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Min S, Picou C, Jeong HJ, Bower A, Jeong K, Chung JK. Melittin-Phospholipase A 2 Synergism Is Mediated by Liquid-Liquid Miscibility Phase Transition in Giant Unilamellar Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:7456-7462. [PMID: 38546877 DOI: 10.1021/acs.langmuir.3c03920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
The primary constituents of honeybee venom, melittin and phospholipase A2 (PLA2), display toxin synergism in which the PLA2 activity is significantly enhanced by the presence of melittin. It has been shown previously that this is accomplished by the disruption in lipid packing, which allows PLA2 to become processive on the membrane surface. In this work, we show that melittin is capable of driving miscibility phase transition in giant unilamellar vesicles (GUVs) and that it raises the miscibility transition temperature (Tmisc) in a concentration-dependent manner. The induced phase separation enhances the processivity of PLA2, particularly at its boundaries, where a substantial difference in domain thickness creates a membrane discontinuity. The catalytic action of PLA2, in response, induces changes in the membrane, rendering it more conducive to melittin binding. This, in turn, facilitates further lipid phase separation and eventual vesicle lysis. Overall, our results show that melittin has powerful membrane-altering capabilities that activate PLA2 in various membrane contexts. More broadly, they exemplify how this biochemical system actively modulates and capitalizes on the spatial distribution of membrane lipids to efficiently achieve its objectives.
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Affiliation(s)
- Sein Min
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
| | - Cyrus Picou
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
| | - Hye Jin Jeong
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
| | - Adam Bower
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
| | - Keunhong Jeong
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
| | - Jean K Chung
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 United States
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2
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Grusky DS, Bhattacharya A, Boxer SG. Secondary Ion Mass Spectrometry of Single Giant Unilamellar Vesicles Reveals Compositional Variability. J Am Chem Soc 2023; 145:27521-27530. [PMID: 38056605 PMCID: PMC10904076 DOI: 10.1021/jacs.3c09039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Giant unilamellar vesicles (GUVs) are a widely used model system to interrogate lipid phase behavior, study biomembrane mechanics, reconstitute membrane proteins, and provide a chassis for synthetic cells. It is generally assumed that the composition of individual GUVs is the same as the nominal stock composition; however, there may be significant compositional variability between individual GUVs. Although this compositional heterogeneity likely impacts phase behavior, the function and incorporation of membrane proteins, and the encapsulation of biochemical reactions, it has yet to be directly quantified. To assess heterogeneity, we use secondary ion mass spectrometry (SIMS) to probe the composition of individual GUVs using non-perturbing isotopic labels. Both 13C- and 2H-labeled lipids are incorporated into a ternary mixture, which is then used to produce GUVs via gentle hydration or electroformation. Simultaneous detection of seven different ion species via SIMS allows for the concentration of 13C- and 2H-labeled lipids in single GUVs to be quantified using calibration curves, which correlate ion intensity to composition. Additionally, the relative concentration of 13C- and 2H-labeled lipids is assessed for each GUV via the ion ratio 2H-/13C-, which is highly sensitive to compositional differences between individual GUVs and circumvents the need for calibration by using standards. Both quantification methods suggest that gentle hydration produces GUVs with greater compositional variability than those formed by electroformation. However, both gentle hydration and electroformation display standard deviations in composition (n = 30 GUVs) on the order of 1-4 mol %, consistent with variability seen in previous indirect measurements.
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Affiliation(s)
- Dashiel S Grusky
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Ahanjit Bhattacharya
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
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3
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Lee IH, Passaro S, Ozturk S, Ureña J, Wang W. Intelligent fluorescence image analysis of giant unilamellar vesicles using convolutional neural network. BMC Bioinformatics 2022; 23:48. [PMID: 35062867 PMCID: PMC8783447 DOI: 10.1186/s12859-022-04577-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 01/11/2022] [Indexed: 11/23/2022] Open
Abstract
Background Fluorescence image analysis in biochemical science often involves the complex tasks of identifying samples for analysis and calculating the desired information from the intensity traces. Analyzing giant unilamellar vesicles (GUVs) is one of these tasks. Researchers need to identify many vesicles to statistically analyze the degree of molecular interaction or state of molecular organization on the membranes. This analysis is complicated, requiring a careful manual examination by researchers, so automating the analysis can significantly aid in improving its efficiency and reliability. Results We developed a convolutional neural network (CNN) assisted intelligent analysis routine based on the whole 3D z-stack images. The programs identify the vesicles with desired morphology and analyzes the data automatically. The programs can perform protein binding analysis on the membranes or state decision analysis of domain phase separation. We also show that the method can easily be applied to similar problems, such as intensity analysis of phase-separated protein droplets. CNN-based classification approach enables the identification of vesicles even from relatively complex samples. We demonstrate that the proposed artificial intelligence-assisted classification can further enhance the accuracy of the analysis close to the performance of manual examination in vesicle selection and vesicle state determination analysis. Conclusions We developed a MATLAB based software capable of efficiently analyzing confocal fluorescence image data of giant unilamellar vesicles. The program can automatically identify GUVs with desired morphology and perform intensity-based calculation and state decision for each vesicle. We expect our method of CNN implementation can be expanded and applied to many similar problems in image data analysis. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-022-04577-2.
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Zong W, Shao X, Chai Y, Wang X, Han S, Chu H, Zhu C, Zhang X. Liposomes encapsulating artificial cytosol as drug delivery system. Biophys Chem 2021; 281:106728. [PMID: 34864227 DOI: 10.1016/j.bpc.2021.106728] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 11/14/2021] [Accepted: 11/15/2021] [Indexed: 02/06/2023]
Abstract
The fabrication of cell models containing artificial cytosol is challenging. Herein we constructed an artificial cytosol contained cell model by electroformation method. Agarose was selected as the main component of the artificial cytosol, and sucrose was added into the agarose to regulate the sol viscosity and the phase transition temperature. The viscosity of the sol with the mass ratio (agarose-sucrose) 1:9 was closest to the natural cytosol. DSPC/20 mol% cholesterol was used to form large unilamellar vesicles (LUVs) as cell model compartment. The rhodamine release experiment confirmed that the unique release profile of agarose-sucrose@LUVs is suitable as a drug carrier. Doxorubicin is loaded in the agarose-sucrose@LUVs, and their half maximum inhibition concentration on HeLa cells is 0.016 μmol L-1, which means 28.7 times increase in inhibition efficiency over free doxorubicin.
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Affiliation(s)
- Wei Zong
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China.
| | - Xiaotong Shao
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
| | - Yunhe Chai
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
| | - Xiuwen Wang
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
| | - Shuang Han
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
| | - Hongtao Chu
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
| | - Chuntao Zhu
- School of Chemistry Engineering, Northeast Electric Power University, No.169, ChangChun Road, Jilin 132012, China
| | - Xunan Zhang
- College of Chemistry and Chemical Engineering, Qiqihar University, No.42 Wenhua Street, Qiqihar 161006, China
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5
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Endoplasmic reticulum phospholipid scramblase activity revealed after protein reconstitution into giant unilamellar vesicles containing a photostable lipid reporter. Sci Rep 2021; 11:14364. [PMID: 34257324 PMCID: PMC8277826 DOI: 10.1038/s41598-021-93664-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 06/28/2021] [Indexed: 02/04/2023] Open
Abstract
Transbilayer movement of phospholipids in biological membranes is mediated by a diverse set of lipid transporters. Among them are scramblases that facilitate a rapid bi-directional movement of lipids without metabolic energy input. Here, we established a new fluorescence microscopy-based assay for detecting phospholipid scramblase activity of membrane proteins upon their reconstitution into giant unilamellar vesicles formed from proteoliposomes by electroformation. The assay is based on chemical bleaching of fluorescence of a photostable ATTO-dye labeled phospholipid with the membrane-impermeant reductant sodium dithionite. We demonstrate that this new methodology is suitable for the study of the scramblase activity of the yeast endoplasmic reticulum at single vesicle level.
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6
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Diederichs T, Tampé R. Single Cell-like Systems Reveal Active Unidirectional and Light-Controlled Transport by Nanomachineries. ACS NANO 2021; 15:6747-6755. [PMID: 33724767 PMCID: PMC8157534 DOI: 10.1021/acsnano.0c10139] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Cellular life depends on transport and communication across membranes, which is emphasized by the fact that membrane proteins are prime drug targets. The cell-like environment of membrane proteins has gained increasing attention based on its important role in function and regulation. As a versatile scaffold for bottom-up synthetic biology and nanoscience, giant liposomes represent minimalistic models of living cells. Nevertheless, the incorporation of fragile multiprotein membrane complexes still remains a major challenge. Here, we report on an approach for the functional reconstitution of membrane assemblies exemplified by human and bacterial ATP-binding cassette (ABC) transporters. We reveal that these nanomachineries transport substrates unidirectionally against a steep concentration gradient. Active substrate transport can be spatiotemporally resolved in single cell-like compartments by light, enabling real-time tracking of substrate export and import in individual liposomes. This approach will help to construct delicate artificial cell-like systems.
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Affiliation(s)
- Tim Diederichs
- Institute of Biochemistry, Biocenter,
Goethe-University Frankfurt, Max-von Laue-Straße 9,
60438 Frankfurt a.M., Germany
| | - Robert Tampé
- Institute of Biochemistry, Biocenter,
Goethe-University Frankfurt, Max-von Laue-Straße 9,
60438 Frankfurt a.M., Germany
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7
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Wang X, Du H, Wang Z, Mu W, Han X. Versatile Phospholipid Assemblies for Functional Synthetic Cells and Artificial Tissues. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2002635. [PMID: 32830387 DOI: 10.1002/adma.202002635] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/09/2020] [Indexed: 06/11/2023]
Abstract
The bottom-up construction of a synthetic cell from nonliving building blocks capable of mimicking cellular properties and behaviors helps to understand the particular biophysical properties and working mechanisms of a cell. A synthetic cell built in this way possesses defined chemical composition and structure. Since phospholipids are native biomembrane components, their assemblies are widely used to mimic cellular structures. Here, recent developments in the formation of versatile phospholipid assemblies are described, together with the applications of these assemblies for functional membranes (protein reconstituted giant unilamellar vesicles), spherical and nonspherical protoorganelles, and functional synthetic cells, as well as the high-order hierarchical structures of artificial tissues. Their biomedical applications are also briefly summarized. Finally, the challenges and future directions in the field of synthetic cells and artificial tissues based on phospholipid assemblies are proposed.
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Affiliation(s)
- Xuejing Wang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China
| | - Hang Du
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China
- Marine Antifouling Engineering Technology Center of Shangdong Province, Harbin Institute of Technology, Weihai, 264209, China
| | - Zhao Wang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China
| | - Wei Mu
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China
| | - Xiaojun Han
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China
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8
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Zartner L, Garni M, Craciun I, Einfalt T, Palivan CG. How Can Giant Plasma Membrane Vesicles Serve as a Cellular Model for Controlled Transfer of Nanoparticles? Biomacromolecules 2020; 22:106-115. [PMID: 32648740 DOI: 10.1021/acs.biomac.0c00624] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Cellular model systems are essential platforms used across multiple research fields for exploring the fundaments of biology and biochemistry. Here, we present giant plasma membrane vesicles (GPMVs) as a platform of cell-like compartments that will facilitate the study of particles within a biorelevant environment and promote their further development. We studied how cellularly taken up nanoparticles (NPs) can be transferred into formed GPMVs and which are the molecular factors that play a role in successful transfer (size, concentration, and surface charge along with 3 different cell lines: HepG2, HeLa, and Caco-2). We observed that polystyrene (PS) carboxylated NPs with a size of 40 and 100 nm were successfully and efficiently transferred to GPMVs derived from all cell lines. We then investigated the distribution of NPs inside formed GPMVs and established the average number of NPs/GPMVs and the percentage of all GPMVs with NPs in their cavity. We pave the way for GPMV usage as superior cell-like mimics in medically relevant applications.
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Affiliation(s)
- Luisa Zartner
- Department of Chemistry, University of Basel, Mattenstrasse 24a, BPR 1096, P.O. Box 3350, CH-4002 Basel, Switzerland
| | - Martina Garni
- Department of Chemistry, University of Basel, Mattenstrasse 24a, BPR 1096, P.O. Box 3350, CH-4002 Basel, Switzerland
| | - Ioana Craciun
- Department of Chemistry, University of Basel, Mattenstrasse 24a, BPR 1096, P.O. Box 3350, CH-4002 Basel, Switzerland
| | - Tomaž Einfalt
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Technology, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel, Mattenstrasse 24a, BPR 1096, P.O. Box 3350, CH-4002 Basel, Switzerland
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9
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Raghuraman H, Chatterjee S, Das A. Site-Directed Fluorescence Approaches for Dynamic Structural Biology of Membrane Peptides and Proteins. Front Mol Biosci 2019; 6:96. [PMID: 31608290 PMCID: PMC6774292 DOI: 10.3389/fmolb.2019.00096] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 09/11/2019] [Indexed: 12/31/2022] Open
Abstract
Membrane proteins mediate a number of cellular functions and are associated with several diseases and also play a crucial role in pathogenicity. Due to their importance in cellular structure and function, they are important drug targets for ~60% of drugs available in the market. Despite the technological advancement and recent successful outcomes in determining the high-resolution structural snapshot of membrane proteins, the mechanistic details underlining the complex functionalities of membrane proteins is least understood. This is largely due to lack of structural dynamics information pertaining to different functional states of membrane proteins in a membrane environment. Fluorescence spectroscopy is a widely used technique in the analysis of functionally-relevant structure and dynamics of membrane protein. This review is focused on various site-directed fluorescence (SDFL) approaches and their applications to explore structural information, conformational changes, hydration dynamics, and lipid-protein interactions of important classes of membrane proteins that include the pore-forming peptides/proteins, ion channels/transporters and G-protein coupled receptors.
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Affiliation(s)
- H. Raghuraman
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Homi Bhabha National Institute, Kolkata, India
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10
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Sikkema HR, Gaastra BF, Pols T, Poolman B. Cell Fuelling and Metabolic Energy Conservation in Synthetic Cells. Chembiochem 2019; 20:2581-2592. [PMID: 31381223 DOI: 10.1002/cbic.201900398] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Indexed: 12/14/2022]
Abstract
We are aiming for a blue print for synthesizing (moderately complex) subcellular systems from molecular components and ultimately for constructing life. However, without comprehensive instructions and design principles, we rely on simple reaction routes to operate the essential functions of life. The first forms of synthetic life will not make every building block for polymers de novo according to complex pathways, rather they will be fed with amino acids, fatty acids and nucleotides. Controlled energy supply is crucial for any synthetic cell, no matter how complex. Herein, we describe the simplest pathways for the efficient generation of ATP and electrochemical ion gradients. We have estimated the demand for ATP by polymer synthesis and maintenance processes in small cell-like systems, and we describe circuits to control the need for ATP. We also present fluorescence-based sensors for pH, ionic strength, excluded volume, ATP/ADP, and viscosity, which allow the major physicochemical conditions inside cells to be monitored and tuned.
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Affiliation(s)
- Hendrik R Sikkema
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Bauke F Gaastra
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Tjeerd Pols
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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11
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Okamura E. Solution NMR to Quantify Mobility in Membranes: Diffusion, Protrusion, and Drug Transport Processes. Chem Pharm Bull (Tokyo) 2019; 67:308-315. [DOI: 10.1248/cpb.c18-00946] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Emiko Okamura
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University
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12
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Rideau E, Wurm FR, Landfester K. Self‐Assembly of Giant Unilamellar Vesicles by Film Hydration Methodologies. ACTA ACUST UNITED AC 2019; 3:e1800324. [DOI: 10.1002/adbi.201800324] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/01/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Emeline Rideau
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Frederik R. Wurm
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
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13
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Betaneli V, Mücksch J, Schwille P. Fluorescence Correlation Spectroscopy to Examine Protein-Lipid Interactions in Membranes. Methods Mol Biol 2019; 2003:415-447. [PMID: 31218628 DOI: 10.1007/978-1-4939-9512-7_18] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) is a versatile technique to study membrane dynamics and protein-lipid interactions. It can provide information about diffusion coefficients, concentrations, and molecular interactions of proteins and lipids in the membrane. These parameters allow for the determination of protein partitioning into different lipid environments, the identification of lipid domains, and the detection of lipid-protein complexes on the membrane. During the last decades, FCS studies were successfully performed on model membrane systems as also on living cells, to characterize protein-lipid interactions. Recent developments of the method described here improved quantitative measurements on membranes and decreased the number of potential artifacts. The aim of this chapter is to provide the reader with the necessary information and some practical guidelines to perform FCS studies on artificial and cellular membranes.
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Affiliation(s)
- Viktoria Betaneli
- Medical Faculty "Carl Gustav Carus", Institute of Physiological Chemistry, Technische Universität Dresden, Dresden, Germany
| | - Jonas Mücksch
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Petra Schwille
- Max Planck Institute of Biochemistry, Martinsried, Germany.
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14
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Sugár IP, Bonanno AP, Chong PLG. Gramicidin Lateral Distribution in Phospholipid Membranes: Fluorescence Phasor Plots and Statistical Mechanical Model. Int J Mol Sci 2018; 19:E3690. [PMID: 30469389 PMCID: PMC6274966 DOI: 10.3390/ijms19113690] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/14/2018] [Accepted: 11/15/2018] [Indexed: 11/16/2022] Open
Abstract
When using small mole fraction increments to study gramicidins in phospholipid membranes, we found that the phasor dots of intrinsic fluorescence of gramicidin D and gramicidin A in dimyristoyl-sn-glycero-3-phosphocholine (DMPC) unilamellar and multilamellar vesicles exhibit a biphasic change with peptide content at 0.143 gramicidin mole fraction. To understand this phenomenon, we developed a statistical mechanical model of gramicidin/DMPC mixtures. Our model assumes a sludge-like mixture of fluid phase and aggregates of rigid clusters. In the fluid phase, gramicidin monomers are randomly distributed. A rigid cluster is formed by a gramicidin dimer and DMPC molecules that are condensed to the dimer, following particular stoichiometries (critical gramicidin mole fractions, Xcr including 0.143). Rigid clusters form aggregates in which gramicidin dimers are regularly distributed, in some cases, even to superlattices. At Xcr, the size of cluster aggregates and regular distributions reach a local maximum. Before a similar model was developed for cholesterol/DMPC mixtures (Sugar and Chong (2012) J. Am. Chem. Soc. 134, 1164⁻1171) and here the similarities and differences are discussed between these two models.
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Affiliation(s)
- István P Sugár
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
| | - Alexander P Bonanno
- Department of Medical Genetics and Molecular Biochemistry, The Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA.
| | - Parkson Lee-Gau Chong
- Department of Medical Genetics and Molecular Biochemistry, The Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA.
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15
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Vitkova V, Mitkova D, Antonova K, Popkirov G, Dimova R. Sucrose solutions alter the electric capacitance and dielectric permittivity of lipid bilayers. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.05.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Methods of reconstitution to investigate membrane protein function. Methods 2018; 147:126-141. [DOI: 10.1016/j.ymeth.2018.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 02/13/2018] [Indexed: 02/06/2023] Open
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17
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Pick H, Alves AC, Vogel H. Single-Vesicle Assays Using Liposomes and Cell-Derived Vesicles: From Modeling Complex Membrane Processes to Synthetic Biology and Biomedical Applications. Chem Rev 2018; 118:8598-8654. [PMID: 30153012 DOI: 10.1021/acs.chemrev.7b00777] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The plasma membrane is of central importance for defining the closed volume of cells in contradistinction to the extracellular environment. The plasma membrane not only serves as a boundary, but it also mediates the exchange of physical and chemical information between the cell and its environment in order to maintain intra- and intercellular functions. Artificial lipid- and cell-derived membrane vesicles have been used as closed-volume containers, representing the simplest cell model systems to study transmembrane processes and intracellular biochemistry. Classical examples are studies of membrane translocation processes in plasma membrane vesicles and proteoliposomes mediated by transport proteins and ion channels. Liposomes and native membrane vesicles are widely used as model membranes for investigating the binding and bilayer insertion of proteins, the structure and function of membrane proteins, the intramembrane composition and distribution of lipids and proteins, and the intermembrane interactions during exo- and endocytosis. In addition, natural cell-released microvesicles have gained importance for early detection of diseases and for their use as nanoreactors and minimal protocells. Yet, in most studies, ensembles of vesicles have been employed. More recently, new micro- and nanotechnological tools as well as novel developments in both optical and electron microscopy have allowed the isolation and investigation of individual (sub)micrometer-sized vesicles. Such single-vesicle experiments have revealed large heterogeneities in the structure and function of membrane components of single vesicles, which were hidden in ensemble studies. These results have opened enormous possibilities for bioanalysis and biotechnological applications involving unprecedented miniaturization at the nanometer and attoliter range. This review will cover important developments toward single-vesicle analysis and the central discoveries made in this exciting field of research.
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Affiliation(s)
- Horst Pick
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Ana Catarina Alves
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Horst Vogel
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
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18
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A convenient protocol for generating giant unilamellar vesicles containing SNARE proteins using electroformation. Sci Rep 2018; 8:9422. [PMID: 29930377 PMCID: PMC6013450 DOI: 10.1038/s41598-018-27456-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/29/2018] [Indexed: 01/05/2023] Open
Abstract
Reconstitution of membrane proteins in artificial membranes is an essential prerequisite for functional studies that depend on the context of an intact membrane. While straight-forward protocols for reconstituting proteins in small unilamellar vesicles were developed many years ago, it is much more difficult to prepare large membranes containing membrane proteins at biologically relevant concentrations. Giant unilamellar vesicles (GUVs) represent a model system that is characterised by low curvature, controllable tension, and large surface that can be easily visualised with microscopy, but protein insertion is notoriously difficult. Here we describe a convenient method for efficient generation of GUVs containing functionally active SNARE proteins that govern exocytosis of synaptic vesicles. Preparation of proteo-GUVs requires a simple, in-house-built device, standard and inexpensive electronic equipment, and employs a straight-forward protocol that largely avoids damage of the proteins. The procedure allows upscaling and multiplexing, thus providing a platform for establishing and optimizing preparation of GUVs containing membrane proteins for a diverse array of applications.
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Park S, Majd S. Reconstitution and functional studies of hamster P-glycoprotein in giant liposomes. PLoS One 2018; 13:e0199279. [PMID: 29912971 PMCID: PMC6005519 DOI: 10.1371/journal.pone.0199279] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 06/05/2018] [Indexed: 11/18/2022] Open
Abstract
This paper describes the preparation of giant unilamellar vesicles with reconstituted hamster P-glycoprotein (Pgp, ABCB1) for studying the transport activity of this efflux pump in individual liposomes using optical microscopy. Pgp, a member of ABC (ATP-binding cassette) transporter family, is known to contribute to the cellular multidrug resistance (MDR) against variety of drugs. The efficacy of many therapeutics is, thus, hampered by this efflux pump, leading to a high demand for simple and effective strategies to monitor the interactions of candidate drugs with this protein. Here, we applied small Pgp proteoliposomes to prepare giant Pgp-bearing liposomes via modified electroformation techniques. The presence of Pgp in the membrane of giant proteoliposomes was confirmed using immunohistochemistry. Assessment of Pgp ATPase activity suggested that this transporter retained its activity upon reconstitution into giant liposomes, with an ATPase specific activity of 439 ± 103 nmol/mg protein/min. For further confirmation, we assessed the transport activity of Pgp in these proteoliposomes by monitoring the translocation of rhodamine 123 (Rho123) across the membrane using confocal microscopy at various ATP concentrations (0-2 mM) and in the presence of Pgp inhibitors. Rate of change in Rho123 concentration inside the liposomal lumen was used to estimate the Rho123 transport rates (1/s) for various ATP concentrations, which were then applied to retrieve the Michaelis-Menten constant (Km) of ATP in Rho123 transport (0.42 ± 0.75 mM). Similarly, inhibitory effects of verapamil, colchicine, and cyclosporin A on Pgp were studied in this system and the IC50 values for these Pgp inhibitors were found 26.6 ± 6.1 μM, 94.6 ± 47.6 μM, and 0.21 ± 0.07 μM, respectively. We further analyzed the transport data using a kinetic model that enabled dissecting the passive diffusion of Rho123 from its Pgp-mediated transport across the membrane. Based on this model, the permeability coefficient of Rho123 across the liposomal membrane was approximately 1.25×10-7 cm/s. Comparing the membrane permeability in liposomes with and without Pgp revealed that the presence of this protein did not have a significant impact on membrane integrity and permeability. Furthermore, we used this model to obtain transport rate constants for the Pgp-mediated transport of Rho123 (m3/mol/s) at various ATP and inhibitor concentrations, which were then applied to estimate values of 0.53 ± 0.66 mM for Km of ATP and 25.2 ± 5.0 μM for verapamil IC50, 61.8 ± 34.8 μM for colchicine IC50, and 0.23 ± 0.09 μM for cyclosporin A IC50. The kinetic parameters obtained from the two analyses were comparable, suggesting a minimal contribution from the passive Rho123 diffusion across the membrane. This approach may, therefore, be applied for screening the transport activity of Pgp against potential drug candidates.
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Affiliation(s)
- SooHyun Park
- The Brown Foundation Institute of Molecular Medicine and Texas Therapeutics Institute, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Sheereen Majd
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States of America
- * E-mail:
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20
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Abstract
Patch-clamp electrophysiology is the standard technique used for the high-resolution functional measurements on ion channels. While studies using patch clamp are commonly carried out following ion channel expression in a heterologous system such as Xenopus oocytes or tissue culture cells, these studies can also be carried out using ion channels reconstituted into lipid vesicles. In this chapter, we describe the methodology for reconstituting ion channels into liposomes and the procedure for the generation of unilamellar blisters from these liposomes that are suitable for patch clamp. Here, we focus on the bacterial K+ channel KcsA, although the methodologies described in this chapter should be applicable for the functional analysis of other ion channels.
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Affiliation(s)
- Kimberly Matulef
- Program in Chemical Biology, Department of Physiology and Pharmacology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code L334, Portland, OR, 97239, USA
| | - Francis I Valiyaveetil
- Department of Physiology and Pharmacology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code L334, Portland, OR, 97239, USA.
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21
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 PMCID: PMC5303729 DOI: 10.3389/fphys.2017.00063] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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22
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 DOI: 10.3389/fphys.2017.00063/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 05/27/2023] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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Mohammad MM, Tomita N, Ohta M, Movileanu L. The Transmembrane Domain of a Bicomponent ABC Transporter Exhibits Channel-Forming Activity. ACS Chem Biol 2016; 11:2506-18. [PMID: 27379442 PMCID: PMC5026576 DOI: 10.1021/acschembio.6b00383] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that expresses two unique forms of lipopolysaccharides (LPSs) on its bacterial surface, the A- and B-bands. The A-band polysaccharides (A-band PSs) are thought to be exported into the periplasm via a bicomponent ATP-binding cassette (ABC) transporter located within the inner membrane. This ABC protein complex consists of the transmembrane (TMD) Wzm and nucleotide-binding (NBD) Wzt domain proteins. Here, we were able to probe ∼1.36 nS-average conductance openings of the Wzm-based protein complex when reconstituted into a lipid membrane buffered by a 200 mM KCl solution, demonstrating the large-conductance, channel-forming ability of the TMDs. In agreement with this finding, transmission electron microscopy (TEM) imaging revealed the ring-shaped structure of the transmembrane Wzm protein complex. As hypothesized, using liposomes, we demonstrated that Wzm interacts with Wzt. Further, the Wzt polypeptide indeed hydrolyzed ATP but exhibited a ∼75% reduction in the ATPase activity when its Walker A domain was deleted. The distribution and average unitary conductance of the TMD Wzm protein complex were altered by the presence of the NBD Wzt protein, confirming the regulatory role of the latter polypeptide. To our knowledge, the large-conductance, channel-like activity of the Wzm protein complex, although often hypothesized, has not previously been demonstrated. These results constitute a platform for future structural, biophysical, and functional explorations of this bicomponent ABC transporter.
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Affiliation(s)
- Mohammad M. Mohammad
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
| | - Noriko Tomita
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Makoto Ohta
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
- Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, New York 13244-4100, USA
- The Syracuse Biomaterials Institute, Syracuse University, 121 Link Hall, Syracuse, New York 13244, USA
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24
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Jørgensen IL, Kemmer GC, Pomorski TG. Membrane protein reconstitution into giant unilamellar vesicles: a review on current techniques. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 46:103-119. [DOI: 10.1007/s00249-016-1155-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 06/18/2016] [Accepted: 07/03/2016] [Indexed: 12/11/2022]
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25
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Uytterhoeven V, Lauwers E, Maes I, Miskiewicz K, Melo MN, Swerts J, Kuenen S, Wittocx R, Corthout N, Marrink SJ, Munck S, Verstreken P. Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy. Neuron 2016; 88:735-48. [PMID: 26590345 DOI: 10.1016/j.neuron.2015.10.012] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 09/10/2015] [Accepted: 09/28/2015] [Indexed: 11/26/2022]
Abstract
Synapses are often far from their cell bodies and must largely independently cope with dysfunctional proteins resulting from synaptic activity and stress. To identify membrane-associated machines that can engulf synaptic targets destined for degradation, we performed a large-scale in vitro liposome-based screen followed by functional studies. We identified a presynaptically enriched chaperone Hsc70-4 that bends membranes based on its ability to oligomerize. This activity promotes endosomal microautophagy and the turnover of specific synaptic proteins. Loss of microautophagy slows down neurotransmission while gain of microautophagy increases neurotransmission. Interestingly, Sgt, a cochaperone of Hsc70-4, is able to switch the activity of Hsc70-4 from synaptic endosomal microautophagy toward chaperone activity. Hence, Hsc70-4 controls rejuvenation of the synaptic protein pool in a dual way: either by refolding proteins together with Sgt, or by targeting them for degradation by facilitating endosomal microautophagy based on its membrane deforming activity.
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Affiliation(s)
- Valerie Uytterhoeven
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Elsa Lauwers
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium.
| | - Ine Maes
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Katarzyna Miskiewicz
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Manuel N Melo
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Jef Swerts
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Sabine Kuenen
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Rafaël Wittocx
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium
| | - Nikky Corthout
- VIB Bio-Imaging Core Facility, Herestraat 49, 3000 Leuven, Belgium
| | - Siewert-Jan Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Sebastian Munck
- VIB Bio-Imaging Core Facility, Herestraat 49, 3000 Leuven, Belgium
| | - Patrik Verstreken
- KU Leuven, Center for Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium; VIB Center for the Biology of Disease, Leuven Institute for Neurodegenerative Disease (LIND), Laboratory of Neuronal Communication, Herestraat 49, 3000 Leuven, Belgium.
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26
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Lagny TJ, Bassereau P. Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations. Interface Focus 2015; 5:20150038. [PMID: 26464792 PMCID: PMC4590427 DOI: 10.1098/rsfs.2015.0038] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell-cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?
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Affiliation(s)
- Thibaut J Lagny
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
| | - Patricia Bassereau
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
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27
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Motta I, Gohlke A, Adrien V, Li F, Gardavot H, Rothman JE, Pincet F. Formation of Giant Unilamellar Proteo-Liposomes by Osmotic Shock. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7091-7099. [PMID: 26038815 PMCID: PMC4950989 DOI: 10.1021/acs.langmuir.5b01173] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Giant unilamellar vesicles (GUVs), composed of a phospholipid bilayer, are often used as a model system for cell membranes. However, the study of proteo-membrane interactions in this system is limited as the incorporation of integral and lipid-anchored proteins into GUVs remains challenging. Here, we present a simple generic method to incorporate proteins into GUVs. The basic principle is to break proteo-liposomes with an osmotic shock. They subsequently reseal into larger vesicles which, if necessary, can endure the same to obtain even larger proteo-GUVs. This process does not require specific lipids or reagents, works under physiological conditions with high concentrations of protein, the proteins remains functional after incorporation. The resulting proteo-GUVs can be micromanipulated. Moreover, our protocol is valid for a wide range of protein substrates. We have successfully reconstituted three structurally different proteins, two trans-membrane proteins (TolC and the neuronal t-SNARE), and one lipid-anchored peripheral protein (GABARAP-Like 1 (GL1)). In each case, we verified that the protein remains active after incorporation and in its correctly folded state. We also measured their mobility by performing diffusion measurements via fluorescence recovery after photobleaching (FRAP) experiments on micromanipulated single GUVs. The diffusion coefficients are in agreement with previous data.
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Affiliation(s)
- Isabelle Motta
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - Andrea Gohlke
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Vladimir Adrien
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Laboratoire de Cristallographie et RMN Biologiques, Université Paris Descartes, CNRS, UMR 8015, Paris, France
| | - Feng Li
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Hélène Gardavot
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - James E. Rothman
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frederic Pincet
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
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28
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Itel F, Najer A, Palivan CG, Meier W. Dynamics of Membrane Proteins within Synthetic Polymer Membranes with Large Hydrophobic Mismatch. NANO LETTERS 2015; 15:3871-8. [PMID: 26013972 DOI: 10.1021/acs.nanolett.5b00699] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The functioning of biological membrane proteins (MPs) within synthetic block copolymer membranes is an intriguing phenomenon that is believed to offer great potential for applications in life and medical sciences and engineering. The question why biological MPs are able to function in this completely artificial environment is still unresolved by any experimental data. Here, we have analyzed the lateral diffusion properties of different sized MPs within poly(dimethylsiloxane) (PDMS)-containing amphiphilic block copolymer membranes of membrane thicknesses between 9 and 13 nm, which results in a hydrophobic mismatch between the membrane thickness and the size of the proteins of 3.3-7.1 nm (3.5-5 times). We show that the high flexibility of PDMS, which provides membrane fluidities similar to phospholipid bilayers, is the key-factor for MP incorporation.
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Affiliation(s)
- Fabian Itel
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Adrian Najer
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Wolfgang Meier
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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29
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Rørvig-Lund A, Bahadori A, Semsey S, Bendix PM, Oddershede LB. Vesicle Fusion Triggered by Optically Heated Gold Nanoparticles. NANO LETTERS 2015; 15:4183-4188. [PMID: 26010468 DOI: 10.1021/acs.nanolett.5b01366] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Membrane fusion can be accelerated by heating that causes membrane melting and expansion. We locally heated the membranes of two adjacent vesicles by laser irradiating gold nanoparticles, thus causing vesicle fusion with associated membrane and cargo mixing. The mixing time scales were consistent with diffusive mixing of the membrane dyes and the aqueous content. This method is useful for nanoscale reactions as demonstrated here by I-BAR protein-mediated membrane tubulation triggered by fusion.
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Affiliation(s)
- Andreas Rørvig-Lund
- †Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
| | - Azra Bahadori
- †Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
- ‡Lundbeck Foundation Center of Excellence for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Szabolcs Semsey
- †Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
| | - Poul Martin Bendix
- †Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
| | - Lene B Oddershede
- †Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
- ‡Lundbeck Foundation Center of Excellence for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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30
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Garten M, Aimon S, Bassereau P, Toombes GES. Reconstitution of a transmembrane protein, the voltage-gated ion channel, KvAP, into giant unilamellar vesicles for microscopy and patch clamp studies. J Vis Exp 2015:52281. [PMID: 25650630 DOI: 10.3791/52281] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Giant Unilamellar Vesicles (GUVs) are a popular biomimetic system for studying membrane associated phenomena. However, commonly used protocols to grow GUVs must be modified in order to form GUVs containing functional transmembrane proteins. This article describes two dehydration-rehydration methods - electroformation and gel-assisted swelling - to form GUVs containing the voltage-gated potassium channel, KvAP. In both methods, a solution of protein-containing small unilamellar vesicles is partially dehydrated to form a stack of membranes, which is then allowed to swell in a rehydration buffer. For the electroformation method, the film is deposited on platinum electrodes so that an AC field can be applied during film rehydration. In contrast, the gel-assisted swelling method uses an agarose gel substrate to enhance film rehydration. Both methods can produce GUVs in low (e.g., 5 mM) and physiological (e.g., 100 mM) salt concentrations. The resulting GUVs are characterized via fluorescence microscopy, and the function of reconstituted channels measured using the inside-out patch-clamp configuration. While swelling in the presence of an alternating electric field (electroformation) gives a high yield of defect-free GUVs, the gel-assisted swelling method produces a more homogeneous protein distribution and requires no special equipment.
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Affiliation(s)
- Matthias Garten
- Institut Curie, Centre de Recherche, CNRS, UMR 168, PhysicoChimie Curie, Université Pierre et Marie Curie
| | - Sophie Aimon
- Kavli Institute for Brain and Mind, University of California, San Diego
| | - Patricia Bassereau
- Institut Curie, Centre de Recherche, CNRS, UMR 168, PhysicoChimie Curie, Université Pierre et Marie Curie;
| | - Gilman E S Toombes
- Molecular Physiology and Biophysics Section, National Institute for Neurological Disorders and Stroke, National Institute of Health
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31
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Hermann E, Ries J, García-Sáez AJ. Scanning fluorescence correlation spectroscopy on biomembranes. Methods Mol Biol 2015; 1232:181-197. [PMID: 25331137 DOI: 10.1007/978-1-4939-1752-5_15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) is a powerful quantitative method to study dynamical properties of biophysical systems. It exploits the temporal autocorrelation of fluorescence intensity fluctuations originating from a tiny volume (~fL). A theoretical model function can be then fitted to the measured auto-correlation curve to obtain physical parameters such as local concentration and diffusion time. However, the application of FCS on membranes is coupled to several difficulties like accurate positioning and stability of the set-up. In this book chapter, we explain the theoretical framework of point FCS and Scanning FCS (SFCS), which is a variation especially suitable for membrane studies. We present a list of materials necessary for SFCS studies on Giant Unilamellar Vesicles (GUVs). Finally, we provide simple protocols for the preparation of GUVs, calibration of the microscope setup, and acquisition and analysis of SFCS data to determine diffusion coefficients and concentrations of fluorescent particles embedded in lipid membranes.
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Affiliation(s)
- Eduard Hermann
- Max Planck Institute for Intelligent Systems, Heisenbergstr 3, 70569, Stuttgart, Germany,
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32
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Sharma S, Zaveri A, Visweswariah SS, Krishnan Y. A fluorescent nucleic acid nanodevice quantitatively images elevated cyclic adenosine monophosphate in membrane-bound compartments. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:4276-80. [PMID: 25044725 DOI: 10.1002/smll.201400833] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 06/03/2014] [Indexed: 05/09/2023]
Abstract
cAMPhor: In the presence of cAMP, cAMPhor folds into a structure that binds DFHBI (green), increasing its fluorescence, while Alexa 647 (red) functions as a normalizing dye. It can thus be used to spatially image cAMP quantitatively in membrane-bound compartments.
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Affiliation(s)
- Suruchi Sharma
- Department Biophysics and Biochemistry, National Centre for Biological Sciences, UAS-GKVK, Bellary Road, Bangalore-, 560065, India
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33
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Horger KS, Liu H, Rao DK, Shukla S, Sept D, Ambudkar SV, Mayer M. Hydrogel-assisted functional reconstitution of human P-glycoprotein (ABCB1) in giant liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:643-53. [PMID: 25450342 DOI: 10.1016/j.bbamem.2014.10.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 09/17/2014] [Accepted: 10/20/2014] [Indexed: 11/24/2022]
Abstract
This paper describes the formation of giant proteoliposomes containing P-glycoprotein (P-gp) from a solution of small proteoliposomes that had been deposited and partially dried on a film of agarose. This preparation method generated a significant fraction of giant proteoliposomes that were free of internalized vesicles, making it possible to determine the accessible liposome volume. Measuring the intensity of the fluorescent substrate rhodamine 123 (Rho123) inside and outside these giant proteoliposomes determined the concentration of transported substrates of P-gp. Fitting a kinetic model to the fluorescence data revealed the rate of passive diffusion as well as active transport by reconstituted P-gp in the membrane. This approach determined estimates for the membrane permeability coefficient (Ps) of passive diffusion and rate constants of active transport (kT) by P-gp as a result of different experimental conditions. The Ps value for Rho123 was larger in membranes containing P-gp under all assay conditions than in membranes without P-gp indicating increased leakiness in the presence of reconstituted transmembrane proteins. For P-gp liposomes, the kT value was significantly higher in the presence of ATP than in its absence or in the presence of ATP and the competitive inhibitor verapamil. This difference in kT values verified that P-gp was functionally active after reconstitution and quantified the rate of active transport. Lastly, patch clamp experiments on giant proteoliposomes showed ion channel activity consistent with a chloride ion channel protein that co-purified with P-gp. Together, these results demonstrate several advantages of using giant rather than small proteoliposomes to characterize transport properties of transport proteins and ion channels.
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Affiliation(s)
- Kim S Horger
- Department of Chemical Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109, USA
| | - Haiyan Liu
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA
| | - Divya K Rao
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20814, USA
| | - David Sept
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA; Center for Computational Medicine and Bioinformatics, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20814, USA
| | - Michael Mayer
- Department of Chemical Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA.
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34
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Bassereau P, Sorre B, Lévy A. Bending lipid membranes: experiments after W. Helfrich's model. Adv Colloid Interface Sci 2014; 208:47-57. [PMID: 24630341 DOI: 10.1016/j.cis.2014.02.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/02/2014] [Accepted: 02/03/2014] [Indexed: 10/25/2022]
Abstract
Current description of biomembrane mechanics originates for a large part from W. Helfrich's model. Based on his continuum theory, many experiments have been performed in the past four decades on simplified membranes in order to characterize the mechanical properties of lipid membranes and the contribution of polymers or proteins. The long-term goal was to develop a better understanding of the mechanical properties of cell membranes. In this paper, we will review representative experimental approaches that were developed during this period and the main results that were obtained.
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35
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Kusters I, van Oijen AM, Driessen AJM. Membrane-on-a-chip: microstructured silicon/silicon-dioxide chips for high-throughput screening of membrane transport and viral membrane fusion. ACS NANO 2014; 8:3380-92. [PMID: 24601516 DOI: 10.1021/nn405884a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Screening of transport processes across biological membranes is hindered by the challenge to establish fragile supported lipid bilayers and the difficulty to determine at which side of the membrane reactants reside. Here, we present a method for the generation of suspended lipid bilayers with physiological relevant lipid compositions on microstructured Si/SiO2 chips that allow for high-throughput screening of both membrane transport and viral membrane fusion. Simultaneous observation of hundreds of single-membrane channels yields statistical information revealing population heterogeneities of the pore assembly and conductance of the bacterial toxin α-hemolysin (αHL). The influence of lipid composition and ionic strength on αHL pore formation was investigated at the single-channel level, resolving features of the pore-assembly pathway. Pore formation is inhibited by a specific antibody, demonstrating the applicability of the platform for drug screening of bacterial toxins and cell-penetrating agents. Furthermore, fusion of H3N2 influenza viruses with suspended lipid bilayers can be observed directly using a specialized chip architecture. The presented micropore arrays are compatible with fluorescence readout from below using an air objective, thus allowing high-throughput screening of membrane transport in multiwell formats in analogy to plate readers.
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Affiliation(s)
- Ilja Kusters
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 7, Groningen, The Netherlands
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36
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Protein-mediated transformation of lipid vesicles into tubular networks. Biophys J 2014; 105:711-9. [PMID: 23931319 DOI: 10.1016/j.bpj.2013.06.039] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 06/16/2013] [Accepted: 06/28/2013] [Indexed: 11/22/2022] Open
Abstract
Key cellular processes are frequently accompanied by protein-facilitated shape changes in the plasma membrane. N-BAR-domain protein modules generate curvature by means of complex interactions with the membrane surface. The way they assemble and the mechanism by which they operate are largely dependent on their binding density. Although the mechanism at lower densities has recently begun to emerge, how membrane scaffolds form at high densities remains unclear. By combining electron microscopy and multiscale simulations, we show that N-BAR proteins at high densities can transform a lipid vesicle into a 3D tubular network. We show that this process is a consequence of excess adhesive energy combined with the local stiffening of the membrane, which occurs in a narrow range of mechanical properties of both the membrane and the protein. We show that lipid diffusion is significantly reduced by protein binding at this density regime and even more in areas of high Gaussian curvature, indicating a potential effect on molecular transport in cells. Finally, we reveal that the breaking of the bilayer topology is accompanied by the nematic arrangement of the protein on the surface, a structural motif that likely drives the formation of reticular structures in living cells.
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37
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Fenz SF, Sachse R, Schmidt T, Kubick S. Cell-free synthesis of membrane proteins: tailored cell models out of microsomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1382-8. [PMID: 24370776 DOI: 10.1016/j.bbamem.2013.12.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/27/2013] [Accepted: 12/16/2013] [Indexed: 10/25/2022]
Abstract
Incorporation of proteins in biomimetic giant unilamellar vesicles (GUVs) is one of the hallmarks towards cell models in which we strive to obtain a better mechanistic understanding of the manifold cellular processes. The reconstruction of transmembrane proteins, like receptors or channels, into GUVs is a special challenge. This procedure is essential to make these proteins accessible to further functional investigation. Here we describe a strategy combining two approaches: cell-free eukaryotic protein expression for protein integration and GUV formation to prepare biomimetic cell models. The cell-free protein expression system in this study is based on insect lysates, which provide endoplasmic reticulum derived vesicles named microsomes. It enables signal-induced translocation and posttranslational modification of de novo synthesized membrane proteins. Combining these microsomes with synthetic lipids within the electroswelling process allowed for the rapid generation of giant proteo-liposomes of up to 50 μm in diameter. We incorporated various fluorescent protein-labeled membrane proteins into GUVs (the prenylated membrane anchor CAAX, the heparin-binding epithelial growth factor like factor Hb-EGF, the endothelin receptor ETB, the chemokine receptor CXCR4) and thus presented insect microsomes as functional modules for proteo-GUV formation. Single-molecule fluorescence microscopy was applied to detect and further characterize the proteins in the GUV membrane. To extend the options in the tailoring cell models toolbox, we synthesized two different membrane proteins sequentially in the same microsome. Additionally, we introduced biotinylated lipids to specifically immobilize proteo-GUVs on streptavidin-coated surfaces. We envision this achievement as an important first step toward systematic protein studies on technical surfaces.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands
| | - Rita Sachse
- Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany
| | - Thomas Schmidt
- Leiden Institute of Physics, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands
| | - Stefan Kubick
- Fraunhofer IBMT, Branch Potsdam-Golm, Group of Cell-free Protein Synthesis, Am Mühlenberg 13, 14476 Potsdam, Germany.
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38
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Hansen JS, Thompson JR, Hélix-Nielsen C, Malmstadt N. Lipid directed intrinsic membrane protein segregation. J Am Chem Soc 2013; 135:17294-7. [PMID: 24180248 DOI: 10.1021/ja409708e] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We demonstrate a new approach for direct reconstitution of membrane proteins during giant vesicle formation. We show that it is straightforward to create a tissue-like giant vesicle film swelled with membrane protein using aquaporin SoPIP2;1 as an illustration. These vesicles can also be easily harvested for individual study. By controlling the lipid composition we are able to direct the aquaporin into specific immiscible liquid domains in giant vesicles. The oligomeric α-helical protein cosegregates with the cholesterol-poor domains in phase separating ternary mixtures.
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Affiliation(s)
- Jesper S Hansen
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California , 925 Bloom Walk, Los Angeles, California 90089, United States
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39
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Liu YJ, Hansen GPR, Venancio-Marques A, Baigl D. Cell-free preparation of functional and triggerable giant proteoliposomes. Chembiochem 2013; 14:2243-7. [PMID: 24115581 DOI: 10.1002/cbic.201300501] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Indexed: 01/15/2023]
Abstract
Heat, we leak: We express a membrane protein outside well-defined giant liposomes obtained by gravity-transferred sucrose-in-oil droplets into a cell-free, reconstituted expression system. We show that the presence of the liposome is necessary during expression for efficient protein insertion into the membrane and that temperature can trigger the resulting membrane function.
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Affiliation(s)
- Yan-Jun Liu
- Department of Chemistry, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France) http://www.baigllab.com/; Université Pierre et Marie Curie Paris 6, 4 place Jussieu, 75005 Paris (France); UMR 8640, CNRS, 3 rue Michel-Ange, 75016 Paris (France)
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40
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Miyoshi H, Tsubota KI, Hoyano T, Adachi T, Liu H. Three-dimensional modulation of cortical plasticity during pseudopodial protrusion of mouse leukocytes. Biochem Biophys Res Commun 2013; 438:594-9. [PMID: 23939049 DOI: 10.1016/j.bbrc.2013.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 08/03/2013] [Indexed: 01/25/2023]
Abstract
Leukocytes can rapidly migrate virtually within any substrate found in the body at speeds up to 100 times faster than mesenchymal cells that remain firmly attached to a substrate even when migrating. To understand the flexible migration strategy utilized by leukocytes, we experimentally investigated the three-dimensional modulation of cortical plasticity during the formation of pseudopodial protrusions by mouse leukocytes isolated from blood. The surfaces of viable leukocytes were discretely labeled with fluorescent beads that were covalently conjugated with concanavalin A receptors. The movements of these fluorescent beads were different at the rear, central, and front surfaces. The beads initially present on the rear and central dorsal surfaces of the cell body flowed linearly toward the rear peripheral surface concomitant with a significant collapse of the cell body in the dorsal-ventral direction. In contrast, those beads initially on the front surface moved into a newly formed pseudopodium and exhibited rapid, random movements within this pseudopodium. Bead movements at the front surface were hypothesized to have resulted from rupture of the actin cytoskeleton and detachment of the plasma membrane from the actin cytoskeletal cortex, which allowed leukocytes to migrate while being minimally constrained by a substrate.
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Affiliation(s)
- Hiromi Miyoshi
- Ultrahigh Precision Optics Technology Team, RIKEN Center for Advanced Photonics, Saitama, Japan
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41
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Lateral diffusion of lipids separated from rotational and translational diffusion of a fluid large unilamellar vesicle. Colloids Surf B Biointerfaces 2013; 106:22-7. [PMID: 23434687 DOI: 10.1016/j.colsurfb.2013.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 01/09/2013] [Accepted: 01/09/2013] [Indexed: 11/20/2022]
Abstract
A new method to separate lateral diffusion of lipids in spherical large unilamellar vesicles from the rotational and the translational diffusion of the vesicle as a whole is proposed. The lateral diffusion coefficient DL is obtained as a time-dependent part of the observed diffusion coefficient in vesicles of 800-nm diameters, by systematically changing the diffusion time interval of the high-field-gradient NMR measurement. Although the lipid is in a confined space, the DL of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is (1.5±0.6)×10(-11) m(2) s(-1) in the fluid state at 45°C, more than one order of magnitude faster than the rotational and the translational diffusion coefficients of the vesicle by the hydrodynamic continuum model. The method provides a potential for quantifying the lateral diffusion of lipids and proteins in fluid bilayer vesicles as model cell membranes in a natural manner.
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42
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43
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Korman CE, Megens M, Ajo-Franklin CM, Horsley DA. Nanopore-spanning lipid bilayers on silicon nitride membranes that seal and selectively transport ions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:4421-4425. [PMID: 23528109 DOI: 10.1021/la305064j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report the formation of POPC lipid bilayers that span 130 nm pores in a freestanding silicon nitride film supported on a silicon substrate. These solvent-free lipid membranes self-assemble on organosilane-treated Si3N4 via the fusion of 200 nm unilamellar vesicles. Membrane fluidity is verified by fluorescence recovery after photobleaching (FRAP), and membrane resistance in excess of 1 GΩ is demonstrated using electrical impedance spectroscopy (EIS). An array of 40,000 membranes maintained high impedance over 72 h, followed by rupture of most of the membranes by 82 h. Membrane incorporation of gramicidin, a model ion channel, resulted in increased membrane conductance. This membrane conductance was diminished when the gramicidin channels were blocked with CaCl2, indicating that the change in membrane conductance results from gramicidin-mediated ion transport. These very stable, biologically functional pore-spanning membranes open many possibilities for silicon-based ion-channel devices for applications such as biosensors and high-throughput drug screening.
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Affiliation(s)
- Christopher E Korman
- Department of Mechanical and Aerospace Engineering, University of California, Davis, California 95616, USA
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44
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Abstract
Liposome structures have a wide range of applications in biology, biochemistry, and biophysics. As a result, several methods for forming liposomes have been developed. This review provides a critical comparison of existing microfluidic technologies for forming liposomes and, when applicable, a comparison with their analogous macroscale counterparts. The properties of the generated liposomes, including size, size distribution, lamellarity, membrane composition, and encapsulation efficiency, form the basis for comparison. We hope that this critique will allow the reader to make an informed decision as to which method should be used for a given biological application.
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Affiliation(s)
- Dirk van Swaay
- Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland
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45
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Unsay JD, García-Sáez AJ. Scanning fluorescence correlation spectroscopy in model membrane systems. Methods Mol Biol 2013; 1033:185-205. [PMID: 23996179 DOI: 10.1007/978-1-62703-487-6_13] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) is an emerging technique employed in biophysical studies that exploits the temporal autocorrelation of fluorescence intensity fluctuations measured in a tiny volume (in the order of fL). The autocorrelation curve derived from the fluctuations can then be fitted with diffusion models to obtain parameters such as diffusion time and number of particles in the diffusion volume/area. Application of FCS to membranes allows studying membrane component dynamics, which includes mobility and interactions between the components. However, FCS encounters several difficulties like accurate positioning and stability of the setup when applied to membranes. Here, we describe the theoretical basis of point FCS as well as the scanning FCS (SFCS) approach, which is a practical way to address the challenges of FCS with membranes. We also list materials necessary for FCS experiments on two model membrane systems: (1) supported lipid bilayers and (2) giant unilamellar vesicles. Finally, we present simple protocols for the preparation of these model membrane systems, calibration of the microscope setup for FCS, and acquisition and analysis of point FCS and SFCS data so that diffusion coefficients and concentrations of fluorescent probes within lipid membranes can be calculated.
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46
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Betaneli V, Schwille P. Fluorescence correlation spectroscopy to examine protein-lipid interactions in membranes. Methods Mol Biol 2013; 974:253-278. [PMID: 23404280 DOI: 10.1007/978-1-62703-275-9_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) is a versatile technique to study membrane dynamics and protein-lipid interactions. It can provide information about diffusion coefficients, concentrations, and molecular interactions of proteins and lipids in the membrane. These parameters allow the determination of protein partitioning into different lipid environments, the identification of lipid domains, and the detection of lipid-protein complexes on the membrane. During the last decade, FCS studies were successfully performed on model membrane systems as also on living cells, to characterize protein-lipid interactions. Recent developments of the method described here improved quantitative measurements on membranes and decreased the number of potential artifacts. The aim of this chapter is to provide the reader with the necessary information and some practical guidelines to perform FCS studies on artificial and cellular membranes.
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Affiliation(s)
- Viktoria Betaneli
- Biophysics, BIOTEC, Technische Universitat Dresden, Dresden, Germany
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47
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Cell-Free Systems: Functional Modules for Synthetic and Chemical Biology. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2013; 137:67-102. [DOI: 10.1007/10_2013_185] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
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48
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NMR methods for measuring lateral diffusion in membranes. Chem Phys Lipids 2013; 166:31-44. [DOI: 10.1016/j.chemphyslip.2012.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/11/2012] [Accepted: 12/12/2012] [Indexed: 02/07/2023]
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49
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Bartsch P, Walter C, Selenschik P, Honigmann A, Wagner R. Horizontal Bilayer for Electrical and Optical Recordings. MATERIALS 2012. [PMCID: PMC5449052 DOI: 10.3390/ma5122705] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Philipp Bartsch
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Ionovation GmbH, Westerbreite 7, Osnabrueck 49084, Germany
| | - Claudius Walter
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Ionovation GmbH, Westerbreite 7, Osnabrueck 49084, Germany
| | - Philipp Selenschik
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
| | - Alf Honigmann
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
| | - Richard Wagner
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-541-969-2398; Fax: +49-541-969-2243
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50
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Sezgin E, Schwille P. Model membrane platforms to study protein-membrane interactions. Mol Membr Biol 2012; 29:144-54. [DOI: 10.3109/09687688.2012.700490] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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