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Xu H, Tae H, Cho NJ, Huang C, Hsia KJ. Thermodynamic Modeling of Solvent-Assisted Lipid Bilayer Formation Process. MICROMACHINES 2022; 13:mi13010134. [PMID: 35056299 PMCID: PMC8777629 DOI: 10.3390/mi13010134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 12/22/2022]
Abstract
The solvent-assisted lipid bilayer (SALB) formation method provides a simple and efficient, microfluidic-based strategy to fabricate supported lipid bilayers (SLBs) with rich compositional diversity on a wide range of solid supports. While various studies have been performed to characterize SLBs formed using the SALB method, relatively limited work has been carried out to understand the underlying mechanisms of SALB formation under various experimental conditions. Through thermodynamic modeling, we studied the experimental parameters that affect the SALB formation process, including substrate surface properties, initial lipid concentration, and temperature. It was found that all the parameters are critically important to successfully form high-quality SLBs. The model also helps to identify the range of parameter space within which conformal, homogeneous SLBs can be fabricated, and provides mechanistic guidance to optimize experimental conditions for lipid membrane-related applications.
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Affiliation(s)
- Hongmei Xu
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore;
| | - Hyunhyuk Tae
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore;
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore;
- Correspondence: (N.-J.C.); (C.H.); (K.J.H.)
| | - Changjin Huang
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore;
- Correspondence: (N.-J.C.); (C.H.); (K.J.H.)
| | - K. Jimmy Hsia
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore;
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459, Singapore
- Correspondence: (N.-J.C.); (C.H.); (K.J.H.)
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2
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Baccile N, Derj A, Boissière C, Humblot V, Deniset-Besseau A. Homogeneous supported monolayer from microbial glycolipid biosurfactant. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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3
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Paulowski L, Donoghue A, Nehls C, Groth S, Koistinen M, Hagge SO, Böhling A, Winterhalter M, Gutsmann T. The Beauty of Asymmetric Membranes: Reconstitution of the Outer Membrane of Gram-Negative Bacteria. Front Cell Dev Biol 2020; 8:586. [PMID: 32766244 PMCID: PMC7381204 DOI: 10.3389/fcell.2020.00586] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/16/2020] [Indexed: 11/23/2022] Open
Abstract
The architecture of the lipid matrix of the outer membrane of Gram-negative bacteria is extremely asymmetric: Whereas the inner leaflet is composed of a phospholipid mixture, the outer leaflet is built up by glycolipids. For most Gram-negative species, these glycolipids are lipopolysaccharides (LPS), for a few species, however, glycosphingolipids. We demonstrate experimental approaches for the reconstitution of these asymmetric membranes as (i) solid supported membranes prepared by the Langmuir-Blodgett technique, (ii) planar lipid bilayers prepared by the Montal-Mueller technique, and (iii) giant unilamellar vesicles (GUVs) prepared by the phase transfer method. The asymmetric GUVs (aGUVs) composed of LPS on one leaflet are shown for the first time. They are characterized with respect to their phase behavior, flip-flop of lipids and their usability to investigate the interaction with membrane active peptides or proteins. For the antimicrobial peptide LL-32 and for the bacterial porin OmpF the specificity of the interaction with asymmetric membranes is shown. The three reconstitution systems are compared with respect to their usability to investigate domain formation and interactions with peptides and proteins.
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Affiliation(s)
- Laura Paulowski
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
- Division of Diagnostic Mycobacteriology, Priority Research Area Infection, National Reference Center for Mycobacteria, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Annemarie Donoghue
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
- Department of Life Sciences & Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Christian Nehls
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Sabrina Groth
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Max Koistinen
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Sven O. Hagge
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Arne Böhling
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
| | - Mathias Winterhalter
- Department of Life Sciences & Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Thomas Gutsmann
- Division of Biophysics, Priority Research Area Infection, Research Center Borstel Leibniz Lung Center, Borstel, Germany
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4
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Munusamy S, Conde R, Bertrand B, Munoz-Garay C. Biophysical approaches for exploring lipopeptide-lipid interactions. Biochimie 2020; 170:173-202. [PMID: 31978418 PMCID: PMC7116911 DOI: 10.1016/j.biochi.2020.01.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 01/19/2020] [Indexed: 02/07/2023]
Abstract
In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed. A brief overview of topics to understand the generalities of lipopeptide (LP) science. Main analytical techniques used to reveal the interaction and the distorting effect of LP on artificial membranes. Guidelines for selecting of the most adequate membrane models for the given analytical technique.
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Affiliation(s)
- Sathishkumar Munusamy
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico
| | - Renaud Conde
- Centro de Investigación Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico
| | - Brandt Bertrand
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico
| | - Carlos Munoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico.
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5
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Kurniawan J, Ventrici de Souza JF, Dang AT, Liu GY, Kuhl TL. Preparation and Characterization of Solid-Supported Lipid Bilayers Formed by Langmuir-Blodgett Deposition: A Tutorial. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:15622-15639. [PMID: 30465730 DOI: 10.1021/acs.langmuir.8b03504] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The structure, phase behavior, and properties of cellular membranes are derived from their composition, which includes phospholipids, sphingolipids, sterols, and proteins with various levels of glycosylation. Because of the intricate nature of cellular membranes, a plethora of in vitro studies have been carried out with model membrane systems that capture particular properties such as fluidity, permeability, and protein binding but vastly simplify the membrane composition in order to focus in detail on a specialized property or function. Supported lipid bilayers (SLB) are widely used as archetypes for cellular membranes, and this instructional review primarily focuses on the preparation and characterization of SLB systems formed by Langmuir deposition methods. Typical characterization methods, which take advantage of the planar orientation of SLBs, are illustrated, and references that go into more depth are included. This invited instructional review is written so that nonexperts can quickly gain in-depth knowledge regarding the preparation and characterization of SLBs. In addition, this work goes beyond traditional instructional reviews to provide expert readers with new results that cover a wider range of SLB systems than those previously reported in the literature. The quality of an SLB is frequently not well described, and details such as topological defects can influence the results and conclusions of an individual study. This article quantifies and compares the quality of SLBs fabricated from a variety of gel and fluid compositions, in correlation with preparation techniques and parameters, to generate general rules of thumb to guide the construction of designed SLB systems.
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6
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Marquardt D, Heberle FA, Miti T, Eicher B, London E, Katsaras J, Pabst G. 1H NMR Shows Slow Phospholipid Flip-Flop in Gel and Fluid Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3731-3741. [PMID: 28106399 PMCID: PMC5397887 DOI: 10.1021/acs.langmuir.6b04485] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We measured the transbilayer diffusion of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in large unilamellar vesicles, in both the gel (Lβ') and fluid (Lα) phases. The choline resonance of headgroup-protiated DPPC exchanged into the outer leaflet of headgroup-deuterated DPPC-d13 vesicles was monitored using 1H NMR spectroscopy, coupled with the addition of a paramagnetic shift reagent. This allowed us to distinguish between the inner and outer bilayer leaflet of DPPC, to determine the flip-flop rate as a function of temperature. Flip-flop of fluid-phase DPPC exhibited Arrhenius kinetics, from which we determined an activation energy of 122 kJ mol-1. In gel-phase DPPC vesicles, flip-flop was not observed over the course of 250 h. Our findings are in contrast to previous studies of solid-supported bilayers, where the reported DPPC translocation rates are at least several orders of magnitude faster than those in vesicles at corresponding temperatures. We reconcile these differences by proposing a defect-mediated acceleration of lipid translocation in supported bilayers, where long-lived, submicron-sized holes resulting from incomplete surface coverage are the sites of rapid transbilayer movement.
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Affiliation(s)
- Drew Marquardt
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail: (D.M.)
| | - Frederick A. Heberle
- The Bredesen
Center and Department of Physics and Astronomy, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Biological Sciences, Biology and Soft
Matter Division, and Shull Wollan
Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- E-mail: (F.A.H.)
| | - Tatiana Miti
- Department
of Physics, University of South Florida, Tampa, Florida 33620,United States
| | - Barbara Eicher
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
| | - Erwin London
- Department
of Biochemistry and Cell Biology, Stony Brook, New York 11794, United States
| | - John Katsaras
- The Bredesen
Center and Department of Physics and Astronomy, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Biological Sciences, Biology and Soft
Matter Division, and Shull Wollan
Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Georg Pabst
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail: (G.P.)
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Freudenthal O, Quilès F, Francius G, Wojszko K, Gorczyca M, Korchowiec B, Rogalska E. Nanoscale investigation of the interaction of colistin with model phospholipid membranes by Langmuir technique, and combined infrared and force spectroscopies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2592-2602. [PMID: 27480806 DOI: 10.1016/j.bbamem.2016.07.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 07/26/2016] [Accepted: 07/27/2016] [Indexed: 12/31/2022]
Abstract
Colistin (Polymyxin E), an antimicrobial peptide, is increasingly put forward as salvage for severe multidrug-resistant infections. Unfortunately, colistin is potentially toxic to mammalian cells. A better understanding of the interaction with specific components of the cell membranes may be helpful in controlling the factors that may enhance toxicity. Here, we report a physico-chemical study of model phospholipid (PL) mono- and bilayers exposed to colistin at different concentrations by Langmuir technique, atomic force microscopy (AFM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The effect of colistin on chosen PL monolayers was examined. Insights into the topographical and elastic changes in the PL bilayers within time after peptide injection are presented via AFM imaging and force spectra. Finally, changes in the PL bilayers' ATR-FTIR spectra as a function of time within three bilayer compositions, and the influence of colistin on their spectral fingerprint are examined together with the time-evolution of the Amide II and νCO band integrated intensity ratios. Our study reveals a great importance in the role of the PL composition as well as the peptide concentration on the action of colistin on PL model membranes.
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Affiliation(s)
- Oona Freudenthal
- Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès-Nancy F-54600, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès- Nancy F-54600, France; Université de Lorraine, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France
| | - Fabienne Quilès
- Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès-Nancy F-54600, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès- Nancy F-54600, France
| | - Grégory Francius
- Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès-Nancy F-54600, France; CNRS, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME, UMR 7564, Villers-lès- Nancy F-54600, France.
| | - Kamila Wojszko
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland; Université de Lorraine, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France
| | - Marcelina Gorczyca
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland; Université de Lorraine, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France
| | - Beata Korchowiec
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland; Université de Lorraine, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France
| | - Ewa Rogalska
- Université de Lorraine, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France; CNRS, Structure et Réactivité des Systèmes Moléculaires Complexes, SRSMC, UMR7565, Vandœuvre-lès-Nancy, cedex, F-54506, France
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8
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Physicochemical Properties of Lipids and Macromolecules in Higher Level Organization. ACTA ACUST UNITED AC 2016. [DOI: 10.1007/978-3-319-30277-5_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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9
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Shan Y, Wang H. The structure and function of cell membranes examined by atomic force microscopy and single-molecule force spectroscopy. Chem Soc Rev 2016; 44:3617-38. [PMID: 25893228 DOI: 10.1039/c4cs00508b] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The cell membrane is one of the most complicated biological complexes, and long-term fierce debates regarding the cell membrane persist because of technical hurdles. With the rapid development of nanotechnology and single-molecule techniques, our understanding of cell membranes has substantially increased. Atomic force microscopy (AFM) has provided several unprecedented advances (e.g., high resolution, three-dimensional and in situ measurements) in the study of cell membranes and has been used to systematically dissect the membrane structure in situ from both sides of membranes; as a result, novel models of cell membranes have recently been proposed. This review summarizes the new progress regarding membrane structure using in situ AFM and single-molecule force spectroscopy (SMFS), which may shed light on the study of the structure and functions of cell membranes.
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Affiliation(s)
- Yuping Shan
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China.
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10
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Liu CK, Warr GG. Self-assembly of didodecyldimethylammonium surfactants modulated by multivalent, hydrolyzable counterions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2936-2945. [PMID: 25180627 DOI: 10.1021/la502930p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The self-assembly behavior of double-chained didodecyldimethylammonium (DDA(+)) surfactants with hydrolyzable phosphate (PO4(3-), HPO4(2-), and H2PO4(-)), oxalate (HC2O4(-) and C2O4(2-)), and carbonate (HCO3(-)/CO3(2-)) counterions was found to depend on both the counterion and its hydrolysis state, as determined by the pH of the system. Carbonate and phosphate ions at all hydrolysis states successfully stabilize an extended isotropic micellar solution region. These micelles are well-described as prolate ellipsoids which vary in size and aspect ratio depending on the surfactant concentration and hydrolysis state of the counterion. Both oxalate counterions form bilayer structures in dilute solution. The structures found with divalent oxalate, C2O4(2-), ions possessed very limited swelling capacity compared to the bilayer structures formed with monovalent oxalate, HC2O4(-), ions. The lamellar (Lα) phase was universally formed at sufficiently high surfactant concentrations for all hydrolyzable counterions. Two intermediate structures corresponding to a disordered mesh (Lα(D)) and tetragonal ordered mesh (T) phase were found to form with DDA2HPO4 prior to the Lα phase but not with other phosphate counterions.
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Affiliation(s)
- Connie K Liu
- School of Chemistry F11, The University of Sydney, Sydney, NSW 2006, Australia
| | - Gregory G Warr
- School of Chemistry F11, The University of Sydney, Sydney, NSW 2006, Australia
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11
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Naulin PA, Alveal NA, Barrera NP. Toward atomic force microscopy and mass spectrometry to visualize and identify lipid rafts in plasmodesmata. FRONTIERS IN PLANT SCIENCE 2014; 5:234. [PMID: 24910637 PMCID: PMC4038920 DOI: 10.3389/fpls.2014.00234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Accepted: 05/11/2014] [Indexed: 05/08/2023]
Abstract
Plant cell-to-cell communication is mediated by nanopores called plasmodesmata (PDs) which are complex structures comprising plasma membrane (PM), highly packed endoplasmic reticulum and numerous membrane proteins. Although recent advances on proteomics have led to insights into mechanisms of transport, there is still an inadequate characterization of the lipidic composition of the PM where membrane proteins are inserted. It has been postulated that PDs could be formed by lipid rafts, however no structural evidence has shown to visualize and analyse their lipid components. In this perspective article, we discuss proposed experiments to characterize lipid rafts and proteins in the PDs. By using atomic force microscopy (AFM) and mass spectrometry (MS) of purified PD vesicles it is possible to determine the presence of lipid rafts, specific bound proteins and the lipidomic profile of the PD under physiological conditions and after changing transport permeability. In addition, MS can determine the stoichiometry of intact membrane proteins inserted in lipid rafts. This will give novel insights into the role of membrane proteins and lipid rafts on the PD structure.
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Affiliation(s)
| | | | - Nelson P. Barrera
- *Correspondence: Nelson P. Barrera, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Alameda 340, Santiago 8331150, Chile e-mail:
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12
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Redondo-Morata L, Giannotti MI, Sanz F. Structural impact of cations on lipid bilayer models: Nanomechanical properties by AFM-force spectroscopy. Mol Membr Biol 2013; 31:17-28. [DOI: 10.3109/09687688.2013.868940] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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13
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Preparation of DOPC and DPPC Supported Planar Lipid Bilayers for Atomic Force Microscopy and Atomic Force Spectroscopy. Int J Mol Sci 2013; 14:3514-39. [PMID: 23389046 PMCID: PMC3588056 DOI: 10.3390/ijms14023514] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 01/29/2013] [Accepted: 02/01/2013] [Indexed: 11/16/2022] Open
Abstract
Cell membranes are typically very complex, consisting of a multitude of different lipids and proteins. Supported lipid bilayers are widely used as model systems to study biological membranes. Atomic force microscopy and force spectroscopy techniques are nanoscale methods that are successfully used to study supported lipid bilayers. These methods, especially force spectroscopy, require the reliable preparation of supported lipid bilayers with extended coverage. The unreliability and a lack of a complete understanding of the vesicle fusion process though have held back progress in this promising field. We document here robust protocols for the formation of fluid phase DOPC and gel phase DPPC bilayers on mica. Insights into the most crucial experimental parameters and a comparison between DOPC and DPPC preparation are presented. Finally, we demonstrate force spectroscopy measurements on DOPC surfaces and measure rupture forces and bilayer depths that agree well with X-ray diffraction data. We also believe our approach to decomposing the force-distance curves into depth sub-components provides a more reliable method for characterising the depth of fluid phase lipid bilayers, particularly in comparison with typical image analysis approaches.
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14
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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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15
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Sarangi NK, Patnaik A. L-Tryptophan-Induced Electron Transport across Supported Lipid Bilayers: an Alkyl-Chain Tilt-Angle, and Bilayer-Symmetry Dependence. Chemphyschem 2012; 13:4258-70. [DOI: 10.1002/cphc.201200655] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 09/20/2012] [Indexed: 11/11/2022]
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16
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Morandat S, Azouzi S, Beauvais E, Mastouri A, El Kirat K. Atomic force microscopy of model lipid membranes. Anal Bioanal Chem 2012; 405:1445-61. [DOI: 10.1007/s00216-012-6383-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 08/02/2012] [Accepted: 08/24/2012] [Indexed: 10/27/2022]
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17
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18
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Interaction of the cationic peptide bactenecin with mixed phospholipid monolayers at the air-water interface. J Colloid Interface Sci 2011; 359:279-88. [PMID: 21501845 DOI: 10.1016/j.jcis.2011.03.081] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/26/2011] [Accepted: 03/29/2011] [Indexed: 01/02/2023]
Abstract
The initial mechanism by which antimicrobial peptides target microbes occurs via electrostatic interactions; however, the mechanism is not well understood. We investigate the interaction of the antimicrobial peptide bactenecin with a 50:50 w:w% 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG) phospholipid mixture at the air-water interface with different NaCl concentrations (0.01, 0.05, 0.1, 0.5 M) in the subphase. A larger shift of DPPC:DMPG isotherms was obtained for 0.1 M salt concentration at lower and higher pressures, demonstrating the influence of the negative charge of DMPG molecules and the screening of the electrostatic interaction by the salt concentration. Raman spectroscopy of monolayers demonstrated the presence of cysteine-cysteine bridges in bactenecin loops. The peptide adsorption in DPPC:DMPG monolayers observed by AFM images suggests a self-assembled aggregation process, starting with filament-like networks. Domains similar to carpets were formed and pore structures were obtained after a critical peptide concentration, according to the carpet model.
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Romão RIS, Ferreira Q, Morgado J, Martinho JMG, Gonçalves da Silva AMPS. Microphase separation in mixed monolayers of DPPG with a double hydrophilic block copolymer at the air-water interface: a BAM, LSCFM, and AFM study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:17165-17177. [PMID: 20964300 DOI: 10.1021/la103029d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Phase separation and interactions in mixed monolayers of dipalmitoylphosphatidylglycerol (DPPG) with the rhodamine B end-labeled double-hydrophilic block copolymer (DHBC), poly(N,N-dimethylacrylamide)-block-poly(N,N-diethylacrylamide) (RhB-PDMA(207)-b-PDEA(177)), was studied at the air-water interface. Surface pressure versus area isotherms indicate that both components behave almost independently. Brewster angle microscopy (BAM) images show a random distribution of liquid condensed (LC) domains of DPPG in an apparent homogeneous matrix of DHBC, excluding the macroscopic phase separation. The laser scanning confocal fluorescence microscopy (LSCFM) of the rhodamine dye at the end of the PDMA chain showed how the DHBC is distributed in Langmuir-Blodgett (LB) mixed monolayers. The high spatial resolution of atomic force microscopy (AFM) combined with the LCSFM images indicates that DHBC incorporates in the expanded phase of DPPG to form mixed domains, being excluded from the condensed regions. Upon compression, nanosized LC domains of DPPG nucleate inside the mixed domains corralled in the nanopatterning of pure DHBC. The negatively charged polar group of DPPG inhibits rhodamine aggregation, while the long polymer chains promote the formation of corralled nanodomains of DPPG in two dimensions.
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Affiliation(s)
- Rute I S Romão
- Centro de Química Estrutural, Instituto Superior Técnico, Avenida Rovisco Pais, P-1049-001 Lisboa, Portugal
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Bitler A, Lev N, Fridmann-Sirkis Y, Blank L, Cohen SR, Shai Y. Kinetics of interaction of HIV fusion protein (gp41) with lipid membranes studied by real-time AFM imaging. Ultramicroscopy 2010; 110:694-700. [DOI: 10.1016/j.ultramic.2010.02.034] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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El Kirat K, Morandat S, Dufrêne YF. Nanoscale analysis of supported lipid bilayers using atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:750-65. [DOI: 10.1016/j.bbamem.2009.07.026] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/17/2009] [Accepted: 07/23/2009] [Indexed: 12/11/2022]
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Miao S, Leeman H, De Feyter S, Schoonheydt R. Three-Component Langmuir-Blodgett Films Consisting of Surfactant, Clay Mineral, and Lysozyme: Construction and Characterization. Chemistry 2010; 16:2461-9. [DOI: 10.1002/chem.200900584] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Picas L, Suárez-Germà C, Teresa Montero M, Hernández-Borrell J. Force Spectroscopy Study of Langmuir−Blodgett Asymmetric Bilayers of Phosphatidylethanolamine and Phosphatidylglycerol. J Phys Chem B 2010; 114:3543-9. [DOI: 10.1021/jp910882e] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Laura Picas
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, 08028-Barcelona, Spain, and Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona (IN2UB), 08028-Barcelona, Spain
| | - Carme Suárez-Germà
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, 08028-Barcelona, Spain, and Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona (IN2UB), 08028-Barcelona, Spain
| | - M. Teresa Montero
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, 08028-Barcelona, Spain, and Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona (IN2UB), 08028-Barcelona, Spain
| | - Jordi Hernández-Borrell
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, 08028-Barcelona, Spain, and Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona (IN2UB), 08028-Barcelona, Spain
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Zhang Y, Cheng X, Wang J, Zhou F. Bi- and tetra-layered dipalmitoyl phosphatidylserine (DPPS) patterns produced by hydration of Langmuir–Blodgett monolayers and the subsequent enzymatic digestion. Colloids Surf A Physicochem Eng Asp 2009. [DOI: 10.1016/j.colsurfa.2008.11.050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Picas L, Montero MT, Morros A, Oncins G, Hernández-Borrell J. Phase Changes in Supported Planar Bilayers of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine. J Phys Chem B 2008; 112:10181-7. [DOI: 10.1021/jp8037522] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Laura Picas
- Departament de Fisicoquímica, Facultat de Farmàcia UB, 08028-Barcelona, Spain, Unitat de Biofísica, Departament de Bioquímica i Biología Molecular, Facultat de Medicina, UAB, 08193-Bellaterra (Barcelona), Spain, and Serveis Científico Tècnics UB, 08028-Barcelona, Spain
| | - M. Teresa Montero
- Departament de Fisicoquímica, Facultat de Farmàcia UB, 08028-Barcelona, Spain, Unitat de Biofísica, Departament de Bioquímica i Biología Molecular, Facultat de Medicina, UAB, 08193-Bellaterra (Barcelona), Spain, and Serveis Científico Tècnics UB, 08028-Barcelona, Spain
| | - Antoni Morros
- Departament de Fisicoquímica, Facultat de Farmàcia UB, 08028-Barcelona, Spain, Unitat de Biofísica, Departament de Bioquímica i Biología Molecular, Facultat de Medicina, UAB, 08193-Bellaterra (Barcelona), Spain, and Serveis Científico Tècnics UB, 08028-Barcelona, Spain
| | - Gerard Oncins
- Departament de Fisicoquímica, Facultat de Farmàcia UB, 08028-Barcelona, Spain, Unitat de Biofísica, Departament de Bioquímica i Biología Molecular, Facultat de Medicina, UAB, 08193-Bellaterra (Barcelona), Spain, and Serveis Científico Tècnics UB, 08028-Barcelona, Spain
| | - Jordi Hernández-Borrell
- Departament de Fisicoquímica, Facultat de Farmàcia UB, 08028-Barcelona, Spain, Unitat de Biofísica, Departament de Bioquímica i Biología Molecular, Facultat de Medicina, UAB, 08193-Bellaterra (Barcelona), Spain, and Serveis Científico Tècnics UB, 08028-Barcelona, Spain
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Mao Y, Tero R, Imai Y, Hoshino T, Urisu T. The morphology of GM1x/SM0.6−x/Chol0.4 planar bilayers supported on SiO2 surfaces. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.05.097] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Dimitrievski K, Kasemo B. Simulations of lipid vesicle adsorption for different lipid mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:4077-4091. [PMID: 18318551 DOI: 10.1021/la703021u] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Numerous experimental studies of lipid vesicle adsorption on solid surfaces show that electrostatic interactions play an important role for the kinetics and end result. The latter can, e.g., be intact vesicles or supported lipid bilayers (SLB). Despite an accumulated quite large experimental data base, the understanding of the underlying processes is still poor, and mathematical models are scarce. We have developed a phenomenological model of a vesicle adsorbing on a substrate, where the charge of the surface and the charge and polar state of the lipid headgroup can be varied. With physically reasonable assumptions and input parameters, we reproduce many key experimental observations, clarify the details of some experiments, and give predictions and suggestions for future experiments. Specifically, we have investigated the influence of different lipid mixtures (different charges of the headgroups) in the vesicle on the outcome of a vesicle adsorption event. For different mixtures of zwitterionic lipids with positive and negative lipids, we investigated whether the vesicle adsorbs or not, and--if it adsorbs--to what extent it gets deformed and when it ruptures spontaneously. Diffusion of neutral vesicles on different types of negatively charged substrates was also simulated. The mean surface charge density of the substrate was varied, including or excluding local fluctuations in the surface charge density. The simulations are compared to available experiments. A consistent picture of the influence of different lipid mixtures in the vesicle on adsorption, and the influence of different types of substrates on vesicle diffusion, appear as a result of the simulation data.
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Blistering of supported lipid membranes induced by Phospholipase D, as observed by real-time atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:276-82. [DOI: 10.1016/j.bbamem.2007.09.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 09/11/2007] [Accepted: 09/28/2007] [Indexed: 11/21/2022]
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Ira, Johnston LJ. Sphingomyelinase generation of ceramide promotes clustering of nanoscale domains in supported bilayer membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:185-97. [PMID: 17988649 DOI: 10.1016/j.bbamem.2007.09.021] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 09/20/2007] [Accepted: 09/21/2007] [Indexed: 11/29/2022]
Abstract
The effects of ceramide incorporation in supported bilayers prepared from ternary lipid mixtures which have small nanoscale domains have been examined using atomic force and fluorescence microscopy. Both direct ceramide incorporation in vesicles used to prepare the supported bilayers and enzymatic hydrolysis of SM by sphingomyelinase were compared for membranes prepared from 5:5:1 DOPC/sphingomyelin/cholesterol mixtures. Both methods of ceramide incorporation resulted in enlargement of the initial small ordered domains. However, enzymatic ceramide generation led to a much more pronounced restructuring of the bilayer to give large clusters of domains with adjacent areas of a lower phase. The individual domains were heterogeneous with two distinct heights, the highest of which is assigned to a ceramide-rich phase which is hypothesized to occur via ceramide flip-flop to the lower leaflet with formation of a raised domain due to negative membrane curvature. A combination of AFM and fluorescence showed that the bilayer restructuring starts rapidly after enzyme addition, with formation of large clusters of domains at sites of high enzyme activity. The clustering of domains is accompanied by redistribution of fluid phase to the periphery of the domain clusters and there is a continued slow evolution of the bilayer over a period of an hour or more after the enzyme is removed. The relevance of the observed clustering of small nanoscale domains to the postulated coalescence of raft domains to form large signaling platforms is discussed.
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Affiliation(s)
- Ira
- Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6
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Vallejo AA, Velázquez JB, Fernández MS. Lateral organization of mixed, two-phosphatidylcholine liposomes as investigated by GPS, the slope of Laurdan generalized polarization spectra. Arch Biochem Biophys 2007; 466:145-54. [PMID: 17679103 DOI: 10.1016/j.abb.2007.06.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 06/29/2007] [Accepted: 06/30/2007] [Indexed: 11/18/2022]
Abstract
The effect of the excitation or emission wavelengths on Laurdan generalized polarization (GP) can be evaluated by GPS, a quantitative, simplified determination of the GP spectrum slope, the thermotropic dependence of which allows the assessment of phospholipid lamellar membrane phase, as shown in a recent publication of our laboratory [J.B. Velázquez, M.S. Fernández, Arch. Biochem. Biophys. 455 (2006) 163-174]. In the present work, we applied Laurdan GPS to phase transition studies of mixed, two-phosphatidylcholine liposomes prepared from variable proportions of dimyristoyl- and dipalmitoylphosphatidylcholine (DMPC and DPPC, respectively). We have found that the GPS function reports a clear limit between the gel/liquid-crystalline phase coexistence region and the liquid-crystalline state, not only at a certain temperature T(c) for liposomes of constant composition submitted to temperature scans, but also at a defined mole fraction X(c), for two-component liposomes of variable composition at constant temperature. The T(c) or the X(c) values obtained from GPS vs. temperature or GPS vs. composition plots, respectively, allow the construction of a partial phase diagram for the DMPC-DPPC mixtures, showing the boundary between the two-phase coexisting region and the liquid-crystalline state. Likewise, at the onset of the transition region, i.e., the two-phase coexisting region as detected by GPS, it is possible to determine, although with less precision, a temperature T(o) or a mole fraction X(o) defining a boundary located below but near the limit between the gel and ripple phase, reported in the literature. These GPS results are consistent with the proposal by several authors that a fraction of L(alpha) phospholipids coexists with gel phospholipids in the rippled phase.
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Affiliation(s)
- Alba A Vallejo
- Department of Biochemistry, Centro de Investigación y de Estudios Avanzados del I.P.N., P.O. Box 14.740, 07000 México D. F., Mexico
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Johnston LJ. Nanoscale imaging of domains in supported lipid membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:5886-95. [PMID: 17428076 DOI: 10.1021/la070108t] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The formation of domains in supported lipid membranes has been studied extensively as a model for the 2D organization of cell membranes. The compartmentalization of biological membranes to give domains such as cholesterol-rich rafts plays an important role in many biological processes. This article summarizes experiments from the author's laboratory in which a combination of atomic force microscopy and near-field scanning optical microscopy is used to probe phase separation in supported monolayers and bilayers as models for membrane rafts. These techniques are used to study binary and ternary lipid mixtures that have gel-phase or liquid-ordered domains that vary in size from tens of nanometers to tens of micrometers, surrounded by a fluid-disordered membrane. Examples are presented in which these models are used to investigate the distribution of glycolipid membrane raft markers and the preference for peptide and protein localization in ordered versus fluid membrane phases. Finally, the enzyme-mediated restructuring of membranes containing liquid-ordered domains provides an in vitro model for the coalescence of membrane rafts to give signaling platforms. Overall, the results demonstrate the importance of using techniques that can probe the nanoscale organization of membranes and of combining techniques that yield complementary information. Furthermore, the ability of supported lipid bilayers to model some aspects of membrane compartmentalization provides an important approach to understanding natural membranes.
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Affiliation(s)
- Linda J Johnston
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, Canada.
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Alessandrini A, Valdrè G, Valdrè U, Muscatello U. Defects in ordered aggregates of cardiolipin visualized by atomic force microscopy. Chem Phys Lipids 2007; 146:111-24. [PMID: 17274972 DOI: 10.1016/j.chemphyslip.2007.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 01/01/2007] [Accepted: 01/09/2007] [Indexed: 11/23/2022]
Abstract
The formation and the nature of defects in ordered aggregates of cardiolipin (tetra acyl diphosphatidylglycerol) supported on solid substrates have been investigated by atomic force microscopy (AFM). The experiments were performed on two model systems, i.e. three-dimensional liquid crystals dispersed in water and partially de-hydrated on a hydrophilic surface, and two-dimensional films of molecules self-assembled onto an isotropic hydrophobic surface. Defects were induced both by varying the preparation temperature and by treatment with specific chemicals known to modify the order parameters in natural and artificial membranes, specifically: 2,4-dinitro-phenol (DNP) and pentachloro-phenol (PCP). The effect of lipid oxidation on the nanocrystalline order was also investigated. The images obtained by AFM allow to characterize the type of defects and their local density at nanoscale level. They also provide additional information to differentiate the specific role of acyl chains and polar heads in the process of lipid self-organization.
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Affiliation(s)
- Andrea Alessandrini
- CNR-INFM-S3 NanoStructures and BioSystems at Surfaces, Via Campi 213/A, I-41100, Modena, Italy.
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Ganchev DN, Hasper HE, Breukink E, de Kruijff B. Size and orientation of the lipid II headgroup as revealed by AFM imaging. Biochemistry 2006; 45:6195-202. [PMID: 16681392 DOI: 10.1021/bi051913e] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, we investigated the size and orientation of the bacterial Lipid II (L II) headgroup when the L II molecule is present in liquid-crystalline domains of DOPC in a supported DPPC bilayer. Using atomic force microscopy, we detected that L II causes the appearance of a 1.9 nm thick layer, situated over the DOPC headgroup region. With an increased scanning force, this layer can be penetrated by the AFM tip down to the level of the DOPC bilayer. Using different L II precursor molecules, we demonstrated that the detected layer consists of the headgroups of L II and that the MurNAc-pentapeptide unit of the headgroup is responsible for the measured 1.9 nm height of that layer. Monolayer experiments provided information about the in-plane dimensions of the L II headgroup. On the basis of these results and considerations of the molecular dimensions of L II headgroup constituents, we propose a model for the orientation of the L II headgroup in the membrane. In this model, the pentapeptide of the L II headgroup is rather extended and points away from the bilayer surface, which could be important for biological processes, in which L II is involved.
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Affiliation(s)
- D N Ganchev
- Institute of Biomembranes, Department of Biochemistry of Membranes, Faculty of Chemistry, Utrecht University, Utrecht, The Netherlands.
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Sharp JM, Duran RS, Dickinson RB. Direct measurement of forces between a colloidal particle and a phospholipid bilayer. J Colloid Interface Sci 2006; 299:182-90. [PMID: 16500670 DOI: 10.1016/j.jcis.2006.02.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 02/01/2006] [Accepted: 02/01/2006] [Indexed: 10/25/2022]
Abstract
Colloidal interaction forces between a silica particle and a solid-supported Langmuir-Schaefer phospholipid bilayer were directly measured using a gradient optical trap and evanescent wave light scattering. A small custom-built Langmuir trough was integrated with an optical trapping microscope to allow force measurements on a single particle within the subphase of the trough after the dip of the substrate was completed. The novel method allows the force measurements to be conducted without transferring the substratum across an air/water interface. The fluctuating particle position near the bilayer was tracked by evanescent wave light scattering to determine the deflection due to surface forces, and the relaxation time of particle fluctuations was measured to simultaneously determine the viscous forces. Measured equilibrium and viscous force-distance profiles of silica microspheres with diameters of 1 and 5 microm on bilayers of dipalmitoyl phosphatidyl choline (DPPC) were markedly different than force-distance on bare mica and DPPC monolayers under the same electrolyte conditions.
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Affiliation(s)
- Jeffrey M Sharp
- Department of Chemical Engineering, University of Florida, P.O. Box 116005, Gainesville, FL 32611-6005, USA
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Connell SD, Smith DA. The atomic force microscope as a tool for studying phase separation in lipid membranes. Mol Membr Biol 2006; 23:17-28. [PMID: 16600898 DOI: 10.1080/09687860500501158] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Atomic force microscopy has developed into a powerful tool in the study of phase separation in lipid bilayers. Its ability to image a semi-fluid surface under buffer at nanometre lateral resolution and Angstrom resolution vertically allows us to distinguish phase separated lipid domains, models of the elusive rafts postulated to exist as functional platforms in the cellular membrane, which may only rise 0.3 nm above the surrounding membrane. This review charts the history of this development, and includes a description of sample preparation techniques, factors affecting image contrast mechanisms, its use in the investigation of the pre-transition ripple phase, and in the localization of cell surface proteins.
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Affiliation(s)
- Simon D Connell
- Astbury Centre for Structural Molecular Biology and School of Physics and Astronomy, University of Leeds, UK
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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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Girard-Egrot AP, Godoy S, Blum LJ. Enzyme association with lipidic Langmuir-Blodgett films: interests and applications in nanobioscience. Adv Colloid Interface Sci 2005; 116:205-25. [PMID: 16181605 DOI: 10.1016/j.cis.2005.04.006] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 04/07/2005] [Indexed: 11/22/2022]
Abstract
This review presents the recent advances in the achievement of organized proteo-lipidic nanostructures based on Langmuir-Blodgett technology and their potential applications in the nanobioscience area. By using the self-assembled properties of amphiphilic biomolecules at the air-water interface, the Langmuir-Blodgett (LB) technique offers the possibility to prepare ultrathin layers suitable for biomolecule immobilization at the molecular level. This review will provide a general overview of the enzyme association with preformed Langmuir-Blodgett films in connection with their potential applications in biosensing device developments, and then introduce the design of a new functionalised biomimetic nanostructure with oriented recognition site. The potential applications of such an organized proteo-lipidic nanostructure for biocatalysis investigations of an immobilised enzyme in a biomimetic situation and for the development of bioelectronic devices are finally discussed.
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Affiliation(s)
- Agnès P Girard-Egrot
- Laboratoire de Génie Enzymatique et Biomoléculaire, EMB2/UMR 5013, CNRS/UCBL, Université Claude Bernard Lyon 1, 43 Bd du 11 novembre 1918, F-69622 Villeurbanne Cedex, France.
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Cannon B, Weaver N, Pu Q, Thiagarajan V, Liu S, Huang J, Vaughn MW, Cheng KH. Cholesterol modulated antibody binding in supported lipid membranes as determined by total internal reflectance microscopy on a microfabricated high-throughput glass chip. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:9666-74. [PMID: 16207051 DOI: 10.1021/la0502645] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A high-throughput microfabricated all-glass microchip, lipid biochip, was created and used to measure fluorescently tagged antibody binding to dinitrophenol (DNP) haptens in planar supported phospholipid/cholesterol lipid bilayers as a function of cholesterol-to-lipid molar ratio (X(CHOL)). Multiple parallel microchannels etched in the lipid biochip allowed simultaneous measurement of antibody binding to hapten-containing and hapten-free lipid bilayers, for a range of aqueous antibody concentrations. Specific and nonspecific antibody binding to the supported lipid bilayers was determined from the internally calibrated intensity of the surface fluorescence using total internal reflectance fluorescence (TIRF) microscopy. The TIRF intensity data of the specific antibody binding were fitted to the Langmuir isotherm and Hill equation models to determine the apparent dissociation constant K(d), the maximum fluorescence parameter F(infinity), and binding cooperativity n. As X(CHOL) increased from 0 to 0.50, K(d) exhibited a minimum of approximately 4 microM and n reached a maximum of approximately 2.2 at X(CHOL) approximately 0.20. However, F(infinity) appeared to be insensitive to the cholesterol content. The nonspecific binding fraction (NS), defined as the ratio of the TIRF intensity for hapten-free bilayers to that with hapten, showed a minimum of approximately 0.08 also at X(CHOL) approximately 0.20. The results suggest that cholesterol regulates the specific binding affinity and cooperativity, as well as suppresses nonspecific binding of aqueous antibody to a planar supported lipid bilayer surface at an optimal cholesterol content of X(CHOL) approximately 0.20. Interestingly, for X(CHOL) approximately 0.40, NS reached a maximum of approximately 0.57, suggesting significant packing defects in the lipid bilayer surface, possibly as a result of lipid domain formation as predicted by the lipid superlattice model. We conclude that cholesterol plays a significant role in regulating both specific and nonspecific antibody/antigen binding events on the lipid bilayer surface and that our lipid biochip represents a new and useful high-resolution microfluidic device for measuring lipid/protein surface binding activities in a parallel and high-throughput fashion.
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Affiliation(s)
- Brian Cannon
- Department of Physics, Texas Tech University, Lubbock, TX 79409, USA
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Sparr E, Ganchev DN, Snel MME, Ridder ANJA, Kroon-Batenburg LMJ, Chupin V, Rijkers DTS, Killian JA, de Kruijff B. Molecular Organization in Striated Domains Induced by Transmembrane α-Helical Peptides in Dipalmitoyl Phosphatidylcholine Bilayers. Biochemistry 2004; 44:2-10. [PMID: 15628840 DOI: 10.1021/bi048047a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transmembrane (TM) alpha-helical peptides with neutral flanking residues such as tryptophan form highly ordered striated domains when incorporated in gel-state 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers and inspected by atomic force microscopy (AFM) (1). In this study, we analyze the molecular organization of these striated domains using AFM, photo-cross-linking, fluorescence spectroscopy, nuclear magnetic resonance (NMR), and X-ray diffraction techniques on different functionalized TM peptides. The results demonstrate that the striated domains consist of linear arrays of single TM peptides with a dominantly antiparallel organization in which the peptides interact with each other and with lipids. The peptide arrays are regularly spaced by +/-8.5 nm and are separated by somewhat perturbed gel-state lipids with hexagonally organized acyl chains, which have lost their tilt. This system provides an example of how domains of peptides and lipids can be formed in membranes as a result of a combination of specific peptide-peptide and peptide-lipid interactions.
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Affiliation(s)
- Emma Sparr
- Department of Biochemistry of Membranes, Institute of Biomembranes, Utrecht University, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
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40
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Plénat T, Deshayes S, Boichot S, Milhiet PE, Cole RB, Heitz F, Le Grimellec C. Interaction of primary amphipathic cell-penetrating peptides with phospholipid-supported monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:9255-9261. [PMID: 15461515 DOI: 10.1021/la048622b] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The mesoscopic organization adopted by two primary amphipathic peptides, P(beta) and P(alpha), in Langmuir-Blodgett (LB) films made of either the pure peptide or peptide-phospholipid mixtures was examined by atomic force microscopy. P(beta), a potent cell-penetrating peptide (CPP), and P(alpha) mainly differ by their conformational states, predominantly a beta-sheet for P(beta) and an alpha-helix for P(alpha), as determined by Fourier transform infrared spectroscopy. LB films of pure peptide, transferred significantly below their collapse pressure, were characterized by the presence of supramolecular structures, globular aggregates for P(beta) and filaments for P(alpha), inserted into the monomolecular film. In mixed peptide-phospholipid films, similar structures could be observed, as a function of the phospholipid headgroup and acyl chain saturation. They often coexisted with a liquid-expanded phase composed of miscible peptide-lipid. These data strongly suggest that primary amphipathic CPP and antimicrobial peptides may share, to some extent, common mechanisms of interaction with membranes.
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Affiliation(s)
- Thomas Plénat
- Nanostructures et Complexes Membranaires, CBS, CNRS UMR5048-INSERM U554, 29 rue de Navacelles, 34090 Montpellier Cedex, France
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41
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Benz M, Gutsmann T, Chen N, Tadmor R, Israelachvili J. Correlation of AFM and SFA measurements concerning the stability of supported lipid bilayers. Biophys J 2004; 86:870-9. [PMID: 14747322 PMCID: PMC1303934 DOI: 10.1016/s0006-3495(04)74162-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Phospholipid bilayers were studied by means of atomic force microscopy (AFM) and a surface force apparatus (SFA). The stability of the supported bilayers was described by the amount of irregularities in the topography of the membrane by means of AFM and by the occurrence of hemifusion in the SFA, which is an indicator of defective bilayers. The bilayers, composed of lipids having the same headgroup but different chain lengths in the two leaflets, were prepared by Langmuir-Blodgett deposition and transferred at different surface pressures. The topography of the supported bilayers in aqueous solution, as imaged by AFM, revealed an increasing number of defects in the supported lipid membranes with decreased deposition pressure of the outer lipid layer. These defects, which appeared in the form of monolayer and bilayer (self-assembled) thick holes within the membrane, were energetically favorable over an evenly depleted bilayer. We found that the quantity of these defects (holes of </=0.5 micro m diameter and covering up to 30% of the surface area) correlated well with the stability of the bilayers as measured by SFA, a truly complementary instrument.
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Affiliation(s)
- Marcel Benz
- Department of Chemical Engineering, Department of Physics, and Materials Research Laboratory, University of California, Santa Barbara, California 93106, USA
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42
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Hyde S, Schröder G. Novel surfactant mesostructural topologies: between lamellae and columnar (hexagonal) forms. Curr Opin Colloid Interface Sci 2003. [DOI: 10.1016/s1359-0294(03)00014-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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43
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Yuan C, Furlong J, Burgos P, Johnston LJ. The size of lipid rafts: an atomic force microscopy study of ganglioside GM1 domains in sphingomyelin/DOPC/cholesterol membranes. Biophys J 2002; 82:2526-35. [PMID: 11964241 PMCID: PMC1302043 DOI: 10.1016/s0006-3495(02)75596-3] [Citation(s) in RCA: 242] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Atomic force microscopy has been used to study the distribution of ganglioside GM1 in model membranes composed of ternary lipid mixtures that mimic the composition of lipid rafts. The results demonstrate that addition of 1% GM1 to 1:1:1 sphingomyelin/dioleoylphosphatidylcholine/cholesterol monolayers leads to the formation of small ganglioside-rich microdomains (40-100 nm in size) that are localized preferentially in the more ordered sphingomyelin/cholesterol-rich phase. With 5% GM1 some GM1 microdomains are also detected in the dioleoylphosphatidylcholine-rich phase. A similar preferential localization of GM1 in the ordered phase is observed for bilayers with the same ternary lipid mixture in the upper leaflet. The small GM1-rich domains observed in these experiments are similar to the sizes for lipid rafts in natural membranes but considerably smaller than the ordered bilayer domains that have been shown to be enriched in GM1 in recent fluorescence microscopy studies of lipid bilayers. The combined data from a number of studies of model membranes indicate that lateral organization occurs on a variety of length scales and mimics many of the properties of natural membranes.
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Affiliation(s)
- Chunbo Yuan
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
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44
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Kaasgaard T, Mouritsen OG, Jørgensen K. Lipid domain formation and ligand-receptor distribution in lipid bilayer membranes investigated by atomic force microscopy. FEBS Lett 2002; 515:29-34. [PMID: 11943189 DOI: 10.1016/s0014-5793(02)02391-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A novel experimental technique, based on atomic force microscopy (AFM), is proposed to visualize the lateral organization of membrane systems in the nanometer range. The technique involves the use of a ligand-receptor pair, biotin-avidin, which introduces a height variation on a solid-supported lipid bilayer membrane. This leads to a height amplification of the lateral membrane organization that is large enough to be clearly imaged by scanning AFM. The power of the technique is demonstrated for a binary dipalmitoylphosphocholine-diarachidoylphosphocholine lipid mixture which is shown to exhibit a distinct lateral lipid domain formation. The new and simple ligand-receptor-based AFM approach opens up new ways to investigate lipid membrane microstructure in the nanometer range as well as the lateral distribution of ligand-lipid and receptor-protein complexes in supported membrane systems.
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Affiliation(s)
- Thomas Kaasgaard
- Department of Chemistry, Technical University of Denmark, DK-2800, Lyngby, Denmark
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45
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Abstract
The introduction of functional imaging tools and techniques that operate at molecular-length scales has provided investigators with unique approaches to characterizing biomolecular structure and function relationships. Recent advances in the field of scanning probe techniques and, in particular, atomic force microscopy have yielded tantalizing insights into the dynamics of protein self-assembly and the mechanics of protein unfolding.
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Affiliation(s)
- C M Yip
- Department of Chemical Engineering, Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario, Canada.
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46
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Abstract
Lateral segregation in biomembranes can lead to the formation of biologically functional domains. This paper reviews atomic force microscopy studies on domain formation in model membranes, with special emphasis on transbilayer asymmetry, and on lateral domains induced by lipid-lipid interactions or by peptide-lipid interactions.
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Affiliation(s)
- H A Rinia
- Department of Biochemistry of Membranes, CBLE, Institute of Biopmembranes, Utrecht university, Netherlands.
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47
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Yuan C, Johnston LJ. Atomic force microscopy studies of ganglioside GM1 domains in phosphatidylcholine and phosphatidylcholine/cholesterol bilayers. Biophys J 2001; 81:1059-69. [PMID: 11463647 PMCID: PMC1301575 DOI: 10.1016/s0006-3495(01)75763-3] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The distribution of ganglioside in supported lipid bilayers has been studied by atomic force microscopy. Hybrid dipalmitoylphosphatidylcholine (DPPC)/dipalmitoylphosphatidylethanolamine (DPPE) and (2:1 DPPC/cholesterol)/DPPE bilayers were prepared using the Langmuir Blodgett technique. Egg PC and DPPC bilayers were prepared by vesicle fusion. Addition of ganglioside GM1 to each of the lipid bilayers resulted in the formation of heterogeneous surfaces that had numerous small raised domains (30--200 nm in diameter). Incubation of these bilayers with cholera toxin B subunit resulted in the detection of small protein aggregates, indicating specific binding of the protein to the GM1-rich microdomains. Similar results were obtained for DPPC, DPPC/cholesterol, and egg PC, demonstrating that the overall bilayer morphology was not dependent on the method of bilayer preparation or the fluidity of the lipid mixture. However, bilayers produced by vesicle fusion provided evidence for asymmetrically distributed GM1 domains that probably reflect the presence of ganglioside in both inner and outer monolayers of the initial vesicle. The results are discussed in relation to recent inconsistencies in the estimation of sizes of lipid rafts in model and natural membranes. It is hypothesized that small ganglioside-rich microdomains may exist within larger ordered domains in both natural and model membranes.
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Affiliation(s)
- C Yuan
- Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON K1A 0R6 Canada
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48
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Dufrêne YF, Lee GU. Advances in the characterization of supported lipid films with the atomic force microscope. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1509:14-41. [PMID: 11118515 DOI: 10.1016/s0005-2736(00)00346-1] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
During the past decade, the atomic force microscope (AFM) has become a key technique in biochemistry and biophysics to characterize supported lipid films, as testified by the continuous growth in the number of papers published in the field. The unique capabilities of AFM are: (i) capacity to probe, in real time and in aqueous environment, the surface structure of lipid films; (ii) ability to directly measure physical properties at high spatial resolution; (iii) possibility to modify the film structure and biophysical processes in a controlled way. Such experiments, published up to June 2000, are the focus of the present review. First, we provide a general introduction on the preparation and characterization of supported lipid films as well as on the principles of AFM. The section 'Structural properties' focuses on the various applications of AFM for characterizing the structure of supported lipid films: visualization of molecular structure, formation of structural defects, effect of external agents, formation of supported films, organization of phase-separated films (coexistence region, mixed films) and, finally, the use of supported lipid bilayers for anchoring biomolecules such as DNA, enzymes and crystalline protein arrays. The section 'Physical properties' introduces the principles of force measurements by AFM, interpretation of these measurements and their recent application to supported lipid films and related structures. Finally, we highlight the major achievements brought by the technique and some of the current limitations.
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Affiliation(s)
- Y F Dufrêne
- Unité de chimie des interfaces, Université catholique de Louvain, Belgium.
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49
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Yuan C, Johnston LJ. Distribution of ganglioside GM1 in L-alpha-dipalmitoylphosphatidylcholine/cholesterol monolayers: a model for lipid rafts. Biophys J 2000; 79:2768-81. [PMID: 11053150 PMCID: PMC1301158 DOI: 10.1016/s0006-3495(00)76516-7] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The distribution of low concentrations of ganglioside GM1 in L-alpha-dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol monolayers supported on mica has been studied using atomic force microscopy (AFM). The monolayers studied correspond to a pure gel phase and a mixture of liquid-expanded (LE) and liquid-condensed (LC) phases for DPPC and to a single homogeneous liquid-ordered phase for 2:1 DPPC/cholesterol. The addition of 2.5-5% GM1 to phase-separated DPPC monolayers resulted in small round ganglioside-rich microdomains in the center and at the edges of the LC domains. Higher amounts of GM1 (10%) give numerous filaments in the center of the LC domains and larger patches at the edges. A gel phase DPPC monolayer containing GM1 showed large domains containing a network of GM1-rich filaments. The addition of GM1 to a liquid-ordered 2:1 DPPC/cholesterol monolayer gives small, round domains that vary in size from 50 to 150 nm for a range of surface pressures. Larger amounts of GM1 lead to coalescence of the small, round domains to give longer filaments that cover 30-40% of the monolayer surface for 10 mol % GM1. The results indicate that biologically relevant GM1 concentrations lead to submicron-sized domains in a cholesterol-rich liquid-ordered phase that is analogous to that found in detergent-insoluble membrane fractions, and are thought to be important in membrane microdomains or rafts. This demonstrates that AFM studies of model monolayers and bilayers provide a powerful method for the direct detection of microdomains that are too small for study with most other techniques.
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Affiliation(s)
- C Yuan
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
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50
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Rinia HA, Kik RA, Demel RA, Snel MM, Killian JA, van Der Eerden JP, de Kruijff B. Visualization of highly ordered striated domains induced by transmembrane peptides in supported phosphatidylcholine bilayers. Biochemistry 2000; 39:5852-8. [PMID: 10801336 DOI: 10.1021/bi000010c] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We used atomic force microscopy (AFM) to study the lateral organization of transmembrane TmAW(2)(LA)(n)W(2)Etn peptides (WALP peptides) incorporated in phospholipid bilayers. These well-studied model peptides consist of a hydrophobic alanine-leucine stretch of variable length, flanked on each side by two tryptophans. They were incorporated in saturated phosphatidylcholine (PC) vesicles, which were deposited on a solid substrate via the vesicle fusion method, yielding hydrated gel-state supported bilayers. At low concentrations (1 mol %) WALP peptides induced primarily line-type depressions in the bilayer. In addition, striated lateral domains were observed, which increased in amount and size (from 25 nm up to 10 microm) upon increasing peptide concentration. At high peptide concentration (10 mol %), the bilayer consisted mainly of striated domains. The striated domains consist of line-type depressions and elevations with a repeat distance of 8 nm, which form an extremely ordered, predominantly hexagonal pattern. Overall, this pattern was independent of the length of the peptides (19-27 amino acids) and the length of the lipid acyl chains (16-18 carbon atoms). The striated domains could be pushed down reversibly by the AFM tip and are thermodynamically stable. This is the first direct visualization of alpha-helical transmembrane peptide-lipid domains in a bilayer. We propose that these striated domains consist of arrays of WALP peptides and fluidlike PC molecules, which appear as low lines. The presence of the peptides perturbs the bilayer organization, resulting in a decrease in the tilt of the lipids between the peptide arrays. These lipids therefore appear as high lines.
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Affiliation(s)
- H A Rinia
- Department of Biochemistry of Membranes, Institute of Biomembranes, CBLE, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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