1
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Socrier L, Steinem C. Pore-spanning membranes as a tool to investigate lateral lipid membrane heterogeneity. Methods Enzymol 2024; 700:455-483. [PMID: 38971610 DOI: 10.1016/bs.mie.2024.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2024]
Abstract
Over the years, it has become more and more obvious that lipid membranes show a very complex behavior. This behavior arises in part from the large number of different kinds of lipids and proteins and how they dynamically interact with each other. In vitro studies using artificial membrane systems have shed light on the heterogeneity based on lipid-lipid interactions in multicomponent bilayer mixtures. Inspired by the raft hypothesis, the coexistence of liquid-disordered (ld) and liquid-ordered (lo) phases has drawn much attention. It was shown that ternary lipid mixtures containing low- and high-melting temperature lipids and cholesterol can phase separate into a lo phase enriched in the high-melting lipids and cholesterol and a ld phase enriched in the low-melting lipids. Depending on the model membrane system under investigation, different domain sizes, shapes, and mobilities have been found. Here, we describe how to generate phase-separated lo/ld phases in model membrane systems termed pore-spanning membranes (PSMs). These PSMs are prepared on porous silicon substrates with pore sizes in the micrometer regime. A proper functionalization of the top surface of the substrates is required to achieve the spreading of giant unilamellar vesicles (GUVs) to obtain PSMs. Starting with lo/ld phase-separated GUVs lead to membrane heterogeneities in the PSMs. Depending on the functionalization strategy of the top surface of the silicon substrate, different membrane heterogeneities are observed in the PSMs employing fluorescence microscopy. A quantitative analysis of the heterogeneity as well as the dynamics of the lipid domains is described.
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Affiliation(s)
- Larissa Socrier
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Claudia Steinem
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany; Institute of Organic and Biomolecular Chemistry, Georg-August Universität, Göttingen, Germany.
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2
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Baek JM, Jung WH, Yu ES, Ahn DJ, Ryu YS. In Vitro Membrane Platform for the Visualization of Water Impermeability across the Liquid-Ordered Phase under Hypertonic Conditions. J Am Chem Soc 2022; 144:21887-21896. [PMID: 36367984 DOI: 10.1021/jacs.2c06626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Passive water penetration across the cell membrane by osmotic diffusion is essential for the homeostasis of cell volume, in addition to the protein-assisted active transportation of water. Since membrane components can regulate water permeability, controlling compositional variation during the volume regulatory process is a prerequisite for investigating the underlying mechanisms of water permeation and related membrane dynamics. However, the lack of a viable in vitro membrane platform in hypertonic solutions impedes advanced knowledge of cell volume regulation processes, especially cholesterol-enriched lipid domains called lipid rafts. By reconstituting the liquid-ordered (Lo) domain as a likeness of lipid rafts, we verified suppressed water permeation across the Lo domains, which had yet to be confirmed with experimental demonstrations despite a simulation approach. With the help of direct transfer of the Lo domains from vesicles to supported lipid membranes, the biological roles of lipid composition in suppressed water translocation were experimentally confirmed. Additionally, the improvement in membrane stability under hypertonic conditions was demonstrated based on molecular dynamics simulations.
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Affiliation(s)
- Ji Min Baek
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea.,Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Woo Hyuk Jung
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Eui-Sang Yu
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Dong June Ahn
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.,KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Yong-Sang Ryu
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea.,KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
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3
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Sannigrahi A, Rai VH, Chalil MV, Chakraborty D, Meher SK, Roy R. A Versatile Suspended Lipid Membrane System for Probing Membrane Remodeling and Disruption. MEMBRANES 2022; 12:1190. [PMID: 36557095 PMCID: PMC9784602 DOI: 10.3390/membranes12121190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/12/2022] [Accepted: 10/18/2022] [Indexed: 06/17/2023]
Abstract
Artificial membrane systems can serve as models to investigate molecular mechanisms of different cellular processes, including transport, pore formation, and viral fusion. However, the current, such as SUVs, GUVs, and the supported lipid bilayers suffer from issues, namely high curvature, heterogeneity, and surface artefacts, respectively. Freestanding membranes provide a facile solution to these issues, but current systems developed by various groups use silicon or aluminum oxide wafers for fabrication that involves access to a dedicated nanolithography facility and high cost while conferring poor membrane stability. Here, we report the development, characterization and applications of an easy-to-fabricate suspended lipid bilayer (SULB) membrane platform leveraging commercial track-etched porous filters (PCTE) with defined microwell size. Our SULB system offers a platform to study the lipid composition-dependent structural and functional properties of membranes with exceptional stability. With dye entrapped in PCTE microwells by SULB, we show that sphingomyelin significantly augments the activity of pore-forming toxin, Cytolysin A (ClyA) and the pore formation induces lipid exchange between the bilayer leaflets. Further, we demonstrate high efficiency and rapid kinetics of membrane fusion by dengue virus in our SULB platform. Our suspended bilayer membrane mimetic offers a novel platform to investigate a large class of biomembrane interactions and processes.
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4
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Zhou T, Wu Z, Das S, Eslami H, Müller-Plathe F. How Ethanolic Disinfectants Disintegrate Coronavirus Model Membranes: A Dissipative Particle Dynamics Simulation Study. J Chem Theory Comput 2022; 18:2597-2615. [PMID: 35286098 PMCID: PMC8938819 DOI: 10.1021/acs.jctc.1c01120] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Indexed: 01/03/2023]
Abstract
We have developed dissipative particle dynamics models for pure dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), and dimyristoylphosphatidylcholine (DMPC) as well as their binary and ternary mixed membranes, as coronavirus model membranes. The stabilities of pure and mixed membranes, surrounded by aqueous solutions containing up to 70 mol % ethanol (alcoholic disinfectants), have been investigated at room temperature. We found that aqueous solutions containing 5-10 mol % ethanol already have a significant weakening effect on the pure and mixed membranes. The magnitude of the effect depends on the membrane composition and the ethanol concentration. Ethanol permeabilizes the membrane, causing its lateral swelling and thickness shrinking and reducing the orientational order of the hydrocarbon tail of the bilayer. The free energy barrier for the permeation of ethanol in the bilayers is considerably reduced by the ethanol uptake. The rupture-critical ethanol concentrations causing the membrane failure are 20.7, 27.5, and 31.7 mol % in the aqueous phase surrounding pure DMPC, DOPC, and DPPC membranes, respectively. Characterizing the failure of lipid membranes by a machine-learning neural network framework, we found that all mixed binary and/or ternary membranes disrupt when immersed in an aqueous solution containing a rupture-critical ethanol concentration, ranging from 20.7 to 31.7 mol %, depending on the composition of the membrane; the DPPC-rich membranes are more intact, while the DMPC-rich membranes are least intact. Due to the tight packing of long, saturated hydrocarbon tails in DPPC, increasing the DPPC content of the mixed membrane increases its stability against the disinfectant. At high DPPC concentrations, where the DOPC and DMPC molecules are confined between the DPPC lipids, the ordered hydrocarbon tails of DPPC also induce order in the DOPC and DMPC molecules and, hence, stabilize the membrane more. Our simulations on pure and mixed membranes of a diversity of compositions reveal that a maximum ethanol concentration of 32 mol % (55 wt %) in the alcohol-based disinfectants is enough to disintegrate any membrane composed of these three lipids.
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Affiliation(s)
- Tianhang Zhou
- Eduard-Zintl-Institut für Anorganische und
Physikalische Chemie, Technische Universität Darmstadt,
Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Zhenghao Wu
- Eduard-Zintl-Institut für Anorganische und
Physikalische Chemie, Technische Universität Darmstadt,
Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Shubhadip Das
- Eduard-Zintl-Institut für Anorganische und
Physikalische Chemie, Technische Universität Darmstadt,
Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Hossein Eslami
- Eduard-Zintl-Institut für Anorganische und
Physikalische Chemie, Technische Universität Darmstadt,
Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
- College of Sciences, Persian Gulf
University, Boushehr 75168, Iran
| | - Florian Müller-Plathe
- Eduard-Zintl-Institut für Anorganische und
Physikalische Chemie, Technische Universität Darmstadt,
Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
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5
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Carey AB, Ashenden A, Köper I. Model architectures for bacterial membranes. Biophys Rev 2022; 14:111-143. [PMID: 35340604 PMCID: PMC8921416 DOI: 10.1007/s12551-021-00913-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/14/2021] [Indexed: 02/06/2023] Open
Abstract
The complex composition of bacterial membranes has a significant impact on the understanding of pathogen function and their development towards antibiotic resistance. In addition to the inherent complexity and biosafety risks of studying biological pathogen membranes, the continual rise of antibiotic resistance and its significant economical and clinical consequences has motivated the development of numerous in vitro model membrane systems with tuneable compositions, geometries, and sizes. Approaches discussed in this review include liposomes, solid-supported bilayers, and computational simulations which have been used to explore various processes including drug-membrane interactions, lipid-protein interactions, host-pathogen interactions, and structure-induced bacterial pathogenesis. The advantages, limitations, and applicable analytical tools of all architectures are summarised with a perspective for future research efforts in architectural improvement and elucidation of resistance development strategies and membrane-targeting antibiotic mechanisms. Supplementary Information The online version contains supplementary material available at 10.1007/s12551-021-00913-7.
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Affiliation(s)
- Ashley B. Carey
- Institute for Nanoscale Science and Technology, College for Science and Engineering, Flinders University, Adelaide, SA 5042 Australia
| | - Alex Ashenden
- Institute for Nanoscale Science and Technology, College for Science and Engineering, Flinders University, Adelaide, SA 5042 Australia
| | - Ingo Köper
- Institute for Nanoscale Science and Technology, College for Science and Engineering, Flinders University, Adelaide, SA 5042 Australia
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6
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Viscoelastic properties of epithelial cells. Biochem Soc Trans 2021; 49:2687-2695. [PMID: 34854895 DOI: 10.1042/bst20210476] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/16/2021] [Accepted: 10/08/2021] [Indexed: 11/17/2022]
Abstract
Epithelial cells form tight barriers that line both the outer and inner surfaces of organs and cavities and therefore face diverse environmental challenges. The response to these challenges relies on the cells' dynamic viscoelastic properties, playing a pivotal role in many biological processes such as adhesion, growth, differentiation, and motility. Therefore, the cells usually adapt their viscoelastic properties to mirror the environment that determines their fate and vitality. Albeit not a high-throughput method, atomic force microscopy is still among the dominating methods to study the mechanical properties of adherent cells since it offers a broad range of forces from Piconewtons to Micronewtons at biologically significant time scales. Here, some recent work of deformation studies on epithelial cells is reviewed with a focus on viscoelastic models suitable to describe force cycle measurements congruent with the architecture of the actin cytoskeleton. The prominent role of the cortex in the cell's response to external forces is discussed also in the context of isolated cortex extracts on porous surfaces.
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7
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Labbé E, Buriez O. Electrode‐supported and free‐standing bilayer lipid membranes: Formation and uses in molecular electrochemistry. ELECTROCHEMICAL SCIENCE ADVANCES 2021. [DOI: 10.1002/elsa.202100170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Eric Labbé
- PASTEUR Département de Chimie Ecole Normale Supérieure PSL University Sorbonne Université CNRS Paris 75005 France
| | - Olivier Buriez
- PASTEUR Département de Chimie Ecole Normale Supérieure PSL University Sorbonne Université CNRS Paris 75005 France
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8
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Janshoff A. Viscoelasticity of basal plasma membranes and cortices derived from MDCK II cells. BIOPHYSICAL REPORTS 2021; 1:100024. [PMID: 36425463 PMCID: PMC9680774 DOI: 10.1016/j.bpr.2021.100024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 09/08/2021] [Indexed: 06/16/2023]
Abstract
The mechanical properties of cells are largely determined by the architecture and dynamics of their viscoelastic cortex, which consists of a contractile, cross-linked actin mesh attached to the plasma membrane via linker proteins. Measuring the mechanical properties of adherent, polarized epithelial cells is usually limited to the upper, i.e., apical side, of the cells because of their accessibility on culture dishes. Therefore, less is known about the viscoelastic properties of basal membranes. Here, I investigate the viscoelastic properties of basolateral membranes derived from polarized MDCK II epithelia in response to external deformation and compare them to living cells probed at the apical side. MDCK II cells were grown on porous surfaces to confluence, and the upper cell body was removed via a squirting-lysis protocol. The free-standing, defoliated basal membranes were subject to force indentation and relaxation experiments permitting a precise assessment of cortical viscoelasticity. A new theoretical framework to describe the force cycles is developed and applied to obtain the time-dependent area compressibility modulus of cell cortices from adherent cells. Compared with the viscoelastic response of living cells, the basolateral membranes are substantially less fluid and stiffer but obey to the same universal scaling law if excess area is taken correctly into account.
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Affiliation(s)
- Andreas Janshoff
- Department of Chemistry, Institute of Physical Chemistry, Göttingen
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9
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Ansardamavandi A, Tafazzoli-Shadpour M. The functional cross talk between cancer cells and cancer associated fibroblasts from a cancer mechanics perspective. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119103. [PMID: 34293346 DOI: 10.1016/j.bbamcr.2021.119103] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/13/2021] [Accepted: 07/18/2021] [Indexed: 12/12/2022]
Abstract
The function of biological tissues in health and disease is regulated at cellular level and is highly influenced by the physical microenvironment, through the interaction of forces between cells and ECM, which are perceived through mechanosensing pathways. In cancer, both chemical and physical signaling cascades and their interactions are involved during cell-cell and cell-ECM communications to meet requirements of tumor growth. Among stroma cells, cancer associated fibroblasts (CAFs) play key role in tumor growth and pave the way for cancer cells to initiate metastasis and invasion to other tissues, and without recruitment of CAFs, the process of cancer invasion is dysfunctional. This is through an intense chemical and physical cross talks with tumor cells, and interactive remodeling of ECM. During such interaction CAFs apply traction forces and depending on the mechanical properties, deform ECM and in return receive physical signals from the micromechanical environment. Such interaction leads to ECM remodeling by manipulating ECM structure and its mechanical properties. The results are in form of deposition of extra fibers, stiffening, rearrangement and reorganization of fibrous structure, and degradation which are due to a complex secretion and expression of different markers triggered by mechanosensing of tumor cells, specially CAFs. Such events define cancer progress and invasion of cancer cells. A systemic knowledge of chemical and physical factors provides a holistic view of how cancer process and enhances the current treatment methods to provide more diversity among targets that involves tumor cells and ECM structure.
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Affiliation(s)
- Arian Ansardamavandi
- Faculty of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran
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10
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Ramalakshmi S, Ramanan RN, Madhavan S, Ooi CW, Chang CCH, Harper IS, Lewis DM, Lee AK, He L, Seenichamy A. Investigation of selective release of periplasmic proteins through pore size analysis and single-cell microscopy in Escherichia coli. Biochem Eng J 2021. [DOI: 10.1016/j.bej.2021.108009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Hossein A, Deserno M. Stiffening transition in asymmetric lipid bilayers: The role of highly ordered domains and the effect of temperature and size. J Chem Phys 2021; 154:014704. [PMID: 33412863 DOI: 10.1063/5.0028255] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cellular membranes consist of a large variety of lipids and proteins, with a composition that generally differs between the two leaflets of the same bilayer. One consequence of this asymmetry is thought to be the emergence of differential stress, i.e., a mismatch in the lateral tension of the two leaflets. This can affect a membrane's mechanical properties; for instance, it can increase the bending rigidity once the differential stress exceeds a critical threshold. Using coarse-grained molecular dynamics simulations based on the MARTINI model, we show that this effect arises due to the formation of more highly ordered domains in the compressed leaflet. The threshold asymmetry increases with temperature, indicating that the transition to a stiffened regime might be restricted to a limited temperature range above the gel transition. We also show that stiffening occurs more readily for larger membranes with smaller typical curvatures, suggesting that the stiffening transition is easier to observe experimentally than in the small-scale systems accessible to simulation.
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Affiliation(s)
- Amirali Hossein
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
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12
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Wang W, Arias DS, Deserno M, Ren X, Taylor RE. Emerging applications at the interface of DNA nanotechnology and cellular membranes: Perspectives from biology, engineering, and physics. APL Bioeng 2020; 4:041507. [PMID: 33344875 PMCID: PMC7725538 DOI: 10.1063/5.0027022] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/17/2020] [Indexed: 12/17/2022] Open
Abstract
DNA nanotechnology has proven exceptionally apt at probing and manipulating biological environments as it can create nanostructures of almost arbitrary shape that permit countless types of modifications, all while being inherently biocompatible. Emergent areas of particular interest are applications involving cellular membranes, but to fully explore the range of possibilities requires interdisciplinary knowledge of DNA nanotechnology, cell and membrane biology, and biophysics. In this review, we aim for a concise introduction to the intersection of these three fields. After briefly revisiting DNA nanotechnology, as well as the biological and mechanical properties of lipid bilayers and cellular membranes, we summarize strategies to mediate interactions between membranes and DNA nanostructures, with a focus on programmed delivery onto, into, and through lipid membranes. We also highlight emerging applications, including membrane sculpting, multicell self-assembly, spatial arrangement and organization of ligands and proteins, biomechanical sensing, synthetic DNA nanopores, biological imaging, and biomelecular sensing. Many critical but exciting challenges lie ahead, and we outline what strikes us as promising directions when translating DNA nanostructures for future in vitro and in vivo membrane applications.
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Affiliation(s)
- Weitao Wang
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - D. Sebastian Arias
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Xi Ren
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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13
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Miller EJ, Ratajczak AM, Anthony AA, Mottau M, Rivera Gonzalez XI, Honerkamp-Smith AR. Divide and conquer: How phase separation contributes to lateral transport and organization of membrane proteins and lipids. Chem Phys Lipids 2020; 233:104985. [DOI: 10.1016/j.chemphyslip.2020.104985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 09/18/2020] [Accepted: 09/28/2020] [Indexed: 01/06/2023]
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14
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Desmosome architecture derived from molecular dynamics simulations and cryo-electron tomography. Proc Natl Acad Sci U S A 2020; 117:27132-27140. [PMID: 33067392 PMCID: PMC7959525 DOI: 10.1073/pnas.2004563117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The desmosome is a major cell–cell junction connecting cells in tissues under high mechanical load. Currently, while structures of the constituent cadherins are known, the desmosome architecture has remained elusive. The primary reason is the high plasticity of the cadherins. As many other cellular structures, their high flexibility cannot be easily addressed by conventional structural techniques that rely on averaging many identical structures. For this, we combine high-end cryo-electron tomography with large-scale molecular dynamics simulations to produce a molecular model of the desmosome that integrates new with decades-old observations, accounts for the remarkable biophysical properties, and maps the intermolecular interactions. Desmosomes are cell–cell junctions that link tissue cells experiencing intense mechanical stress. Although the structure of the desmosomal cadherins is known, the desmosome architecture—which is essential for mediating numerous functions—remains elusive. Here, we recorded cryo-electron tomograms (cryo-ET) in which individual cadherins can be discerned; they appear variable in shape, spacing, and tilt with respect to the membrane. The resulting sub-tomogram average reaches a resolution of ∼26 Å, limited by the inherent flexibility of desmosomes. To address this challenge typical of dynamic biological assemblies, we combine sub-tomogram averaging with atomistic molecular dynamics (MD) simulations. We generate models of possible cadherin arrangements and perform an in silico screening according to biophysical and structural properties extracted from MD simulation trajectories. We find a truss-like arrangement of cadherins that resembles the characteristic footprint seen in the electron micrograph. The resulting model of the desmosomal architecture explains their unique biophysical properties and strength.
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15
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Hubrich H, Mey IP, Brückner BR, Mühlenbrock P, Nehls S, Grabenhorst L, Oswald T, Steinem C, Janshoff A. Viscoelasticity of Native and Artificial Actin Cortices Assessed by Nanoindentation Experiments. NANO LETTERS 2020; 20:6329-6335. [PMID: 32786944 DOI: 10.1021/acs.nanolett.0c01769] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cell cortices are responsible for the resilience and morphological dynamics of cells. Measuring their mechanical properties is impeded by contributions from other filament types, organelles, and the crowded cytoplasm. We established a versatile concept for the precise assessment of cortical viscoelasticity based on force cycle experiments paired with continuum mechanics. Apical cell membranes of confluent MDCK II cells were deposited on porous substrates and locally deformed. Force cycles could be described with a time-dependent area compressibility modulus obeying the same power law as employed for whole cells. The reduced fluidity of apical cell membranes compared to living cells could partially be restored by reactivating myosin motors. A comparison with artificial minimal actin cortices (MACs) reveals lower stiffness and higher fluidity attributed to missing cross-links in MACs.
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Affiliation(s)
- Hanna Hubrich
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Ingo P Mey
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Bastian R Brückner
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Peter Mühlenbrock
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Stefan Nehls
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Lennart Grabenhorst
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
| | - Tabea Oswald
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Claudia Steinem
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Göttingen 37077, Germany
| | - Andreas Janshoff
- Department of Chemistry, Institute of Physical Chemistry, Göttingen 37077, Germany
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16
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Sun Y, Zang X, Sun Y, Wang L, Gao Z. Lipid membranes supported by planar porous substrates. Chem Phys Lipids 2020; 228:104893. [PMID: 32097619 DOI: 10.1016/j.chemphyslip.2020.104893] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 02/10/2020] [Indexed: 12/18/2022]
Abstract
Biological membranes play key roles in cell life, but their intrinsic complexity motivated the study and development of artificial lipid membranes with the primary aim to reconstitute and understand the natural functions in vitro. Porous-supported lipid membrane (pSLM) has emerged as a flexible platform for studying the surface chemistry of the cell due to their high stability and fluidity, and their ability to study the transmembrane process of the molecules. In this review, the pSLM, for the first time, to our knowledge, was divided into three types according to the way of the porous materials support the lipid membrane, containing the lipid membrane on the pores of the porous materials, the lipid membrane on both sides of the porous materials, the lipid membrane in the pores of the porous materials. All of these pSLMs were systematically elaborated from several aspects, including the substrates, formation, and characterization. Meanwhile, the advantages and disadvantages of each model membranes were summarized. Finally, suggestions for selecting appropriate pSLM and future directions in this area are discussed.
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Affiliation(s)
- Yanping Sun
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Xianghuan Zang
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Yongjun Sun
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China
| | - Long Wang
- State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Department of Family and Consumer Sciences, California State University, Long Beach, CA, 90840, USA.
| | - Zibin Gao
- Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, 050018, China; State Key Laboratory Breeding Base - Hebei Province Key Laboratory of Molecular Chemistry for Drugs, Hebei University of Science and Technology, Shijiazhuang, 050018, China; Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China.
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17
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Hossein A, Deserno M. Spontaneous Curvature, Differential Stress, and Bending Modulus of Asymmetric Lipid Membranes. Biophys J 2019; 118:624-642. [PMID: 31954503 DOI: 10.1016/j.bpj.2019.11.3398] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/20/2019] [Accepted: 11/25/2019] [Indexed: 12/24/2022] Open
Abstract
Lipid bilayers can exhibit asymmetric states, in which the physical characteristics of one leaflet differ from those of the other. This most visibly manifests in a different lipid composition, but it can also involve opposing lateral stresses in each leaflet that combine to an overall vanishing membrane tension. Here, we use theoretical modeling and coarse-grained simulation to explore the interplay between a compositional asymmetry and a nonvanishing differential stress. Minimizing the total elastic energy leads to a preferred spontaneous curvature that balances torques due to both bending moments and differential stress, with sometimes unexpected consequences. For instance, asymmetric flat bilayers, whose specific areas in each leaflet are matched to those of corresponding tensionless symmetric flat membranes, still exhibit a residual differential stress because the conditions of vanishing area strain and vanishing bending moment differ. We also measure the curvature rigidity of asymmetric bilayers and find that a sufficiently strong differential stress, but not compositional asymmetry alone, can increase the bending modulus. The likely cause is a stiffening of the compressed leaflet, which appears to be related to its gel transition but not identical with it. We finally show that the impact of cholesterol on differential stress depends on the relative strength of elastic and thermodynamic driving forces: if cholesterol solvates equally well in both leaflets, it will redistribute to cancel both leaflet tensions almost completely, but if its partitioning free energy prefers one leaflet over the other, the resulting distribution bias may even create differential stress. Because cells keep most of their lipid bilayers in an asymmetric nonequilibrium steady state, our findings suggest that biomembranes are elastically more complex than previously thought: besides a spontaneous curvature, they might also exhibit significant differential stress, which could strongly affect their curvature energetics.
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Affiliation(s)
- Amirali Hossein
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania.
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18
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Dai Z, Yu M, Yi X, Wu Z, Tian F, Miao Y, Song W, He S, Ahmad E, Guo S, Zhu C, Zhang X, Li Y, Shi X, Wang R, Gan Y. Chain-Length- and Saturation-Tuned Mechanics of Fluid Nanovesicles Direct Tumor Delivery. ACS NANO 2019; 13:7676-7689. [PMID: 31187973 DOI: 10.1021/acsnano.9b01181] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Small unilamellar vesicles (SUVs), ubiquitous in organisms, play key and active roles in various biological processes. Although the physical properties of the constituent lipid molecules (i.e., the acyl chain length and saturation) are known to affect the mechanical properties of SUVs and consequently regulate their biological behaviors and functions, the underlying mechanism remains elusive. Here, we combined theoretical modeling and experimental investigation to probe the mechanical behaviors of SUVs with different lipid compositions. The membrane bending rigidity of SUVs increased with increasing chain length and saturation, resulting in differences in the vesicle rigidity and deformable capacity. Furthermore, we tested the tumor delivery capacity of liposomes with low, intermediate, and high rigidity as typical models for SUVs. Interestingly, liposomes with intermediate rigidity exhibited better tumor extracellular matrix diffusion and multicellular spheroid (MCS) penetration and retention than that of their stiffer or softer counterparts, contributing to improved tumor suppression. Stiff SUVs had superior cellular internalization capacity but intermediate tumor delivery efficacy. Stimulated emission depletion microscopy directly showed that the optimal formulation was able to transform to a rod-like shape in MCSs, which stimulated fast transport in tumor tissues. In contrast, stiff liposomes hardly deformed, whereas soft liposomes changed their shape irregularly, which slowed their MCS penetration. Our findings introduce special perspectives from which to map the detailed mechanical properties of SUVs with different compositions, provide clues for understanding the biological functions of SUVs, and suggest that liposome mechanics may be a design parameter for enhancing drug delivery.
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Affiliation(s)
- Zhuo Dai
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Miaorong Yu
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xin Yi
- Beijing Innovation Center for Engineering Science and Advanced Technology, and Department of Mechanics and Engineering Science, College of Engineering , Peking University , Beijing 100871 , China
| | - Zeming Wu
- Beijing Innovation Center for Engineering Science and Advanced Technology, and Department of Mechanics and Engineering Science, College of Engineering , Peking University , Beijing 100871 , China
| | - Falin Tian
- CAS Key Laboratory for Nanosystem and Hierarchy Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology , Chinese Academy of Sciences , Beijing 100190 , China
| | - Yunqiu Miao
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Wenyi Song
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Shufang He
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Ejaj Ahmad
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Shiyan Guo
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Chunliu Zhu
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Xinxin Zhang
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Yiming Li
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
| | - Xinghua Shi
- University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Key Laboratory for Nanosystem and Hierarchy Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology , Chinese Academy of Sciences , Beijing 100190 , China
| | - Rui Wang
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
| | - Yong Gan
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
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19
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Wan M, Gao L, Fang W. Implicit-solvent dissipative particle dynamics force field based on a four-to-one coarse-grained mapping scheme. PLoS One 2018; 13:e0198049. [PMID: 29795682 PMCID: PMC5967728 DOI: 10.1371/journal.pone.0198049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 05/12/2018] [Indexed: 11/30/2022] Open
Abstract
A new set of efficient solvent-free dissipative particle dynamics (DPD) force fields was developed for phospholipids and peptides. To enhance transferability, this model maps around four heavy atoms and their connected hydrogen atoms into a coarse-grained elementary bead based on functional group. The effective hybrid potential between any pair of beads is composed of a short-range repulsive soft-core potential that directly adopts the form of an explicit-solvent DPD model and a long-range attractive hydrophobic potential. The parameters of the attractive potentials for lipid molecules were obtained by fitting the explicit-solvent DPD simulation of one bead of any type in a water box, then finely tuning it until the bilayer membrane properties obtained in the explicit-solvent model were matched. These parameters were further extended to amino acids according to bead type. The structural and elastic properties of bilayer membranes, free energy profiles for a lipid flip-flop and amino acid analogues translocating across the membrane, and membrane pore formation induced by antimicrobial peptides obtained from this solvent-free DPD force field considerably agreed with the explicit-solvent DPD results. Importantly, the efficiency of this method is guaranteed to accelerate the assembly of vesicles composed of several thousand lipids by up to 50-fold, rendering the experimental liposome dynamics as well as membrane-peptide interactions feasible at accessible computational expense.
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Affiliation(s)
- Mingwei Wan
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, China
| | - Lianghui Gao
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, China
- * E-mail:
| | - Weihai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, China
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20
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Kim JH, Riehemann K, Fuchs H. Force Spectroscopy on a Cell Drum: AFM Measurements on the Basolateral Side of Cells via Inverted Cell Cultures. ACS APPLIED MATERIALS & INTERFACES 2018; 10:12485-12490. [PMID: 29595251 DOI: 10.1021/acsami.8b01990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The elasticity of a cell is one of the most critical measures of the difference between cancerous cells and healthy cells: cancer cells tend to be softer than healthy cells, and highly invasive cells tend to be more elastic than less aggressive cells. In this work, we present the novel "bottom-up" cell force spectroscopy method for the biophysical characterization of cancer cells, in which an atomic force microscopy (AFM) tip approach from the backside of a net-shaped culture substrate exposing the basolateral cell membrane drum, and compare it with the conventional "top-down" AFM measurements. We used two different human pancreatic carcinoma cell lines, PaTu8988S and PaTu8988T. Our bottom-up AFM tip approach provided a more statistically synchronized distribution of the measured elastic moduli of the cells, demonstrating its superior applicability for the clinical use of force spectroscopy, which is not attainable with the conventional top-down AFM approach.
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Affiliation(s)
- Joo Hyoung Kim
- Institute of Physics , University of Münster , D-48149 Münster , Germany
- Center for Nanotechnology (CeNTech) , D-48149 Münster , Germany
| | - Kristina Riehemann
- Institute of Physics , University of Münster , D-48149 Münster , Germany
- Center for Nanotechnology (CeNTech) , D-48149 Münster , Germany
| | - Harald Fuchs
- Institute of Physics , University of Münster , D-48149 Münster , Germany
- Center for Nanotechnology (CeNTech) , D-48149 Münster , Germany
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21
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Vorselen D, Marchetti M, López-Iglesias C, Peters PJ, Roos WH, Wuite GJL. Multilamellar nanovesicles show distinct mechanical properties depending on their degree of lamellarity. NANOSCALE 2018; 10:5318-5324. [PMID: 29504612 DOI: 10.1039/c7nr09224e] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Small multilamellar vesicles may have benefits over unilamellar vesicles for drug delivery, such as an increased volume for hydrophobic drugs. In addition, their altered mechanical properties might be beneficial for cellular uptake. Here, we show how atomic force microscopy (AFM) can be used to detect and characterize multilamellar vesicles. We quantify the size of each break event occurring during AFM nanoindentations, which shows good agreement with the thickness of supported lipid bilayers. Analyzing the size and number of these events for individual vesicles allows us to distinguish between vesicles consisting of 1 up to 5 bilayers. We validate these results by comparison with correlative cryo-electron microscopy (cryo-EM) data at the vesicle population level. Finally, we quantify the vesicle geometry and mechanical properties, and show that with additional bilayers adherent vesicles are more spherical and stiffer. Surprisingly, at ∼20% stiffening for each additional bilayer, the vesicle stiffness scales only weakly with lamellarity. Our results show the potential of AFM for studying liposomal nanoparticles and suggest that small multilamellar vesicles may have beneficial mechanical properties for cellular uptake.
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Affiliation(s)
- Daan Vorselen
- Department of Physics and Astronomy and LaserLab, Vrije Universiteit, Amsterdam, 1081 HV, The Netherlands.
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22
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Glazier R, Salaita K. Supported lipid bilayer platforms to probe cell mechanobiology. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2017; 1859:1465-1482. [PMID: 28502789 PMCID: PMC5531615 DOI: 10.1016/j.bbamem.2017.05.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 05/09/2017] [Accepted: 05/09/2017] [Indexed: 12/15/2022]
Abstract
Mammalian and bacterial cells sense and exert mechanical forces through the process of mechanotransduction, which interconverts biochemical and physical signals. This is especially important in contact-dependent signaling, where ligand-receptor binding occurs at cell-cell or cell-ECM junctions. By virtue of occurring within these specialized junctions, receptors engaged in contact-dependent signaling undergo oligomerization and coupling with the cytoskeleton as part of their signaling mechanisms. While our ability to measure and map biochemical signaling within cell junctions has advanced over the past decades, physical cues remain difficult to map in space and time. Recently, supported lipid bilayer (SLB) technologies have emerged as a flexible platform to mimic and perturb cell-cell and cell-ECM junctions, allowing one to study membrane receptor mechanotransduction. Changing the lipid composition and underlying substrate tunes bilayer fluidity, and lipid and ligand micro- and nano-patterning spatially control positioning and clustering of receptors. Patterning metal gridlines within SLBs confines lipid mobility and introduces mechanical resistance. Here we review fundamental SLB mechanics and how SLBs can be engineered as tunable cell substrates for mechanotransduction studies. Finally, we highlight the impact of this work in understanding the biophysical mechanisms of cell adhesion. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
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Affiliation(s)
- Roxanne Glazier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, GA 30322, United States
| | - Khalid Salaita
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, GA 30322, United States; Department of Chemistry, Emory University, Atlanta, GA 30322, United States..
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23
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Effect of Statins on the Nanomechanical Properties of Supported Lipid Bilayers. Biophys J 2017; 111:363-372. [PMID: 27463138 DOI: 10.1016/j.bpj.2016.06.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 05/25/2016] [Accepted: 06/15/2016] [Indexed: 11/23/2022] Open
Abstract
Many drugs and other xenobiotics may reach systemic concentrations where they interact not only with the proteins that are their therapeutic targets but also modify the physicochemical properties of the cell membrane, which may lead to altered function of many transmembrane proteins beyond the intended targets. These changes in bilayer properties may contribute to nonspecific, promiscuous changes in membrane protein and cell function because membrane proteins are energetically coupled to their host lipid bilayer. It is thus important, for both pharmaceutical and biophysical reasons, to understand the bilayer-modifying effect of amphiphiles (including therapeutic agents). Here we use atomic force microscopy topography imaging and nanomechanical mapping to monitor the effect of statins, a family of hypolipidemic drugs, on synthetic lipid membranes. Our results reveal that statins alter the nanomechanical stability of the bilayers and increase their elastic moduli depending on the lipid bilayer order. Our results also suggest that statins increase bilayer heterogeneity, which may indicate that statins form nanometer-sized aggregates in the membrane. This is further evidence that changes in bilayer nanoscale mechanical properties may be a signature of lipid bilayer-mediated effects of amphiphilic drugs.
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24
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Blachon F, Harb F, Munteanu B, Piednoir A, Fulcrand R, Charitat T, Fragneto G, Pierre-Louis O, Tinland B, Rieu JP. Nanoroughness Strongly Impacts Lipid Mobility in Supported Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:2444-2453. [PMID: 28219008 DOI: 10.1021/acs.langmuir.6b03276] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In vivo lipid membranes interact with rough supramolecular structures such as protein clusters and fibrils. How these features whose size ranges from a few nanometers to a few tens of nanometers impact lipid and protein mobility is still being investigated. Here, we study supported phospholipid bilayers, a unique biomimetic model, deposited on etched surfaces bearing nanometric corrugations. The surface roughness and mean curvature are carefully characterized by AFM imaging using ultrasharp tips. Neutron specular reflectivity supplements this surface characterization and indicates that the bilayers follow the large-scale corrugations of the substrate. We measure the lateral mobility of lipids in both the fluid and gel phases by fluorescence recovery after patterned photobleaching. Although the mobility is independent of the roughness in the gel phase, it exhibits a 5-fold decrease in the fluid phase when the roughness increases from 0.2 to 10 nm. These results are interpreted with a two-phase model allowing for a strong decrease in the lipid mobility in highly curved or defect-induced gel-like nanoscale regions. This suggests a strong link between membrane curvature and fluidity, which is a key property for various cell functions such as signaling and adhesion.
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Affiliation(s)
- Florence Blachon
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Frédéric Harb
- Doctoral School for Science and Technology, Platform for Research in NanoSciences and Nanotechnology, Campus Pierre Gemayel, Lebanese University , Fanar-Metn BP 90239 Beirut, Lebanon
| | - Bogdan Munteanu
- CNRS, INSA de Lyon, LaMCoS, UMR5259, Université de Lyon , 69621 Lyon, France
| | - Agnès Piednoir
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Rémy Fulcrand
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Thierry Charitat
- Université de Strasbourg, Institut Charles Sadron , UPR22, CNRS, 67034 Strasbourg Cedex 2, France
| | - Giovanna Fragneto
- Institut Laue-Langevin , 71 Avenue des Martyrs, F-38042 Grenoble, France
| | - Olivier Pierre-Louis
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Bernard Tinland
- CINaM-CNRS, Aix-Marseille Université , UMR7325, 13288 Marseille, France
| | - Jean-Paul Rieu
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
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25
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Maher S, Basit H, Forster RJ, Keyes TE. Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity. Bioelectrochemistry 2016; 112:16-23. [DOI: 10.1016/j.bioelechem.2016.07.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 07/04/2016] [Accepted: 07/04/2016] [Indexed: 12/18/2022]
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26
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Li X, Gao L, Fang W. Dissipative Particle Dynamics Simulations for Phospholipid Membranes Based on a Four-To-One Coarse-Grained Mapping Scheme. PLoS One 2016; 11:e0154568. [PMID: 27137463 PMCID: PMC4854440 DOI: 10.1371/journal.pone.0154568] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 04/15/2016] [Indexed: 11/19/2022] Open
Abstract
In this article, a new set of parameters compatible with the dissipative particle dynamics (DPD) force field is developed for phospholipids. The coarse-grained (CG) models of these molecules are constructed by mapping four heavy atoms and their attached hydrogen atoms to one bead. The beads are divided into types distinguished by charge type, polarizability, and hydrogen-bonding capacity. First, we derive the relationship between the DPD repulsive force and Flory-Huggins χ-parameters based on this four-to-one CG mapping scheme. Then, we optimize the DPD force parameters for phospholipids. The feasibility of this model is demonstrated by simulating the structural and thermodynamic properties of lipid bilayer membranes, including the membrane thickness, the area per lipid, the lipid tail orientation, the bending rigidity, the rupture behavior, and the potential of mean force for lipid flip-flop.
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Affiliation(s)
- Xiaoxu Li
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Lianghui Gao
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Weihai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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27
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Wang X, Deserno M. Determining the Lipid Tilt Modulus by Simulating Membrane Buckles. J Phys Chem B 2016; 120:6061-73. [DOI: 10.1021/acs.jpcb.6b02016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Xin Wang
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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28
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29
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Assemblies of pore-forming toxins visualized by atomic force microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:500-11. [PMID: 26577274 DOI: 10.1016/j.bbamem.2015.11.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 10/23/2015] [Accepted: 11/09/2015] [Indexed: 02/05/2023]
Abstract
A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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30
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Diggins P, McDargh ZA, Deserno M. Curvature Softening and Negative Compressibility of Gel-Phase Lipid Membranes. J Am Chem Soc 2015; 137:12752-5. [PMID: 26413857 DOI: 10.1021/jacs.5b06800] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We show that gel-phase lipid membranes soften upon bending, leading to curvature localization and a negative compressibility. Using simulations of two very different lipid models to quantify shape and stress-strain relation of buckled membranes, we demonstrate that gel phase bilayers do not behave like Euler elastica and hence are not well described by a quadratic Helfrich Hamiltonian, much unlike their fluid-phase counterparts. We propose a theoretical framework which accounts for the observed softening through an energy density that smoothly crosses over from a quadratic to a linear curvature dependence beyond a critical new scale [Formula: see text](-1). This model captures both the shape and the stress-strain relation for our two sets of simulations and permits the extraction of bending moduli, which are found to be about an order of magnitude larger than the corresponding fluid phase values. We also find surprisingly large crossover lengths [Formula: see text], several times bigger than the bilayer thickness, rendering the exotic elasticity of gel-phase membranes more strongly pronounced than that of homogeneous compressible sheets and artificial metamaterials. We suggest that such membranes have unexpected potential as nanoscale systems with striking materials characteristics.
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Affiliation(s)
- Patrick Diggins
- Department of Physics, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Zachary A McDargh
- Department of Physics, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
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31
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Dupré de Baubigny J, Benzaquen M, Fabié L, Delmas M, Aimé JP, Legros M, Ondarçuhu T. Shape and Effective Spring Constant of Liquid Interfaces Probed at the Nanometer Scale: Finite Size Effects. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:9790-9798. [PMID: 26295187 DOI: 10.1021/acs.langmuir.5b02607] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with in situ micromanipulation techniques. In both cases, the interface is probed with a cylindrical nanofiber with radius R of the order of 25-100 nm. The effective spring constant of the nanomeniscus oscillated around its equilibrium position is determined by static and frequency-modulation (FM) AFM modes. In the case of an unbounded meniscus, we find that the effective spring constant k is proportional to the surface tension γ of the liquid through k = (0.51 ± 0.06)γ, regardless of the excitation frequency from quasi-static up to 450 kHz. A model based on the equilibrium shape of the meniscus reproduces well the experimental data. Electron microscopy allowed to visualize the meniscus profile around the fiber with a lateral resolution of the order of 10 nm and confirmed its catenary shape. The influence of a lateral confinement of the interface is also investigated. We showed that the lateral extension L of the meniscus influences the effective spring constant following a logarithmic evolution k ∼ 2πγ/ln(L/R) deduced from the model. This comprehensive study of liquid interface properties over more than 4 orders of magnitude in meniscus size shows that advanced FM-AFM and SEM techniques are promising tools for the investigation of mechanical properties of liquids down to nanometer scale.
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Affiliation(s)
- Julien Dupré de Baubigny
- CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
- Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
| | - Michael Benzaquen
- Laboratoire de Physico-Chimie Théorique, CNRS UMR 7083 Gulliver, ESPCI ParisTech, PSL Research University , 10 rue Vauquelin, 75231 Paris, Cedex 5, France
| | - Laure Fabié
- CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
- Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
| | - Mathieu Delmas
- CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
| | | | - Marc Legros
- CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
| | - Thierry Ondarçuhu
- CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France
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32
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Janshoff A, Steinem C. Mechanics of lipid bilayers: What do we learn from pore-spanning membranes? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2977-83. [PMID: 26025679 DOI: 10.1016/j.bbamcr.2015.05.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 11/18/2022]
Abstract
The mechanical properties of biological membranes have become increasingly important not only from a biophysical viewpoint but also as they play a substantial role in the information transfer in cells and tissues. This minireview summarizes some of our recent understanding of the mechanical properties of artificial model membranes with particular emphasis on membranes suspending an array of pores, so called pore-spanning membranes. A theoretical description of the mechanical properties of these membranes might pave the way to biophysically describe and understand the complex behavior of native biological membranes. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Andreas Janshoff
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Claudia Steinem
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany; Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
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33
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Teng W, Ban C, Hahn JH. Formation of lipid bilayer membrane in a poly(dimethylsiloxane) microchip integrated with a stacked polycarbonate membrane support and an on-site nanoinjector. BIOMICROFLUIDICS 2015; 9:024120. [PMID: 26015832 PMCID: PMC4409621 DOI: 10.1063/1.4919066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/14/2015] [Indexed: 06/04/2023]
Abstract
This paper describes a new and facile approach for the formation of pore-spanning bilayer lipid membranes (BLMs) within a poly(dimethylsiloxane) (PDMS) microfluidic device. Commercially, readily available polycarbonate (PC) membranes are employed for the support of BLMs. PC sheets with 5 μm, 2 μm, and 0.4 μm pore diameters, respectively, are thermally bonded into a multilayer-stack, reducing the pore density of 0.4 μm-pore PC by a factor of 200. The BLMs on this support are considerably stable (a mean lifetime: 17 h). This multilayer-stack PC (MSPC) membrane is integrated into the PDMS chip by an epoxy bonding method developed to secure durable bonding under the use of organic solvents. The microchip has a special channel for guiding a micropipette in the proximity of the MSPC support. With this on-site injection technique, tens to hundreds of nanoliters of solutions can be directly dispensed to the support. Incorporating gramicidin ion channels into BLMs on the MSPC support has confirmed the formation of single BLMs, which is based on the observation from current signals of 20 pS conductance that is typical to single channel opening. Based on the bilayer capacitance (1.4 pF), about 15% of through pores across the MSPC membrane are estimated to be covered with BLMs.
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Affiliation(s)
- Wei Teng
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
| | - Changill Ban
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
| | - Jong Hoon Hahn
- Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology , 77 Cheongam-Ro, Nam-Gu, 790-784 Pohang, South Korea
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34
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Volkov V. Tip-induced deformation of a phospholipid bilayer: theoretical perspective of sum frequency generation imaging. J Chem Phys 2014; 141:154201. [PMID: 25338888 DOI: 10.1063/1.4897987] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The paper addresses theory of Sum Frequency Generation imaging of an atomic force microscopy tip-induced deformation of a bilayer phospholipid membrane deposited over a pore: known as a nano-drum system. Image modeling employed nonlinearities of the normal modes specific to hydrocarbon terminal methyls, which are distributed about the deformed surfaces of inner and outer leaflets. The deformed profiles are according to the solutions of shape equation for Canham-Helfrich Hamiltonian accounting properties of four membranes, which differ in elasticity and adhesion. The results indicate that in continuous deformed surfaces, the difference in the curvature of the outer and inner leaflets dominates in the imaged nonlinearity. This is different comparing to the results for a perfect bilayer spherical cap system (the subject of previous study), where nonlinear image response is dominated by the mismatch of the inner and outer leaflets' surface areas (as projected to the image plane) at the edge of perfectly spherical structure. The results of theoretical studies, here, demonstrate that Sum Frequency Generation imaging in continuous and deformed bilayer surfaces are helpful to address curvature locally and anticipate mechanical properties of membrane. The articles discuss applicability and practical limitations of the approach. Combination of Atomic Force Microscopy and Sum Frequency Generation imaging under controlled tip-induced deformation provides a good opportunity to probe and test membranes physical properties with rigor of adopted theory.
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Affiliation(s)
- Victor Volkov
- Bereozovaya 2A, Konstantinovo, Moscow Region 140207, Russian Federation
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35
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Alessandrini A, Facci P. Phase transitions in supported lipid bilayers studied by AFM. SOFT MATTER 2014; 10:7145-7164. [PMID: 25090108 DOI: 10.1039/c4sm01104j] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the capabilities of Atomic Force Microscopy (AFM) in the study of phase transitions in Supported Lipid Bilayers (SLBs). AFM represents a powerful technique to cover the resolution range not available to fluorescence imaging techniques and where spectroscopic data suggest what the relevant lateral scale for domain formation might be. Phase transitions of lipid bilayers involve the formation of domains characterized by different heights with respect to the surrounding phase and are therefore easily identified by AFM in liquid solution once the bilayer is confined to a flat surface. Even if not endowed with high time resolution, AFM allows light to be shed on some aspects related to lipid phase transitions in the case of both a single lipid component and lipid mixtures containing sterols also. We discuss here the obtained results in light of the peculiarities of supported lipid bilayer model systems.
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Affiliation(s)
- Andrea Alessandrini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Via Campi 213/A, 41125, Modena, Italy.
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36
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Wu HL, Sheng YJ, Tsao HK. Phase behaviors and membrane properties of model liposomes: Temperature effect. J Chem Phys 2014; 141:124906. [DOI: 10.1063/1.4896382] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- Hsing-Lun Wu
- Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Yu-Jane Sheng
- Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Heng-Kwong Tsao
- Department of Chemical and Materials Engineering, Department of Physics, National Central University, Jhongli 320, Taiwan
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37
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Hertrich S, Stetter F, Rühm A, Hugel T, Nickel B. Highly hydrated deformable polyethylene glycol-tethered lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9442-7. [PMID: 25046694 DOI: 10.1021/la4045804] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The realization of a solid-supported lipid bilayer acting as a workbench for the study of membrane processes is a difficult task. For robustness, the bilayer has to be tethered to the substrate. At the same time, diffusion of the lipids and plastic deformations of the membrane should not be obstructed. Furthermore, a highly hydrated surrounding is mandatory. Here, we show that grafting of a polyethylene glycol-lipid construct (PEG2000-DSPE) to a silicon oxide surface via multiple-step silane chemistry and subsequent deposition of lipids by spin-coating result in a cushioned membrane that has the desired properties. Neutron and X-ray reflectometry measurements are combined to access thickness, density, and hydration of the bilayer and the PEG cushion. We observe a spacer of 55 Å thickness between lipid bilayer and silicon-oxide surface with a rather high hydration of up to 90 ± 3% water. While 11.5 ± 3% of the lipids are grafted to the surface, as determined from the neutron data, the diffusion constant of the lipids, as probed by diffusion of 0.5% Texas Red labeled lipids, remains rather large (D = 2.1 ± 0.1 μm(2)/s), which is a reduction of only 12% compared to a supported lipid bilayer reference without immobilized lipids. Finally, AFM indentation confirms the plastic behavior of the membrane against deformation. We show that rupture of the bilayer does not occur before the deformation exceeds 40 Å. Altogether, the presented PEG-tethered lipid bilayer mimics the deformability of natural cell membranes much better than standard solid-supported lipid bilayers.
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Affiliation(s)
- Samira Hertrich
- Fakultät für Physik & CeNS, Ludwig-Maximilians-Universität , Geschwister-Scholl-Platz 1, 80539 Munich, Germany
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38
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Kuhlmann JW, Mey IP, Steinem C. Modulating the lateral tension of solvent-free pore-spanning membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8186-8192. [PMID: 24950370 DOI: 10.1021/la5019086] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The plasma membrane of animal cells is attached to the cytoskeleton, which significantly contributes to the lateral tension of the membrane. Lateral membrane tension has been shown to be an important physical regulator of cellular processes such as cell motility and morphology as well as exo- and endocytosis. Here, we report on lipid bilayers spanning highly ordered pore arrays, where we can control the lateral membrane tension by chemically varying the surface functionalization of the porous substrate. Surface functionalization was achieved by a gold coating on top of the pore rims of the hexagonal array of pores in silicon nitride substrates with pore radii of 600 nm followed by subsequent incubation with various n-propanolic mixtures of 6-mercapto-1-hexanol (6MH) and O-cholesteryl N-(8'-mercapto-3',6'-dioxaoctyl)carbamate (CPEO3). Pore-spanning membranes composed of 1,2-diphytanoyl-sn-glycero-3-phosphocholine were prepared by spreading giant unilamellar vesicles on these functionalized porous silicon nitride substrates. Different mixtures of 6MH and CPEO3 provided self-assembled monolayers (SAMs) with different compositions as analyzed by contact angle and PM-IRRAS measurements. Site specific force-indentation experiments on the pore-spanning membranes attached to the different SAMs revealed a clear dependence of the amount of CPEO3 in the monolayer on the lateral membrane tension. While bilayers on pure 6MH monolayers show an average lateral membrane tension of 1.4 mN m(-1), a mixed monolayer of CPEO3 and 6MH obtained from a solution with 9.1 mol % CPEO3 exhibits a lateral tension of 5.0 mN m(-1). From contact angle and PM-IRRAS results, the mole fraction of CPEO3 in solution can be roughly translated into a CPEO3 surface concentration of 40 mol %. Our results clearly demonstrate that the free energy difference between the supported and freestanding part of the membrane depends on the chemical composition of the SAM, which controls the lateral membrane tension.
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Affiliation(s)
- Jan W Kuhlmann
- Institute of Organic and Biomolecular Chemistry, University of Göttingen , Tammannstraße 2, 37077 Göttingen, Germany
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39
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Ramachandran S, Arce FT, Patel NR, Quist AP, Cohen DA, Lal R. Structure and permeability of ion-channels by integrated AFM and waveguide TIRF microscopy. Sci Rep 2014; 4:4424. [PMID: 24651823 PMCID: PMC3961736 DOI: 10.1038/srep04424] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 03/03/2014] [Indexed: 11/09/2022] Open
Abstract
Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal reflection fluorescence microscopy (TIRFM) for high resolution imaging and molecular transport measurement. Significantly, membranes over the nanopore were stable for repeated AFM imaging. We studied structure-activity relationship of gap junction hemichannels reconstituted in lipid bilayers. Individual hemichannels in the membrane overlying the nanopore were resolved and transport of hemichannel-permeant LY dye was visualized when the hemichannel was opened by lowering calcium in the medium. This integrated technique will allow direct structure-permeability relationship of many ion channels and receptors.
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Affiliation(s)
- Srinivasan Ramachandran
- 1] Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093 [2]
| | - Fernando Teran Arce
- 1] Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093 [2]
| | - Nirav R Patel
- Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
| | - Arjan P Quist
- RC Nano Corporation, 2210 Midwest Road, Oak Brook, IL 60523, USA. Current Address: Innovation and New Ventures Office, Northwestern University, 1800 Sherman Ave., Evanston IL 60201
| | - Daniel A Cohen
- Department of Materials, University of California Santa Barbara, CA 93106
| | - Ratnesh Lal
- Department of Bioengineering; Department of Mechanical & Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
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40
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Messina P, Lemaître F, Huet F, Ngo KA, Vivier V, Labbé E, Buriez O, Amatore C. Monitoring and Quantifying the Passive Transport of Molecules Through Patch-Clamp Suspended Real and Model Cell Membranes. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201308990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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Messina P, Lemaître F, Huet F, Ngo KA, Vivier V, Labbé E, Buriez O, Amatore C. Monitoring and quantifying the passive transport of molecules through patch-clamp suspended real and model cell membranes. Angew Chem Int Ed Engl 2014; 53:3192-6. [PMID: 24519879 DOI: 10.1002/anie.201308990] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/06/2013] [Indexed: 11/11/2022]
Abstract
Transport of active molecules across biological membranes is a central issue for the success of many pharmaceutical strategies. Herein, we combine the patch-clamp principle with amperometric detection for monitoring fluxes of redox-tagged molecular species across a suspended membrane patched from a macrophage. Solvent- and protein-free lipid bilayers (DPhPC, DOPC, DOPG) patched from single-wall GUV have been thoroughly investigated and the corresponding fluxes measurements quantified. The quality of the patches and their proper sealing were successfully characterized by electrochemical impedance spectroscopy. This procedure appears versatile and perfectly adequate to allow the investigation of transport and quantification of the transport properties through direct measurement of the coefficients of partition and diffusion of the compound in the membrane, thus offering insight on such important biological and pharmacological issues.
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Affiliation(s)
- Pierluca Messina
- Ecole Normale Supérieure, Département de Chimie, UMR CNRS-ENS-UPMC 8640 "PASTEUR", 24 rue Lhomond, 75231 Paris cedex 05 (France)
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42
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Kong X, Qin S, Lu D, Liu Z. Surface tension effects on the phase transition of a DPPC bilayer with and without protein: a molecular dynamics simulation. Phys Chem Chem Phys 2014; 16:8434-40. [DOI: 10.1039/c3cp55524k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A coarse-grained molecular dynamics simulation was applied to illustrate the phase transition behavior of the pure DPPC bilayer and aquaporin-embedded DPPC bilayer under different surface tensions.
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Affiliation(s)
- Xian Kong
- Department of Chemical Engineering
- Tsinghua University
- Beijing, China
| | - Shanshan Qin
- Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education)
- Department of Chemistry
- Tsinghua University
- Beijing 100084, P. R. China
| | - Diannan Lu
- Department of Chemical Engineering
- Tsinghua University
- Beijing, China
| | - Zheng Liu
- Department of Chemical Engineering
- Tsinghua University
- Beijing, China
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43
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Hardy GJ, Nayak R, Zauscher S. Model cell membranes: Techniques to form complex biomimetic supported lipid bilayers via vesicle fusion. Curr Opin Colloid Interface Sci 2013; 18:448-458. [PMID: 24031164 DOI: 10.1016/j.cocis.2013.06.004] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vesicle fusion has long provided an easy and reliable method to form supported lipid bilayers (SLBs) from simple, zwitterionic vesicles on siliceous substrates. However, for complex compositions, such as vesicles with high cholesterol content and multiple lipid types, the energy barrier for the vesicle-to-bilayer transition is increased or the required vesicle-vesicle and vesicle-substrate interactions are insufficient for vesicle fusion. Thus, for vesicle compositions that more accurately mimic native membranes, vesicle fusion often fails to form SLBs. In this paper, we review three approaches to overcome these barriers to form complex, biomimetic SLBs via vesicle fusion: (i) optimization of experimental conditions (e.g., temperature, buffer ionic strength, osmotic stress, cation valency, and buffer pH), (ii) α-helical (AH) peptide-induced vesicle fusion, and (iii) bilayer edge-induced vesicle fusion. AH peptide-induced vesicle fusion can form complex SLBs on multiple substrate types without the use of additional equipment. Bilayer edge-induced vesicle fusion uses microfluidics to form SLBs from vesicles with complex composition, including vesicles derived from native cell membranes. Collectively, this review introduces vesicle fusion techniques that can be generalized for many biomimetic vesicle compositions and many substrate types, and thus will aid efforts to reliably create complex SLB platforms on a range of substrates.
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Affiliation(s)
- Gregory J Hardy
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, NC 27708, USA. ; Tel: +1 (919) 660-5360
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44
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Cell shape can mediate the spatial organization of the bacterial cytoskeleton. Biophys J 2013; 104:541-52. [PMID: 23442905 DOI: 10.1016/j.bpj.2012.12.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 12/10/2012] [Accepted: 12/11/2012] [Indexed: 01/08/2023] Open
Abstract
The bacterial cytoskeleton guides the synthesis of cell wall and thus regulates cell shape. Because spatial patterning of the bacterial cytoskeleton is critical to the proper control of cell shape, it is important to ask how the cytoskeleton spatially self-organizes in the first place. In this work, we develop a quantitative model to account for the various spatial patterns adopted by bacterial cytoskeletal proteins, especially the orientation and length of cytoskeletal filaments such as FtsZ and MreB in rod-shaped cells. We show that the combined mechanical energy of membrane bending, membrane pinning, and filament bending of a membrane-attached cytoskeletal filament can be sufficient to prescribe orientation, e.g., circumferential for FtsZ or helical for MreB, with the accuracy of orientation increasing with the length of the cytoskeletal filament. Moreover, the mechanical energy can compete with the chemical energy of cytoskeletal polymerization to regulate filament length. Notably, we predict a conformational transition with increasing polymer length from smoothly curved to end-bent polymers. Finally, the mechanical energy also results in a mutual attraction among polymers on the same membrane, which could facilitate tight polymer spacing or bundling. The predictions of the model can be verified through genetic, microscopic, and microfluidic approaches.
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45
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Chwastek G, Schwille P. A monolayer assay tailored to investigate lipid-protein systems. Chemphyschem 2013; 14:1877-81. [PMID: 23606346 DOI: 10.1002/cphc.201300035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Indexed: 11/10/2022]
Abstract
Model membrane systems have become invaluable tools to investigate specific features of cellular membranes. Although a variety of different experimental assays does exist, many of them are rather complicated in their preparation and difficult in their practical realisation. Here, we propose a new simple miniaturised monolayer assay that can easily be combined with standard analytical techniques such as confocal fluorescence microscopy and fluorescence correlation spectroscopy (FCS).
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46
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Sachan AK, Galla HJ. Bidirectional surface analysis of monomolecular membrane harboring nanoscale reversible collapse structures. NANO LETTERS 2013; 13:961-966. [PMID: 23391449 DOI: 10.1021/nl303928m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Determination of orientation of nanoscale collapse structures formed within a Langmuir film at the air-aqueous interface has not been possible by existing experimental techniques. This is however of special importance for pulmonary surfactant films, which form reversible surface-associated reservoirs (SARs) under dynamic lateral compression and expansion. The direction of these SARs with respect to the interface has hitherto remained uncertain. We designed a methodological approach to investigate the directionality of SARs formed in a functional analogue of the pulmonary surfactant lining, where we transferred the compressed film on a holey substrate and performed bidirectional surface imaging of the hole spanning monomolecular membrane harboring SARs. This unambiguously showed association of SARs with the membrane toward the air-side, in contrast to the up to now commonly accepted view of an orientation toward the aqueous phase.
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Affiliation(s)
- Amit K Sachan
- Institute of Biochemistry, Westfälische Wilhelms Universität, Wilhelm-Klemm-Strasse2, 48149 Münster, Germany
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47
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Picas L, Milhiet PE, Hernández-Borrell J. Atomic force microscopy: a versatile tool to probe the physical and chemical properties of supported membranes at the nanoscale. Chem Phys Lipids 2012. [PMID: 23194897 DOI: 10.1016/j.chemphyslip.2012.10.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Atomic force microscopy (AFM) was developed in the 1980s following the invention of its precursor, scanning tunneling microscopy (STM), earlier in the decade. Several modes of operation have evolved, demonstrating the extreme versatility of this method for measuring the physicochemical properties of samples at the nanoscopic scale. AFM has proved an invaluable technique for visualizing the topographic characteristics of phospholipid monolayers and bilayers, such as roughness, height or laterally segregated domains. Implemented modes such as phase imaging have also provided criteria for discriminating the viscoelastic properties of different supported lipid bilayer (SLB) regions. In this review, we focus on the AFM force spectroscopy (FS) mode, which enables determination of the nanomechanical properties of membrane models. The interpretation of force curves is presented, together with newly emerging techniques that provide complementary information on physicochemical properties that may contribute to our understanding of the structure and function of biomembranes. Since AFM is an imaging technique, some basic indications on how real-time AFM imaging is evolving are also presented at the end of this paper.
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Affiliation(s)
- Laura Picas
- Institut Curie, CNRS UMR 144, 26 rue d'Ulm, 75248 Paris, France
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48
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Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets.
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49
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Zhu ZW, Wang Y, Zhang X, Sun CF, Li MG, Yan JW, Mao BW. Electrochemical impedance spectroscopy and atomic force microscopic studies of electrical and mechanical properties of nano-black lipid membranes and size dependence. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:14739-14746. [PMID: 22985346 DOI: 10.1021/la303047v] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present electrochemical impedance spectroscopic (EIS) and two-chamber AFM investigations of the electrical and mechanical properties of solvent-containing nano-BLMs suspended on chip-based nanopores of diameter of 200, 400, and 700 nm. The chips containing nanoporous silicon nitride membranes are fabricated based on low-cost colloidal lithography with low aspect ratio of the nanopores. BLMs of DPhPC lipid molecules are constructed across the nanopores by the painting method. Two equivalent circuits are compared in view of their adequacy in description of the EIS performances of the nano-BLMs and more importantly the structures associated with the nano-BLMs systems. The BLM resistance and capacitance as well as their size and time dependence are studied by EIS. The breakthrough forces, elasticity in terms of apparent spring constant, and lateral tension of the solvent-containing nano-BLMs are investigated by AFM force measurements. The exact relationship of the breakthrough force of the nano-BLM as a function of pore size is revealed. Both EIS and AFM studies show increasing lifetime and mechanical stability of the nano-BLMs with decreasing pore size. Finally, the robust 200 nm diameter nanopores are used to accommodate functional BLMs containing DPhPC lipid molecules and gramicidins by using a painting method with drop of mixture solutions of DPhPC and gramicidins. EIS investigation of the functional nano-BLMs is also performed.
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Affiliation(s)
- Zai-Wen Zhu
- State Key Laboratory of Physical Chemistry of the Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China
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50
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Kocun M, Janshoff A. Pulling tethers from pore-spanning bilayers: towards simultaneous determination of local bending modulus and lateral tension of membranes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:847-51. [PMID: 22228680 DOI: 10.1002/smll.201101557] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/31/2011] [Indexed: 05/16/2023]
Affiliation(s)
- Marta Kocun
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany
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