51
|
Zhu T, Jiang Z, Ma Y, Hu Y. Preservation of Supported Lipid Membrane Integrity from Thermal Disruption: Osmotic Effect. ACS APPLIED MATERIALS & INTERFACES 2016; 8:5857-5866. [PMID: 26886864 DOI: 10.1021/acsami.5b12153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Preservation of structural integrity under various environmental conditions is one major concern in the development of the supported lipid membrane (SLM)-based devices. It is common for SLMs to experience temperature shifts from manufacture, processing, storage, and transport to operation. In this work, we studied the thermal adaption of the supported membranes on silica substrates. Homogenous SLMs with little defects were formed through the vesicle fusion method. The mass and fluidity of the bilayers were found to deteriorate from a heating process but not a cooling process. Fluorescence characterizations showed that the membranes initially budded as a result of heating-induced lipid lateral area expansion, followed by the possible fates including maintenance, retraction, and fission, among which the last contributes to the irreversible compromise of the SLM integrity and spontaneous release of the interlipid stress accumulated. Based on the mechanism, we developed a strategy to protect SLMs from thermal disruption by increasing the solute concentration in medium. An improved preservation of the membrane mass and fluidity against the heating process was observed, accompanied by a decrease in the retraction and fission of the buds. Theoretical analysis revealed a high osmotic energy penalty for the fission, which accounts for the depressed disruption. This osmotic-based protection strategy is facile, solute nonspecific, and long-term efficient and has little impact on the original SLM properties. The results may help broaden SLM applications and sustain the robustness of SLM-based devices under multiple thermal conditions.
Collapse
Affiliation(s)
- Tao Zhu
- Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University , Nanjing 210093, China
| | - Zhongying Jiang
- School of Electronics and Information Engineering, Yi Li Normal University , Yining 835000, China
- Laboratory of Solid State Microstructures, Nanjing University , Nanjing 210093, China
| | - Yuqiang Ma
- Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University , Nanjing 210093, China
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University , Suzhou 215006, China
| | - Yong Hu
- College of Engineering and Applied Sciences, Nanjing University , Nanjing 210093, China
| |
Collapse
|
52
|
Wu HL, Tong Y, Peng Q, Li N, Ye S. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). Phys Chem Chem Phys 2016; 18:1411-21. [DOI: 10.1039/c5cp04960a] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).
Collapse
Affiliation(s)
- Heng-Liang Wu
- Catalysis Research Center
- Hokkaido University
- Sapporo 001-0021
- Japan
| | - Yujin Tong
- Catalysis Research Center
- Hokkaido University
- Sapporo 001-0021
- Japan
| | - Qiling Peng
- Catalysis Research Center
- Hokkaido University
- Sapporo 001-0021
- Japan
| | - Na Li
- Catalysis Research Center
- Hokkaido University
- Sapporo 001-0021
- Japan
| | - Shen Ye
- Catalysis Research Center
- Hokkaido University
- Sapporo 001-0021
- Japan
| |
Collapse
|
53
|
Lor C, Hirst LS. Effects of Low Concentrations of Docosahexaenoic Acid on the Structure and Phase Behavior of Model Lipid Membranes. MEMBRANES 2015; 5:857-74. [PMID: 26690231 PMCID: PMC4704016 DOI: 10.3390/membranes5040857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/25/2015] [Indexed: 11/21/2022]
Abstract
In this paper we report an X-ray diffraction study on the phase behavior of binary lipid mixtures of 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (DHA-PE) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at low concentrations below 5.0 mol% DHA-PE. Our results show that DHA-PE induces phase separation into a DHA rich liquid crystalline (Lα) phase and a DHA poor gel (Lβ') phase at overall DHA-PE concentrations as low as 0.1 mol%. In addition, we find that the structure of the Lβ' phase, from which the DHA-PE molecules are largely excluded, is modified in the phase-separated state at low DHA-PE concentrations, with a decrease in bilayer thickness of 1.34 nm for 0.1 mol% at room temperature, compared to pure DPPC bilayers. This result is contrary to that seen in similar studies on mono-unsaturated lipids where an increase in bilayer thickness is observed. The surprising effect of such low DHA-PE concentrations on membrane structure may be important in understanding the role of highly polyunsaturated lipids in biological membrane-based structures and similar artificial surfactant systems.
Collapse
Affiliation(s)
- Chai Lor
- Bioengineering and Small Scale Technologies, School of Engineering, University of California, Merced, CA 95343, USA.
| | - Linda S Hirst
- Department of Physics, School of Natural Sciences, University of California, Merced, CA 95343, USA.
| |
Collapse
|
54
|
Beedle AEM, Williams A, Relat-Goberna J, Garcia-Manyes S. Mechanobiology - chemical origin of membrane mechanical resistance and force-dependent signaling. Curr Opin Chem Biol 2015; 29:87-93. [PMID: 26517566 DOI: 10.1016/j.cbpa.2015.09.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 09/15/2015] [Indexed: 11/16/2022]
Abstract
The cell membrane is a highly complex designed material with remarkable physicochemical properties; comprised mainly of lipid moieties, it is capable of self-assembling, changing morphology, housing a range of distinct proteins, and withstanding electrical, chemical and mechanical perturbations. All of these fundamental cellular functions occurring within a 5nm thick film is an astonishing feat of engineering, made possible due to the interplay of a variety of intermolecular forces. Elucidating how the interactions within the chemically distinct partners influence the nanomechanical properties of the membrane is essential to gain a comprehensive understanding of a wide-variety of both force-triggered and force-sensing mechanisms that dictate essential cellular processes.
Collapse
Affiliation(s)
- Amy E M Beedle
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, Strand, London WC2R 2LS, UK
| | - Aisling Williams
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, Strand, London WC2R 2LS, UK
| | - Josep Relat-Goberna
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, Strand, London WC2R 2LS, UK
| | - Sergi Garcia-Manyes
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, Strand, London WC2R 2LS, UK.
| |
Collapse
|
55
|
Seghezza S, Dante S, Diaspro A, Canale C. High resolution nanomechanical characterization of multi-domain model membranes by fast Force Volume. J Mol Recognit 2015. [DOI: 10.1002/jmr.2490] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Silvia Seghezza
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
| | - Silvia Dante
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
| | - Alberto Diaspro
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
- University of Genova; Department of Physics; Genova GE Italy
| | - Claudio Canale
- Fondazione Istituto Italiano di Tecnologia; Nanophysics; Via Morego 30 Genova GE 16163 Italy
| |
Collapse
|
56
|
Angle MR, Wang A, Thomas A, Schaefer AT, Melosh NA. Penetration of cell membranes and synthetic lipid bilayers by nanoprobes. Biophys J 2015; 107:2091-100. [PMID: 25418094 DOI: 10.1016/j.bpj.2014.09.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/08/2014] [Accepted: 09/16/2014] [Indexed: 11/28/2022] Open
Abstract
Nanoscale devices have been proposed as tools for measuring and controlling intracellular activity by providing electrical and/or chemical access to the cytosol. Unfortunately, nanostructures with diameters of 50-500 nm do not readily penetrate the cell membrane, and rationally optimizing nanoprobes for cell penetration requires real-time characterization methods that are capable of following the process of membrane penetration with nanometer resolution. Although extensive work has examined the rupture of supported synthetic lipid bilayers, little is known about the applicability of these model systems to living cell membranes with complex lipid compositions, cytoskeletal attachment, and membrane proteins. Here, we describe atomic force microscopy (AFM) membrane penetration experiments in two parallel systems: live HEK293 cells and stacks of synthetic lipid bilayers. By using the same probes in both systems, we were able to clearly identify membrane penetration in synthetic bilayers and compare these events with putative membrane penetration events in cells. We examined membrane penetration forces for three tip geometries and 18 chemical modifications of the probe surface, and in all cases the median forces required to penetrate cellular and synthetic lipid bilayers with nanoprobes were greater than 1 nN. The penetration force was sensitive to the probe's sharpness, but not its surface chemistry, and the force did not depend on cell surface or cytoskeletal properties, with cells and lipid stacks yielding similar forces. This systematic assessment of penetration under various mechanical and chemical conditions provides insights into nanoprobe-cell interactions and informs the design of future intracellular nanoprobes.
Collapse
Affiliation(s)
- Matthew R Angle
- Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Andrew Wang
- Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Aman Thomas
- Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Andreas T Schaefer
- Department of Materials Science and Engineering, Stanford University, Stanford, California
| | - Nicholas A Melosh
- Department of Materials Science and Engineering, Stanford University, Stanford, California.
| |
Collapse
|
57
|
Unsay JD, Cosentino K, García-Sáez AJ. Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers. J Vis Exp 2015:e52867. [PMID: 26273958 PMCID: PMC4545161 DOI: 10.3791/52867] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Atomic force microscopy (AFM) is a versatile, high-resolution imaging technique that allows visualization of biological membranes. It has sufficient magnification to examine membrane substructures and even individual molecules. AFM can act as a force probe to measure interactions and mechanical properties of membranes. Supported lipid bilayers are conventionally used as membrane models in AFM studies. In this protocol, we demonstrate how to prepare supported bilayers and characterize their structure and mechanical properties using AFM. These include bilayer thickness and breakthrough force. The information provided by AFM imaging and force spectroscopy help define mechanical and chemical properties of membranes. These properties play an important role in cellular processes such as maintaining cell hemostasis from environmental stress, bringing membrane proteins together, and stabilizing protein complexes.
Collapse
Affiliation(s)
- Joseph D Unsay
- Interfaculty Institute for Biochemistry; Max Planck Institute for Intelligent Systems; German Cancer Research Center;
| | - Katia Cosentino
- Interfaculty Institute for Biochemistry; Max Planck Institute for Intelligent Systems
| | - Ana J García-Sáez
- Interfaculty Institute for Biochemistry; Max Planck Institute for Intelligent Systems
| |
Collapse
|
58
|
Gumí-Audenis B, Sanz F, Giannotti MI. Impact of galactosylceramides on the nanomechanical properties of lipid bilayer models: an AFM-force spectroscopy study. SOFT MATTER 2015; 11:5447-5454. [PMID: 26058499 DOI: 10.1039/c5sm01252j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Galactosylceramides (GalCer) are glycosphingolipids bound to a monosaccharide group, responsible for inducing extensive hydrogen bonds that yield their alignment and accumulation in the outer leaflet of the biological membrane together with cholesterol (Chol) in rafts. In this work, the influence of GalCer on the nanomechanical properties of supported lipid bilayers (SLBs) based on DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and DLPC (1,2-didodecanoyl-sn-glycero-3-phosphocoline) as model systems was assessed. Phosphatidylcholine (PC):GalCer SLBs were characterized by means of differential scanning calorimetry (DSC) and atomic force microscopy (AFM), in both imaging and force spectroscopy (AFM-FS) modes. Comparing both PC systems, we determined that the behaviour of SLB mixtures is governed by the PC phase-like state at the working temperature. While a phase segregated system is observed for DLPC:GalCer SLBs, GalCer are found to be dissolved in DPPC SLBs for GalCer contents up to 20 mol%. In both systems, the incorporation of GalCer intensifies the nanomechanical properties of SLBs. Interestingly, segregated domains of exceptionally high mechanical stability are formed in DLPC:GalCer SLBs. Finally, the role of 20 mol% Chol in GalCer organization and function in the membranes was assessed. Both PC model systems displayed phase segregation and remarkable nanomechanical stability when GalCer and Chol coexist in SLBs.
Collapse
Affiliation(s)
- Berta Gumí-Audenis
- Institute for Bioengineering of Catalonia (IBEC), Baldiri Reixac 10-12, Barcelona, 08028, Spain.
| | | | | |
Collapse
|
59
|
Wang M, Zander T, Liu X, Liu C, Raj A, Florian Wieland D, Garamus VM, Willumeit-Römer R, Claesson PM, Dėdinaitė A. The effect of temperature on supported dipalmitoylphosphatidylcholine (DPPC) bilayers: Structure and lubrication performance. J Colloid Interface Sci 2015; 445:84-92. [DOI: 10.1016/j.jcis.2014.12.042] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/09/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
|
60
|
Saita EA, de Mendoza D. Thermosensing via transmembrane protein-lipid interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1757-64. [PMID: 25906947 DOI: 10.1016/j.bbamem.2015.04.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 11/25/2022]
Abstract
Cell membranes are composed of a lipid bilayer containing proteins that cross and/or interact with lipids on either side of the two leaflets. The basic structure of cell membranes is this bilayer, composed of two opposing lipid monolayers with fascinating properties designed to perform all the functions the cell requires. To coordinate these functions, lipid composition of cellular membranes is tailored to suit their specialized tasks. In this review, we describe the general mechanisms of membrane-protein interactions and relate them to some of the molecular strategies organisms use to adjust the membrane lipid composition in response to a decrease in environmental temperature. While the activities of all biomolecules are altered as a function of temperature, the thermosensors we focus on here are molecules whose temperature sensitivity appears to be linked to changes in the biophysical properties of membrane lipids. This article is part of a Special Issue entitled: Lipid-protein interactions.
Collapse
Affiliation(s)
- Emilio A Saita
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Predio CONICET, 2000-Rosario, Argentina
| | - Diego de Mendoza
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Predio CONICET, 2000-Rosario, Argentina.
| |
Collapse
|
61
|
García-Arribas AB, Busto JV, Alonso A, Goñi FM. Atomic force microscopy characterization of palmitoylceramide and cholesterol effects on phospholipid bilayers: a topographic and nanomechanical study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3135-3145. [PMID: 25693914 DOI: 10.1021/la504047n] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Supported planar bilayers (SPBs) on mica substrates have been studied at 23 °C under atomic force microscopy (AFM)-based surface topography and force spectroscopy with two main objectives: (i) to characterize palmitoylceramide (pCer)-induced gel (Lβ) domains in binary mixtures with either its sphingolipid relative palmitoylsphingomyelin (pSM) or the glycerophospholipid dipalmitoylphosphorylcholine (DPPC) and (ii) to evaluate effects of incorporating cholesterol (Chol) into the previous mixtures in terms of Cer and Chol cooperation for the generation of lamellar gel (Lβ) phases of ternary composition. Binary phospholipid/pCer mixtures at XpCer < 0.33 promote the generation of laterally segregated micron-sized pCer-rich domains. Their analysis at different phospholipid/pCer ratios, by means of domain thickness, roughness, and mechanical resistance to tip piercing, reveals unvarying AFM-derived features over increasing pCer concentrations. These results suggest that the domains grow in size with increasing pCer concentrations while keeping a constant phospholipid/pCer stoichiometry. Moreover, the data show important differences between pCer interactions with pSM or DPPC. Gel domains generated in pSM/pCer bilayers are thinner than the pSM-rich surrounding phase, while the opposite is observed in DPPC/pCer mixtures. Furthermore, a higher breakthrough force is observed for pSM/pCer as compared to DPPC/pCer domains, which can be associated with the preferential pCer interaction with its sphingolipid relative pSM. Cholesterol incorporation into both binary mixtures at a high Chol and pCer ratio abolishes any phospholipid/pCer binary domains. Bilayers with properties different from any of the pure or binary samples are observed instead. The data support no displacement of Chol by pCer or vice versa under these conditions, but rather a preferential interaction between the two hydrophobic lipids.
Collapse
Affiliation(s)
- Aritz B García-Arribas
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, P.O. Box 644, 48080 Bilbao, Spain
| | - Jon V Busto
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, P.O. Box 644, 48080 Bilbao, Spain
| | - Alicia Alonso
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, P.O. Box 644, 48080 Bilbao, Spain
| | - Félix M Goñi
- Unidad de Biofísica (CSIC, UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, P.O. Box 644, 48080 Bilbao, Spain
| |
Collapse
|
62
|
Zacheo A, Quarta A, Zizzari A, Monteduro AG, Maruccio G, Arima V, Gigli G. One step preparation of quantum dot-embedded lipid nanovesicles by a microfluidic device. RSC Adv 2015. [DOI: 10.1039/c5ra18862h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synthetic carriers that mimic “natural lipid-based vesicles” (micro/nanovesicles, exosomes) have found broad application in biomedicine for the delivery of biomolecules and drugs. Here, an innovative approach for their production is presented.
Collapse
Affiliation(s)
- A. Zacheo
- Department of Mathematics and Physics “Ennio De Giorgi”
- Università del Salento
- 73100 Lecce
- Italy
- CNR–Istituto di Nanotecnologia (NANOTEC)
| | - A. Quarta
- CNR–Istituto di Nanotecnologia (NANOTEC)
- 73100 Lecce
- Italy
| | - A. Zizzari
- Department of Mathematics and Physics “Ennio De Giorgi”
- Università del Salento
- 73100 Lecce
- Italy
| | - A. G. Monteduro
- Department of Mathematics and Physics “Ennio De Giorgi”
- Università del Salento
- 73100 Lecce
- Italy
- CNR–Istituto di Nanotecnologia (NANOTEC)
| | - G. Maruccio
- Department of Mathematics and Physics “Ennio De Giorgi”
- Università del Salento
- 73100 Lecce
- Italy
- CNR–Istituto di Nanotecnologia (NANOTEC)
| | - V. Arima
- CNR–Istituto di Nanotecnologia (NANOTEC)
- 73100 Lecce
- Italy
| | - G. Gigli
- Department of Mathematics and Physics “Ennio De Giorgi”
- Università del Salento
- 73100 Lecce
- Italy
- CNR–Istituto di Nanotecnologia (NANOTEC)
| |
Collapse
|
63
|
Li Y, Zhu C, Zhu J, Liang H, Chen D, Zhao H, Liu B. Nanomechanics of phospholipid LB film studied layer by layer with AFM. Chem Cent J 2014; 8:71. [PMID: 25614761 PMCID: PMC4279057 DOI: 10.1186/s13065-014-0071-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 11/11/2014] [Indexed: 11/21/2022] Open
Abstract
Background Phospholipid, a main component of cell membrane, has been explored as a model system of the cell membrane and temporary scaffold materials in recent studies. The mechanical properties of phospholipid layers are essentially interesting since it is involved in several biological processes. Results Here, the nanomechanical properties such as indentation force, adhesion force and DMT (Derjaguin-Müller-Toporov) modulus of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) Langmuir-Blodgett (LB) films were analyzed layer by layer with Atomic Force Microscope (AFM) under deionized water condition. Conclusions The penetration distances in the indentation force curves are equal to the thicknesses of phospholipid films, and the yield forces of DSPC LB films in deionized water are smaller than that of similar lipid films in buffered solutions due to the influence of ions. Moreover, the DMT modulus of upper layer DSPC LB film is different from that of monolayer DSPC LB film due to the influence of their different substrates. Our results suggest that environment such as surrounding ions and substrate will strongly influence the measured nano-mechanical properties of the lipid bilayer, especially that of the down layer. A process about the exploration of nanomechanics of DSPC LB film. ![]()
Collapse
Affiliation(s)
- Yinli Li
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Changjiang Zhu
- College of Software, Henan University, Kaifeng, 475004 Henan PR China
| | - Jichun Zhu
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Hao Liang
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Dong Chen
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Huiling Zhao
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| | - Bo Liu
- Institute of Photo-biophysics, School of Physics and Electronic, Henan University, Kaifeng, 475004 Henan PR China
| |
Collapse
|
64
|
Caron B, Mark AE, Poger D. Some Like It Hot: The Effect of Sterols and Hopanoids on Lipid Ordering at High Temperature. J Phys Chem Lett 2014; 5:3953-3957. [PMID: 26276476 DOI: 10.1021/jz5020778] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Sterols and hopanoids have been suggested to reinforce membranes and protect against unfavorable environmental conditions. In particular, hopanoids are found in high concentrations in membranes of thermotolerant and thermophilic bacteria. However, the mechanism whereby sterols and hopanoids stabilize membranes at elevated temperatures is poorly understood. Here, the effect of temperature on the ordering of lipids in bilayers containing cholesterol or the hopanoids bacteriohopanetetrol and diplopterol was explored using molecular dynamics simulations. It is shown that cholesterol induces a high level of ordering over a wide range of temperatures. Bacteriohopanetetrol promotes order within the lipid tails but enhances fluid-like properties of the head groups at high temperatures. In contrast, diplopterol partitions in the midplane of the bilayer. This suggests that individual hopanoids fulfill distinct functions in membranes, with the ordering properties of bacteriohopanetetrol being particularly well suited to maintain the integrity of membranes at temperatures preferred by thermotolerant and thermophilic bacteria.
Collapse
Affiliation(s)
- Bertrand Caron
- †School of Chemistry and Molecular Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Alan E Mark
- †School of Chemistry and Molecular Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - David Poger
- †School of Chemistry and Molecular Biosciences and ‡Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| |
Collapse
|
65
|
Effect of temperature on the phase behaviour of fully saturated DAPC lipid bilayer: a comparative molecular dynamics simulation study. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014. [PMID: 25408349 DOI: 10.1007/978-3-319-11280-0_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
|
66
|
Ionic strength and composition govern the elasticity of biological membranes. A study of model DMPC bilayers by force- and transmission IR spectroscopy. Chem Phys Lipids 2014; 186:17-29. [PMID: 25447291 DOI: 10.1016/j.chemphyslip.2014.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 11/05/2014] [Accepted: 11/11/2014] [Indexed: 12/15/2022]
Abstract
Infrared (IR) spectroscopy was used to quantify the ion mixture effect of seawater (SW), particularly the contribution of Mg(2+) and Ca(2+) as dominant divalent cations, on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-posphocholine (DMPC) bilayers. The changed character of the main transition at 24 °C from sharp to gradual in films and the 1 °C shift of the main transition temperature in dispersions reflect the interactions of lipid headgroups with the ions in SW. Force spectroscopy was used to quantify the nanomechanical hardness of a DMPC supported lipid bilayer (SLB). Considering the electrostatic and ion binding equilibrium contributions while systematically probing the SLB in various salt solutions, we showed that ionic strength had a decisive influence on its nanomechanics. The mechanical hardness of DMPC SLBs in the liquid crystalline phase linearly increases with the increasing fraction of all ion-bound lipids in a series of monovalent salt solutions. It also linearly increases in the gel phase but almost three times faster (the corresponding slopes are 4.9 nN/100 mM and 13.32 nN/100 mM, respectively). We also showed that in the presence of divalent ions (Ca(2+) and Mg(2+)) the bilayer mechanical hardness was unproportionally increased, and that was accompanied with the decrease of Na(+) ion and increase of Cl(-) ion bound lipids. The underlying process is a cooperative and competitive ion binding in both the gel and the liquid crystalline phase. Bilayer hardness thus turned out to be very sensitive to ionic strength as well as to ionic composition of the surrounding medium. In particular, the indicated correlation helped us to emphasize the colligative properties of SW as a naturally occurring complex ion mixture.
Collapse
|
67
|
Alessandrini A, Facci P. Phase transitions in supported lipid bilayers studied by AFM. SOFT MATTER 2014; 10:7145-7164. [PMID: 25090108 DOI: 10.1039/c4sm01104j] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the capabilities of Atomic Force Microscopy (AFM) in the study of phase transitions in Supported Lipid Bilayers (SLBs). AFM represents a powerful technique to cover the resolution range not available to fluorescence imaging techniques and where spectroscopic data suggest what the relevant lateral scale for domain formation might be. Phase transitions of lipid bilayers involve the formation of domains characterized by different heights with respect to the surrounding phase and are therefore easily identified by AFM in liquid solution once the bilayer is confined to a flat surface. Even if not endowed with high time resolution, AFM allows light to be shed on some aspects related to lipid phase transitions in the case of both a single lipid component and lipid mixtures containing sterols also. We discuss here the obtained results in light of the peculiarities of supported lipid bilayer model systems.
Collapse
Affiliation(s)
- Andrea Alessandrini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Via Campi 213/A, 41125, Modena, Italy.
| | | |
Collapse
|
68
|
Suárez-Germà C, Morros A, Montero M, Hernández-Borrell J, Domènech Ò. Combined force spectroscopy, AFM and calorimetric studies to reveal the nanostructural organization of biomimetic membranes. Chem Phys Lipids 2014; 183:208-17. [DOI: 10.1016/j.chemphyslip.2014.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 07/14/2014] [Accepted: 07/28/2014] [Indexed: 01/12/2023]
|
69
|
Morphological and physical analysis of natural phospholipids-based biomembranes. PLoS One 2014; 9:e107435. [PMID: 25238543 PMCID: PMC4169657 DOI: 10.1371/journal.pone.0107435] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 08/11/2014] [Indexed: 01/15/2023] Open
Abstract
Background Liposomes are currently an important part of biological, pharmaceutical, medical and nutritional research, as they are considered to be among the most effective carriers for the introduction of various types of bioactive agents into target cells. Scope of Review In this work, we study the lipid organization and mechanical properties of biomembranes made of marine and plant phospholipids. Membranes based on phospholipids extracted from rapeseed and salmon are studied in the form of liposome and as supported lipid bilayer. Dioleylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) are used as references to determine the lipid organization of marine and plant phospholipid based membranes. Atomic force microscopy (AFM) imaging and force spectroscopy measurements are performed to investigate the membranes' topography at the micrometer scale and to determine their mechanical properties. Major Conclusions The mechanical properties of the membranes are correlated to the fatty acid composition, the morphology, the electrophoretic mobility and the membrane fluidity. Thus, soft and homogeneous mechanical properties are evidenced for salmon phospholipids membrane containing various polyunsaturated fatty acids. Besides, phase segregation in rapeseed membrane and more important mechanical properties were emphasized for this type of membranes by contrast to the marine phospholipids based membranes. General Significance This paper provides new information on the nanomechanical and morphological properties of membrane in form of liposome by AFM. The originality of this work is to characterize the physico-chemical properties of the nanoliposome from the natural sources containing various fatty acids and polar head.
Collapse
|
70
|
Ramkaran M, Badia A. Gel-to-Fluid Phase Transformations in Solid-Supported Phospholipid Bilayers Assembled by the Langmuir–Blodgett Technique: Effect of the Langmuir Monolayer Phase State and Molecular Density. J Phys Chem B 2014; 118:9708-21. [DOI: 10.1021/jp504092b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Mohini Ramkaran
- Department of Chemistry,
FRQNT Centre for Self-Assembled Chemical Structures, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Antonella Badia
- Department of Chemistry,
FRQNT Centre for Self-Assembled Chemical Structures, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| |
Collapse
|
71
|
Lee J, Gillman AL, Jang H, Ramachandran S, Kagan BL, Nussinov R, Teran Arce F. Role of the fast kinetics of pyroglutamate-modified amyloid-β oligomers in membrane binding and membrane permeability. Biochemistry 2014; 53:4704-14. [PMID: 24950761 PMCID: PMC4215883 DOI: 10.1021/bi500587p] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
Membrane
permeability to ions and small molecules is believed to
be a critical step in the pathology of Alzheimer’s disease
(AD). Interactions of oligomers formed by amyloid-β (Aβ)
peptides with the plasma cell membrane are believed to play a fundamental
role in the processes leading to membrane permeability. Among the
family of Aβs, pyroglutamate (pE)-modified Aβ peptides
constitute the most abundant oligomeric species in the brains of AD
patients. Although membrane permeability mechanisms have been studied
for full-length Aβ1–40/42 peptides, these
have not been sufficiently characterized for the more abundant AβpE3–42 fragment. Here we have compared the adsorbed
and membrane-inserted oligomeric species of AβpE3–42 and Aβ1–42 peptides. We find lower concentrations
and larger dimensions for both species of membrane-associated AβpE3–42 oligomers. The larger dimensions are attributed
to the faster self-assembly kinetics of AβpE3–42, and the lower concentrations are attributed to weaker interactions
with zwitterionic lipid headgroups. While adsorbed oligomers produced
little or no significant membrane structural damage, increased membrane
permeabilization to ionic species is understood in terms of enlarged
membrane-inserted oligomers. Membrane-inserted AβpE3–42 oligomers were also found to modify the mechanical properties of
the membrane. Taken together, our results suggest that membrane-inserted
oligomers are the primary species responsible for membrane permeability.
Collapse
Affiliation(s)
- Joon Lee
- Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States
| | | | | | | | | | | | | |
Collapse
|
72
|
|
73
|
Lipid bilayers supported on bare and modified gold – Formation, characterization and relevance of lipid rafts. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2013.07.117] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
74
|
Migliardo F, Salmeron C, Bayan N. Mobility and temperature resistance of trehalose mycolates as key characteristics of the outer membrane ofMycobacterium tuberculosis. J Biomol Struct Dyn 2014; 33:447-59. [DOI: 10.1080/07391102.2014.887032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
75
|
Dividing cells regulate their lipid composition and localization. Cell 2014; 156:428-39. [PMID: 24462247 PMCID: PMC3909459 DOI: 10.1016/j.cell.2013.12.015] [Citation(s) in RCA: 215] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 10/16/2013] [Accepted: 12/04/2013] [Indexed: 12/18/2022]
Abstract
Although massive membrane rearrangements occur during cell division, little is known about specific roles that lipids might play in this process. We report that the lipidome changes with the cell cycle. LC-MS-based lipid profiling shows that 11 lipids with specific chemical structures accumulate in dividing cells. Using AFM, we demonstrate differences in the mechanical properties of live dividing cells and their isolated lipids relative to nondividing cells. In parallel, systematic RNAi knockdown of lipid biosynthetic enzymes identified enzymes required for division, which highly correlated with lipids accumulated in dividing cells. We show that cells specifically regulate the localization of lipids to midbodies, membrane-based structures where cleavage occurs. We conclude that cells actively regulate and modulate their lipid composition and localization during division, with both signaling and structural roles likely. This work has broader implications for the active and sustained participation of lipids in basic biology. Systematic, comprehensive lipid analyses in dividing cells and midbodies AFM shows dividing cells and their lipids have specific physical properties Screen of lipid biosynthetic enzymes reveals 23 genes required for division Perturbing lipid levels alters actin cytoskeleton and cell stiffness
Collapse
|
76
|
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]
|
77
|
Barthel E, Roquigny R, Serreau L, Denoyel R, Clerc-Imperor M, Drummond C. Contact interaction of double-chained surfactant layers on silica: bilayer rupture and capillary bridge formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14473-14481. [PMID: 24171391 DOI: 10.1021/la403044x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The contact between two layers of double-chained C18 surfactants adsorbed on silica has been investigated. Using a custom-made surface forces apparatus with high stiffness, we have studied the process of (1) compression and collapse of the layers and (2) surface separation after layer collapse. A continuum mechanics model accounts for the compression and collapse of the surfactant layers. The layer compressibility and molecular energy of rupture can be inferred directly. When the surfaces are rinsed in deionized water, an intriguing structural force is observed: the resulting attractive interaction induces the diffusion of surfactant to the contact area, with the gradual buildup of a capillary bridge of the pure smectic phase of the surfactant. Models are proposed to analyze the force profile.
Collapse
Affiliation(s)
- Etienne Barthel
- Surface du Verre et Interfaces, CNRS/Saint-Gobain , BP 135, 93303 Aubervilliers Cedex, France
| | | | | | | | | | | |
Collapse
|
78
|
Stetter FWS, Hugel T. The nanomechanical properties of lipid membranes are significantly influenced by the presence of ethanol. Biophys J 2013; 104:1049-55. [PMID: 23473487 DOI: 10.1016/j.bpj.2013.01.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/16/2012] [Accepted: 01/14/2013] [Indexed: 12/27/2022] Open
Abstract
Ethanol has a profound impact on biological systems and is moreover used in various medical and nonmedical applications. Its interaction with the lipid part of biological membranes has been the subject of intensive studies, but surprisingly, to our knowledge, no study has examined the influence of ethanol on lipid bilayer nanomechanics. We performed atomic force microscopy-based measurements to assess the influence of ethanol on the nanomechanical properties of fluid supported lipid bilayers. Ethanol significantly reduces membrane stability, bilayer thickness, Young's modulus, area stretch modulus, and bending stiffness. Altogether, our data suggest that ethanol addition to supported lipid bilayers supports both the hydrophobic and the hydrophilic permeation pathways by a decrease of bilayer thickness and reduced stability, respectively.
Collapse
Affiliation(s)
- Frank W S Stetter
- IMETUM, Physik-Department, E22a, Technische Universität München, Munich, Germany
| | | |
Collapse
|
79
|
Lima LMC, Giannotti MI, Redondo-Morata L, Vale MLC, Marques EF, Sanz F. Morphological and nanomechanical behavior of supported lipid bilayers on addition of cationic surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:9352-61. [PMID: 23782267 DOI: 10.1021/la400067n] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The addition of surfactants to lipid bilayers is important for the modulation of lipid bilayer properties (e.g., in protein reconstitution and development of nonviral gene delivery vehicles) and to provide insight on the properties of natural biomembranes. In this work, the thermal behavior, organization, and nanomechanical stability of model cationic lipid-surfactant bilayers have been investigated. Two different cationic surfactants, hexadecyltrimethylammonium bromide (CTAB) and a novel derivative of the amino acid serine (Ser16TFAc), have been added (up to 50 mol %) to both liposomes and supported lipid bilayers (SLBs) composed by the zwitterionic phospholipid DPPC. The thermal phase behavior of mixed liposomes has been probed by differential scanning calorimetry (DSC), and the morphology and nanomechanical properties of mixed SLBs by atomic force microscopy-based force spectroscopy (AFM-FS). Although DSC thermograms show different results for the two mixed liposomes, when both are deposited on mica substrates similar trends on the morphology and the mechanical response of the lipid-surfactant bilayers are observed. DSC thermograms indicate microdomain formation in both systems, but while CTAB decreases the degree of organization on the liposome bilayer, Ser16TFAc ultimately induces the opposite effect. Regarding the AFM-FS studies, they show that microphase segregation occurs for these systems and that the effect is dependent on the surfactant content. In both SLB systems, different microdomains characterized by their height and breakthrough force Fb are formed. The molecular organization and composition is critically discussed in the light of our experimental results and literature data on similar lipid-surfactant systems.
Collapse
Affiliation(s)
- Lia M C Lima
- Centro de Investigação em Química, Department of Chemistry and Biochemistry, University of Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
| | | | | | | | | | | |
Collapse
|
80
|
Hoyo J, Guaus E, Oncins G, Torrent-Burgués J, Sanz F. Incorporation of ubiquinone in supported lipid bilayers on ITO. J Phys Chem B 2013; 117:7498-506. [PMID: 23725098 DOI: 10.1021/jp4004517] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Ubiquinone (UQ) is one of the main electron and proton shuttle molecules in biological systems, and dipalmitoylphosphatidylcholine (DPPC) is one of the most used model lipids. Supported planar bilayers (SPBs) are extensively accepted as biological model membranes. In this study, SPBs have been deposited on ITO, which is a semiconductor with good electrical and optical features. Specifically, topographic atomic force microscopy (AFM) images and force curves have been performed on SPBs with several DPPC:UQ ratios to study the location and the interaction of UQ in the SPB. Additionally, cyclic voltammetry has been used to understand the electrochemical behavior of DPPC:UQ SPBs. Obtained results show that, in our case, UQ is placed in two main different positions in SPBs. First, between the DPPC hydrophobic chains, fact that originates a decrease in the breakthrough force of the bilayer, and the second between the two leaflets that form the SPBs. This second position occurs when increasing the UQ content, fact that eventually forms UQ aggregates at high concentrations. The formation of aggregates produces an expansion of the SPB average height and a bimodal distribution of the breakthrough force. The voltammetric response of UQ depends on its position on the bilayer.
Collapse
Affiliation(s)
- Javier Hoyo
- Universitat Politècnica de Catalunya, Dpt. Enginyeria Química, 08222 Terrassa (Barcelona), Spain
| | | | | | | | | |
Collapse
|
81
|
Kagawa R, Hirano Y, Taiji M, Yasuoka K, Yasui M. Dynamic interactions of cations, water and lipids and influence on membrane fluidity. J Memb Sci 2013. [DOI: 10.1016/j.memsci.2013.02.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
82
|
Alessandrini A, Seeger HM, Caramaschi T, Facci P. Dynamic force spectroscopy on supported lipid bilayers: effect of temperature and sample preparation. Biophys J 2012; 103:38-47. [PMID: 22828330 DOI: 10.1016/j.bpj.2012.05.039] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/16/2012] [Accepted: 05/24/2012] [Indexed: 11/29/2022] Open
Abstract
Biological membranes are constantly exposed to forces. The stress-strain relation in membranes determines the behavior of many integral membrane proteins or other membrane related-proteins that show a mechanosensitive behavior. Here, we studied by force spectroscopy the behavior of supported lipid bilayers (SLBs) subjected to forces perpendicular to their plane. We measured the lipid bilayer mechanical properties and the force required for the punch-through event characteristic of atomic force spectroscopy on SLBs as a function of the interleaflet coupling. We found that for an uncoupled bilayer, the overall tip penetration occurs sequentially through the two leaflets, giving rise to two penetration events. In the case of a bilayer with coupled leaflets, penetration of the atomic force microscope tip always occurred in a single step. Considering the dependence of the jump-through force value on the tip speed, we also studied the process in the context of dynamic force spectroscopy (DFS). We performed DFS experiments by changing the temperature and cantilever spring constant, and analyzed the results in the context of the developed theories for DFS. We found that experiments performed at different temperatures and with different cantilever spring constants enabled a more effective comparison of experimental data with theory in comparison with previously published data.
Collapse
Affiliation(s)
- Andrea Alessandrini
- Centro S3, CNR-Istituto Nanoscienze, University of Modena and Reggio Emilia, Modena, Italy.
| | | | | | | |
Collapse
|
83
|
Nanoscale mechanical properties of lipid bilayers and their relevance in biomembrane organization and function. Micron 2012; 43:1212-23. [DOI: 10.1016/j.micron.2012.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 12/27/2022]
|
84
|
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.
Collapse
Affiliation(s)
- Laura Picas
- Institut Curie, CNRS UMR 144, 26 rue d'Ulm, 75248 Paris, France
| | | | | |
Collapse
|
85
|
Harb F, Sarkis J, Ferte N, Tinland B. Beyond Saffman-Delbruck approximation: a new regime for 2D diffusion of α-hemolysin complexes in supported lipid bilayer. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:118. [PMID: 23160766 DOI: 10.1140/epje/i2012-12118-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 09/10/2012] [Accepted: 10/11/2012] [Indexed: 06/01/2023]
Abstract
Cell mechanisms are actively modulated by membrane dynamics. We studied the dynamics of a first-stage biomimetic system by Fluorescence Recovery After Patterned Photobleaching. Using this simple biomimetic system, constituted by α -hemolysin from Staphylococcus aureus inserted as single heptameric pore or complexes of pores in a glass-supported DMPC bilayer, we observed true diffusion behavior, with no immobile fraction. We find two situations: i) when incubation is shorter than 15 hours, the protein inserts as a heptameric pore and diffuses roughly three times more slowly than its host lipid bilayer; ii) incubation longer than 15 hours leads to the formation of larger complexes which diffuse more slowly. Our results indicate that, while the Saffman-Delbruck model adequately describes the diffusion coefficient D for small radii, D of the objects decreases as 1/R(2) for the size range explored in this study. Additionally, in the presence of inserted proteins, the gel-to-fluid transition of the supported bilayer as well as a temperature shift in the gel-to-fluid transition are observed.
Collapse
Affiliation(s)
- Frédéric Harb
- CNRS, UMR, Aix-Marseille Université, CINaM, Marseille, France
| | | | | | | |
Collapse
|
86
|
Structure of solid-supported lipid membrane probed by noble metal nanoparticle deposition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2884-91. [DOI: 10.1016/j.bbamem.2012.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 07/04/2012] [Accepted: 07/11/2012] [Indexed: 11/20/2022]
|
87
|
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]
|
88
|
Redondo-Morata L, Giannotti MI, Sanz F. Influence of cholesterol on the phase transition of lipid bilayers: a temperature-controlled force spectroscopy study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:12851-12860. [PMID: 22873775 DOI: 10.1021/la302620t] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Cholesterol (Chol) plays the essential function of regulating the physical properties of the cell membrane by controlling the lipid organization and phase behavior and, thus, managing the membrane fluidity and its mechanical strength. Here, we explore the model system DPPC:Chol by means of temperature-controlled atomic force microscopy (AFM) imaging and AFM-based force spectroscopy (AFM-FS) to assess the influence of Chol on the membrane ordering and stability. We analyze the system in a representative range of compositions up to 50 mol % Chol studying the phase evolution upon temperature increase (from room temperature to temperatures high above the T(m) of the DPPC bilayer) and the corresponding (nano)mechanical stability. By this means, we correlate the mechanical behavior and composition with the lateral order of each phase present in the bilayers. We prove that low Chol contents lead to a phase-segregated system, whereas high contents of Chol can give a homogeneous bilayer. In both cases, Chol enhances the mechanical stability of the membrane, and an extraordinarily stable system is observed for equimolar fractions (50 mol % Chol). In addition, even when no thermal transition is detected by the traditional bulk analysis techniques for liposomes with high Chol content (40 and 50 mol %), we demonstrate that temperature-controlled AFM-FS is capable of identifying a thermal transition for the supported lipid bilayers. Finally, our results validate the AFM-FS technique as an ideal platform to differentiate phase coexistence and transitions in lipid bilayers and bridge the gap between the results obtained by traditional methods for bulk analysis, the theoretical predictions, and the behavior of these systems at the nanoscale.
Collapse
Affiliation(s)
- Lorena Redondo-Morata
- Institute for Bioengineering of Catalonia (IBEC), Baldiri i Reixac 15-21, 08028, Barcelona, Spain
| | | | | |
Collapse
|
89
|
Redondo-Morata L, Giannotti MI, Sanz F. AFM-based force-clamp monitors lipid bilayer failure kinetics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:6403-6410. [PMID: 22443887 DOI: 10.1021/la3005147] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The lipid bilayer rupture phenomenon is here explored by means of atomic force microscopy (AFM)-based force clamp, for the first time to our knowledge, to evaluate how lipid membranes respond when compressed under an external constant force, in the range of nanonewtons. Using this method, we were able to directly quantify the kinetics of the membrane rupture event and the associated energy barriers, for both single supported bilayers and multibilayers, in contradistinction to the classic studies performed at constant velocity. Moreover, the affected area of the membrane during the rupture process was calculated using an elastic deformation model. The elucidated information not only contributes to a better understanding of such relevant process, but also proves the suitability of AFM-based force clamp to study model structures as lipid bilayers. These findings on the kinetics of lipid bilayers rupture could be extended and applied to the study of other molecular thin films. Furthermore, systems of higher complexity such as models mimicking cell membranes could be studied by means of AFM-based force-clamp technique.
Collapse
Affiliation(s)
- Lorena Redondo-Morata
- Institute for Bioengineering of Catalonia (IBEC), 15-21 Baldiri I Reixac, 08028 Barcelona, Spain
| | | | | |
Collapse
|
90
|
Redondo-Morata L, Oncins G, Sanz F. Force spectroscopy reveals the effect of different ions in the nanomechanical behavior of phospholipid model membranes: the case of potassium cation. Biophys J 2012; 102:66-74. [PMID: 22225799 DOI: 10.1016/j.bpj.2011.10.051] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 10/06/2011] [Accepted: 10/24/2011] [Indexed: 10/14/2022] Open
Abstract
How do metal cations affect the stability and structure of phospholipid bilayers? What role does ion binding play in the insertion of proteins and the overall mechanical stability of biological membranes? Investigators have used different theoretical and microscopic approaches to study the mechanical properties of lipid bilayers. Although they are crucial for such studies, molecular-dynamics simulations cannot yet span the complexity of biological membranes. In addition, there are still some experimental difficulties when it comes to testing the ion binding to lipid bilayers in an accurate way. Hence, there is a need to establish a new approach from the perspective of the nanometric scale, where most of the specific molecular phenomena take place. Atomic force microscopy has become an essential tool for examining the structure and behavior of lipid bilayers. In this work, we used force spectroscopy to quantitatively characterize nanomechanical resistance as a function of the electrolyte composition by means of a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve. By systematically probing a set of bilayers of different composition immersed in electrolytes composed of a variety of monovalent and divalent metal cations, we were able to obtain a wealth of information showing that each ion makes an independent and important contribution to the gross mechanical resistance and its plastic properties. This work addresses the need to assess the effects of different ions on the structure of phospholipid membranes, and opens new avenues for characterizing the (nano)mechanical stability of membranes.
Collapse
Affiliation(s)
- Lorena Redondo-Morata
- Institute for Bioengineering of Catalonia, University of Barcelona, Barcelona, Spain
| | | | | |
Collapse
|
91
|
Dols-Perez A, Fumagalli L, Simonsen AC, Gomila G. Ultrathin spin-coated dioleoylphosphatidylcholine lipid layers in dry conditions: a combined atomic force microscopy and nanomechanical study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13165-13172. [PMID: 21936555 DOI: 10.1021/la202942j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Atomic force microscopy (AFM) has been used to study the structural and mechanical properties of low concentrated spin-coated dioleoylphosphatidylcholine (DOPC) layers in dry environment (RH ≈ 0%) at the nanoscale. It is shown that for concentrations in the 0.1-1 mM range the structure of the DOPC spin-coated samples consists of an homogeneous lipid monolayer ∼1.3 nm thick covering the whole substrate on top of which lipid bilayer (or multilayer) micro- and nanometric patches and rims are formed. The thickness of the bilayer structures is found to be ∼4.5 nm (or multiples of this value for multilayer structures), while the lateral dimensions range from micrometers to tens of nanometer depending on the lipid concentration. The force required to break a bilayer (breakthrough force) is found to be ∼0.24 nN. No dependence of the mechanical values on the lateral dimensions of the bilayer structures is evidenced. Remarkably, the thickness and breakthrough force values of the bilayers measured in dry environment are very similar to values reported in the literature for supported DOPC bilayers in pure water.
Collapse
Affiliation(s)
- Aurora Dols-Perez
- Nanobioelec group, Institut de Bioenginyeria de Catalunya (IBEC), Baldiri i Reixac 15-21, 08028 Barcelona, Spain.
| | | | | | | |
Collapse
|
92
|
Sheikh KH, Giordani C, Kilpatrick JI, Jarvis SP. Direct submolecular scale imaging of mesoscale molecular order in supported dipalmitoylphosphatidylcholine bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3749-3753. [PMID: 21370902 DOI: 10.1021/la104640v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Supported dipalmitoylphosphatidylcholine (DPPC) bilayers are widely used membrane systems in biophysical and biochemical studies. Previously, short-range positional and orientational order of lipid headgroups of supported DPPC bilayers was observed at room temperature using low deflection noise frequency modulation atomic force microscopy (FM-AFM). While this ordering was supported by X-ray diffraction studies, it conflicted with diffusion coefficient measurements of gel-phase bilayers determined from fluorescence photobleaching experiments. In this work, we have directly imaged mica-supported DPPC bilayers with submolecular resolution over scan ranges up to 146 nm using low deflection noise FM-AFM. Both orientational and positional molecular ordering were observed in the mesoscale, indicative of crystalline order. We discuss these results in relation to previous biophysical studies and propose that the mica support induces mesoscopic crystalline order of the DPPC bilayer at room temperature. This study also demonstrates the recent advance in the scan range of submolecular scale AFM imaging.
Collapse
Affiliation(s)
- Khizar H Sheikh
- Nanoscale Function Group, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland.
| | | | | | | |
Collapse
|
93
|
Nikiforov MP, Hohlbauch S, King WP, Voïtchovsky K, Contera SA, Jesse S, Kalinin SV, Proksch R. Temperature-dependent phase transitions in zeptoliter volumes of a complex biological membrane. NANOTECHNOLOGY 2011; 22:055709. [PMID: 21178256 DOI: 10.1088/0957-4484/22/5/055709] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60 °C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 ± 5 °C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.
Collapse
Affiliation(s)
- Maxim P Nikiforov
- The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | | | | | | | | | | | | |
Collapse
|
94
|
Morandat S, El Kirat K. Cytochrome c provokes the weakening of zwitterionic membranes as measured by force spectroscopy. Colloids Surf B Biointerfaces 2011; 82:111-7. [DOI: 10.1016/j.colsurfb.2010.08.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 08/16/2010] [Accepted: 08/18/2010] [Indexed: 11/29/2022]
|
95
|
Ferber UM, Kaggwa G, Jarvis SP. Direct imaging of salt effects on lipid bilayer ordering at sub-molecular resolution. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2010; 40:329-38. [PMID: 21153636 DOI: 10.1007/s00249-010-0650-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/21/2010] [Accepted: 11/23/2010] [Indexed: 11/29/2022]
Abstract
The interactions of salts with lipid bilayers are known to alter the properties of membranes and therefore influence their structure and dynamics. Sodium and calcium cations penetrate deeply into the headgroup region and bind to the lipids, whereas potassium ions only loosely associate with lipid molecules and mostly remain outside of the headgroup region. We investigated a dipalmitoylphosphatidylcholine (DPPC) bilayer in the gel phase in the presence of all three cations with a concentration of Ca²+ ions an order of magnitude smaller than the Na+ and K+ ions. Our findings indicate that the area per unit cell does not significantly change in these three salt solutions. However the lipid molecules do re-order non-isotropically under the influence of the three different cations. We attribute this reordering to a change in the highly directional intermolecular interactions caused by a variation in the dipole-dipole bonding arising from a tilt of the headgroup out of the membrane plane. Measurements in different NaCl concentrations also show a non-isotropic re-ordering of the lipid molecules.
Collapse
Affiliation(s)
- Urs M Ferber
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | | | | |
Collapse
|
96
|
Langford KW, Penkov B, Derrington IM, Gundlach JH. Unsupported planar lipid membranes formed from mycolic acids of Mycobacterium tuberculosis. J Lipid Res 2010; 52:272-7. [PMID: 21076119 DOI: 10.1194/jlr.m012013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cell wall of mycobacteria includes a thick, robust, and highly impermeable outer membrane made from long-chain mycolic acids. These outer membranes form a primary layer of protection for mycobacteria and directly contribute to the virulence of diseases such as tuberculosis and leprosy. We have formed in vitro planar membranes using pure mycolic acids on circular apertures 20 to 90 μm in diameter. We find these membranes to be long lived and highly resistant to irreversible electroporation, demonstrating their general strength. Insertion of the outer membrane channel MspA into the membranes was observed indicating that the artificial mycolic acid membranes are suitable for controlled studies of the mycobacterial outer membrane and can be used in nanopore DNA translocation experiments.
Collapse
Affiliation(s)
- Kyle W Langford
- Department of Physics, University of Washington, Seattle, WA 351560, USA
| | | | | | | |
Collapse
|
97
|
Yarrow F, Kuipers BWM. AFM study of the thermotropic behaviour of supported DPPC bilayers with and without the model peptide WALP23. Chem Phys Lipids 2010; 164:9-15. [PMID: 20932964 DOI: 10.1016/j.chemphyslip.2010.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Revised: 09/02/2010] [Accepted: 09/27/2010] [Indexed: 10/19/2022]
Abstract
Temperature-controlled Atomic Force Microscopy (TC-AFM) in Contact Mode is used here to directly image the mechanisms by which melting and crystallization of supported, hydrated DPPC bilayers proceed in the presence and absence of the model peptide WALP23. Melting from the gel L(β)' to the liquid-crystalline L(α) phase starts at pre-existing line-type packing defects (grain boundaries) in absence of the peptide. The exact transition temperature is shown to be influenced by the magnitude of the force exerted by the AFM probe on the bilayer, but is higher than the main transition temperature of non-supported DPPC vesicles in all cases due to bilayer-substrate interactions. Cooling of the fluid L(α) bilayer shows the formation of the line-type defects at the borders between different gel-phase regions that originate from different nuclei. The number of these defects depends directly on the rate of cooling through the transition, as predicted by classical nucleation theory. The presence of the transmembrane, synthetic model peptide WALP23 is known to give rise to heterogeneity in the bilayer as microdomains with a striped appearance are formed in the DPPC bilayer. This striated phase consists of alternating lines of lipids and peptide. It is shown here that melting starts with the peptide-associated lipids in the domains, whose melting temperature is lowered by 0.8-2.0°C compared to the remaining, peptide-free parts of the bilayer. The stabilization of the fluid phase is ascribed to adaptations of the lipids to the shorter peptide. The lipids not associated with the peptide melt at the same temperature as those in the pure DPPC supported bilayer.
Collapse
Affiliation(s)
- F Yarrow
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Science Faculty, Utrecht University, P.O. Box 80000, 3508 TA, Utrecht, The Netherlands.
| | | |
Collapse
|
98
|
Garcia-Manyes S, Redondo-Morata L, Oncins G, Sanz F. Nanomechanics of Lipid Bilayers: Heads or Tails? J Am Chem Soc 2010; 132:12874-86. [DOI: 10.1021/ja1002185] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Sergi Garcia-Manyes
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Lorena Redondo-Morata
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Gerard Oncins
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Fausto Sanz
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| |
Collapse
|
99
|
Stability and tribological performances of fluid phospholipid bilayers: effect of buffer and ions. Colloids Surf B Biointerfaces 2010; 80:232-9. [PMID: 20634046 DOI: 10.1016/j.colsurfb.2010.06.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 05/21/2010] [Accepted: 06/17/2010] [Indexed: 11/24/2022]
Abstract
We have investigated the mechanical and tribological properties of supported Dioleoyl phosphatidylcholine (DOPC) bilayers in different solutions: ultrapure water (pH 5.5), saline solution (150 mM NaCl, pH 5.8), Tris buffer (pH 7.2) and Tris saline buffer (150 mM NaCl, pH 7.2). Friction forces are measured using a homemade biotribometer. Lipid bilayer degradation is controlled in situ during friction tests using fluorescence microscopy. Mechanical resistance to indentation is measured by force spectroscopy with an atomic force microscope. This study confirms that mechanical stability under shear or normal load is essential to obtain low and constant friction coefficients. In ultrapure water, bilayers are not resistant and have poor lubricant properties. On the other hand, in Tris saline buffer, they fully resist to indentation and exhibit low (micro=0.035) and stable friction coefficient with no visible wear during the 50 min of the friction test. The unbuffered saline solution improves the mechanical resistance to indentation but not the lubrication. These results suggest that the adsorption of ions to the zwiterrionic bilayers has different effects on the mechanical and tribological properties of bilayers: higher resistance to normal indentation due to an increase in bilayer cohesion, higher lubrication due to an increase in bilayer-bilayer repulsion.
Collapse
|
100
|
Kaufman Y, Berman A, Freger V. Supported lipid bilayer membranes for water purification by reverse osmosis. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:7388-95. [PMID: 20099798 DOI: 10.1021/la904411b] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Some biological plasma membranes pass water with a permeability and selectivity largely exceeding those of commercial membranes for water desalination using specialized trans-membrane proteins aquaporins. However, highly selective transport of water through aquaporins is usually driven by an osmotic rather mechanical pressure, which is not as attractive from the engineering point of view. The feasibility of adopting biomimetic membranes for water purification driven by a mechanical pressure, i.e., filtration is explored in this paper. Toward this goal, it is proposed to use a commercial nanofiltration (NF) membrane as a support for biomimetic lipid bilayer membranes to render them robust enough to withstand the required pressures. It is shown in this paper for the first time that by properly tuning molecular interactions supported phospholipid bilayers (SPB) can be prepared on a commercial NF membrane. The presence of SPB on the surface was verified and quantified by several spectroscopic and microscopic techniques, which showed morphology close to the desired one with very few defects. As an ultimate test it is shown that hydraulic permeability of the SPB supported on the NF membrane (NTR-7450) approaches the values deduced from the typical osmotic permeabilities of intact continuous bilayers. This permeability was unaffected by the trans-membrane flow of water and by repeatedly releasing and reapplying a 10 bar pressure. Along with a parallel demonstration that aquaporins could be incorporated in a similar bilayer on mica, this demonstrates the feasibility of the proposed approach. The prepared SPB structure may be used as a platform for preparing biomimetic filtration membranes with superior performance based on aquaporins. The concept of SPBs on permeable substrates of the present type may also be useful in the future for studying transport of various molecules through trans-membrane proteins.
Collapse
Affiliation(s)
- Yair Kaufman
- The Jacob Blaustein Institutes for desert Research, Environmental engineering unit, Ben-Gurion University of the Negev, Sede Boqer Campus, Israel
| | | | | |
Collapse
|