1
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Cornet J, Coulonges N, Pezeshkian W, Penissat-Mahaut M, Desgrez-Dautet H, Marrink SJ, Destainville N, Chavent M, Manghi M. There and back again: bridging meso- and nano-scales to understand lipid vesicle patterning. SOFT MATTER 2024; 20:4998-5013. [PMID: 38884641 DOI: 10.1039/d4sm00089g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
We describe a complete methodology to bridge the scales between nanoscale molecular dynamics and (micrometer) mesoscale Monte Carlo simulations in lipid membranes and vesicles undergoing phase separation, in which curving molecular species are furthermore embedded. To go from the molecular to the mesoscale, we notably appeal to physical renormalization arguments enabling us to rigorously infer the mesoscale interaction parameters from its molecular counterpart. We also explain how to deal with the physical timescales at stake at the mesoscale. Simulating the as-obtained mesoscale system enables us to equilibrate the long wavelengths of the vesicles of interest, up to the vesicle size. Conversely, we then backmap from the meso- to the nano-scale, which enables us to equilibrate in turn the short wavelengths down to the molecular length-scales. By applying our approach to the specific situation of patterning a vesicle membrane, we show that macroscopic membranes can thus be equilibrated at all length-scales in achievable computational time offering an original strategy to address the fundamental challenge of timescale in simulations of large bio-membrane systems.
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Affiliation(s)
- Julie Cornet
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, France.
| | - Nelly Coulonges
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, France.
- Institut de Pharmacologie et Biologie Structurale, Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier, 31400, Toulouse, France.
| | - Weria Pezeshkian
- Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
| | - Maël Penissat-Mahaut
- Institut de Pharmacologie et Biologie Structurale, Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier, 31400, Toulouse, France.
| | - Hermes Desgrez-Dautet
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, France
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | | | - Matthieu Chavent
- Institut de Pharmacologie et Biologie Structurale, Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier, 31400, Toulouse, France.
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, France
| | - Manoel Manghi
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, France.
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2
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Deng Z, You X, Lin Z, Dong X, Yuan B, Yang K. Membrane-Active Peptides Attack Cell Membranes in a Lipid-Regulated Curvature-Generating Mode. J Phys Chem Lett 2023:6422-6430. [PMID: 37432779 DOI: 10.1021/acs.jpclett.3c01115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/13/2023]
Abstract
Membrane-active peptides (MAPs) exhibit great potential in biomedical applications due to their unique ability to overcome the cell membrane barrier. However, the interactions between MAPs and membranes are complex, and little is known about the possibility of MAP action being specific to certain types of membranes. In this study, a combination of molecular dynamics simulations and theoretical analysis was utilized to investigate the interactions between typical MAPs and realistic cell membrane systems. Remarkably, the simulations revealed that MAPs can attack membranes by generating and sensing positive mean curvature, which is dependent on lipid composition. Furthermore, theoretical calculations demonstrated that this lipid-regulated curvature-based membrane attack mechanism is an integrated result of multiple effects, including peptide-induced membrane wedge and softening effects, the lipid shape effect, the area-difference elastic effect, and the boundary edge effect of formed peptide-lipid nanodomains. This study enhances our comprehension of MAP-membrane interactions and highlights the potential for developing membrane-specific MAP-based agents.
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Affiliation(s)
- Zhixiong Deng
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, Jiangsu, China
| | - Xin You
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, Jiangsu, China
| | - Zhao Lin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xuewei Dong
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, Jiangsu, China
| | - Bing Yuan
- Songshan Lake Materials Laboratory, Dongguan 523808 Guangdong, China
| | - Kai Yang
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, Jiangsu, China
- Songshan Lake Materials Laboratory, Dongguan 523808 Guangdong, China
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3
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Wongsirojkul N, Masuta A, Shimokawa N, Takagi M. Control of Line Tension at Phase-Separated Lipid Domain Boundaries: Monounsaturated Fatty Acids with Different Chain Lengths and Osmotic Pressure. MEMBRANES 2022; 12:membranes12080781. [PMID: 36005696 PMCID: PMC9415386 DOI: 10.3390/membranes12080781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 08/04/2022] [Accepted: 08/12/2022] [Indexed: 06/01/2023]
Abstract
Line tension at phase-separated lipid domain boundaries is an important factor that governs the stability of the phase separation. We studied the control of the line tension in lipid membranes composed of dioleoylphosphocholine (DOPC), dipalmitoylphosphocholine (DPPC), and cholesterol (Chol) by the addition of the following three monounsaturated fatty acids (MUFAs) with different chain lengths: palmitoleic acid (PaA), oleic acid (OA), and eicosenoic acid (EiA). In addition, we attempted to alter the line tension by applying osmotic pressure. The phase behavior of the MUFA-containing lipid membranes in the presence and absence of osmotic stress was observed by fluorescence and confocal laser scanning microscopy. The line tension was quantitatively measured from the domain boundary fluctuation by flicker spectroscopy, and the interactions between the lipids and MUFAs were examined by differential scanning calorimetry. PaA and OA, which are shorter MUFAs, decreased the line tension, whereas EiA changed the liquid domain to a solid domain. The osmotic pressure increased the line tension, even in the presence of MUFAs. It may be possible to control the line tension by combining the chemical approach of MUFA addition and the physical approach of applying osmotic pressure.
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Affiliation(s)
| | | | | | - Masahiro Takagi
- Correspondence: (N.S.); (M.T.); Tel.: +81-761-51-1650 (M.T.)
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4
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Destainville N, Coulonges N. Boundary fluctuation dynamics of a phase-separated domain in planar geometry. Phys Rev E 2022; 105:064115. [PMID: 35854539 DOI: 10.1103/physreve.105.064115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Using phase-ordering kinetics and of renormalization group theories, we derive analytically the relaxation times of the long wavelength fluctuations of a phase-separated domain boundary in the vicinity of (and below) the critical temperature in the planar Ising universality class. For a conserved order parameter, the relaxation time grows like Λ^{3} at wavelength Λ and can be expressed in terms of parameters relevant at the microscopic scale: lattice spacing, bulk diffusion coefficient of the minority phase, and temperature. These results are supported by numerical simulations of 2D Ising models, enabling in addition calculating the nonuniversal numerical prefactor. We discuss the applications of these findings to the determination of the real timescale associated with elementary Monte Carlo moves from the measurement of long wavelength relaxation times on experimental systems or molecular dynamics simulations.
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Affiliation(s)
- Nicolas Destainville
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Nelly Coulonges
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, Toulouse, France
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5
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Recent Advances in Fluorescence Recovery after Photobleaching for Decoupling Transport and Kinetics of Biomacromolecules in Cellular Physiology. Polymers (Basel) 2022; 14:polym14091913. [PMID: 35567083 PMCID: PMC9105003 DOI: 10.3390/polym14091913] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/27/2022] [Accepted: 04/29/2022] [Indexed: 12/16/2022] Open
Abstract
Among the new molecular tools available to scientists and engineers, some of the most useful include fluorescently tagged biomolecules. Tools, such as green fluorescence protein (GFP), have been applied to perform semi-quantitative studies on biological signal transduction and cellular structural dynamics involved in the physiology of healthy and disease states. Such studies focus on drug pharmacokinetics, receptor-mediated endocytosis, nuclear mechanobiology, viral infections, and cancer metastasis. In 1976, fluorescence recovery after photobleaching (FRAP), which involves the monitoring of fluorescence emission recovery within a photobleached spot, was developed. FRAP allowed investigators to probe two-dimensional (2D) diffusion of fluorescently-labelled biomolecules. Since then, FRAP has been refined through the advancements of optics, charged-coupled-device (CCD) cameras, confocal microscopes, and molecular probes. FRAP is now a highly quantitative tool used for transport and kinetic studies in the cytosol, organelles, and membrane of a cell. In this work, the authors intend to provide a review of recent advances in FRAP. The authors include epifluorescence spot FRAP, total internal reflection (TIR)/FRAP, and confocal microscope-based FRAP. The underlying mathematical models are also described. Finally, our understanding of coupled transport and kinetics as determined by FRAP will be discussed and the potential for future advances suggested.
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6
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Pusterla JM, Cannas SA, Schneck E, Oliveira RG. Purified myelin lipids display a critical mixing point at low surface pressure. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183874. [PMID: 35120896 DOI: 10.1016/j.bbamem.2022.183874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Lipids extracted from Purified Myelin Membranes (LPMM) were spread as monomolecular films at the air/aqueous interface. The films were visualized by Brewster Angle Microscopy (BAM) at different lateral pressures (π) and ionic environments. Coexistence of Liquid-Expanded (LE) and cholesterol-enriched (CE) rounded domains persisted up to π ≈ 5 mN/m but the monolayers became homogeneous at higher surface pressures. Before mixing, the domains distorted to non-rounded domains. We experimentally measured the line tension (λ) for the lipid monolayers at the domain borders by a shape relaxation technique using non-homogeneous electric fields. Regardless of the subphase conditions, the obtained line tensions are of the order of pN and tended to decrease as lateral pressure increased toward the mixing point. From the mean square displacement of nested trapped domains, we also calculated the dipole density difference between phases (μ). A non-linear drop was detected in this parameter as the mixing point is approached. Here we quantitively evaluated the π-dependance of both parameters with proper power laws in the vicinity of the critical mixing surface pressure, and the exponents showed to be consistent with a critical phenomenon in the two-dimensional Ising universality class. This idea of bidimensionality was found to be compatible only for simplified lipidic systems, while for whole myelin monolayers, that means including proteins, no critical mixing point was detected. Finally, the line tension values were related with the thickness differences between phases (Δt) near the critical point.
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Affiliation(s)
- Julio M Pusterla
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC)-Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina; Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany.
| | - Sergio A Cannas
- Instituto de Física Enrique Gaviola (IFEG-CONICET), Facultad de Matemática Astronomía Física y Computación, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
| | - Emanuel Schneck
- Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany.
| | - Rafael G Oliveira
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC)-Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
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7
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Fauquignon M, Ibarboure E, Le Meins JF. Hybrid polymer/lipid vesicles: Influence of polymer architecture and molar mass on line tension. Biophys J 2022; 121:61-67. [PMID: 34890579 PMCID: PMC8758416 DOI: 10.1016/j.bpj.2021.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 10/27/2021] [Accepted: 12/06/2021] [Indexed: 01/07/2023] Open
Abstract
Hybrid polymer/lipid vesicles are self-assembled structures that have been the subject of an increasing number of studies in recent years. They are particularly promising tools in the development of cell membrane models because they offer the possibility to fine-tune their membrane structure by adjusting the distribution of components (presence or absence of "raft-like" lipid domains), which is of prime importance to control their membrane properties. Line tension in multiphase membranes is known to be a key parameter on membrane structuration, but remains unexplored, either experimentally or by computer modeling for hybrid polymer/lipid vesicles. In this study, we were able to measure the line tension on different budded hybrid vesicles, using a micropipette aspiration technique, and show the influence of the molar mass and the architecture of block copolymers on line tension and its consequences for membrane structuration.
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Affiliation(s)
- Martin Fauquignon
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, Pessac, France
| | - Emmanuel Ibarboure
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, Pessac, France
| | - Jean-François Le Meins
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, Pessac, France,Corresponding author
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8
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Nair KS, Raj NB, Nampoothiri KM, Mohanan G, Acosta-Gutiérrez S, Bajaj H. Curved membrane structures induced by native lipids in giant vesicles. J Colloid Interface Sci 2021; 611:397-407. [PMID: 34963074 DOI: 10.1016/j.jcis.2021.12.098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 10/19/2022]
Abstract
Native lipids in cell-membrane support crucial functions like intercell communication via their ability to deform into curved membrane structures. Cell membrane mimicking Giant unilamellar vesicles (GUV) is imperative in understanding native lipid's role in membrane transformation however remains challenging to assemble. We construct two giant vesicle models mimicking bacterial inner-membrane (IM) and outer-membrane (OM) under physiological conditions using single-step gel-assisted lipid swelling. IM vesicles composed of native bacterial lipids undergo small-scale membrane remodeling into bud and short-nanotube structures. In contrast, OM vesicles asymmetrically assembled from Lipopolysaccharide (LPS) and bacterial lipids underwent global membrane deformation under controlled osmotic stress. Remarkably, highly-curved structures mimicking cell-membrane architectures, including daughter vesicle networks interconnected by necks and nano-tubes ranging from micro to nanoscale, are generated in OM vesicles at osmotic stress comparable to that applied in IM vesicles. Further, we provide a quantitative description of the membrane structures by experimentally determining membrane elastic parameters, i.e., neck curvature and bending rigidity. We can conclude that a larger spontaneous curvature estimated from the neck curvature and softer membranes in OM vesicles is responsible for large-scale deformation compared to IM vesicles. Our findings will help comprehend the shape dynamics of complex native bacterial lipid membranes.
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Affiliation(s)
- Karthika S Nair
- Microbial Processes and Technology Division, CSIR- National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695019, Kerala, India
| | - Neethu B Raj
- Microbial Processes and Technology Division, CSIR- National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695019, Kerala, India
| | - K Madhavan Nampoothiri
- Microbial Processes and Technology Division, CSIR- National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695019, Kerala, India; Academy of Scientific and Innovative Research (AcSIR), CSIR-Human Resource Development Centre, Ghaziabad 201002, India
| | - Gayathri Mohanan
- Microbial Processes and Technology Division, CSIR- National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695019, Kerala, India
| | - Silvia Acosta-Gutiérrez
- Department of Chemistry, Institute of Structural and Molecular Biology, University College London, UK.
| | - Harsha Bajaj
- Microbial Processes and Technology Division, CSIR- National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695019, Kerala, India; Academy of Scientific and Innovative Research (AcSIR), CSIR-Human Resource Development Centre, Ghaziabad 201002, India.
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9
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Feigenson GW. On the small size of liquid-disordered + liquid-ordered nanodomains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183685. [PMID: 34175299 DOI: 10.1016/j.bbamem.2021.183685] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Revised: 06/09/2021] [Accepted: 06/17/2021] [Indexed: 11/15/2022]
Abstract
Four-component phase diagrams reveal that Liquid-disordered + liquid-ordered (Ld + Lo) nanodomains are exclusively found adjacent to a three-phase region, and so cannot be a one-phase microemulsion. Of importance for understanding biological membranes, a small change in lipid bilayer composition can change the size of these coexisting phase domains hundreds of fold, between tens of nanometers and microns. Nanodomain diameter, measured from small angle neutron scattering, is in the range 15-35 nm, consistent with stabilization by repulsive dipole fields. Ld/Lo line tension controls the Ld + Lo domain size transition. Other than size, chemical and physical properties of the phase domains do not seem to change during the transition. Unfavorable lipid-lipid pairwise interactions, rather than phase thickness mismatch, seem to be the main reason for Ld + Lo immiscibility. Pairwise interactions of cholesterol-phospholipid seem to be favorable, whereas pairwise interactions of high-melting phospholipid with low-melting phospholipid are unfavorable. Measured Ld/Lo line tension, like the phase separation, is created mainly by unfavorable lipid-lipid pairwise interactions. Lipid dipole-dipole repulsion opposes these unfavorable lipid-lipid pairwise interactions and thus, in a sense, is the reason that nanodomains form. Bilayer physical and chemical properties measured from macroscopic domains of coexisting Ld + Lo phases should be good approximations for the properties of coexisting nanoscopic domains.
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Affiliation(s)
- Gerald W Feigenson
- Cornell University Department of Molecular Biology and Genetics, Room 201 Biotechnology Building, 215 Tower Rd. Ithaca, New York 14853, United States.
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10
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Souissi M, Pernier J, Rossier O, Giannone G, Le Clainche C, Helfer E, Sengupta K. Integrin-Functionalised Giant Unilamellar Vesicles via Gel-Assisted Formation: Good Practices and Pitfalls. Int J Mol Sci 2021; 22:6335. [PMID: 34199292 PMCID: PMC8231826 DOI: 10.3390/ijms22126335] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/26/2021] [Accepted: 06/08/2021] [Indexed: 01/16/2023] Open
Abstract
Giant unilamellar vesicles (GUV) are powerful tools to explore physics and biochemistry of the cell membrane in controlled conditions. For example, GUVs were extensively used to probe cell adhesion, but often using non-physiological linkers, due to the difficulty of incorporating transmembrane adhesion proteins into model membranes. Here we describe a new protocol for making GUVs incorporating the transmembrane protein integrin using gel-assisted swelling. We report an optimised protocol, enumerating the pitfalls encountered and precautions to be taken to maintain the robustness of the protocol. We characterise intermediate steps of small proteoliposome formation and the final formed GUVs. We show that the integrin molecules are successfully incorporated and are functional.
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Affiliation(s)
- Mariem Souissi
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
| | - Julien Pernier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France; (J.P.); (C.L.C.)
| | - Olivier Rossier
- Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France; (O.R.); (G.G.)
| | - Gregory Giannone
- Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France; (O.R.); (G.G.)
| | - Christophe Le Clainche
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France; (J.P.); (C.L.C.)
| | - Emmanuèle Helfer
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
| | - Kheya Sengupta
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
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11
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Investigation of the domain line tension in asymmetric vesicles prepared via hemifusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183586. [PMID: 33647248 DOI: 10.1016/j.bbamem.2021.183586] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/28/2021] [Accepted: 02/12/2021] [Indexed: 12/20/2022]
Abstract
The plasma membrane (PM) is asymmetric in lipid composition. The distinct and characteristic lipid compositions of the exoplasmic and cytoplasmic leaflets lead to different lipid-lipid interactions and physical-chemical properties in each leaflet. The exoplasmic leaflet possesses an intrinsic ability to form coexisting ordered and disordered fluid domains, whereas the cytoplasmic leaflet seems to form a single fluid phase. To better understand the interleaflet interactions that influence domains, we compared asymmetric model membranes that capture salient properties of the PM with simpler symmetric membranes. Using asymmetric giant unilamellar vesicles (aGUVs) prepared by hemifusion with a supported lipid bilayer, we investigate the domain line tension that characterizes the behavior of coexisting ordered + disordered domains. The line tension can be related to the contact perimeter of the different phases. Compared to macroscopic phase separation, the appearance of modulated phases was found to be a robust indicator of a decrease in domain line tension. Symmetric GUVs of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC)/cholesterol (chol) were formed into aGUVs by replacing the GUV outer leaflet with DOPC/chol = 0.8/0.2 in order to create a cytoplasmic leaflet model. These aGUVs revealed lower line tension for the ordered + disordered domains of the exoplasmic model leaflet.
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12
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Fonda P, Al-Izzi SC, Giomi L, Turner MS. Measuring Gaussian Rigidity Using Curved Substrates. PHYSICAL REVIEW LETTERS 2020; 125:188002. [PMID: 33196252 DOI: 10.1103/physrevlett.125.188002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 10/02/2020] [Indexed: 06/11/2023]
Abstract
The Gaussian (saddle splay) rigidity of fluid membranes controls their equilibrium topology but is notoriously difficult to measure. In lipid mixtures, typical of living cells, linear interfaces separate liquid ordered (LO) from liquid disordered (LD) bilayer phases at subcritical temperatures. Here, we consider such membranes supported by curved substrates that thereby control the membrane curvatures. We show how spectral analysis of the fluctuations of the LO-LD interface provides a novel way of measuring the difference in Gaussian rigidity between the two phases. We provide a number of conditions for such interface fluctuations to be both experimentally measurable and sufficiently sensitive to the value of the Gaussian rigidity, while remaining in the perturbative regime of our analysis.
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Affiliation(s)
- Piermarco Fonda
- Theory & Bio-Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - Sami C Al-Izzi
- School of Physics & EMBL-Australia node in Single Molecule Science, University of New South Wales, 2052 Sydney, Australia
- Department of Mathematics, University of Warwick, Coventry CV4 7AL, United Kingdom
- Institut Curie, PSL Research University, CNRS, Physical Chemistry Curie, F-75005, Paris, France
| | - Luca Giomi
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - Matthew S Turner
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
- Centre for Complexity Science, University of Warwick, Coventry CV4 7AL, United Kingdom
- Department of Chemical Engineering, University of Kyoto, Kyoto 615-8510, Japan
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13
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Luo Y, Maibaum L. Modulated and spiral surface patterns on deformable lipid vesicles. J Chem Phys 2020; 153:144901. [PMID: 33086800 DOI: 10.1063/5.0020087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We investigate the behavior of two-dimensional systems that exhibit a transition between homogeneous and spatially inhomogeneous phases, which have spherical topology, and whose mechanical properties depend on the local value of the order parameter. One example of such a system is multicomponent lipid bilayer vesicles, which serve as a model to study cellular membranes. Under certain conditions, such bilayers separate into coexisting liquid-ordered and liquid-disordered regions. When arranged into the shape of small vesicles, this phase coexistence can result in spatial patterns that are more complex than the basic two-domain configuration encountered in typical bulk systems. The difference in bending rigidity between the liquid-ordered and liquid-disordered regions couples the shape of the vesicle to the local composition. We show that this interplay gives rise to a rich phase diagram that includes homogeneous, separated, and axisymmetric modulated phases that are divided by regions of spiral patterns in the surface morphology.
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Affiliation(s)
- Yongtian Luo
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Lutz Maibaum
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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14
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Huang J, Hiraki S, Feigenson GW. Calculation of Liquid-Disordered/Liquid-Ordered Line Tension from Pairwise Lipid Interactions. J Phys Chem B 2020; 124:4949-4959. [DOI: 10.1021/acs.jpcb.0c03329] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- J. Huang
- Department of Physics and Astronomy, Texas Tech University, Box 41051, Lubbock, Texas 79409, United States
| | - S. Hiraki
- Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan
| | - G. W. Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States
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15
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Sarmento MJ, Hof M, Šachl R. Interleaflet Coupling of Lipid Nanodomains - Insights From in vitro Systems. Front Cell Dev Biol 2020; 8:284. [PMID: 32411705 PMCID: PMC7198703 DOI: 10.3389/fcell.2020.00284] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/02/2020] [Indexed: 01/09/2023] Open
Abstract
The plasma membrane is a complex system, consisting of two layers of lipids and proteins compartmentalized into small structures called nanodomains. Despite the asymmetric composition of both leaflets, coupling between the layers is surprisingly strong. This can be evidenced, for example, by recent experimental studies performed on phospholipid giant unilamellar vesicles showing that nanodomains formed in the outer layer are perfectly registered with those in the inner leaflet. Similarly, microscopic phase separation in one leaflet can induce phase separation in the opposing leaflet that would otherwise be homogeneous. In this review, we summarize the current theoretical and experimental knowledge that led to the current view that domains are – irrespective of their size – commonly registered across the bilayer. Mechanisms inducing registration of nanodomains suggested by theory and calculations are discussed. Furthermore, domain coupling is evidenced by experimental studies based on the sparse number of methods that can resolve registered from independent nanodomains. Finally, implications that those findings using model membrane studies might have for cellular membranes are discussed.
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Affiliation(s)
- Maria J Sarmento
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova, Prague, Czechia
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16
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Iyer SS, Negi A, Srivastava A. Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization. J Chem Theory Comput 2020; 16:2736-2750. [DOI: 10.1021/acs.jctc.9b00929] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Sahithya S. Iyer
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Archit Negi
- Department of Physics, Indian Institute of Technology, Bombay, Mumbai 400076, India
| | - Anand Srivastava
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
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17
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Rufeil Fiori E, Downing R, Bossa GV, May S. Influence of spontaneous curvature on the line tension of phase-coexisting domains in a lipid monolayer: A Landau-Ginzburg model. J Chem Phys 2020; 152:054707. [DOI: 10.1063/1.5138192] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Affiliation(s)
- Elena Rufeil Fiori
- Facultad de Matemática, Astronomía, Física y Computación and Instituto de Física Enrique Gaviola (IFEG), CONICET, Universidad Nacional de Córdoba, X5000HUA Córdoba, Argentina
| | - Rachel Downing
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Guilherme Volpe Bossa
- Department of Physics, São Paulo State University (UNESP), Institute of Biosciences, Humanities and Exact Sciences, São José do Rio Preto, SP 15054-000, Brazil
| | - Sylvio May
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA
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18
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Stottrup BL, TigreLazo J, Bagonza VB, Kunz JC, Zasadzinski JA. Comparison of Line Tension Measurement Methods for Lipid Monolayers at Liquid-Liquid Coexistence. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:16053-16061. [PMID: 31343892 PMCID: PMC6896218 DOI: 10.1021/acs.langmuir.9b01696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Several methods of measuring the line tension between phase-separated liquid-ordered-liquid -disordered domains in phospholipid-cholesterol systems have been proposed. These experimental techniques are typically internally self-consistent, but the measured line tension values vary widely among these techniques. To date, no measurement of line tension has utilized multiple experimental techniques to look at the same monolayer system. Here we compare two nonperturbative methods, Fourier analysis of boundary fluctuations (BA) and one proposed by Israelachvili involving the analysis of domain size distributions (SD), to extract the line tension in a 70 mol % DMPC/30 mol % dihydrocholesterol (DChol) mixture as a function of surface pressure. We show that BA predicts the expected variation in line tension measurements consistent with the theoretical critical exponent whereas SD does not. From this comparison, we conclude that the size distribution of monolayer domains is metastable and primarily determined by the kinetics of domain nucleation and subsequent aging.
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Affiliation(s)
- Benjamin L. Stottrup
- Department of Physics, Augsburg University, Minneapolis, Minnesota 55454, United States
| | - Juan TigreLazo
- Department of Physics, Augsburg University, Minneapolis, Minnesota 55454, United States
| | - Vision B. Bagonza
- Department of Physics, Augsburg University, Minneapolis, Minnesota 55454, United States
| | - Joan C. Kunz
- Department of Chemistry, Augsburg University, Minneapolis, Minnesota 55454, United States
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19
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Bandara A, Panahi A, Pantelopulos GA, Nagai T, Straub JE. Exploring the impact of proteins on the line tension of a phase-separating ternary lipid mixture. J Chem Phys 2019; 150:204702. [PMID: 31153187 DOI: 10.1063/1.5091450] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The separation of lipid mixtures into thermodynamically stable phase-separated domains is dependent on lipid composition, temperature, and system size. Using molecular dynamics simulations, the line tension between thermodynamically stable lipid domains formed from ternary mixtures of di-C16:0 PC:di-C18:2 PC:cholesterol at 40:40:20 mol. % ratio was investigated via two theoretical approaches. The line tension was found to be 3.1 ± 0.2 pN by capillary wave theory and 4.7 ± 3.7 pN by pressure tensor anisotropy approaches for coarse-grained models based on the Martini force field. Using an all-atom model of the lipid membrane based on the CHARMM36 force field, the line tension was found to be 3.6 ± 0.9 pN using capillary wave theory and 1.8 ± 2.2 pN using pressure anisotropy approaches. The discrepancy between estimates of the line tension based on capillary wave theory and pressure tensor anisotropy methods is discussed. Inclusion of protein in Martini membrane lipid mixtures was found to reduce the line tension by 25%-35% as calculated by the capillary wave theory approach. To further understand and predict the behavior of proteins in phase-separated membranes, we have formulated an analytical Flory-Huggins model and parameterized it against the simulation results. Taken together these results suggest a general role for proteins in reducing the thermodynamic cost associated with domain formation in lipid mixtures and quantifies the thermodynamic driving force promoting the association of proteins to domain interfaces.
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Affiliation(s)
- Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Afra Panahi
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - George A Pantelopulos
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Tetsuro Nagai
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - John E Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
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20
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Dang AT, Kuhl TL. Mind the Line Tension: New Criteria for Nanodomains in Biological Membranes. Biophys J 2019; 112:1291-1292. [PMID: 28402871 DOI: 10.1016/j.bpj.2017.02.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 02/22/2017] [Accepted: 02/24/2017] [Indexed: 12/01/2022] Open
Affiliation(s)
- Amanda T Dang
- Department of Materials Science and Engineering, University of California, Davis, California.
| | - Tonya L Kuhl
- Department of Chemical Engineering, University of California, Davis, California
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21
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Tsai WC, Feigenson GW. Lowering line tension with high cholesterol content induces a transition from macroscopic to nanoscopic phase domains in model biomembranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:478-485. [PMID: 30529459 DOI: 10.1016/j.bbamem.2018.11.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 11/26/2018] [Accepted: 11/27/2018] [Indexed: 11/25/2022]
Abstract
Chemically simplified lipid mixtures are used here as models of the cell plasma membrane exoplasmic leaflet. In such models, phase separation and morphology transitions controlled by line tension in the liquid-disordered (Ld) + liquid-ordered (Lo) coexistence regime have been described [1]. Here, we study two four-component lipid mixtures at different cholesterol fractions: brain sphingomyelin (BSM) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). On giant unilamellar vesicles (GUVs) display a nanoscopic-to-macroscopic transition of Ld + Lo phase domains as POPC is replaced by DOPC, and this transition also depends on the cholesterol fraction. Line tension decreases with increasing cholesterol mole fractions in both lipid mixtures. For the ternary BSM/DOPC/Chol mixture, the published phase diagram [19] requires a modification to show that when cholesterol mole fraction is >~0.33, coexisting phase domains become nanoscopic.
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Affiliation(s)
- Wen-Chyan Tsai
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, United States of America
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, United States of America.
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22
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Luo Y, Maibaum L. Phase diagrams of multicomponent lipid vesicles: Effects of finite size and spherical geometry. J Chem Phys 2018; 149:174901. [DOI: 10.1063/1.5045499] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Yongtian Luo
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Lutz Maibaum
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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23
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Cristofolini L, Orsi D, Isa L. Characterization of the dynamics of interfaces and of interface-dominated systems via spectroscopy and microscopy techniques. Curr Opin Colloid Interface Sci 2018. [DOI: 10.1016/j.cocis.2018.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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24
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Effects of electroformation protocol parameters on quality of homogeneous GUV populations. Chem Phys Lipids 2018; 212:88-95. [DOI: 10.1016/j.chemphyslip.2018.01.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 12/28/2017] [Accepted: 01/08/2018] [Indexed: 12/22/2022]
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25
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Shimokawa N, Mukai R, Nagata M, Takagi M. Formation of modulated phases and domain rigidification in fatty acid-containing lipid membranes. Phys Chem Chem Phys 2018; 19:13252-13263. [PMID: 28492655 DOI: 10.1039/c7cp01201b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the phase behavior of lipid membranes containing fatty acids (FAs) by microscopy and differential scanning calorimetry. We used palmitic acid (saturated FA), oleic acid (cis-isomer of unsaturated FA), elaidic acid (trans-isomer of unsaturated FA), and phytanic acid (branched FA) and examined the effects of FAs on phase-separated structures in lipid bilayer membranes consisting of dioleolylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol). Palmitic acid and elaidic acid exclude Chol from the DPPC-rich phase. As a result, the liquid-ordered phase formed by DPPC and Chol transforms into a solid-ordered phase. Oleic acid and phytanic acid significantly reduce the line tension at the liquid domain boundary. This decrease in line tension leads to the formation of modulated phases, such as striped, hexagonal, and polygonal domains. We measured the line tension and the interdomain interaction in these specific domains by an image analysis. The result showed that oleic acid and phytanic acid-containing vesicles as well as palmitic acid-containing vesicles are not spherical, and this domain-induced deformation is explained theoretically.
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Affiliation(s)
- Naofumi Shimokawa
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi City, Ishikawa 923-1292, Japan.
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26
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Heberle FA, Pabst G. Complex biomembrane mimetics on the sub-nanometer scale. Biophys Rev 2017; 9:353-373. [PMID: 28717925 PMCID: PMC5578918 DOI: 10.1007/s12551-017-0275-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 06/26/2017] [Indexed: 12/12/2022] Open
Abstract
Biomimetic lipid vesicles are indispensable tools for gaining insight into the biophysics of cell physiology on the molecular level. The level of complexity of these model systems has steadily increased, and now spans from domain-forming lipid mixtures to asymmetric lipid bilayers. Here, we review recent progress in the development and application of elastic neutron and X-ray scattering techniques for studying these systems in situ and under physiologically relevant conditions on the nanometer to sub-nanometer length scales. In particular, we focus on: (1) structural details of coexisting liquid-ordered and liquid-disordered domains, including their thickness and lipid packing mismatch as a function of a size transition from nanoscopic to macroscopic domains; (2) membrane-mediated protein partitioning into lipid domains; (3) the role of the aqueous medium in tuning interactions between membranes and domains; and (4) leaflet-specific structure in asymmetric bilayers and passive lipid flip-flop.
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Affiliation(s)
- Frederick A Heberle
- The Bredesen Center, University of Tennessee, Knoxville, TN, 37996, USA.,Joint Institute for Biological Sciences and Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, 8010, Graz, Austria. .,BioTechMed-Graz, 8010, Graz, Austria.
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27
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Thermal Stability of Phase-Separated Domains in Multicomponent Lipid Membranes with Local Anesthetics. MEMBRANES 2017; 7:membranes7030033. [PMID: 28661445 PMCID: PMC5618118 DOI: 10.3390/membranes7030033] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/23/2017] [Accepted: 06/23/2017] [Indexed: 11/25/2022]
Abstract
The functional mechanisms of local anesthetics (LAs) have not yet been fully explained, despite their importance in modern medicine. Recently, an indirect interaction between channel proteins and LAs was proposed as follows: LAs alter the physical properties of lipid membranes, thus affecting the channel proteins. To examine this hypothesis, we investigated changes in thermal stability in lipid membranes consisting of dioleoylphosphocholine, dipalmitoylphosphocholine, and cholesterol by adding the LAs, lidocaine and tetracaine. The miscibility temperature of liquid-ordered (Lo) and liquid-disordered (Ld) phase separation was lowered, whereas that of phase separation between solid-ordered (So) and Ld phases was unchanged by LAs. Furthermore, we measured the line tension at the Lo/Ld interface from domain boundary fluctuation and found that it was significantly decreased by LAs. Finally, differential scanning calorimetry (DSC) revealed a change in the lipid main transition temperature on the addition of LAs. Based on the DSC measurements, we considered that LAs are partitioned into two coexisting phases.
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28
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Usery RD, Enoki TA, Wickramasinghe SP, Weiner MD, Tsai WC, Kim MB, Wang S, Torng TL, Ackerman DG, Heberle FA, Katsaras J, Feigenson GW. Line Tension Controls Liquid-Disordered + Liquid-Ordered Domain Size Transition in Lipid Bilayers. Biophys J 2017; 112:1431-1443. [PMID: 28402885 DOI: 10.1016/j.bpj.2017.02.033] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/27/2017] [Accepted: 02/16/2017] [Indexed: 12/28/2022] Open
Abstract
To better understand animal cell plasma membranes, we studied simplified models, namely four-component lipid bilayer mixtures. Here we describe the domain size transition in the region of coexisting liquid-disordered (Ld) + liquid-ordered (Lo) phases. This transition occurs abruptly in composition space with domains increasing in size by two orders of magnitude, from tens of nanometers to microns. We measured the line tension between coexisting Ld and Lo domains close to the domain size transition for a variety of lipid mixtures, finding that in every case the transition occurs at a line tension of ∼0.3 pN. A computational model incorporating line tension and dipole repulsion indicated that even small changes in line tension can result in domains growing in size by several orders of magnitude, consistent with experimental observations. We find that other properties of the coexisting Ld and Lo phases do not change significantly in the vicinity of the abrupt domain size transition.
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Affiliation(s)
- Rebecca D Usery
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Thais A Enoki
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Sanjula P Wickramasinghe
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Biochemistry and Biophysics at the University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Wen-Chyan Tsai
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Mary B Kim
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Shu Wang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Harvard Medical School Library of Integrated Network-based Cellular Signatures Center and Laboratory of Systems Pharmacology, Harvard University, Boston, Massachusetts
| | - Thomas L Torng
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Biochemistry, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire
| | - David G Ackerman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Scientific Computing, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, Virginia
| | - Frederick A Heberle
- Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee
| | - John Katsaras
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York.
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29
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Sachan AK, Choi SQ, Kim KH, Tang Q, Hwang L, Lee KYC, Squires TM, Zasadzinski JA. Interfacial rheology of coexisting solid and fluid monolayers. SOFT MATTER 2017; 13:1481-1492. [PMID: 28125114 PMCID: PMC5720834 DOI: 10.1039/c6sm02797k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Biologically relevant monolayer and bilayer films often consist of micron-scale high viscosity domains in a continuous low viscosity matrix. Here we show that this morphology can cause the overall monolayer fluidity to vary by orders of magnitude over a limited range of monolayer compositions. Modeling the system as a two-dimensional suspension in analogy with classic three-dimensional suspensions of hard spheres in a liquid solvent explains the rheological data with no adjustable parameters. In monolayers with ordered, highly viscous domains dispersed in a continuous low viscosity matrix, the surface viscosity increases as a power law with the area fraction of viscous domains. Changing the phase of the continuous matrix from a disordered fluid phase to a more ordered, condensed phase dramatically changes the overall monolayer viscosity. Small changes in the domain density and/or continuous matrix composition can alter the monolayer viscosity by orders of magnitude.
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Affiliation(s)
- A K Sachan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | - S Q Choi
- Departments of Chemical and Biomolecular Engineering and KINC, KAIST, Daejeon, 305-701, Korea
| | - K H Kim
- Departments of Chemical and Biomolecular Engineering and KINC, KAIST, Daejeon, 305-701, Korea
| | - Q Tang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | - L Hwang
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - K Y C Lee
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - T M Squires
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - J A Zasadzinski
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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30
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Ackerman DG, Feigenson GW. Effects of Transmembrane α-Helix Length and Concentration on Phase Behavior in Four-Component Lipid Mixtures: A Molecular Dynamics Study. J Phys Chem B 2016; 120:4064-77. [PMID: 27081858 DOI: 10.1021/acs.jpcb.6b00611] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We used coarse-grained molecular dynamics simulations to examine the effects of transmembrane α-helical WALP peptides on the behavior of four-component lipid mixtures. These mixtures contain a high-melting temperature (high-Tm) lipid, a nanodomain-inducing low-Tm lipid, a macrodomain-inducing low-Tm lipid and cholesterol to model the outer leaflet of cell plasma membranes. In a series of simulations, we incrementally replace the nanodomain-inducing low-Tm lipid by the macrodomain-inducing low-Tm lipid and measure how lipid and phase properties are altered by the addition of WALPs of different length. Regardless of the ratio of the two low-Tm lipids, shorter WALPs increase domain size and all WALPs increase domain alignment between the two leaflets. These effects are smallest for the longest WALP tested, and increase with increasing WALP concentration. Thus, our simulations explain the experimental observation that WALPs induce macroscopic domains in otherwise nanodomain-forming lipid-only mixtures (unpublished). Since the cell plasma membrane contains a large fraction of transmembrane proteins, these findings link the behavior of lipid-only model membranes in vitro to phase behavior in vivo.
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Affiliation(s)
- David G Ackerman
- Department of Molecular Biology and Genetics, Cornell University , Ithaca, New York 14853, United States
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University , Ithaca, New York 14853, United States
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31
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Camley BA, Brown FLH. Fluctuating hydrodynamics of multicomponent membranes with embedded proteins. J Chem Phys 2015; 141:075103. [PMID: 25149817 DOI: 10.1063/1.4892802] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A simulation method for the dynamics of inhomogeneous lipid bilayer membranes is presented. The membrane is treated using stochastic Saffman-Delbrück hydrodynamics, coupled to a phase-field description of lipid composition and discrete membrane proteins. Multiple applications are considered to validate and parameterize the model. The dynamics of membrane composition fluctuations above the critical point and phase separation dynamics below the critical point are studied in some detail, including the effects of adding proteins to the mixture.
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Affiliation(s)
- Brian A Camley
- Department of Physics and Center for Theoretical Biological Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - Frank L H Brown
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
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32
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Galimzyanov TR, Molotkovsky RJ, Bozdaganyan ME, Cohen FS, Pohl P, Akimov SA. Elastic Membrane Deformations Govern Interleaflet Coupling of Lipid-Ordered Domains. PHYSICAL REVIEW LETTERS 2015; 115:088101. [PMID: 26340212 PMCID: PMC4750487 DOI: 10.1103/physrevlett.115.088101] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Indexed: 05/19/2023]
Abstract
The mechanism responsible for domain registration in two membrane leaflets has thus far remained enigmatic. Using continuum elasticity theory, we show that minimum line tension is achieved along the rim between thicker (ordered) and thinner (disordered) domains by shifting the rims in opposing leaflets by a few nanometers relative to each other. Increasing surface tension yields an increase in line tension, resulting in larger domains. Because domain registration is driven by lipid deformation energy, it does not require special lipid components or interactions at the membrane midplane.
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Affiliation(s)
- Timur R Galimzyanov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
- National University of Science and Technology "MISiS", 4 Leninskiy prospekt, Moscow 119049, Russia
| | - Rodion J Molotkovsky
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
| | - Marine E Bozdaganyan
- M.V. Lomonosov Moscow State University, 1 Leninskie Gory, Moscow 119991, Russia
- Federal Research Clinical Center of the Specialized Types of Health Care and Medical Technologies FMBA of Russia, 28 Orekhovyi bulvar, Moscow 115692, Russia
| | - Fredric S Cohen
- Rush University Medical Center, 1750 W. Harrison Street, Chicago, Illinois 60612, USA
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40-42, Linz 4020, Austria
| | - Sergey A Akimov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
- National University of Science and Technology "MISiS", 4 Leninskiy prospekt, Moscow 119049, Russia
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33
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Schäfer E, Vache M, Kliesch TT, Janshoff A. Mechanical response of adherent giant liposomes to indentation with a conical AFM-tip. SOFT MATTER 2015; 11:4487-95. [PMID: 25946988 DOI: 10.1039/c5sm00191a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Indentation of giant liposomes with a conical indenter is described by means of a tension-based membrane model. We found that nonlinear membrane theory neglecting the impact of bending sufficiently describes the mechanical response of liposomes to indentation as measured by atomic force microscopy. Giant vesicles are gently adsorbed on glassy surfaces via avidin-biotin linkages and indented centrally using an atomic force microscope equipped with conventional sharp tips mounted on top of an inverted microscope. Force indentation curves display a nonlinear response that allows to extract pre-stress of the bilayer T0 and the area compressibility modulus KA by computing the contour of the vesicle at a given force. The values for KA of fluid membranes correspond well to what is known from micropipet suction experiments and inferred from membrane undulation monitoring. Assembly of actin shells inside the liposome considerably stiffens the vesicles resulting in significantly larger area compressibility modules. The analysis can be easily extended to different indenter geometries with rotational symmetry.
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Affiliation(s)
- Edith Schäfer
- Department of Chemistry, University of Goettingen, Goettingen, Germany.
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Aydin F, Ludford P, Dutt M. Phase segregation in bio-inspired multi-component vesicles encompassing double tail phospholipid species. SOFT MATTER 2014; 10:6096-6108. [PMID: 25008809 DOI: 10.1039/c4sm00998c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Our aim is to investigate the phase segregation and the structure of multi-component bio-inspired phospholipid vesicles via dissipative particle dynamics. The chemical distinction in the phospholipid species arises due to different head and tail group moieties, and molecular stiffness of the hydrocarbon tails. The individual amphiphilic phospholipid molecular species are represented by a hydrophilic head group and two hydrophobic tails. The distinct chemical nature of the moieties is modeled effectively via soft repulsive interaction parameters, and the molecular rigidity is tuned via suitable three-body potential constants. We demonstrate the formation of a stable hybrid vesicle through the self-assembly of the amphiphilic phospholipid molecules in the presence of a hydrophilic solvent. We investigate and characterize the phase segregation and the structure of the binary vesicles for different phospholipid mixtures. Our results demonstrate macroscopic phase separation for phospholipid mixtures composed of species with different hydrocarbon tail groups. We also investigate the relationship between the phase segregation and thermodynamic variables such as interfacial line tension and surface tension, and obtain correspondence between existing theory and experiments, and our simulation results. We report variations in the molecular chain stiffness to have negligible contributions to the phase segregation in the mixed bilayer, and to demonstrate shape transformations of the hybrid vesicle. Our results can be used to design novel bio-inspired hybrid vehicles for potential applications in biomedicine, sensing, imaging and sustainability.
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Affiliation(s)
- Fikret Aydin
- Department of Chemical Engineering, Rutgers The State University of New Jersey, Piscataway, NJ 08854, USA.
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Puff N, Watanabe C, Seigneuret M, Angelova MI, Staneva G. Lo/Ld phase coexistence modulation induced by GM1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2105-14. [DOI: 10.1016/j.bbamem.2014.05.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 04/30/2014] [Accepted: 05/03/2014] [Indexed: 01/31/2023]
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36
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Aydin F, Dutt M. Bioinspired Vesicles Encompassing Two-Tail Phospholipids: Self-Assembly and Phase Segregation via Implicit Solvent Coarse-Grained Molecular Dynamics. J Phys Chem B 2014; 118:8614-23. [DOI: 10.1021/jp503376r] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Fikret Aydin
- Department
of Chemical and Biochemical Engineering, Rutgers The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Meenakshi Dutt
- Department
of Chemical and Biochemical Engineering, Rutgers The State University of New Jersey, Piscataway, New Jersey 08854, United States
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Hassan-Zadeh E, Baykal-Caglar E, Alwarawrah M, Huang J. Complex roles of hybrid lipids in the composition, order, and size of lipid membrane domains. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:1361-1369. [PMID: 24456489 DOI: 10.1021/la4044733] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Hybrid lipids (HL) are phospholipids with one saturated chain and one unsaturated chain. HL are hypothesized to act as linactants (i.e., 2D surfactants) in cell membranes, reducing line tension and creating nanoscopic lipid domains. Here we compare three hybrid lipids of different chain unsaturation (16:0-18:1PC (POPC), 16:0-18:2PC (PLPC), and 16:0-20:4PC (PAPC)) in their abilities to alter the composition, line tension, order, and compactness of lipid domains. We found that the liquid-ordered (Lo) and liquid-disordered (Ld) lipid domains in PAPC/di18:0PC(DSPC)/cholesterol and PLPC/DSPC/cholesterol mixtures are micrometer-sized, and only the POPC/DSPC/cholesterol system has nanoscopic domains. The results indicate that some HLs with polyunsaturated chains are not linactants, and the monounsaturated POPC displays both properties of weak linactants and "Ld-phase" lipids such as di18:1PC (DOPC). The obtained phase boundaries from giant unilamellar vesicles (GUV) show that both POPC and PLPC partition well in the Lo phases. Our MD simulations reveal that these hybrid lipids decrease the order and compactness of Lo domains. Thus, hybrid lipids distinguish themselves from other lipid groups in this combined "partitioning and loosening" ability, which could explain why the Lo domains of GUVs, which often do not contain HL, are more compact than the raft domains in cell membranes. Our line tension measurement and Monte Carlo simulation both show that even the monounsaturated POPC is a weak linactant with only modest ability to occupy domain boundaries and reduce line tension. A more important property of HLs is that they can reduce physical property differences of Lo and Ld bulk domains, which also reduces line tension at domain boundaries.
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Affiliation(s)
- Ebrahim Hassan-Zadeh
- Department of Physics, Texas Tech University , Lubbock, Texas 79409, United States
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38
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Coarsening dynamics of domains in lipid membranes. Biophys J 2014; 105:444-54. [PMID: 23870265 DOI: 10.1016/j.bpj.2013.06.013] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 06/07/2013] [Accepted: 06/11/2013] [Indexed: 11/20/2022] Open
Abstract
We investigate isothermal diffusion and growth of micron-scale liquid domains within membranes of free-floating giant unilamellar vesicles with diameters between 80 and 250 μm. Domains appear after a rapid temperature quench, when the membrane is cooled through a miscibility phase transition such that coexisting liquid phases form. In membranes quenched far from a miscibility critical point, circular domains nucleate and then progress within seconds to late stage coarsening in which domains grow via two mechanisms 1), collision and coalescence of liquid domains, and 2), Ostwald ripening. Both mechanisms are expected to yield the same growth exponent, α = 1/3, where domain radius grows as time(α). We measure α = 0.28 ± 0.05, in excellent agreement. In membranes close to a miscibility critical point, the two liquid phases in the membrane are bicontinuous. A quench near the critical composition results in rapid changes in morphology of elongated domains. In this case, we measure α = 0.50 ± 0.16, consistent with theory and simulation.
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Li Z, Gorfe AA. Deformation of a Two-domain Lipid Bilayer due to Asymmetric Insertion of Lipid-modified Ras Peptides. SOFT MATTER 2013; 9:10.1039/C3SM51388B. [PMID: 24358048 PMCID: PMC3864742 DOI: 10.1039/c3sm51388b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ras proteins are attached to the inner leaflet of the plasma membrane via a lipid-modified anchor. Membrane-bound Ras proteins laterally segregate into nanoscale signaling platforms called nanoclusters. It has been shown that the membrane domain preference of Ras nanoclusters varies with the nature of lipidation but their effect on the membrane has not been well understood. To investigate the effect of Ras insertion on membrane structure, we carried out numerous coarse-grained molecular dynamics (CGMD) simulations on a two-domain DPPC/DLiPC/cholesterol lipid bilayer in which different number and type of H-ras peptides were attached on one side. We have shown previously that this lipid mixture forms co-existing liquid-ordered/liquid-disordered (L o /L d ) domains and that different H-ras peptides form clusters that variously accumulate at the L o /L d regions or the boundary between them. Here we show that asymmetric insertion of each of these peptides induces a vertical relative displacement of the domains and deforms the bilayer, with the domain boundary serving as the center of deformation. The extent of the deformation, however, varies with the type and number of lipid modification. This is because the number and type of the Ras lipid tails determines the degree to which the stress caused by asymmetric peptide insertion is relieved by inter-leaflet cholesterol transfer and lipid tilt. In addition, we have characterized the mechanism of bilayer deformation based on the collective effect of the Ras peptides on inter-leaflet surface area, pressure profile and line tension differences. This allowed us to elucidate how Ras lipid modification affects membrane geometry and how a two-domain bilayer adjusts its shape through boundary deformation. The result contributes to a better understanding of Ras signaling platforms and highlights some of the mechanisms by which a multi-domain membrane responds to external perturbation.
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Affiliation(s)
- Zhenlong Li
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030
| | - Alemayehu A. Gorfe
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030
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Kollmitzer B, Heftberger P, Rappolt M, Pabst G. Monolayer spontaneous curvature of raft-forming membrane lipids. SOFT MATTER 2013; 9:10877-10884. [PMID: 24672578 PMCID: PMC3963256 DOI: 10.1039/c3sm51829a] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Monolayer spontaneous curvatures for cholesterol, DOPE, POPE, DOPC, DPPC, DSPC, POPC, SOPC, and egg sphingomyelin were obtained using small-angle X-ray scattering (SAXS) on inverted hexagonal phases (HII). Spontaneous curvatures of bilayer forming lipids were estimated by adding controlled amounts to a HII forming template following previously established protocols. Spontaneous curvatures of both phosphatidylethanolamines and cholesterol were found to be at least a factor of two more negative than those of phosphatidylcholines, whose J0 values are closer to zero. Interestingly, a significant positive J0 value was retrieved for DPPC. We further determined the temperature dependence of the spontaneous curvatures J0(T) in the range from 15 to 55 °C, resulting in a quite narrow distribution of -1 to -3 × 10-3 (nm °C)-1 for most investigated lipids. The data allowed us to estimate the monolayer spontaneous curvatures of ternary lipid mixtures showing liquid ordered/liquid disordered phase coexistence. We report spontaneous curvature phase diagrams for DSPC/DOPC/Chol, DPPC/DOPC/Chol and SM/POPC/Chol and discuss effects on protein insertion and line tension.
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Affiliation(s)
- Benjamin Kollmitzer
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, Austria. ; ; Tel: +43 316 4120-342
| | - Peter Heftberger
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, Austria. ; ; Tel: +43 316 4120-342
| | - Michael Rappolt
- Institute of Inorganic Chemistry, Graz University of Technology, Austria ; School of Food Science and Nutrition, University of Leeds, UK
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, Austria. ; ; Tel: +43 316 4120-342
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41
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Zhou Y, Maxwell KN, Sezgin E, Lu M, Liang H, Hancock JF, Dial EJ, Lichtenberger LM, Levental I. Bile acids modulate signaling by functional perturbation of plasma membrane domains. J Biol Chem 2013; 288:35660-70. [PMID: 24165125 DOI: 10.1074/jbc.m113.519116] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.
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Affiliation(s)
- Yong Zhou
- From the Department of Integrative Biology and Pharmacology, the University of Texas Medical School, Houston, Texas 77030 and
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42
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Schäfer E, Kliesch TT, Janshoff A. Mechanical properties of giant liposomes compressed between two parallel plates: impact of artificial actin shells. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10463-10474. [PMID: 23869855 DOI: 10.1021/la401969t] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The mechanical response of giant liposomes to compression between two parallel plates is investigated in the context of an artificial actin cortex adjacent to the inner leaflet of the bilayer. We found that nonlinear membrane theory neglecting the impact of bending sufficiently describes the mechanical response of liposomes consisting of fluid lipids to compression whereas the formation of an actin cortex or the use of gel-phase lipids generally leads to substantial stiffening of the shell. Giant vesicles are gently adsorbed on glassy surfaces and are compressed with tipless cantilevers using an atomic force microscope. Force-compression curves display a nonlinear response that allows us to determine the membrane tension σ0 and the area compressibility modulus K(A) by computing the contour of the vesicle as a function of the compression depth. The values for KA of fluid membranes correspond well to what is known from micropipet-suction experiments and computed from monitoring membrane undulations. The presence of a thick actin shell adjacent to the inner leaflet of the liposome membrane stiffens the system considerably, as mirrored in a significantly higher apparent area compressibility modulus.
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Affiliation(s)
- Edith Schäfer
- Institute of Physical Chemistry, Georg-August-University of Goettingen, Tammannstr. 6, 37077 Goettingen
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43
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Davis JH, Ziani L, Schmidt ML. Critical fluctuations in DOPC/DPPC-d62/cholesterol mixtures: 2H magnetic resonance and relaxation. J Chem Phys 2013; 139:045104. [DOI: 10.1063/1.4816366] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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44
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Konyakhina TM, Wu J, Mastroianni JD, Heberle FA, Feigenson GW. Phase diagram of a 4-component lipid mixture: DSPC/DOPC/POPC/chol. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2204-14. [PMID: 23747294 DOI: 10.1016/j.bbamem.2013.05.020] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 05/20/2013] [Accepted: 05/22/2013] [Indexed: 11/15/2022]
Abstract
We report the first 4-component phase diagram for the lipid bilayer mixture, DSPC/DOPC/POPC/chol (distearoylphosphatidylcholine/dioleoylphosphatidylcholine/1-palmitoyl, 2-oleoylphosphatidylcholine/cholesterol). This phase diagram, which has macroscopic Ld+Lo phase domains, clearly shows that all phase boundaries determined for the 3-component mixture containing DOPC transition smoothly into the boundaries for the 3-component mixture containing POPC, which has nanoscopic phase domains of Ld+Lo. Our studies start from two published ternary phase diagrams, and show how these can be combined into a quaternary phase diagram by study of a few hundred samples of intermediate compositions.
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Key Words
- 1,1′-didodecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate
- 1,1′-dieicosanyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate
- 1,2-Dilauroyl-sn-glycero-3-phosphocholine
- 1,2-Dioleoyl-sn-glycero-3-phosphocholine
- 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine
- 1,2-Distearoyl-sn-glycero-3-phosphocholine
- 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine
- 1-Stearoyl-2-oleoyl-sn-glycero-3-phosphocholine
- 2-(4,4-Difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine
- 3-Dye method
- 4-Component lipid phase diagram
- BoDIPY-PC
- C12:0-DiI
- C20:0-DiI
- Chol
- Cholesterol
- Competing interaction
- DHE
- DLPC
- DOPC
- DPPC
- DSPC
- Ergosta-5,7,9(11),22-tetraen-3β-ol
- FRET
- Förster resonance energy transfer
- GUV
- Giant unilamellar vesicle
- LHS
- Left hand side refers to left side of phase diagram, i.e. at lower χ(DSPC)
- Lipid raft
- Modulated phase
- PC
- POPC
- Phosphatidylcholine
- Quaternary phase diagram
- REE
- RHS
- RRE
- RSE
- Rapid solvent exchange
- Region of enhanced efficiency
- Region of reduced efficiency
- Right hand side, refers to right side of phase diagram, i.e.,, at higher χ(DSPC)
- SAE
- SM
- SOPC
- Sensitized acceptor emission
- Sphingomyelin
- T1–T6
- TLC
- TOE
- Thin-layer chromatography
- Trajectories 1–6. bSM, sphingomyelin derived from porcine brain
- Trp-Oleoyl Ester, N-oleoyl-dl-tryptophan ethyl ester
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Affiliation(s)
- Tatyana M Konyakhina
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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Heberle FA, Petruzielo RS, Pan J, Drazba P, Kučerka N, Standaert RF, Feigenson GW, Katsaras J. Bilayer thickness mismatch controls domain size in model membranes. J Am Chem Soc 2013; 135:6853-9. [PMID: 23391155 DOI: 10.1021/ja3113615] [Citation(s) in RCA: 224] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The observation of lateral phase separation in lipid bilayers has received considerable attention, especially in connection to lipid raft phenomena in cells. It is widely accepted that rafts play a central role in cellular processes, notably signal transduction. While micrometer-sized domains are observed with some model membrane mixtures, rafts much smaller than 100 nm-beyond the reach of optical microscopy-are now thought to exist, both in vitro and in vivo. We have used small-angle neutron scattering, a probe free technique, to measure the size of nanoscopic membrane domains in unilamellar vesicles with unprecedented accuracy. These experiments were performed using a four-component model system containing fixed proportions of cholesterol and the saturated phospholipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), mixed with varying amounts of the unsaturated phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We find that liquid domain size increases with the extent of acyl chain unsaturation (DOPC:POPC ratio). Furthermore, we find a direct correlation between domain size and the mismatch in bilayer thickness of the coexisting liquid-ordered and liquid-disordered phases, suggesting a dominant role for line tension in controlling domain size. While this result is expected from line tension theories, we provide the first experimental verification in free-floating bilayers. Importantly, we also find that changes in bilayer thickness, which accompany changes in the degree of lipid chain unsaturation, are entirely confined to the disordered phase. Together, these results suggest how the size of functional domains in homeothermic cells may be regulated through changes in lipid composition.
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Affiliation(s)
- Frederick A Heberle
- Biology & Soft Matter, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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46
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Coupling Membrane Elasticity and Structure to Protein Function. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-411515-6.00004-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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47
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Bernardini C, Stoyanov SD, Arnaudov LN, Cohen Stuart MA. Colloids in Flatland: a perspective on 2D phase-separated systems, characterisation methods, and lineactant design. Chem Soc Rev 2013; 42:2100-29. [DOI: 10.1039/c2cs35269a] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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48
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Honerkamp-Smith AR, Machta BB, Keller SL. Experimental observations of dynamic critical phenomena in a lipid membrane. PHYSICAL REVIEW LETTERS 2012; 108:265702. [PMID: 23004996 PMCID: PMC3722069 DOI: 10.1103/physrevlett.108.265702] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Indexed: 05/04/2023]
Abstract
Near a critical point, the time scale of thermally induced fluctuations diverges in a manner determined by the dynamic universality class. Experiments have verified predicted three-dimensional dynamic critical exponents in many systems, but similar experiments in two dimensions have been lacking for the case of conserved order parameter. Here we analyze the time-dependent correlation functions of a quasi-two-dimensional lipid bilayer in water to show that its critical dynamics agree with a recently predicted universality class. In particular, the effective dynamic exponent z(eff) crosses over from ~2 to ~3 as the correlation length of fluctuations exceeds a hydrodynamic length set by the membrane and bulk viscosities.
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Affiliation(s)
| | | | - Sarah L. Keller
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
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50
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Baykal-Caglar E, Hassan-Zadeh E, Saremi B, Huang J. Preparation of giant unilamellar vesicles from damp lipid film for better lipid compositional uniformity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2598-604. [PMID: 22652256 DOI: 10.1016/j.bbamem.2012.05.023] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 05/02/2012] [Accepted: 05/21/2012] [Indexed: 01/25/2023]
Abstract
Giant unilamellar vesicles (GUVs) containing cholesterol often have a wide distribution in lipid composition. In this study, GUVs of 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC)/1,2-distearoyl-sn-glycero-3-phosphocholine(DSPC)/cholesterol and 1,2-diphytanoyl-sn-glycero-3-phosphocholine(diPhyPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC)/cholesterol were prepared from dry lipid films using the standard electroformation method as well as a modified method from damp lipid films, which are made from compositional uniform liposomes prepared using the Rapid Solvent Exchange (RSE) method. We quantified the lipid compositional distributions of GUV by measuring the miscibility transition temperature of GUVs using fluorescence microscopy, since a narrower distribution in the transition temperature should correspond to a more uniform distribution in GUV lipid composition. Cholesterol molecules can demix from other lipids in dry state and form cholesterol crystals. Using optical microscopy, micron-sized crystals were observed in some dry lipid films. Thus, a major cause of GUV lipid compositional heterogeneity is the demixing of lipids in the dry film state. By avoiding the dry film state, GUVs prepared from damp lipid films have a better uniformity in lipid composition, and the standard deviations of miscibility transition temperature are about 2.5 times smaller than that of GUVs prepared from dry lipid films. Comparing the two ternary systems, diPhyPC/DPPC/cholesterol GUVs has a larger cholesterol compositional heterogeneity, which directly correlates with the low maximum solubility of cholesterol in diPhyPC lipid bilayers (40.2±0.5mol%) measured by light scattering. Our data indicate that cholesterol interacts far less favorably with diPhyPC than it does with other PCs. The damp lipid film method also has a potential of preparing GUVs from cell membranes containing native proteins without going through a dry state.
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