.2013.02.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 01/08/2013] [Accepted: 02/18/2013] [Indexed: 12/31/2022]
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97
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Darwish TA, Luks E, Moraes G, Yepuri NR, Holden PJ, James M. Synthesis of deuterated [D32 ]oleic acid and its phospholipid derivative [D64 ]dioleoyl-sn-glycero-3-phosphocholine. J Labelled Comp Radiopharm 2013; 56:520-9. [PMID: 24285531 DOI: 10.1002/jlcr.3088] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 06/12/2013] [Accepted: 06/12/2013] [Indexed: 11/07/2022]
Abstract
Oleic acid and its phospholipid derivatives are fundamental to the structure and function of cellular membranes. As a result, there has been increasing interest in the availability of their deuterated forms for many nuclear magnetic resonance, infrared, mass spectroscopy and neutron scattering studies. Here, we present for the first time a straightforward, large-scale (gram quantities) synthesis of highly deuterated [D32 ]oleic acid by using multiple, yet simple and high yielding reactions. The precursors for the synthesis of [D32 ]oleic acid are [D14 ]azelaic acid and [D17 ]nonanoic acid, which were obtained by complete deuteration (>98% D) of their (1) H forms by using metal catalysed hydrothermal H/D exchange reactions. The oleic acid was produced with ca. 94% D isotopic purity and with no contamination by the trans-isomer (elaidic acid). The subsequent synthesis of [D64 ]dioleoyl-sn-glycero-3-phosphocholine from [D32 ]oleic acid is also described.
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Affiliation(s)
- Tamim A Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001 Kirrawee, DC NSW, 2232, Australia
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98
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Budvytyte R, Valincius G, Niaura G, Voiciuk V, Mickevicius M, Stauffer H, Goh HZ, Shekhar P, Heinrich F, Shenoy S, Lösche M, Vanderah DJ. Structure and properties of tethered bilayer lipid membranes with unsaturated anchor molecules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:8645-56. [PMID: 23745652 PMCID: PMC3753044 DOI: 10.1021/la401132c] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The self-assembled monolayers (SAMs) of new lipidic anchor molecule HC18 [Z-20-(Z-octadec-9-enyloxy)-3,6,9,12,15,18,22-heptaoxatetracont-31-ene-1-thiol] and mixed HC18/β-mercaptoethanol (βME) SAMs were studied by spectroscopic ellipsometry, contact angle measurements, reflection-absorption infrared spectroscopy, and electrochemical impedance spectroscopy (EIS) and were evaluated in tethered bilayer lipid membranes (tBLMs). Our data indicate that HC18, containing a double bond in the alkyl segments, forms highly disordered SAMs up to anchor/βME molar fraction ratios of 80/20 and result in tBLMs that exhibit higher lipid diffusion coefficients relative to those of previous anchor compounds with saturated alkyl chains, as determined by fluorescence correlation spectroscopy. EIS data shows the HC18 tBLMs, completed by rapid solvent exchange or vesicle fusion, form more easily than with saturated lipidic anchors, exhibit excellent electrical insulating properties indicating low defect densities, and readily incorporate the pore-forming toxin α-hemolysin. Neutron reflectivity measurements on HC18 tBLMs confirm the formation of complete tBLMs, even at low tether compositions and high ionic lipid compositions. Our data indicate that HC18 results in tBLMs with improved physical properties for the incorporation of integral membrane proteins (IMPs) and that 80% HC18 tBLMs appear to be optimal for practical applications such as biosensors where high electrical insulation and IMP/peptide reconstitution are imperative.
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Affiliation(s)
- Rima Budvytyte
- Institute of Biochemistry, Vilnius University, Vilnius, LT-08662, Lithuania
| | - Gintaras Valincius
- Institute of Biochemistry, Vilnius University, Vilnius, LT-08662, Lithuania
| | - Gediminas Niaura
- Institute of Biochemistry, Vilnius University, Vilnius, LT-08662, Lithuania
| | - Vladislava Voiciuk
- Institute of Biochemistry, Vilnius University, Vilnius, LT-08662, Lithuania
| | | | - Hilary Stauffer
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Hood College, Frederick, MD 21701
| | - Haw-Zan Goh
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213
| | | | - Frank Heinrich
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Siddharth Shenoy
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Mathias Lösche
- Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - David J. Vanderah
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Institute for Bioscience and Biotechnology Research, Rockville, MD 20850
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99
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Romero D. Bacterial determinants of the social behavior of Bacillus subtilis. Res Microbiol 2013; 164:788-98. [PMID: 23791621 DOI: 10.1016/j.resmic.2013.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 05/23/2013] [Indexed: 10/26/2022]
Abstract
Bacteria utilize sophisticated cellular machinery to sense environmental changes and coordinate the most appropriate response. Fine sensors located on cell surfaces recognize a myriad of triggers and initiate genetic cascades leading to activation or repression of certain groups of genes. Structural elements such as pilli, exopolysaccharides and flagella are also exposed at the cell surface and contribute to modulating the intimate interaction with surfaces and host cells. This review will cover the latest advances in our understanding of the biology and functionality of these bacterial determinants within the context of biofilm formation of Bacillus subtilis.
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Affiliation(s)
- Diego Romero
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora (IHSM-UMA-CSIC), Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain.
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100
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AβP1-42 incorporation and channel formation in planar lipid membranes: the role of cholesterol and its oxidation products. J Bioenerg Biomembr 2013; 45:369-81. [DOI: 10.1007/s10863-013-9513-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 04/12/2013] [Indexed: 02/06/2023]
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