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Griffo A, Sparn C, Lolicato F, Nolle F, Khangholi N, Seemann R, Fleury JB, Brinkmann M, Nickel W, Hähl H. Mechanics of biomimetic free-standing lipid membranes: insights into the elasticity of complex lipid compositions. RSC Adv 2024; 14:13044-13052. [PMID: 38655466 PMCID: PMC11034475 DOI: 10.1039/d4ra00738g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 04/08/2024] [Indexed: 04/26/2024] Open
Abstract
The creation of free-standing lipid membranes has been so far of remarkable interest to investigate processes occurring in the cell membrane since its unsupported part enables studies in which it is important to maintain cell-like physicochemical properties of the lipid bilayer, that nonetheless depend on its molecular composition. In this study, we prepare pore-spanning membranes that mimic the composition of plasma membranes and perform force spectroscopy indentation measurements to unravel mechanistic insights depending on lipid composition. We show that this approach is highly effective for studying the mechanical properties of such membranes. Furthermore, we identify a direct influence of cholesterol and sphingomyelin on the elasticity of the bilayer and adhesion between the two leaflets. Eventually, we explore the possibilities of imaging in the unsupported membrane regions. For this purpose, we investigate the adsorption and movement of a peripheral protein, the fibroblast growth factor 2, on the complex membrane.
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Affiliation(s)
- Alessandra Griffo
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
- Department of Experimental Physics, Saarland University Saarbrücken Germany
- Biophysical Engineering Group, Max Planck Institute for Medical Research Heidelberg Germany
| | - Carola Sparn
- Heidelberg University Biochemistry Center Heidelberg Germany
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center Heidelberg Germany
| | - Friederike Nolle
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
- Department of Experimental Physics, Saarland University Saarbrücken Germany
| | - Navid Khangholi
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
- Department of Experimental Physics, Saarland University Saarbrücken Germany
| | - Ralf Seemann
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
| | - Jean-Baptiste Fleury
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
- Department of Experimental Physics, Saarland University Saarbrücken Germany
| | - Martin Brinkmann
- Department of Experimental Physics, Saarland University Saarbrücken Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center Heidelberg Germany
| | - Hendrik Hähl
- Center for Biophysics, Experimental Physics, Saarland University Saarbrücken Germany
- Department of Experimental Physics, Saarland University Saarbrücken Germany
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Mardešić I, Boban Z, Raguz M. Electroformation of Giant Unilamellar Vesicles from Damp Lipid Films with a Focus on Vesicles with High Cholesterol Content. MEMBRANES 2024; 14:79. [PMID: 38668107 PMCID: PMC11051717 DOI: 10.3390/membranes14040079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 03/20/2024] [Accepted: 03/26/2024] [Indexed: 04/28/2024]
Abstract
Giant unilamellar vesicles (GUVs) are membrane models used to study membrane properties. Electroformation is one of the methods used to produce GUVs. During electroformation protocol, dry lipid film is formed. The drying of the lipid film induces the cholesterol (Chol) demixing artifact, in which Chol forms anhydrous crystals which do not participate in the formation of vesicles. This leads to a lower Chol concentration in the vesicle bilayers compared to the Chol concentration in the initial lipid solution. To address this problem, we propose a novel electroformation protocol that includes rapid solvent exchange (RSE), plasma cleaning, and spin-coating methods to produce GUVs. We tested the protocol, focusing on vesicles with a high Chol content using different spin-coating durations and vesicle type deposition. Additionally, we compared the novel protocol using completely dry lipid film. The optimal spin-coating duration for vesicles created from the phosphatidylcholine/Chol mixture was 30 s. Multilamellar vesicles (MLVs), large unilamellar vesicles (LUVs) obtained by the extrusion of MLVs through 100 nm membrane pores and LUVs obtained by extrusion of previously obtained LUVs through 50 nm membrane pores, were deposited on an electrode for 1.5/1 Chol/phosphatidylcholine (POPC) lipid mixture, and the results were compared. Electroformation using all three deposited vesicle types resulted in a high GUV yield, but the deposition of LUVs obtained by the extrusion of MLVs through 100 nm membrane pores provided the most reproducible results. Using the deposition of these LUVs, we produced high yield GUVs for six different Chol concentrations (from 0% to 71.4%). Using a protocol that included dry lipid film GUVs resulted in lower yields and induced the Chol demixing artifact, proving that the lipid film should never be subjected to drying when the Chol content is high.
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Affiliation(s)
- Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
- Doctoral Study of Biophysics, Faculty of Science, University of Split, 21000 Split, Croatia
| | - Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
| | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
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Mardešić I, Boban Z, Subczynski WK, Raguz M. Membrane Models and Experiments Suitable for Studies of the Cholesterol Bilayer Domains. MEMBRANES 2023; 13:320. [PMID: 36984707 PMCID: PMC10057498 DOI: 10.3390/membranes13030320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 06/18/2023]
Abstract
Cholesterol (Chol) is an essential component of animal cell membranes and is most abundant in plasma membranes (PMs) where its concentration typically ranges from 10 to 30 mol%. However, in red blood cells and Schwann cells, PMs Chol content is as high as 50 mol%, and in the PMs of the eye lens fiber cells, it can reach up to 66 mol%. Being amphiphilic, Chol molecules are easily incorporated into the lipid bilayer where they affect the membrane lateral organization and transmembrane physical properties. In the aqueous phase, Chol cannot form free bilayers by itself. However, pure Chol bilayer domains (CBDs) can form in lipid bilayer membranes with the Chol content exceeding 50 mol%. The range of Chol concentrations surpassing 50 mol% is less frequent in biological membranes and is consequently less investigated. Nevertheless, it is significant for the normal functioning of the eye lens and understanding how Chol plaques form in atherosclerosis. The most commonly used membrane models are unilamellar and multilamellar vesicles (MLVs) and supported lipid bilayers (SLBs). CBDs have been observed directly using confocal microscopy, X-ray reflectometry and saturation recovery electron paramagnetic resonance (SR EPR). Indirect evidence of CBDs has also been reported by using atomic force microscopy (AFM) and fluorescence recovery after photobleaching (FRAP) experiments. The overall goal of this review is to demonstrate the advantages and limitations of the various membrane models and experimental techniques suitable for the detection and investigation of the lateral organization, function and physical properties of CBDs.
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Affiliation(s)
- Ivan Mardešić
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | - Zvonimir Boban
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
- Faculty of Science, University of Split, Doctoral Study of Biophysics, 21000 Split, Croatia
| | | | - Marija Raguz
- Department of Medical Physics and Biophysics, University of Split School of Medicine, 21000 Split, Croatia; (I.M.); (Z.B.)
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Gupta A, Krupa P, Engberg O, Krupa M, Chaudhary A, Li MS, Huster D, Maiti S. Unusual Robustness of Neurotransmitter Vesicle Membranes against Serotonin-Induced Perturbations. J Phys Chem B 2023; 127:1947-1955. [PMID: 36795947 DOI: 10.1021/acs.jpcb.2c07464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Nature confines hundreds of millimolar of amphiphilic neurotransmitters, such as serotonin, in synaptic vesicles. This appears to be a puzzle, as the mechanical properties of lipid bilayer membranes of individual major polar lipid constituents of synaptic vesicles [phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS)] are significantly affected by serotonin, sometimes even at few millimolar concentrations. These properties are measured by atomic force microscopy, and their results are corroborated by molecular dynamics simulations. Complementary 2H solid-state NMR measurements also show that the lipid acyl chain order parameters are strongly affected by serotonin. The resolution of the puzzle lies in the remarkably different properties displayed by the mixture of these lipids, at molar ratios mimicking those of natural vesicles (PC:PE:PS:Cholesterol = 3:5:2:5). Bilayers constituting of these lipids are minimally perturbed by serotonin, and show only a graded response at physiological concentrations (>100 mM). Significantly, the cholesterol (up to 33% molar ratio) plays only a minor role in dictating these mechanical perturbations, with PC:PE:PS:Cholesterol = 3:5:2:5 and 3:5:2:0 showing similar perturbations. We infer that nature uses an emergent mechanical property of a specific mixture of lipids, all individually vulnerable to serotonin, to appropriately respond to physiological serotonin levels.
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Affiliation(s)
- Ankur Gupta
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Pawel Krupa
- Institute of Physics, Polish Academy of Sciences, Warsaw 02-668, Poland
| | - Oskar Engberg
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16/18, 04107, Leipzig, Germany
| | - Magdalena Krupa
- Institute of Computer Science, Polish Academy of Sciences, Warsaw 01-248, Poland
| | - Ankur Chaudhary
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Mai Suan Li
- Institute of Physics, Polish Academy of Sciences, Warsaw 02-668, Poland
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16/18, 04107, Leipzig, Germany
| | - Sudipta Maiti
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
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Giakoumatos EC, Gascoigne L, Gumí-Audenis B, García ÁG, Tuinier R, Voets IK. Impact of poly(ethylene glycol) functionalized lipids on ordering and fluidity of colloid supported lipid bilayers. SOFT MATTER 2022; 18:7569-7578. [PMID: 36165127 PMCID: PMC9555145 DOI: 10.1039/d2sm00806h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
Colloid supported lipid bilayers (CSLBs) are highly appealing building blocks for functional colloids. In this contribution, we critically evaluate the impact on lipid ordering and CSLB fluidity of inserted additives. We focus on poly(ethylene glycol) (PEG) bearing lipids, which are commonly introduced to promote colloidal stability. We investigate whether their effect on the CSLB is related to the incorporated amount and chemical nature of the lipid anchor. To this end, CSLBs were prepared from lipids with a low or high melting temperature (Tm), DOPC, and DPPC, respectively. Samples were supplemented with either 0, 5 or 10 mol% of either a low or high Tm PEGylated lipid, DOPE-PEG2000 or DSPE-PEG2000, respectively. Lipid ordering was probed via differential scanning calorimetry and fluidity by fluorescence recovery after photobleaching. We find that up to 5 mol% of either PEGylated lipids could be incorporated into both membranes without any pronounced effects. However, the fluorescence recovery of the liquid-like DOPC membrane was markedly decelerated upon incorporating 10 mol% of either PEGylated lipids, whilst insertion of the anchoring lipids (DOPE and DSPE without PEG2000) had no detectable impact. Therefore, we conclude that the amount of incorporated PEG stabilizer, not the chemical nature of the lipid anchor, should be tuned carefully to achieve sufficient colloidal stability without compromising the membrane dynamics. These findings offer guidance for the experimental design of studies using CSLBs, such as those focusing on the consequences of intra- and inter-particle inhomogeneities for multivalent binding and the impact of additive mobility on superselectivity.
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Affiliation(s)
- Emma C Giakoumatos
- Laboratory of Self-Organizing Soft Matter, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Levena Gascoigne
- Laboratory of Self-Organizing Soft Matter, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Berta Gumí-Audenis
- Laboratory of Self-Organizing Soft Matter, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Álvaro González García
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Remco Tuinier
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Ilja K Voets
- Laboratory of Self-Organizing Soft Matter, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
- Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Shimolina L, Gulin A, Khlynova A, Ignatova N, Druzhkova I, Gubina M, Zagaynova E, Kuimova M, Shirmanova M. Development of resistance to 5-fluorouracil affects membrane viscosity and lipid composition of cancer cells. Methods Appl Fluoresc 2022; 10. [PMID: 35970177 DOI: 10.1088/2050-6120/ac89cd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 08/15/2022] [Indexed: 11/12/2022]
Abstract
The investigations reported here were designed to determine whether the bulk plasma membrane is involved in mechanisms of acquired resistance of colorectal cancer cells to 5-fluorouracil (5-FU). Fluorescence lifetime imaging microscopy (FLIM) of live cultured cells stained with viscosity-sensitive probe BODIPY 2 was exploited to non-invasively assess viscosity in the course of treatment and adaptation to the drug. In parallel, lipid composition of membranes was examined with the time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our results showed that a single treatment with 5-FU induced only temporal changes of viscosity in 5-FU sensitive cells immediately after adding the drug. Acquisition of chemoresistance was accompanied by persistent increase of viscosity, which was preserved upon treatment without any changes. Lipidomic analysis revealed that the resistant cells had a lower level of monounsaturated fatty acids and increased sphingomyelin or decreased phosphatidylcholine in their membranes, which partly explain increase of the viscosity. Thus, we propose that a high membrane viscosity mediates the acquisition of resistance to 5-FU.
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Affiliation(s)
- Liubov Shimolina
- Privolzhsky Research Medical University, 10/1 Minin and Pozharsky Sq., Niznij Novgorod, Nižegorodskaâ, 603005, RUSSIAN FEDERATION
| | - Aleksandr Gulin
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygin st. 4, Moskva, Moskva, 119991, RUSSIAN FEDERATION
| | - Aleksandra Khlynova
- Institute of Experimental Oncology and Biomedical Technologies, Privolzhsky Research Medical University, 10/1 Minin and Pozharsky Sq., Niznij Novgorod, Nižegorodskaâ, 603005, RUSSIAN FEDERATION
| | - Nadezhda Ignatova
- Privolzhsky Research Medical University, 10/1 Minin and Pozharsky Sq., Niznij Novgorod, Nižegorodskaâ, 603005, RUSSIAN FEDERATION
| | - Irina Druzhkova
- Privolzhsky Research Medical University, 10/1 Minin and Pozharsky Sq., Niznij Novgorod, Nižegorodskaâ, 603005, RUSSIAN FEDERATION
| | - Margarita Gubina
- Russian Academy of Sciences, Kosygin st. 4, Moskva, Moskva, 119991, RUSSIAN FEDERATION
| | - Elena Zagaynova
- Lobachevsky State University of Nizhny Novgorod, Gagarin Avenue 23, Niznij Novgorod, Nižegorodskaâ, 603950, RUSSIAN FEDERATION
| | - Marina Kuimova
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London , SW7 2AZ, London, SW7 2AZ, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Marina Shirmanova
- Privolzhsky Research Medical University, 10/1 Minin and Pozharsky Sq., Niznij Novgorod, Nižegorodskaâ, 603005, RUSSIAN FEDERATION
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Khadka NK, Mortimer MF, Marosvari M, Timsina R, Mainali L. Membrane elasticity modulated by cholesterol in model of porcine eye lens-lipid membrane. Exp Eye Res 2022; 220:109131. [PMID: 35636489 PMCID: PMC10131281 DOI: 10.1016/j.exer.2022.109131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 05/08/2022] [Accepted: 05/22/2022] [Indexed: 11/29/2022]
Abstract
Experimental evidence shows that the eye lens loses its elasticity dramatically with age. It has also been reported that the cholesterol (Chol) content in the eye lens fiber cell plasma membrane increases significantly with age. High Chol content leads to the formation of cholesterol bilayer domains (CBDs) in the lens membrane. The role of high Chol associated with lens elasticity is unclear. The purpose of this research is to investigate the membrane elasticity of the model of porcine lens-lipid (MPLL) membrane with increasing Chol content to elucidate the role of high Chol in lens membrane elasticity. In this study, we used atomic force microscopy (AFM) to study the mechanical properties (breakthrough force and area compressibility modulus (KA)) of the MPLL membrane with increasing Chol content where KA is the measure of membrane elasticity. We varied Chol concentration in Chol/MPLL membrane from 0 to ∼71 mol%. Supported Chol/MPLL membranes were prepared by fusion of small unilamellar vesicles (SUVs) on top of a flat mica surface. SUVs of the Chol/MPLL lipid mixture were prepared with the rapid solvent exchange method followed by probe-tip sonication. For the Chol/MPLL mixing ratio of 0, AFM image showed the formation of two distinct phases of the membrane, i.e., liquid-disordered phase (ld) and solid-ordered phase (so) membrane. However, with Chol/MPLL mixing ratio of 0.5 and above, only liquid-ordered phase (lo) membrane was formed. Also, two distinct breakthrough forces corresponding to ld and so were observed for Chol/MPLL mixing ratio of 0, whereas only one breakthrough force was observed for membranes with Chol/MPLL mixing ratio of 0.5 and above. No significant difference in the membrane surface roughness was measured with increasing Chol content for these membranes; however, breakthrough force and KA for lo membrane increased when Chol/MPLL mixing ratio was increased from 0.5 to 1. Interestingly above the Chol/MPLL mixing ratio of 1, both breakthrough force and KA decreased, indicating the formation of CBDs. Furthermore, these results showed that membrane elasticity increases at high Chol content, suggesting that high Chol content in lens membrane might be responsible for maintaining lens membrane elasticity.
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Affiliation(s)
- Nawal K Khadka
- Department of Physics, Boise State University, Boise, ID, USA
| | | | - Mason Marosvari
- Department of Physics, Boise State University, Boise, ID, USA
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID, USA
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID, USA; Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA.
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Experimental Investigations on the Conductance of Lipid Membranes under Differential Hydrostatic Pressure. MEMBRANES 2022; 12:membranes12050479. [PMID: 35629805 PMCID: PMC9144669 DOI: 10.3390/membranes12050479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/22/2022] [Accepted: 04/27/2022] [Indexed: 02/05/2023]
Abstract
The unassisted transport of inorganic ions through lipid membranes has become increasingly relevant to an expansive range of biological phenomena. Recent simulations indicate a strong influence of a lipid membrane's curvature on its permeability, which may be part of the overall cell sensitivity to mechanical stimulation. However, most ionic permeability experiments employ a flat, uncurved lipid membrane, which disregards the physiological relevance of curvature on such investigations. To fill this gap in our knowledge, we adapted a traditional experimental system consisting of a planar lipid membrane, which we exposed to a controlled, differential hydrostatic pressure. Our electrophysiology experiments indicate a strong correlation between the changes in membrane geometry elicited by the application of pressure, as inferred from capacitance measurements, and the resulting conductance. Our experiments also confirmed the well-established influence of cholesterol addition to lipid membranes in adjusting their mechanical properties and overall permeability. Therefore, the proposed experimental system may prove useful for a better understanding of the intricate connections between membrane mechanics and adjustments of cellular functionalities upon mechanical stimulation, as well as for confirmation of predictions made by simulations and theoretical modeling.
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Non-raft submicron domain formation in cholesterol-containing lipid bilayers induced by polyunsaturated phosphatidylethanolamine. Colloids Surf B Biointerfaces 2021; 210:112235. [PMID: 34891064 DOI: 10.1016/j.colsurfb.2021.112235] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/08/2021] [Accepted: 11/16/2021] [Indexed: 12/13/2022]
Abstract
Domain formation in "HLC" ternary lipid bilayers, comprising a high transition temperature (High-Tm) lipid, a Low-Tm lipid, and cholesterol (Chol), has been extensively studied as raft-resembling systems. Recently, we reported the formation of submicron domains in an "LLC" lipid bilayer, encompassing Low-Tm phosphatidylethanolamine (PE), Low-Tm phosphatidylcholine (PC), and Chol. We hypothesized that the formation of this unique domain is driven by polyunsaturated PE. In this study, we explored the effects of the degree of PE unsaturation and the double bond distribution at the sn-position on the mechanism of formation and the composition of submicron domains. Supported lipid bilayers (SLBs), comprising PE with various degrees of unsaturation, monounsaturated PC (POPC), and Chol, were investigated using fluorescence microscopy, atomic force microscopy, and the force-distance curve measurement. The area fraction of submicron domains in PE+POPC+Chol-SLB increased with the PE concentration and degree of unsaturation of the PE acyl chain. The results indicated that the submicron domains were enriched with polyunsaturated PE and were in the liquid-disordered-like state, whereas their surrounding regions were in the liquid-ordered-like state. Segregation of polyunsaturated PE from the Chol-containing region generated submicron domains in the LLC lipid bilayer. We propose a mechanism for the formation of these submicron domains based on molecular interactions involving the hydrophobic and hydrophilic parts of the bilayer membrane.
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Muhammed E, Cooper J, Devito D, Mushi R, del Pilar Aguinaga M, Erenso D, Crogman H. Elastic property of sickle cell anemia and sickle cell trait red blood cells. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-210188R. [PMID: 34590447 PMCID: PMC8479689 DOI: 10.1117/1.jbo.26.9.096502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/02/2021] [Indexed: 05/14/2023]
Abstract
SIGNIFICANCE We introduce a model for better calibration of the trapping force using an equal but oppositely directed drag force acting on a trapped red blood cell (RBC). We demonstrate this approach by studying RBCs' elastic properties from deidentified sickle cell anemia (SCA) and sickle cell trait (SCT) blood samples. AIM A laser trapping (LT) force was formulated and analytically calculated in a cylindrical model. Using this trapping force relative percent difference, the maximum (longitudinal) and minimum (transverse) radius rate and stiffness were used to study the elasticity. APPROACH The elastic property of SCA and SCT RBCs was analyzed using LT technique with computer controlled piezo-driven stage, in order to trap and stretch the RBCs. RESULTS For all parameters, the results show that the SCT RBC samples have higher elastic property than the SCA RBCs. The higher rigidity in the SCA cell may be due to the lipid composition of the membrane, which was affected by the cholesterol concentration. CONCLUSIONS By developing a theoretical model for different trapping forces, we have also studied the elasticity of RBCs in SCT (with hemoglobin type HbAS) and in SCA (with hemoglobin type HbSS). The results for the quantities describing the elasticity of the cells consistently showed that the RBCs in the SCT display lower rigidity and higher deformability than the RBCs with SCA.
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Affiliation(s)
- Endris Muhammed
- Addis Ababa University, Department of Physics, Addis Ababa, Ethiopia
| | - James Cooper
- Middle Tennessee State University, Department of Physics, Murfreesboro, Tennessee, United States
| | - Daniel Devito
- Middle Tennessee State University, Department of Physics, Murfreesboro, Tennessee, United States
| | - Robert Mushi
- Meharry Medical College, Meharry Sickle Cell Center, Department of Internal Medicine, Nashville, Tennessee, United States
| | - Maria del Pilar Aguinaga
- Meharry Medical College, Meharry Sickle Cell Center, Department of Internal Medicine, Nashville, Tennessee, United States
- Meharry Medical College, Department of Obstetrics and Gynecology, Nashville, Tennessee, United States
| | - Daniel Erenso
- Middle Tennessee State University, Department of Physics, Murfreesboro, Tennessee, United States
| | - Horace Crogman
- California State University Dominguez Hills, Department of Physics, Carson, California, United States
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11
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Khadka NK, Timsina R, Rowe E, O'Dell M, Mainali L. Mechanical properties of the high cholesterol-containing membrane: An AFM study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183625. [PMID: 33891910 DOI: 10.1016/j.bbamem.2021.183625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 04/02/2021] [Accepted: 04/12/2021] [Indexed: 12/11/2022]
Abstract
Cholesterol (Chol) content in most cellular membranes does not exceed 50 mol%, only in the eye lens's fiber cell plasma membrane, its content surpasses 50 mol%. At this high concentration, Chol induces the formation of pure cholesterol bilayer domains (CBDs), which coexist with the surrounding phospholipid-cholesterol domain (PCD). Here, we applied atomic force microscopy to study the mechanical properties of Chol/phosphatidylcholine membranes where the Chol content was increased from 0 to 75 mol%, relevant to eye lens membranes. The surface roughness of the membrane decreases with an increase of Chol content until it reaches 60 mol%, and roughness increases with a further increment in Chol content. We propose that the increased roughness at higher Chol content results from the formation of CBDs. Force spectroscopy on the membrane with Chol content of 50 mol% or lesser exhibited single breakthrough events, whereas two distinct puncture events were observed for membranes with the Chol content greater than 50 mol%. We propose that the first puncture force corresponds to the membranes containing coexisting PCD and CBDs. In contrast, the second puncture force corresponds to the "CBD water pocket" formed due to coexisting CBDs and PCD. Membrane area compressibility modulus (KA) increases with an increase in Chol content until it reaches 60 mol%, and with further increment in Chol content, CBDs are formed, and KA starts to decrease. Our results report the increase in membrane roughness and decrease KA at very high Chol content (>60 mol%) relevant to the eye lens membrane.
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Affiliation(s)
- Nawal K Khadka
- Department of Physics, Boise State University, Boise, ID, USA
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID, USA
| | - Erica Rowe
- Department of Biology, Boise State University, Boise, ID, USA
| | - Matthew O'Dell
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID, USA; Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA.
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12
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Domingues MM, Gomes B, Hollmann A, Santos NC. 25-Hydroxycholesterol Effect on Membrane Structure and Mechanical Properties. Int J Mol Sci 2021; 22:ijms22052574. [PMID: 33806504 PMCID: PMC7961727 DOI: 10.3390/ijms22052574] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/08/2021] [Accepted: 02/14/2021] [Indexed: 12/20/2022] Open
Abstract
Cholesterol is responsible for the plasticity of plasma membranes and is involved in physiological and pathophysiological responses. Cholesterol homeostasis is regulated by oxysterols, such as 25-hydroxycholesterol. The presence of 25-hydroxycholesterol at the membrane level has been shown to interfere with several viruses’ entry into their target cells. We used atomic force microscopy to assess the effect of 25-hydroxycholesterol on different properties of supported lipid bilayers with controlled lipid compositions. In particular, we showed that 25-hydroxycholesterol inhibits the lipid-condensing effects of cholesterol, rendering the bilayers less rigid. This study indicates that the inclusion of 25-hydroxycholesterol in plasma membranes or the conversion of part of their cholesterol content into 25-hydroxycholesterol leads to morphological alterations of the sphingomyelin (SM)-enriched domains and promotes lipid packing inhomogeneities. These changes culminate in membrane stiffness variations.
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Affiliation(s)
- Marco M. Domingues
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal;
- Correspondence: (M.M.D.); (N.C.S.)
| | - Bárbara Gomes
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal;
| | - Axel Hollmann
- Centro de Investigación en Biofísica Aplicada y Alimentos (CIBAAL), Universidad Nacional de Santiago Del Estero-CONICET, Santiago del Estero 4206, Argentina;
| | - Nuno C. Santos
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal;
- Correspondence: (M.M.D.); (N.C.S.)
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13
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Winkler P, Campelo F, Giannotti MI, Garcia-Parajo MF. Impact of Glycans on Lipid Membrane Dynamics at the Nanoscale Unveiled by Planar Plasmonic Nanogap Antennas and Atomic Force Spectroscopy. J Phys Chem Lett 2021; 12:1175-1181. [PMID: 33480693 PMCID: PMC7869103 DOI: 10.1021/acs.jpclett.0c03439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/19/2021] [Indexed: 05/27/2023]
Abstract
Lateral compartmentalization of the plasma membrane is a prominent feature present at multiple spatiotemporal scales that regulates key cellular functions. The extracellular glycocalyx matrix has recently emerged as an important player that modulates the organization of specific receptors and patterns the lipid bilayer itself. However, experimental limitations in investigating its impact on the membrane nanoscale dynamics have hampered detailed studies. Here, we used photonic nanoantenna arrays combined with fluorescence correlation spectroscopy to investigate the influence of hyaluronic acid (HA), a prominent glycosaminoglycan, on the nanoscale organization of mimetic lipid bilayers. Using atomic force microscopy and force spectroscopy, we further correlated our dynamic measurements with the morphology and mechanical properties of bilayers at the nanoscale. Overall, we find that HA has a profound effect on the dynamics, nanoscale organization, and mechanical properties of lipid bilayers that are enriched in sphingolipids and/or cholesterol, such as those present in living cells.
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Affiliation(s)
- Pamina
M. Winkler
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, 08860 Barcelona, Spain
| | - Felix Campelo
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, 08860 Barcelona, Spain
| | - Marina I. Giannotti
- Biomedical
Research Networking Center on Bioengineering, Biomaterials and Nanomedicine
(CIBER-BBN), 28029 Madrid, Spain
- Institut
de Bioenginyeria de Catalunya (IBEC), The
Barcelona Institute of Science
and Technology, 08860 Barcelona, Spain
- Universitat
de Barcelona (UB), 08007 Barcelona, Spain
| | - Maria F. Garcia-Parajo
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, 08860 Barcelona, Spain
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
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14
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Redondo-Morata L, Losada-Pérez P, Giannotti MI. Lipid bilayers: Phase behavior and nanomechanics. CURRENT TOPICS IN MEMBRANES 2020; 86:1-55. [PMID: 33837691 DOI: 10.1016/bs.ctm.2020.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipid membranes are involved in many physiological processes like recognition, signaling, fusion or remodeling of the cell membrane or some of its internal compartments. Within the cell, they are the ultimate barrier, while maintaining the fluidity or flexibility required for a myriad of processes, including membrane protein assembly. The physical properties of in vitro model membranes as model cell membranes have been extensively studied with a variety of techniques, from classical thermodynamics to advanced modern microscopies. Here we review the nanomechanics of solid-supported lipid membranes with a focus in their phase behavior. Relevant information obtained by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) as complementary techniques in the nano/mesoscale interface is presented. Membrane morphological and mechanical characterization will be discussed in the framework of its phase behavior, phase transitions and coexistence, in simple and complex models, and upon the presence of cholesterol.
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Affiliation(s)
- Lorena Redondo-Morata
- Center for Infection and Immunity of Lille, INSERM U1019, CNRS UMR 8204, Lille, France
| | - Patricia Losada-Pérez
- Experimental Soft Matter and Thermal Physics (EST) Group, Department of Physics, Université Libre de Bruxelles, Brussels, Belgium
| | - Marina Inés Giannotti
- Biomedical Research Networking Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain; Institut de Bioenginyeria de Catalunya (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain; Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Barcelona, Spain.
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15
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Chiodini S, Ruiz-Rincón S, Garcia PD, Martin S, Kettelhoit K, Armenia I, Werz DB, Cea P. Bottom Effect in Atomic Force Microscopy Nanomechanics. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2000269. [PMID: 32761794 DOI: 10.1002/smll.202000269] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 06/04/2020] [Indexed: 05/27/2023]
Abstract
In this work, the influence of the rigid substrate on the determination of the sample Young's modulus, the so-called bottom-effect artifact, is demonstrated by an atomic force microscopy force-spectroscopy experiment. The nanomechanical properties of a one-component supported lipid membrane (SLM) exhibiting areas of two different thicknesses are studied: While a standard contact mechanics model (Sneddon) provides two different elastic moduli for these two morphologies, it is shown that Garcia's bottom-effect artifact correction yields a unique value, as expected for an intrinsic material property. Remarkably, it is demonstrated that the ratio between the contact radius (and not only the indentation) and the sample thickness is the key parameter addressing the relevance of the bottom-effect artifact. The experimental results are validated by finite element method simulations providing a solid support to Garcia's theory. The amphiphilic nature of the investigated material is representative of several kinds of lipids, suggesting that the results have far reaching implications for determining the correct Young's modulus of SLMs. The generality of Garcia's bottom-effect artifact correction allows its application to every kind of supported soft film.
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Affiliation(s)
- Stefano Chiodini
- Instituto de Nanociencia de Aragón (INA), Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Campus Río Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Silvia Ruiz-Rincón
- Instituto de Nanociencia de Aragón (INA), Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Campus Río Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Pablo D Garcia
- Instituto de Ciencia de Materiales, ICMM-CSIC, Campus de Cantoblanco, C/Sor Juana Inés de la Cruz, 3, Madrid, 28049, Spain
| | - Santiago Martin
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
- Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Katharina Kettelhoit
- Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, Braunschweig, 38106, Germany
| | - Ilaria Armenia
- Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
| | - Daniel B Werz
- Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, Braunschweig, 38106, Germany
| | - Pilar Cea
- Instituto de Nanociencia de Aragón (INA), Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Campus Río Ebro, Universidad de Zaragoza, C/Mariano Esquillor s/n, Zaragoza, 50018, Spain
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
- Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, C/Pedro Cerbuna 12, Zaragoza, 50009, Spain
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16
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Saavedra V O, Fernandes TFD, Milhiet PE, Costa L. Compression, Rupture, and Puncture of Model Membranes at the Molecular Scale. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:5709-5716. [PMID: 32427478 DOI: 10.1021/acs.langmuir.0c00247] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Elastic properties of biological membranes are involved in a large number of membrane functionalities and activities. Conventionally characterized in terms of Young's modulus, bending stiffness and stretching modulus, membrane mechanics can be assessed at high lateral resolution by means of atomic force microscopy (AFM). Here we show that the mechanical response of biomimetic model systems such as supported lipid bilayers (SLBs) is highly affected by the size of the AFM tip employed as a membrane indenter. Our study is focused on phase-separated fluid-gel lipid membranes at room temperature. In a small tip radius regime (≈ 2 nm) and in the case of fluid phase membranes, we show that the tip can penetrate through the membrane minimizing molecular vertical compression and in absence of molecular membrane rupture. In this case, AFM indentation experiments cannot assess the vertical membrane Young's modulus. In agreement with the data reported in the literature, in the case of larger indenters (>2 nm) SLBs can be compressed leading to an evaluation of Young's modulus and membrane maximal withstanding force before rupture. We show that such force increases with the indenter in agreement with the existing theoretical frame. Finally, we demonstrate that the latter has no influence on the number of molecules involved in the rupture process that is observed to be constant and rather dependent on the indenter chemical composition.
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Affiliation(s)
- Oscar Saavedra V
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Thales F D Fernandes
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Pierre-Emmanuel Milhiet
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
| | - Luca Costa
- Centre de Biochimie Structurale (CBS), CNRS, INSERM, Univ. Montpellier, 34090 Montpellier, France
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17
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Gao Q, Wu G, Lai KWC. Cholesterol Modulates the Formation of the Aβ Ion Channel in Lipid Bilayers. Biochemistry 2020; 59:992-998. [PMID: 31914730 DOI: 10.1021/acs.biochem.9b00968] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The misfolding of amyloid beta (Aβ) is one of the predominant hallmarks in the pathology of Alzheimer's disease (AD). In this study, we showed that the formation of the Aβ ion channel on the membrane depended on the cholesterol concentration. From a mechanical aspect, we found that cholesterol levels affected the stability and assembly of lipid bilayers. Measurements on planar lipid bilayers indicated that a small amount of cholesterol interacted with Aβ proteins and promoted the insertion process. Conversely, high cholesterol integrated the lipid bilayer and exerted an opposite effect on Aβ insertion. The Aβ ion channel was then detected by graphene-based field-effect transistors. Results demonstrated that the Aβ ion channel promoted a Ca2+ flux in the presence of 15% cholesterol but prevented a Ca2+ flux in high cholesterol. Thus, cholesterol had a complex impact on the Aβ ion channel that can be described as two different effects. First, a small amount of cholesterol interacted with Aβ and facilitated the Aβ ion channel formation in the membrane. Second, a large amount of cholesterol did not induce the ion flux in the membrane, which can be explained by the cholesterol damage to the regular distribution of the lipid bilayer. Overall, this study suggested a possible approach to consider cholesterol levels for the treatment of AD patients.
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Affiliation(s)
- Qi Gao
- Department of Biomedical Engineering, Centre for Robotics and Automation, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Guangfu Wu
- Department of Biomedical Engineering, Centre for Robotics and Automation, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - King Wai Chiu Lai
- Department of Biomedical Engineering, Centre for Robotics and Automation, City University of Hong Kong, Kowloon Tong, Hong Kong
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18
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Lemaalem M, Hadrioui N, Derouiche A, Ridouane H. Structure and dynamics of liposomes designed for drug delivery: coarse-grained molecular dynamics simulations to reveal the role of lipopolymer incorporation. RSC Adv 2020; 10:3745-3755. [PMID: 35492626 PMCID: PMC9048902 DOI: 10.1039/c9ra08632c] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/06/2020] [Indexed: 12/22/2022] Open
Abstract
In this work, coarse-grained molecular dynamics simulations are carried out in NPTH and NVTE statistical ensembles in order to study the structure and dynamics properties of liposomes coated with polyethylene glycol (PEG).
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Affiliation(s)
- Mohammed Lemaalem
- Laboratoire de Physique des Polymères et Phénomènes Critiques Sciences Faculty Ben M'Sik
- Hassan II University
- Casablanca
- Morocco
| | - Nourddine Hadrioui
- Laboratoire de Physique des Polymères et Phénomènes Critiques Sciences Faculty Ben M'Sik
- Hassan II University
- Casablanca
- Morocco
| | - Abdelali Derouiche
- Laboratoire de Physique des Polymères et Phénomènes Critiques Sciences Faculty Ben M'Sik
- Hassan II University
- Casablanca
- Morocco
| | - Hamid Ridouane
- Laboratoire de Physique des Polymères et Phénomènes Critiques Sciences Faculty Ben M'Sik
- Hassan II University
- Casablanca
- Morocco
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19
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Lee TH, Hall K, Aguilar MI. The Effect of Charge on Melittin-Induced Changes in Membrane Structure and Morphology. Aust J Chem 2020. [DOI: 10.1071/ch19500] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The binding of melittin to a range of phospholipid bilayers was studied using dual polarisation interferometry and atomic force microscopy. The phospholipid model membranes included zwitterionic dimyristylphosphatidylcholine (DMPC), together with mixtures of DMPC/dimyristylphosphatidylglycerol (DMPG) and DMPC/DMPG/cholesterol. Melittin caused significant disruption on all bilayers, but differences in morphological changes during binding were different on each membrane. Overall, the results demonstrate that the process of membrane disruption follows distinct structural changes for different lipid mixtures irrespective of the strength of binding to the membrane surface.
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20
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Saeedimasine M, Montanino A, Kleiven S, Villa A. Role of lipid composition on the structural and mechanical features of axonal membranes: a molecular simulation study. Sci Rep 2019; 9:8000. [PMID: 31142762 PMCID: PMC6541598 DOI: 10.1038/s41598-019-44318-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 05/13/2019] [Indexed: 12/16/2022] Open
Abstract
The integrity of cellular membranes is critical for the functionality of axons. Failure of the axonal membranes (plasma membrane and/or myelin sheath) can be the origin of neurological diseases. The two membranes differ in the content of sphingomyelin and galactosylceramide lipids. We investigate the relation between lipid content and bilayer structural-mechanical properties, to better understand the dependency of membrane properties on lipid composition. A sphingomyelin/phospholipid/cholesterol bilayer is used to mimic a plasma membrane and a galactosylceramide/phospholipid/cholesterol bilayer to mimic a myelin sheath. Molecular dynamics simulations are performed at atomistic and coarse-grained levels to characterize the bilayers at equilibrium and under deformation. For comparison, simulations of phospholipid and phospholipid/cholesterol bilayers are also performed. The results clearly show that the bilayer biomechanical and structural features depend on the lipid composition, independent of the molecular models. Both galactosylceramide or sphingomyelin lipids increase the order of aliphatic tails and resistance to water penetration. Having 30% galactosylceramide increases the bilayers stiffness. Galactosylceramide lipids pack together via sugar-sugar interactions and hydrogen-bond phosphocholine with a correlated increase of bilayer thickness. Our findings provide a molecular insight on role of lipid content in natural membranes.
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Affiliation(s)
- Marzieh Saeedimasine
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Annaclaudia Montanino
- Division of Neuronic Engineering, KTH-Royal Institute of Technology, Huddinge, Sweden
| | - Svein Kleiven
- Division of Neuronic Engineering, KTH-Royal Institute of Technology, Huddinge, Sweden
| | - Alessandra Villa
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
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21
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Oroskar PA, Jameson CJ, Murad S. Molecular-Level "Observations" of the Behavior of Gold Nanoparticles in Aqueous Solution and Interacting with a Lipid Bilayer Membrane. Methods Mol Biol 2019; 2000:303-359. [PMID: 31148024 DOI: 10.1007/978-1-4939-9516-5_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We use coarse-grained molecular dynamics simulations to "observe" details of interactions between ligand-covered gold nanoparticles and a lipid bilayer model membrane. In molecular dynamics simulations, one puts the individual atoms and groups of atoms of the physical system to be "observed" into a simulation box, specifies the forms of the potential energies of interactions between them (ultimately quantum based), and lets them individually move classically according to Newton's equations of motion, based on the forces arising from the assumed potential energy forms. The atoms that are chemically bonded to each other stay chemically bonded, following known potentials (force fields) that permit internal degrees of freedom (internal rotation, torsion, vibrations), and the interactions between nonbonded atoms are simplified to Lennard-Jones forms (in our case) and coulombic (where electrical charges are present) in which the parameters are previously optimized to reproduce thermodynamic properties or are based on quantum electronic calculations. The system is started out at a reasonable set of coordinates for all atoms or groups of atoms, and then permitted to develop according to the equations of motion, one small step (usually 10 fs time step) at a time, for millions of steps until the system is at a quasi-equilibrium (usually reached after hundreds of nanoseconds). We then let the system play out its motions further for many nanoseconds to observe the behavior, periodically taking snapshots (saving all positions and energies), and post-processing the snapshots to obtain various average descriptions of the system. Alkanethiols of various lengths serve as examples of hydrophobic ligands and methyl-terminated PEG with various numbers of monomer units serve as examples of hydrophilic ligands. Spherical gold particles of various diameters as well as gold nanorods form the core to which ligands are attached. The nanoparticles are characterized at the molecular level, especially the distributions of ligand configurations and their dependence on ligand length, and surface coverage. Self-assembly of the bilayer from an isotropic solution and observation of membrane properties that correspond well to experimental values validate the simulations. The mechanism of permeation of a gold NP coated with either a hydrophobic or a hydrophilic ligand, and its dependence on surface coverage, ligand length, core diameter, and core shape, is investigated. Lipid response such as lipid flip-flops, lipid extraction, and changes in order parameter of the lipid tails are examined in detail. The mechanism of permeation of a PEGylated nanorod is shown to occur by tilting, lying down, rotating, and straightening up. The nature of the information provided by molecular dynamics simulations permits understanding of the detailed behavior of gold nanoparticles interacting with lipid membranes which in turn helps to understand why some known systems work better than others and aids the design of new particles and improvement of methods for preparing existing ones.
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Affiliation(s)
- Priyanka A Oroskar
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Cynthia J Jameson
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Sohail Murad
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL, USA.
- Department of Chemical Engineering, Illinois Institute of Technology, Chicago, IL, USA.
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22
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Gumí-Audenis B, Illa-Tuset S, Grimaldi N, Pasquina-Lemonche L, Ferrer-Tasies L, Sanz F, Veciana J, Ratera I, Faraudo J, Ventosa N, Giannotti MI. Insights into the structure and nanomechanics of a quatsome membrane by force spectroscopy measurements and molecular simulations. NANOSCALE 2018; 10:23001-23011. [PMID: 30500043 DOI: 10.1039/c8nr07110a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Quatsomes (QS) are unilamellar nanovesicles constituted by quaternary ammonium surfactants and sterols in defined molar ratios. Unlike conventional liposomes, QS are stable upon long storage such as for several years, they show outstanding vesicle-to-vesicle homogeneity regarding size and lamellarity, and they have the structural and physicochemical requirements to be a potential platform for site-specific delivery of hydrophilic and lipophilic molecules. Knowing in detail the structure and mechanical properties of the QS membrane is of great importance for the design of deformable and flexible nanovesicle alternatives, highly pursued in nanomedicine applications such as the transdermal administration route. In this work, we report the first study on the detailed structure of the cholesterol : CTAB QS membrane at the nanoscale, using atomic force microscopy (AFM) and spectroscopy (AFM-FS) in a controlled liquid environment (ionic medium and temperature) to assess the topography of supported QS membranes (SQMs) and to evaluate the local membrane mechanics. We further perform molecular dynamics (MD) simulations to provide an atomistic interpretation of the obtained results. Our results are direct evidence of the bilayer nature of the QS membrane, with characteristics of a fluid-like membrane, compact and homogeneous in composition, and with structural and mechanical properties that depend on the surrounding environment. We show how ions alter the lateral packing, modifying the membrane mechanics. We observe that according to the ionic environment and temperature, different domains may coexist in the QS membranes, ascribed to variations in molecular tilt angles. Our results indicate that QS membrane properties may be easily tuned by altering the lateral interactions with either different environmental ions or counterions.
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Affiliation(s)
- Berta Gumí-Audenis
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.
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23
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Casein interaction with lipid membranes: Are the phase state or charge density of the phospholipids affecting protein adsorption? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2588-2598. [DOI: 10.1016/j.bbamem.2018.09.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 09/11/2018] [Accepted: 09/26/2018] [Indexed: 01/03/2023]
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24
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Cebecauer M, Amaro M, Jurkiewicz P, Sarmento MJ, Šachl R, Cwiklik L, Hof M. Membrane Lipid Nanodomains. Chem Rev 2018; 118:11259-11297. [PMID: 30362705 DOI: 10.1021/acs.chemrev.8b00322] [Citation(s) in RCA: 119] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Lipid membranes can spontaneously organize their components into domains of different sizes and properties. The organization of membrane lipids into nanodomains might potentially play a role in vital functions of cells and organisms. Model membranes represent attractive systems to study lipid nanodomains, which cannot be directly addressed in living cells with the currently available methods. This review summarizes the knowledge on lipid nanodomains in model membranes and exposes how their specific character contrasts with large-scale phase separation. The overview on lipid nanodomains in membranes composed of diverse lipids (e.g., zwitterionic and anionic glycerophospholipids, ceramides, glycosphingolipids) and cholesterol aims to evidence the impact of chemical, electrostatic, and geometric properties of lipids on nanodomain formation. Furthermore, the effects of curvature, asymmetry, and ions on membrane nanodomains are shown to be highly relevant aspects that may also modulate lipid nanodomains in cellular membranes. Potential mechanisms responsible for the formation and dynamics of nanodomains are discussed with support from available theories and computational studies. A brief description of current fluorescence techniques and analytical tools that enabled progress in lipid nanodomain studies is also included. Further directions are proposed to successfully extend this research to cells.
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Affiliation(s)
- Marek Cebecauer
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Mariana Amaro
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Maria João Sarmento
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences , Dolejškova 3 , 18223 Prague 8 , Czech Republic
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Gumí-Audenis B, Costa L, Ferrer-Tasies L, Ratera I, Ventosa N, Sanz F, Giannotti MI. Pulling lipid tubes from supported bilayers unveils the underlying substrate contribution to the membrane mechanics. NANOSCALE 2018; 10:14763-14770. [PMID: 30043793 DOI: 10.1039/c8nr03249a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Cell processes like endocytosis, membrane resealing, signaling and transcription involve conformational changes which depend on the chemical composition and the physicochemical properties of the lipid membrane. The better understanding of the mechanical role of lipids in cell membrane force-triggered and sensing mechanisms has recently become the focus of attention. Different membrane models and experimental methodologies are commonly explored. While general approaches involve controlled vesicle deformation using micropipettes or optical tweezers, due to the local and dynamic nature of the membrane, high spatial resolution atomic force microscopy (AFM) has been widely used to study the mechanical compression and indentation of supported lipid bilayers (SLBs). However, the substrate contribution remains unkown. Here, we demonstrate how pulling lipid tubes with an AFM out of model SLBs can be used to assess the nanomechanics of SLBs through the evaluation of the tube growing force (Ftube), allowing for very local evaluation with high spatial and force resolution of the lipid membrane tension. We first validate this approach to determine the contribution of different phospholipids, by varying the membrane composition, in both one-component and phase-segregated membranes. Finally, we successfully assess the contribution of the underlying substrate to the membrane mechanics, demonstrating that SLB models may represent an intermediate scenario between a free membrane (blebs) and a cytoskeleton supported membrane.
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Affiliation(s)
- Berta Gumí-Audenis
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10-12, 08028 Barcelona, Spain.
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26
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Raghunathan K, Kenworthy AK. Dynamic pattern generation in cell membranes: Current insights into membrane organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2018-2031. [PMID: 29752898 DOI: 10.1016/j.bbamem.2018.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/30/2018] [Accepted: 05/03/2018] [Indexed: 12/18/2022]
Abstract
It has been two decades since the lipid raft hypothesis was first presented. Even today, whether these nanoscale cholesterol-rich domains are present in cell membranes is not completely resolved. However, especially in the last few years, a rich body of literature has demonstrated both the presence and the importance of non-random distribution of biomolecules on the membrane, which is the focus of this review. These new developments have pushed the experimental limits of detection and have brought us closer to observing lipid domains in the plasma membrane of live cells. Characterization of biomolecules associated with lipid rafts has revealed a deep connection between biological regulation and function and membrane compositional heterogeneities. Finally, tantalizing new developments in the field have demonstrated that lipid domains might not just be associated with the plasma membrane of eukaryotes but could potentially be a ubiquitous membrane-organizing principle in several other biological systems. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
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Affiliation(s)
- Krishnan Raghunathan
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, PA 15224, USA.
| | - Anne K Kenworthy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA.
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27
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Belin BJ, Busset N, Giraud E, Molinaro A, Silipo A, Newman DK. Hopanoid lipids: from membranes to plant-bacteria interactions. Nat Rev Microbiol 2018; 16:304-315. [PMID: 29456243 PMCID: PMC6087623 DOI: 10.1038/nrmicro.2017.173] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lipid research represents a frontier for microbiology, as showcased by hopanoid lipids. Hopanoids, which resemble sterols and are found in the membranes of diverse bacteria, have left an extensive molecular fossil record. They were first discovered by petroleum geologists. Today, hopanoid-producing bacteria remain abundant in various ecosystems, such as the rhizosphere. Recently, great progress has been made in our understanding of hopanoid biosynthesis, facilitated in part by technical advances in lipid identification and quantification. A variety of genetically tractable, hopanoid-producing bacteria have been cultured, and tools to manipulate hopanoid biosynthesis and detect hopanoids are improving. However, we still have much to learn regarding how hopanoid production is regulated, how hopanoids act biophysically and biochemically, and how their production affects bacterial interactions with other organisms, such as plants. The study of hopanoids thus offers rich opportunities for discovery.
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Affiliation(s)
- Brittany J. Belin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Nicolas Busset
- Institut de Recherche pour le Développement, LSTM, UMR IRD, SupAgro, INRA, University of Montpellier, CIRAD, France
| | - Eric Giraud
- Institut de Recherche pour le Développement, LSTM, UMR IRD, SupAgro, INRA, University of Montpellier, CIRAD, France
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy
| | - Alba Silipo
- Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy
| | - Dianne K. Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
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28
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Rosilio V. How Can Artificial Lipid Models Mimic the Complexity of Molecule–Membrane Interactions? ACTA ACUST UNITED AC 2018. [DOI: 10.1016/bs.abl.2017.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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29
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Gumí-Audenis B, Costa L, Redondo-Morata L, Milhiet PE, Sanz F, Felici R, Giannotti MI, Carlà F. In-plane molecular organization of hydrated single lipid bilayers: DPPC:cholesterol. NANOSCALE 2017; 10:87-92. [PMID: 29210438 DOI: 10.1039/c7nr07510c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the physical properties of cholesterol-phospholipid systems is essential to gain a better knowledge of the function of each membrane constituent. We present a novel, simple and user-friendly setup that allows for the straightforward grazing incidence X-ray diffraction characterization of hydrated individual supported lipid bilayers. This configuration minimizes the scattering from the liquid and allows the detection of the extremely weak diffracted signal of the membrane, enabling the differentiation of the coexisting domains in DPPC:cholesterol single bilayers.
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30
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Tero R, Fukumoto K, Motegi T, Yoshida M, Niwano M, Hirano-Iwata A. Formation of Cell Membrane Component Domains in Artificial Lipid Bilayer. Sci Rep 2017; 7:17905. [PMID: 29263355 PMCID: PMC5738377 DOI: 10.1038/s41598-017-18242-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 12/07/2017] [Indexed: 12/31/2022] Open
Abstract
The lipid bilayer environment around membrane proteins strongly affects their structure and functions. Here, we aimed to study the fusion of proteoliposomes (PLs) derived from cultured cells with an artificial lipid bilayer membrane and the distribution of the PL components after the fusion. PLs, which were extracted as a crude membrane fraction from Chinese hamster ovary (CHO) cells, formed isolated domains in a supported lipid bilayer (SLB), comprising phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (Chol), after the fusion. Observation with a fluorescence microscope and an atomic force microscope showed that the membrane fusion occurred selectively at microdomains in the PC + PE + Chol-SLB, and that almost all the components of the PL were retained in the domain. PLs derived from human embryonic kidney 293 (HEK) cells also formed isolated domains in the PC + PE + Chol-SLB, but their fusion kinetics was different from that of the CHO-PLs. We attempted to explain the mechanism of the PL-SLB fusion and the difference between CHO- and HEK-PLs, based on a kinetic model. The domains that contained the whole cell membrane components provided environments similar to that of natural cell membranes, and were thus effective for studying membrane proteins using artificial lipid bilayer membranes.
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Affiliation(s)
- Ryugo Tero
- Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580, Japan. .,Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580, Japan.
| | - Kohei Fukumoto
- Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580, Japan
| | - Toshinori Motegi
- Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580, Japan.,Division of Molecular Science, Faculty of Science and Technology, Gunma University, Kiryu, Gunma, 376-8515, Japan
| | - Miyu Yoshida
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Michio Niwano
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi, 980-8577, Japan.,Kansei Fukushi Research Institute, Tohoku Fukushi University, Sendai, Miyagi, 989-3201, Japan
| | - Ayumi Hirano-Iwata
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, Miyagi, 980-8577, Japan
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31
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Piantanida L, Bolt HL, Rozatian N, Cobb SL, Voïtchovsky K. Ions Modulate Stress-Induced Nanotexture in Supported Fluid Lipid Bilayers. Biophys J 2017; 113:426-439. [PMID: 28746853 PMCID: PMC5529180 DOI: 10.1016/j.bpj.2017.05.049] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 05/22/2017] [Accepted: 05/30/2017] [Indexed: 12/13/2022] Open
Abstract
Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of ∼20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membrane’s properties on a length scale of ∼20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton.
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Affiliation(s)
- Luca Piantanida
- Department of Physics, Durham University, Durham, United Kingdom
| | - Hannah L Bolt
- Department of Chemistry, Durham University, Durham, United Kingdom
| | - Neshat Rozatian
- Department of Chemistry, Durham University, Durham, United Kingdom
| | - Steven L Cobb
- Department of Chemistry, Durham University, Durham, United Kingdom
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