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Kiss B, Bozó T, Mudra D, Tordai H, Herényi L, Kellermayer M. Development, structure and mechanics of a synthetic E. coli outer membrane model. NANOSCALE ADVANCES 2021; 3:755-766. [PMID: 36133844 PMCID: PMC9418885 DOI: 10.1039/d0na00977f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 12/09/2020] [Indexed: 06/16/2023]
Abstract
The outer membrane (OM) of Gram-negative bacteria is a complex asymmetric bilayer containing lipids, lipopolysaccharides (LPS) and proteins. While it is a mechanical and chemical barrier, it is also the primary surface of bacterial recognition processes that involve infection by and of the bacterium. Uncovering the mechanisms of these biological functions has been hampered by the lack of suitable model systems. Here we report the step-by-step assembly of a synthetic OM model from its fundamental components. To enable the efficient formation of a supported lipid bilayer at room temperature, dimyristoyl-phosphocholine (DMPC) was used as the lipid component to which we progressively added LPS and OM proteins. The assembled system enabled us to explore the contribution of the molecular components to the topographical structure and stability of the OM. We found that LPS prefers solid-state membrane regions and forms stable vesicles in the presence of divalent cations. LPS can gradually separate from DMPC membranes to form independent vesicles, pointing at the dynamic nature of the lipid-LPS system. The addition of OM proteins from E. coli and saturating levels of LPS to DMPC liposomes resulted in a thicker and more stable bilayer the surface of which displayed a nanoscale texture formed of parallel, curved, long (>500 nm) stripes spaced apart with a 15 nm periodicity. The synthetic membrane may facilitate the investigation of binding and recognition processes on the surface of Gram-negative bacteria.
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Affiliation(s)
- Bálint Kiss
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
| | - Tamás Bozó
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
| | - Dorottya Mudra
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
| | - Hedvig Tordai
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
| | - Levente Herényi
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
| | - Miklós Kellermayer
- Department of Biophysics and Radiation Biology, Semmelweis University Budapest Hungary
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2
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Casuso I, Redondo-Morata L, Rico F. Biological physics by high-speed atomic force microscopy. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190604. [PMID: 33100165 PMCID: PMC7661283 DOI: 10.1098/rsta.2019.0604] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
While many fields have contributed to biological physics, nanotechnology offers a new scale of observation. High-speed atomic force microscopy (HS-AFM) provides nanometre structural information and dynamics with subsecond resolution of biological systems. Moreover, HS-AFM allows us to measure piconewton forces within microseconds giving access to unexplored, fast biophysical processes. Thus, HS-AFM provides a tool to nourish biological physics through the observation of emergent physical phenomena in biological systems. In this review, we present an overview of the contribution of HS-AFM, both in imaging and force spectroscopy modes, to the field of biological physics. We focus on examples in which HS-AFM observations on membrane remodelling, molecular motors or the unfolding of proteins have stimulated the development of novel theories or the emergence of new concepts. We finally provide expected applications and developments of HS-AFM that we believe will continue contributing to our understanding of nature, by serving to the dialogue between biology and physics. This article is part of a discussion meeting issue 'Dynamic in situ microscopy relating structure and function'.
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Affiliation(s)
- Ignacio Casuso
- Aix-Marseile University, Inserm, CNRS, LAI, 163 Av. de Luminy, 13009 Marseille, France
| | - Lorena Redondo-Morata
- Center for Infection and Immunity of Lille, INSERM U1019, CNRS UMR 8204, 59000 Lille, France
| | - Felix Rico
- Aix-Marseile University, Inserm, CNRS, LAI, 163 Av. de Luminy, 13009 Marseille, France
- e-mail:
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3
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Takahashi H, Miyagi A, Redondo-Morata L, Scheuring S. Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:6106-6113. [PMID: 27647753 DOI: 10.1002/smll.201601549] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 07/27/2016] [Indexed: 05/24/2023]
Abstract
With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level.
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Affiliation(s)
- Hirohide Takahashi
- U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 avenue de Luminy, 13009, Marseille, France
| | - Atsushi Miyagi
- U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 avenue de Luminy, 13009, Marseille, France
| | - Lorena Redondo-Morata
- U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 avenue de Luminy, 13009, Marseille, France
| | - Simon Scheuring
- U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 avenue de Luminy, 13009, Marseille, France
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4
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Formation of planar unilamellar phospholipid membranes on oxidized gold substrate. Biointerphases 2016; 11:031017. [DOI: 10.1116/1.4963188] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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5
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Bleecker JV, Cox PA, Foster RN, Litz JP, Blosser MC, Castner DG, Keller SL. Thickness Mismatch of Coexisting Liquid Phases in Noncanonical Lipid Bilayers. J Phys Chem B 2016; 120:2761-70. [PMID: 26890258 DOI: 10.1021/acs.jpcb.5b10165] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Lipid composition dictates membrane thickness, which in turn can influence membrane protein activity. Lipid composition also determines whether a membrane demixes into coexisting liquid-crystalline phases. Previous direct measurements of demixed lipid membranes have always found a liquid-ordered phase that is thicker than the liquid-disordered phase. Here we investigated noncanonical ternary lipid mixtures designed to produce bilayers with thicker disordered phases than ordered phases. The membranes were composed of short, saturated (ordered) lipids; long, unsaturated (disordered) lipids; and cholesterol. We found that few of these systems yield coexisting liquid phases above 10 °C. For membranes that do demix into two liquid phases, we measured the thickness mismatch between the phases by atomic force microscopy and found that not one of the systems yields thicker disordered than ordered phases under standard experimental conditions. We found no monotonic relationship between demixing temperatures of these ternary systems and either estimated thickness mismatches between the liquid phases or the physical parameters of single-component membranes composed of the individual lipids. These results highlight the robustness of a membrane's liquid-ordered phase to be thicker than the liquid-disordered phase, regardless of the membrane's lipid composition.
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Affiliation(s)
- Joan V Bleecker
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - Phillip A Cox
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - Rami N Foster
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - Jonathan P Litz
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - Matthew C Blosser
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - David G Castner
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
| | - Sarah L Keller
- Departments of Chemistry, ‡Chemical Engineering, and §Bioengineering, University of Washington , Seattle, Washington 98195, United States
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6
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Substrate Effects on the Formation Process, Structure and Physicochemical Properties of Supported Lipid Bilayers. MATERIALS 2012. [PMCID: PMC5449048 DOI: 10.3390/ma5122658] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Supported lipid bilayers are artificial lipid bilayer membranes existing at the interface between solid substrates and aqueous solution. Surface structures and properties of the solid substrates affect the formation process, fluidity, two-dimensional structure and chemical activity of supported lipid bilayers, through the 1–2 nm thick water layer between the substrate and bilayer membrane. Even on SiO2/Si and mica surfaces, which are flat and biologically inert, and most widely used as the substrates for the supported lipid bilayers, cause differences in the structure and properties of the supported membranes. In this review, I summarize several examples of the effects of substrate structures and properties on an atomic and nanometer scales on the solid-supported lipid bilayers, including our recent reports.
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Rahman LN, McKay F, Giuliani M, Quirk A, Moffatt BA, Harauz G, Dutcher JR. Interactions of Thellungiella salsuginea dehydrins TsDHN-1 and TsDHN-2 with membranes at cold and ambient temperatures-surface morphology and single-molecule force measurements show phase separation, and reveal tertiary and quaternary associations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:967-80. [PMID: 23219803 DOI: 10.1016/j.bbamem.2012.11.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 10/22/2012] [Accepted: 11/23/2012] [Indexed: 12/28/2022]
Abstract
Dehydrins (group 2 late embryogenesis abundant proteins) are intrinsically-disordered proteins that are expressed in plants experiencing extreme environmental conditions such as drought or low temperature. Their roles include stabilizing cellular proteins and membranes, and sequestering metal ions. Here, we investigate the membrane interactions of the acidic dehydrin TsDHN-1 and the basic dehydrin TsDHN-2 derived from the crucifer Thellungiella salsuginea that thrives in the Canadian sub-Arctic. We show using compression studies with a Langmuir-Blodgett trough that both dehydrins can stabilize lipid monolayers with a lipid composition mimicking the composition of the plant outer mitochondrial membrane, which had previously been shown to induce ordered secondary structures (disorder-to-order transitions) in the proteins. Ellipsometry of the monolayers during compression showed an increase in monolayer thickness upon introducing TsDHN-1 (acidic) at 4°C and TsDHN-2 (basic) at room temperature. Atomic force microscopy of supported lipid bilayers showed temperature-dependent phase transitions and domain formation induced by the proteins. These results support the conjecture that acidic dehydrins interact with and potentially stabilize plant outer mitochondrial membranes in conditions of cold stress. Single-molecule force spectroscopy of both proteins pulled from supported lipid bilayers indicated the induced formation of tertiary conformations in both proteins, and potentially a dimeric association for TsDHN-2.
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Affiliation(s)
- Luna N Rahman
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
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8
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Picas L, Milhiet PE, Hernández-Borrell J. Atomic force microscopy: a versatile tool to probe the physical and chemical properties of supported membranes at the nanoscale. Chem Phys Lipids 2012. [PMID: 23194897 DOI: 10.1016/j.chemphyslip.2012.10.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Atomic force microscopy (AFM) was developed in the 1980s following the invention of its precursor, scanning tunneling microscopy (STM), earlier in the decade. Several modes of operation have evolved, demonstrating the extreme versatility of this method for measuring the physicochemical properties of samples at the nanoscopic scale. AFM has proved an invaluable technique for visualizing the topographic characteristics of phospholipid monolayers and bilayers, such as roughness, height or laterally segregated domains. Implemented modes such as phase imaging have also provided criteria for discriminating the viscoelastic properties of different supported lipid bilayer (SLB) regions. In this review, we focus on the AFM force spectroscopy (FS) mode, which enables determination of the nanomechanical properties of membrane models. The interpretation of force curves is presented, together with newly emerging techniques that provide complementary information on physicochemical properties that may contribute to our understanding of the structure and function of biomembranes. Since AFM is an imaging technique, some basic indications on how real-time AFM imaging is evolving are also presented at the end of this paper.
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Affiliation(s)
- Laura Picas
- Institut Curie, CNRS UMR 144, 26 rue d'Ulm, 75248 Paris, France
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9
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Cacas JL, Furt F, Le Guédard M, Schmitter JM, Buré C, Gerbeau-Pissot P, Moreau P, Bessoule JJ, Simon-Plas F, Mongrand S. Lipids of plant membrane rafts. Prog Lipid Res 2012; 51:272-99. [PMID: 22554527 DOI: 10.1016/j.plipres.2012.04.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lipids tend to organize in mono or bilayer phases in a hydrophilic environment. While they have long been thought to be incapable of coherent lateral segregation, it is now clear that spontaneous assembly of these compounds can confer microdomain organization beyond spontaneous fluidity. Membrane raft microdomains have the ability to influence spatiotemporal organization of protein complexes, thereby allowing regulation of cellular processes. In this review, we aim at summarizing briefly: (i) the history of raft discovery in animals and plants, (ii) the main findings about structural and signalling plant lipids involved in raft segregation, (iii) imaging of plant membrane domains, and their biochemical purification through detergent-insoluble membranes, as well as the existing debate on the topic. We also discuss the potential involvement of rafts in the regulation of plant physiological processes, and further discuss the prospects of future research into plant membrane rafts.
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Affiliation(s)
- Jean-Luc Cacas
- Laboratoire de Biogenèse Membranaire, UMR 5200 CNRS, Université de Bordeaux, 146 Rue Léo Saignat, 33076 Bordeaux, France
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10
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Correlation between the ripple phase and stripe domains in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2849-58. [DOI: 10.1016/j.bbamem.2011.08.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/12/2011] [Accepted: 08/16/2011] [Indexed: 12/19/2022]
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11
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Leidy C, Ocampo J, Duelund L, Mouritsen OG, Jørgensen K, Peters GH. Membrane restructuring by phospholipase A2 is regulated by the presence of lipid domains. Biophys J 2011; 101:90-9. [PMID: 21723818 DOI: 10.1016/j.bpj.2011.02.062] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 02/22/2011] [Accepted: 02/24/2011] [Indexed: 12/13/2022] Open
Abstract
Secretory phospholipase A(2) (sPLA(2)) catalyzes the hydrolysis of glycerophospholipids. This enzyme is sensitive to membrane structure, and its activity has been shown to increase in the presence of liquid-crystalline/gel (L(α)/L(β)) lipid domains. In this work, we explore whether lipid domains can also direct the activity of the enzyme by inducing hydrolysis of certain lipid components due to preferential activity of the enzyme toward lipid domains susceptible to sPLA(2). Specifically, we show that the presence of L(α)/L(β) and L(α)/P(β') phase coexistence in a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2 distearoyl-sn-glycero-3-phosphocholine (DSPC) system results in the preferential hydrolysis of the shorter-chained lipid component in the mixture, leading to an enrichment in the longer-chained component. The restructuring process is monitored by atomic force microscopy on supported single and double bilayers formed by vesicle fusion. We observe that during preferential hydrolysis of the DMPC-rich L(α) regions, the L(β) and P(β') regions grow and reseal, maintaining membrane integrity. This result indicates that a sharp reorganization of the membrane structure can occur during sPLA(2) hydrolysis without necessarily destroying the membrane. We confirm by high-performance liquid chromatography the preferential hydrolysis of DMPC within the phase coexistence region of the DMPC/DSPC phase diagram, showing that this preferential hydrolysis is accentuated close to the solidus phase boundary. Differential scanning calorimetry results show that this preferential hydrolysis in the presence of lipid domains leads to a membrane system with a higher-temperature melting profile due to enrichment in DSPC. Together, these results show that the presence of lipid domains can induce specificity in the hydrolytic activity of the enzyme, resulting in marked differences in the physical properties of the membrane end-product.
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Affiliation(s)
- Chad Leidy
- Department of Physics, Universidad de los Andes, Bogotá, Colombia.
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12
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Favard C, Wenger J, Lenne PF, Rigneault H. FCS diffusion laws in two-phase lipid membranes: determination of domain mean size by experiments and Monte Carlo simulations. Biophys J 2011; 100:1242-51. [PMID: 21354397 PMCID: PMC3043218 DOI: 10.1016/j.bpj.2010.12.3738] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 12/07/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022] Open
Abstract
Many efforts have been undertaken over the last few decades to characterize the diffusion process in model and cellular lipid membranes. One of the techniques developed for this purpose, fluorescence correlation spectroscopy (FCS), has proved to be a very efficient approach, especially if the analysis is extended to measurements on different spatial scales (referred to as FCS diffusion laws). In this work, we examine the relevance of FCS diffusion laws for probing the behavior of a pure lipid and a lipid mixture at temperatures below, within and above the phase transitions, both experimentally and numerically. The accuracy of the microscopic description of the lipid mixtures found here extends previous work to a more complex model in which the geometry is unknown and the molecular motion is driven only by the thermodynamic parameters of the system itself. For multilamellar vesicles of both pure lipid and lipid mixtures, the FCS diffusion laws recorded at different temperatures exhibit large deviations from pure Brownian motion and reveal the existence of nanodomains. The variation of the mean size of these domains with temperature is in perfect correlation with the enthalpy fluctuation. This study highlights the advantages of using FCS diffusion laws in complex lipid systems to describe their temporal and spatial structure.
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Affiliation(s)
- Cyril Favard
- Institut Fresnel, Centre National de la Recherche Scientifique, Aix-Marseille Université, École Centrale Marseille, Marseille, France
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13
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Giocondi MC, Yamamoto D, Lesniewska E, Milhiet PE, Ando T, Le Grimellec C. Surface topography of membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:703-18. [DOI: 10.1016/j.bbamem.2009.09.015] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/11/2009] [Accepted: 09/20/2009] [Indexed: 12/24/2022]
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Peetla C, Stine A, Labhasetwar V. Biophysical interactions with model lipid membranes: applications in drug discovery and drug delivery. Mol Pharm 2009; 6:1264-76. [PMID: 19432455 DOI: 10.1021/mp9000662] [Citation(s) in RCA: 336] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The transport of drugs or drug delivery systems across the cell membrane is a complex biological process, often difficult to understand because of its dynamic nature. In this regard, model lipid membranes, which mimic many aspects of cell-membrane lipids, have been very useful in helping investigators to discern the roles of lipids in cellular interactions. One can use drug-lipid interactions to predict pharmacokinetic properties of drugs, such as their transport, biodistribution, accumulation, and hence efficacy. These interactions can also be used to study the mechanisms of transport, based on the structure and hydrophilicity/hydrophobicity of drug molecules. In recent years, model lipid membranes have also been explored to understand their mechanisms of interactions with peptides, polymers, and nanocarriers. These interaction studies can be used to design and develop efficient drug delivery systems. Changes in the lipid composition of cells and tissue in certain disease conditions may alter biophysical interactions, which could be explored to develop target-specific drugs and drug delivery systems. In this review, we discuss different model membranes, drug-lipid interactions and their significance, studies of model membrane interactions with nanocarriers, and how biophysical interaction studies with lipid model membranes could play an important role in drug discovery and drug delivery.
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Affiliation(s)
- Chiranjeevi Peetla
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
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15
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Abdulreda MH, Moy VT. Investigation of SNARE-Mediated Membrane Fusion Mechanism Using Atomic Force Microscopy. JAPANESE JOURNAL OF APPLIED PHYSICS (2008) 2009; 48:8JA03-8JA0310. [PMID: 20228892 PMCID: PMC2836841 DOI: 10.1143/jjap.48.08ja03] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Membrane fusion is driven by specialized proteins that reduce the free energy penalty for the fusion process. In neurons and secretory cells, soluble N-ethylmaleimide-sensitive factor-attachment protein (SNAP) receptors (SNAREs) mediate vesicle fusion with the plasma membrane during vesicular content release. Although, SNAREs have been widely accepted as the minimal machinery for membrane fusion, the specific mechanism for SNARE-mediated membrane fusion remains an active area of research. Here, we summarize recent findings based on force measurements acquired in a novel experimental system that uses atomic force microscope (AFM) force spectroscopy to investigate the mechanism(s) of membrane fusion and the role of SNAREs in facilitating membrane hemifusion during SNARE-mediated fusion. In this system, protein-free and SNARE-reconstituted lipid bilayers are formed on opposite (trans) substrates and the forces required to induce membrane hemifusion and fusion or to unbind single v-/t-SNARE complexes are measured. The obtained results provide evidence for a mechanism by which the pulling force generated by interacting trans-SNAREs provides critical proximity between the membranes and destabilizes the bilayers at fusion sites by broadening the hemifusion energy barrier and consequently making the membranes more prone to fusion.
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16
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Ulrich K, Sanders M, Grinberg F, Galvosas P, Vasenkov S. Application of pulsed field gradient NMR with high gradient strength for studies of self-diffusion in lipid membranes on the nanoscale. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7365-7370. [PMID: 18553990 DOI: 10.1021/la8002355] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
This work demonstrates the feasibility of noninvasive studies of lipid self-diffusion in model lipid membranes on the nanoscale using proton pulsed field gradient (PFG) NMR spectroscopy with high (up to 35 T/m) gradient amplitudes. Application of high gradients affords for the use of sufficiently small diffusion times under the conditions when the width of the gradient pulses is much smaller than the diffusion time. As a result, PFG NMR studies of partially restricted or anomalous diffusion in lipid bilayers become possible over length scales as small as 100 nm. This length scale is important because it is comparable to the size of membrane domains, or lipid rafts, which are believed to exist in biomembranes. In this work, high-gradient PFG NMR has been applied to study lipid self-diffusion in three-component planar-supported multibilayers (1,2-dioleoyl- sn-glycerol-3-phosphocholine/sphingomyelin/cholesterol). The degree of lipid orientation in the bilayers was determined with (31)P NMR. A special insert was designed to mechanically align the multibilayer stack at the magic angle with respect to the direction of the constant magnetic field to address the detrimental effects of proton dipole-dipole interactions on the NMR signal. This insert is an alternative to the conventional method of magic angle orientation of lipid membranes, the goniometer probe, which is not compatible with commercial high-gradient coils because of the lack of space in the magnet bore. Macroscopic orientation of the multibilayer stacks using the insert was confirmed with (1)H NMR spectroscopic studies and the comparison of results obtained from identical experiments using a goniometer probe for orientation. Diffusion studies were carried out at three different constant magnetic field strengths ( B 0) over a range of temperatures and diffusion times. The measured diffusivities were found to be in agreement with the data obtained previously by techniques that are limited to much larger length scales of diffusion observation than high-gradient PFG NMR.
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Affiliation(s)
- Konstantin Ulrich
- Fakultät für Physik und Geowissenschaften, Universität Leipzig, Leipzig, Germany
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17
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Past, present and future of atomic force microscopy in life sciences and medicine. J Mol Recognit 2008; 20:418-31. [PMID: 18080995 DOI: 10.1002/jmr.857] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
To introduce this special issue of the Journal of Molecular Recognition dedicated to the applications of atomic force microscopy (AFM) in life sciences, this paper presents a short summary of the history of AFM in biology. Based on contributions from the first international conference of AFM in biological sciences and medicine (AFM BioMed Barcelona, 19-21 April 2007), we present and discuss recent progress made using AFM for studying cells and cellular interactions, probing single molecules, imaging biosurfaces at high resolution and investigating model membranes and their interactions. Future prospects in these different fields are also highlighted.
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18
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Park JW, Ahn DJ. Temperature effect on nanometer-scale physical properties of mixed phospholipid monolayers. Colloids Surf B Biointerfaces 2008; 62:157-61. [DOI: 10.1016/j.colsurfb.2007.09.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 09/10/2007] [Accepted: 09/17/2007] [Indexed: 11/16/2022]
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19
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Characterizing the interactions between GPI-anchored alkaline phosphatases and membrane domains by AFM. Pflugers Arch 2007; 456:179-88. [DOI: 10.1007/s00424-007-0409-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Revised: 11/12/2007] [Accepted: 11/20/2007] [Indexed: 12/12/2022]
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20
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Abstract
This study investigated the fusion of apposing floating bilayers of egg L-alpha-phosphatidylcholine (egg PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Atomic force microscope measurements of fusion forces under different compression rates were acquired to reveal the energy landscape of the fusion process under varied lipid composition and temperature. Between compression rates of approximately 1000 and approximately 100,000 pN/s, applied forces in the range from approximately 100 to approximately 500 pN resulted in fusion of floating bilayers. Our atomic force microscope measurements indicated that one main energy barrier dominated the fusion process. The acquired dynamic force spectra were fit with a simple model based on the transition state theory with the assumption that the fusion activation potential is linear. A significant shift in the energy landscape was observed when bilayer fluidity and composition were modified, respectively, by temperature and different cholesterol concentrations (15% < or = chol < or = 25%). Such modifications resulted in a more than twofold increase in the width of the fusion energy barrier for egg PC and 1,2-dimyristoyl-sn-glycero-3-phosphocholine floating bilayers. The addition of 25% cholesterol to egg PC bilayers increased the activation energy by approximately 1.0 k(B)T compared with that of bilayers with egg PC alone. These results reveal that widening of the energy barrier and consequently reduction in its slope facilitated membrane fusion.
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Affiliation(s)
- Midhat H Abdulreda
- Department of Physiology & Biophysics, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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21
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Giocondi MC, Besson F, Dosset P, Milhiet PE, Le Grimellec C. Temperature-dependent localization of GPI-anchored intestinal alkaline phosphatase in model rafts. J Mol Recognit 2007; 20:531-7. [PMID: 17703464 DOI: 10.1002/jmr.835] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In plasma membranes, most of glycosylphosphatidylinositol (GPI)-anchored proteins would be associated with rafts, a category of ordered microdomains enriched in sphingolipids and cholesterol (Ch). They would be also concentrated in the detergent resistant membranes (DRMs), a plasma membrane fraction extracted at low temperature. Preferential localization of GPI-anchored proteins in these membrane domains is essentially governed by their high lipid order, as compared to their environment. Changes in the temperature are expected to modify the membrane lipid order, suggesting that they could affect the distribution of GPI-anchored proteins between membrane domains. Validity of this hypothesis was examined by investigating the temperature-dependent localization of the GPI-anchored bovine intestinal alkaline phophatase (BIAP) into model raft made of palmitoyloleoylphosphatidylcholine/sphingomyelin/cholesterol (POPC/SM/Chl) supported membranes. Atomic force microscopy (AFM) shows that the inserted BIAP is localized in the SM/Chl enriched ordered domains at low temperature. Above 30 degrees C, BIAP redistributes and is present in both the 'fluid' POPC enriched and the ordered SM/Chl domains. These data strongly suggest that in cells the composition of plasma membrane domains at low temperature differs from that at physiological temperature.
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Affiliation(s)
- Marie-Cécile Giocondi
- Institut National de la Santé et de la Recherche Médicale, Unité 554, Montpellier, France
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22
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Buzhynskyy N, Hite RK, Walz T, Scheuring S. The supramolecular architecture of junctional microdomains in native lens membranes. EMBO Rep 2006; 8:51-5. [PMID: 17124511 PMCID: PMC1796741 DOI: 10.1038/sj.embor.7400858] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 10/13/2006] [Accepted: 10/16/2006] [Indexed: 11/08/2022] Open
Abstract
Gap junctions formed by connexons and thin junctions formed by lens-specific aquaporin 0 (AQP0) mediate the tight packing of fibre cells necessary for lens transparency. Gap junctions conduct water, ions and metabolites between cells, whereas junctional AQP0 seems to be involved in cell adhesion. High-resolution atomic force microscopy (AFM) showed the supramolecular organization of these proteins in native lens core membranes, in which AQP0 forms two-dimensional arrays that are surrounded by densely packed gap junction channels. These junctional microdomains simultaneously provide adhesion and communication between fibre cells. The AFM topographs also showed that the extracellular loops of AQP0 in junctional microdomains adopt a conformation that closely resembles the structure of junctional AQP0, in which the water pore is thought to be closed. Finally, time-lapse AFM imaging provided insights into AQP0 array formation. This first high-resolution view of a multicomponent eukaryotic membrane shows how membrane proteins self-assemble into functional microdomains.
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Affiliation(s)
| | - Richard K Hite
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
| | - Simon Scheuring
- Institut Curie, UMR168-CNRS, 26 Rue d'Ulm, 75248 Paris, France
- Tel: +33 1 42 34 67 81; Fax: +33 1 40 51 06 36; E-mail:
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23
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Abstract
We report a new type of gel-liquid phase segregation in giant unilamellar vesicles (GUVs) of mixed lipids. Coexisting patch- and stripe-shaped gel domains in GUV bilayers composed of DOPC/DPPC or DLPC/DPPC are observed by confocal fluorescence microscopy. The lipids in stripe domains are shown to be tilted according to the DiIC18 fluorescence intensity dependence on the excitation polarization. The patch domains are found to be mainly composed of DPPC-d62 according to the coherent anti-Stokes Raman scattering (CARS) images of DOPC/DPPC-d62 bilayers. When cooling GUVs from above the miscibility temperature, the patch domains start to appear between the chain melting and the pretransition temperature of DPPC. In GUVs containing a high molar percentage of DPPC, the stripe domains form below the pretransition temperature. Our observations suggest that the patch and stripe domains are in the Pbeta' and Lbeta' gel phases, respectively. According to the thermoelastic properties of GUVs described by Needham and Evans [(1988) Biochemistry 27, 8261-8269], the Pbeta' and Lbeta' phases are formed at relatively low and high membrane tensions, respectively. GUVs with high DPPC percentage have high membrane surface tension and thus mainly exhibit Lbeta' domains, while GUVs with low DPPC percentage have low membrane surface tension and form Pbeta' domains accordingly. Adding negatively charged lipid to the lipid mixtures or applying an osmotic pressure to GUVs using sucrose solutions releases the surface tension and leads to the disappearance of the Lbeta' gel phase. The relationship between the observed domains in free-standing GUV bilayers and those in supported bilayers is discussed.
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Affiliation(s)
- Li Li
- Weldon School of Biomedical Engineering and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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24
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25
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Chapter 4 Visualization and Characterization of Domains in Supported Model Membranes. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1554-4516(05)03004-8] [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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26
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Tero R, Watanabe H, Urisu T. Supported phospholipid bilayer formation on hydrophilicity-controlled silicon dioxide surfaces. Phys Chem Chem Phys 2006; 8:3885-94. [DOI: 10.1039/b606052h] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Garcia-Manyes S, Oncins G, Sanz F. Effect of temperature on the nanomechanics of lipid bilayers studied by force spectroscopy. Biophys J 2005; 89:4261-74. [PMID: 16150966 PMCID: PMC1366991 DOI: 10.1529/biophysj.105.065581] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 08/15/2005] [Indexed: 11/18/2022] Open
Abstract
The effect of temperature on the nanomechanical response of supported lipid bilayers has been studied by force spectroscopy with atomic force microscopy. We have experimentally proved that the force needed to puncture the lipid bilayer (Fy) is temperature dependent. The quantitative measurement of the evolution of Fy with temperature has been related to the structural changes that the surface undergoes as observed through atomic force microscopy images. These studies were carried out with three different phosphatidylcholine bilayers with different main phase transition temperature (TM), namely, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, and 2-dilauroyl-sn-glycero-3-phosphocholine. The solid-like phase shows a much higher Fy than the liquid-like phase, which also exhibits a jump in the force curve. Within the solid-like phase, Fy decreases as temperature is increased and suddenly drops as it approaches TM. Interestingly, a "well" in the Fy versus temperature plot occurs around TM, thus proving an "anomalous mechanical softening" around TM. Such mechanical softening has been predicted by experimental techniques and also by molecular dynamics simulations and interpreted in terms of water ordering around the phospholipid headgroups. Ion binding has been demonstrated to increase Fy, and its influence on both solid and liquid phases has also been discussed.
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Affiliation(s)
- Sergi Garcia-Manyes
- Department of Physical Chemistry, Universitat de Barcelona, 08028 Barcelona, Spain
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28
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Smith EA, Coym JW, Cowell SM, Tokimoto T, Hruby VJ, Yamamura HI, Wirth MJ. Lipid bilayers on polyacrylamide brushes for inclusion of membrane proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:9644-50. [PMID: 16207048 PMCID: PMC1456321 DOI: 10.1021/la051116h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The ability of neutral polymer cushions to support neutral lipid bilayers for the incorporation of mobile transmembrane proteins was investigated. Polyacrylamide brush layers were grown on fused silica using atom-transfer radical polymerization to provide polymer layers of 2.5-, 5- and 10-nm thickness. Lipid bilayers composed of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) were formed by vesicle fusion onto bare fused silica and onto each of the polyacrylamide layers. Bilayer fluidity was assessed by the diffusion of a probe, NBD-labeled phosphatidylcholine, using fluorescence recovery after photobleaching. A transmembrane protein, the human delta-opioid receptor, was inserted into each lipid bilayer, and its ability to bind a synthetic ligand, DPDPE, cyclic[2-d-penicillamine, 5-d-penicillamine]enkephalin, was detected using single-molecule fluorescence spectroscopy by labeling this ligand with a rhodamine dye. The transmembrane protein was observed to bind the ligand for all bilayers tested. The protein's electrophoretic mobility was probed by monitoring the fluorescence from the bound ligand. The 5-nm polyacrylamide thickness gave the fastest diffusion for the fluorescent lipid probe (D(1) = 2.0(+/-1.2) x 10(-7) and D(2) = 1.2(+/-0.5) x 10(-6) cm(2)/s) and also the largest electrophoretic mobility for the transmembrane protein (3 x 10(-8) cm(2)/V.s). The optimum in polymer thickness is suggested to be a tradeoff between decoupling from the substrate and increasing roughness of the polymer surface.
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Affiliation(s)
- Emily A Smith
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
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29
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Plénat T, Boichot S, Dosset P, Milhiet PE, Le Grimellec C. Coexistence of a two-states organization for a cell-penetrating peptide in lipid bilayer. Biophys J 2005; 89:4300-9. [PMID: 16199494 PMCID: PMC1366994 DOI: 10.1529/biophysj.105.061697] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Primary amphipathic cell-penetrating peptides transport cargoes across cell membranes with high efficiency and low lytic activity. These primary amphipathic peptides were previously shown to form aggregates or supramolecular structures in mixed lipid-peptide monolayers, but their behavior in lipid bilayers remains to be characterized. Using atomic force microscopy, we have examined the interactions of P(alpha), a primary amphipathic cell-penetrating peptide which remains alpha-helical whatever the environment, with dipalmitoylphosphatidylcholine (DPPC) bilayers. Addition of P(alpha) at concentrations up to 5 mol % markedly modified the supported bilayers topography. Long and thin filaments lying flat at the membrane surface coexisted with deeply embedded peptides which induced a local thinning of the bilayer. On the other hand, addition of P(alpha) only exerted very limited effects on the corresponding liposome's bilayer physical state, as estimated from differential scanning calorimetry and diphenylhexatriene fluorescence anisotropy experiments. The use of a gel-fluid phase separated supported bilayers made of a dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine mixture confirmed both the existence of long filaments, which at low peptide concentration were preferentially localized in the fluid phase domains and the membrane disorganizing effects of 5 mol % P(alpha). The simultaneous two-states organization of P(alpha), at the membrane surface and deeply embedded in the bilayer, may be involved in the transmembrane carrier function of this primary amphipathic peptide.
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Affiliation(s)
- Thomas Plénat
- Nanostructures et Complexes Membranaires, Centre de Biochimie Structurale, INSERM UMR 554, CNRS UMR 5048-Université Montpellier I, 34090 Montpellier Cedex, France
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30
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Abstract
We have studied the phase transitions of a phospholipidic single-bilayer supported on a mica substrate by real-time temperature-controlled atomic force microscopy. We show the existence of two phase transitions in this bilayer that we attribute to two gel (L(beta))/fluid (L(alpha)) transitions, corresponding to the independent melting of each leaflet of the bilayer. The ratio of each phase with temperature and the large broadening of the transitions' widths have been interpreted through a basic thermodynamic framework in which the surface tension varies during the transitions. The experimental data can be fit with such a model using known thermodynamic parameters.
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Affiliation(s)
- A Charrier
- Centre de Recherche en Matière Condensée et Nanosciences, Centre National de la Recherche Scientifique, Université de la Méditerranée, Marseille, France.
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31
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Arnold A, Cloutier I, Ritcey AM, Auger M. Temperature and pressure dependent growth and morphology of DMPC/DSPC domains studied by Brewster angle microscopy. Chem Phys Lipids 2004; 133:165-79. [PMID: 15642585 DOI: 10.1016/j.chemphyslip.2004.09.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Revised: 09/30/2004] [Accepted: 09/30/2004] [Indexed: 11/17/2022]
Abstract
In this work, the temperature and pressure dependent growth of domains in DMPC/DSPC monolayers at various molar ratios was studied by Brewster angle microscopy. Upon compression, roughly discoidal domains with some branching are formed. Further compression leads to an increase in both the number and the average size of the domains, which range between ca. 5 and 20 microm. The isobaric heating of the monolayers results in a gradual decrease of the domain size until their disappearance. The size and morphology of the domains depend not only on equilibrium parameters such as temperature, pressure and composition, but appear to be also strongly dependent on non-equilibrium parameters such as the rate of perturbation. The comparison between our results and those previously published for bilayers allows us to infer that the growth behaviour in monolayers can be qualitatively but not quantitatively extrapolated to bilayers.
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Affiliation(s)
- Alexandre Arnold
- Department of Chemistry, Centre de Recherche en Sciences et Ingénierie des Macromolécules, Université Laval, Québec city, Québec, G1K 7P4, Canada
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