1
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Lee WS, Enomoto T, Akimoto AM, Yoshida R. Capsule self-oscillating gels showing cell-like nonthermal membrane/shape fluctuations. MATERIALS HORIZONS 2023; 10:1332-1341. [PMID: 36722870 DOI: 10.1039/d2mh01490d] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
A primary interest in cell membrane and shape fluctuations is establishing experimental models reflecting only nonthermal active contributions. Here we report a millimeter-scaled capsule self-oscillating gel model mirroring the active contribution effect on cell fluctuations. In the capsule self-oscillating gels, the propagating chemical signals during a Belousov-Zhabotinsky (BZ) reaction induce simultaneous local deformations in the various regions, showing cell-like shape fluctuations. The capsule self-oscillating gels do not fluctuate without the BZ reaction, implying that only the active chemical parameter induces the gel fluctuations. The period and amplitude depend on the gel layer thickness and the concentration of the chemical substrate for the BZ reaction. Our results allow for a solid experimental platform showing actively driven cell-like fluctuations, which can potentially contribute to investigating the active parameter effect on cell fluctuations.
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Affiliation(s)
- Won Seok Lee
- Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Takafumi Enomoto
- Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Aya Mizutani Akimoto
- Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Ryo Yoshida
- Department of Materials Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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2
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Chen ZR, Zhou W, Shen L. Scaling Behaviors of Polymers on Lipid Membranes: Coupling of Polymer Chain Dynamics and Surface Thermal Fluctuations. CHINESE JOURNAL OF POLYMER SCIENCE 2022. [DOI: 10.1007/s10118-022-2848-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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3
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Solis-Gonzalez OA, Tse CCW, Smith PJ, Fairclough JPA. Study of Salting Effect of Inorganic Salts on Nano- and Giant Polymersomes. Macromol Res 2022. [DOI: 10.1007/s13233-022-0051-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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4
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Michalak DJ, Lösche M, Hoogerheide DP. Charge Effects Provide Ångström-Level Control of Lipid Bilayer Morphology on Titanium Dioxide Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:3970-3981. [PMID: 33761262 PMCID: PMC10995910 DOI: 10.1021/acs.langmuir.1c00214] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Interfaces between molecular organic architectures and oxidic substrates are a central feature of biosensors and applications of biomimetics in science and technology. For phospholipid bilayers, the large range of pH- and ionic strength-dependent surface charge densities adopted by titanium dioxide and other oxidic surfaces leads to a rich landscape of phenomena that provides exquisite control of membrane interactions with such substrates. Using neutron reflectometry measurements, we report sharp, reversible transitions that occur between closely surface-associated and weakly coupled states. We show that these states arise from a complex interplay of the tunable length scale of electrostatic interactions with the length scale arising from other forces that are independent of solution conditions. A generalized free energy potential, with its inputs only derived from established measurements of surface and bilayer properties, quantitatively describes these and previously reported observations concerning the unbinding of bilayers from supporting substrates.
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Affiliation(s)
- Dennis J Michalak
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - David P Hoogerheide
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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5
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Allard A, Valentino F, Sykes C, Betz T, Campillo C. Fluctuations of a membrane nanotube covered with an actin sleeve. Phys Rev E 2020; 102:052402. [PMID: 33327147 DOI: 10.1103/physreve.102.052402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 08/11/2020] [Indexed: 06/12/2023]
Abstract
Many biological functions rely on the reshaping of cell membranes, in particular into nanotubes, which are covered in vivo by dynamic actin networks. Nanotubes are subject to thermal fluctuations, but the effect of these on cell functions is unknown. Here, we form nanotubes from liposomes using an optically trapped bead adhering to the liposome membrane. From the power spectral density of this bead, we study the nanotube fluctuations in the range of membrane tensions measured in vivo. We show that an actin sleeve covering the nanotube damps its high-frequency fluctuations because of the network viscoelasticity. Our work paves the way for further studies of the effect of nanotube fluctuations on cellular functions.
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Affiliation(s)
- A Allard
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France
- Sorbonne Université, UPMC, Paris 06, Paris, France
- LAMBE, Université d'Évry, CNRS, CEA, Université Paris-Saclay, 91025 Évry-Courcouronnes, France
| | - F Valentino
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France
- Sorbonne Université, UPMC, Paris 06, Paris, France
| | - C Sykes
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France
- Sorbonne Université, UPMC, Paris 06, Paris, France
| | - T Betz
- Institute of Cell Biology, Cells in Motion Interfaculty Center, Centre for Molecular Biology of Inflammation, 48149 Münster, Germany
| | - C Campillo
- LAMBE, Université d'Évry, CNRS, CEA, Université Paris-Saclay, 91025 Évry-Courcouronnes, France
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6
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Statistical Mechanics of an Elastically Pinned Membrane: Equilibrium Dynamics and Power Spectrum. Biophys J 2019; 117:542-552. [PMID: 31349987 DOI: 10.1016/j.bpj.2019.06.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 06/22/2019] [Accepted: 06/26/2019] [Indexed: 11/21/2022] Open
Abstract
In biological settings, membranes typically interact locally with other membranes: the extracellular matrix in the exterior or internal cellular structures such as the cytoskeleton, locally pinning the membrane. Characterizing the dynamical properties of such interactions presents a difficult task. Significant progress has been achieved through simulations and experiments, yet analytical progress in modeling pinned membranes has been impeded by the complexity of governing equations. Here, we circumvent these difficulties by calculating analytically the time-dependent Green's function of the operator governing the dynamics of an elastically pinned membrane in a hydrodynamic surrounding and subject to external forces. This enables us to calculate the equilibrium power spectral density for an overdamped membrane pinned by an elastic, permanently attached spring subject to thermal excitations. By considering the effects of the finite experimental resolution on the measured spectra, we show that the elasticity of the pinning can be extracted from the experimentally measured spectrum. Membrane fluctuations can thus be used as a tool to probe mechanical properties of the underlying structures. Such a tool may be particularly relevant in the context of cell mechanics, in which the elasticity of the membrane's attachment to the cytoskeleton could be measured.
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7
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Kang M, Lee B, Leal C. Three-Dimensional Microphase Separation and Synergistic Permeability in Stacked Lipid-Polymer Hybrid Membranes. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2017; 29:9120-9132. [PMID: 31097879 PMCID: PMC6516788 DOI: 10.1021/acs.chemmater.7b02845] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We present new structures of soft-material thin films that augment the functionality of substrate-mediated delivery systems. A hybrid material composed of phospholipids and block copolymers adopts a multilayered membrane structure supported on a solid surface. The hybrid films comprise intentional intramembrane heterogeneities that register across multilayers. These stacked domains convey unprecedented enhancement and control of permeability of solutes across micrometer-thick films. Using grazing incidence X-ray scattering, phase contrast atomic force microscopy, and confocal microscopy, we observed that in each lamella, lipid and polymers partition unevenly within the membrane plane segregating into lipid- or polymer-rich domains. Interestingly, we found evidence that like-domains align in registry across multilayers, thereby making phase separation three-dimensional. Phase boundaries exist over extended length scales to compensate the height mismatch between lipid and polymer molecules. We show that microphase separation in hybrid films can be exploited to augment the capability of drug-eluting substrates. Lipid-polymer hybrid films loaded with paclitaxel show synergistic permeability of drug compared to single-component counterparts. We present a thorough structural study of stacked lipid-polymer hybrid membranes and propose that the presence of registered domains and domain boundaries impart enhanced drug release functionality. This work offers new perspectives in designing thin films for controlled delivery applications.
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Affiliation(s)
- Minjee Kang
- Department of Materials Science and Engineering, University of Illinois at Urbana–Champaign, Urbana, Illinois 61801, United States
| | - Byeongdu Lee
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Cecilia Leal
- Department of Materials Science and Engineering, University of Illinois at Urbana–Champaign, Urbana, Illinois 61801, United States
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8
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Kowalik B, Schlaich A, Kanduč M, Schneck E, Netz RR. Hydration Repulsion Difference between Ordered and Disordered Membranes Due to Cancellation of Membrane-Membrane and Water-Mediated Interactions. J Phys Chem Lett 2017; 8:2869-2874. [PMID: 28590133 DOI: 10.1021/acs.jpclett.7b00977] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Hydration repulsion acts between all sufficiently polar surfaces in water at small separations and prevents dry adhesion up to kilobar pressures. Yet it remained unclear whether this ubiquitous force depends on surface structure or is a sole water property. We demonstrate that previous deviations among different experimental measurements of hydration pressures in phospholipid bilayer stacks disappear when plotting data consistently as a function of repeat distance or membrane surface distance. The resulting pressure versus distance curves agree quantitatively with our atomistic simulation results and exhibit different decay lengths in the ordered gel and the disordered fluid states. This suggests that hydration forces are not caused by water ordering effects alone. Splitting the simulated total pressure into membrane-membrane and water-mediated parts shows that these contributions are opposite in sign and of similar magnitude, thus they are equally important. The resulting net hydration pressure between membranes is what remains from the near-cancellation of these ambivalent contributions.
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Affiliation(s)
- Bartosz Kowalik
- Department of Physics, Freie Universität Berlin , 14195 Berlin, Germany
| | | | - Matej Kanduč
- Institut für Weiche Materie und Funktionale Materialien, Helmholtz-Zentrum Berlin , 14109 Berlin, Germany
| | - Emanuel Schneck
- Biomaterials Department, Max Planck Institute of Colloids and Interfaces , 14476 Potsdam, Germany
| | - Roland R Netz
- Department of Physics, Freie Universität Berlin , 14195 Berlin, Germany
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9
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Lu BS, Gupta SP, Belička M, Podgornik R, Pabst G. Modulation of Elasticity and Interactions in Charged Lipid Multibilayers: Monovalent Salt Solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:13546-13555. [PMID: 27993014 PMCID: PMC5180256 DOI: 10.1021/acs.langmuir.6b03614] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/22/2016] [Indexed: 05/18/2023]
Abstract
We have studied the electrostatic screening effect of NaCl solutions on the interactions between anionic lipid bilayers in the fluid lamellar phase using a Poisson-Boltzmann-based mean-field approach with constant charge and constant potential limiting charge regulation boundary conditions. The full DLVO potential, including the electrostatic, hydration and van der Waals interactions, was coupled to thermal bending fluctuations of the membranes via a variational Gaussian Ansatz. This allowed us to analyze the coupling between the osmotic pressure and the fluctuation amplitudes and compare them both simultaneously with their measured dependence on the bilayer separation, determined by the small-angle X-ray scattering experiments. High-structural resolution analysis of the scattering data revealed no significant changes of membrane structure as a function of salt concentration. Parsimonious description of our results is consistent with the constant charge limit of the general charge regulation phenomenology, with fully dissociated lipid charge groups, together with a 6-fold reduction of the membranes' bending rigidity upon increasing NaCl concentration.
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Affiliation(s)
- Bing-Sui Lu
- Department
of Theoretical Physics, Jožef Stefan
Institute, 1000 Ljubljana, Slovenia
- School
of Physical and Mathematical Sciences, Nanyang
Technological University, 21 Nanyang Link, 637371 Singapore
- E-mail:
| | - Santosh Prasad Gupta
- Institute
of Molecular Biosciences, Biophysics Division,University of Graz, NAWI Graz, Humboldtstraße 50/III, A-8010 Graz, Austria
- BioTechMed-Graz, A-8010 Graz, Austria
| | - Michal Belička
- Institute
of Molecular Biosciences, Biophysics Division,University of Graz, NAWI Graz, Humboldtstraße 50/III, A-8010 Graz, Austria
- BioTechMed-Graz, A-8010 Graz, Austria
| | - Rudolf Podgornik
- Department
of Theoretical Physics, Jožef Stefan
Institute, 1000 Ljubljana, Slovenia
- Department
of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
- E-mail:
| | - Georg Pabst
- Institute
of Molecular Biosciences, Biophysics Division,University of Graz, NAWI Graz, Humboldtstraße 50/III, A-8010 Graz, Austria
- BioTechMed-Graz, A-8010 Graz, Austria
- E-mail: . Phone: +43 316 380 4989
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10
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Ma Y, Ghosh SK, Bera S, Jiang Z, Schlepütz CM, Karapetrova E, Lurio LB, Sinha SK. Anomalous partitioning of water in coexisting liquid phases of lipid multilayers near 100% relative humidity. Phys Chem Chem Phys 2016; 18:1225-32. [PMID: 26661405 DOI: 10.1039/c5cp04703j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ternary lipid mixtures incorporating cholesterol are well-known to phase separate into liquid-ordered (L(o)) and liquid-disordered (L(d)) phases. In multilayers of these systems, the laterally phase separated domains register in columnar structures with different bilayer periodicities, resulting in hydrophobic mismatch energies at the domain boundaries. In this paper, we demonstrate via synchrotron-based X-ray diffraction measurements that the system relieves the hydrophobic mismatch at the domain boundaries by absorbing larger amounts of inter-bilayer water into the L(d) phase with lower d-spacing as the relative humidity approaches 100%. The lamellar repeat distance of the L(d) phase swells by an extra 4 Å, well beyond the equilibrium spacing predicted by the inter-bilayer forces. This anomalous swelling is caused by the hydrophobic mismatch energy at the domain boundaries, which produces a surprisingly long-range effect. We also demonstrate that the d-spacings of the lipid multilayers at 100% relative humidity do not change when bulk water begins to condense on the sample.
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Affiliation(s)
- Yicong Ma
- Department of Physics, University of California-San Diego, La Jolla, CA-92093, USA.
| | - Sajal K Ghosh
- Department of Physics, University of California-San Diego, La Jolla, CA-92093, USA.
| | - Sambhunath Bera
- Department of Physics, University of California-San Diego, La Jolla, CA-92093, USA.
| | - Zhang Jiang
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL-60439, USA
| | | | | | - Laurence B Lurio
- Department of Physics, Northern Illinois University, DeKalb, IL-60115, USA
| | - Sunil K Sinha
- Department of Physics, University of California-San Diego, La Jolla, CA-92093, USA.
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11
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Monzel C, Schmidt D, Seifert U, Smith AS, Merkel R, Sengupta K. Nanometric thermal fluctuations of weakly confined biomembranes measured with microsecond time-resolution. SOFT MATTER 2016; 12:4755-4768. [PMID: 27142463 DOI: 10.1039/c6sm00412a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We probe the bending fluctuations of bio-membranes using highly deflated giant unilamellar vesicles (GUVs) bound to a substrate by a weak potential arising from generic interactions. The substrate is either homogeneous, with GUVs bound only by the weak potential, or is chemically functionalized with a micro-pattern of very strong specific binders. In both cases, the weakly adhered membrane is seen to be confined at a well-defined distance above the surface while it continues to fluctuate strongly. We quantify the fluctuations of the weakly confined membrane at the substrate proximal surface as well as of the free membrane at the distal surface of the same GUV. This strategy enables us to probe in detail the damping of fluctuations in the presence of the substrate, and to independently measure the membrane tension and the strength of the generic interaction potential. Measurements were done using two complementary techniques - dynamic optical displacement spectroscopy (DODS, resolution: 20 nm, 10 μs), and dual wavelength reflection interference contrast microscopy (DW-RICM, resolution: 4 nm, 50 ms). After accounting for the spatio-temporal resolution of the techniques, an excellent agreement between the two measurements was obtained. For both weakly confined systems we explore in detail the link between fluctuations on the one hand and membrane tension and the interaction potential on the other hand.
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Affiliation(s)
- Cornelia Monzel
- Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France. and Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany
| | - Daniel Schmidt
- II. Institut für Theoretische Physik, Universität Stuttgart, Germany and Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany
| | - Udo Seifert
- II. Institut für Theoretische Physik, Universität Stuttgart, Germany
| | - Ana-Sunčana Smith
- Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany and Division of Physical Chemistry, Ruđer Bošković Institute, 10000 Zagreb, Croatia
| | - Rudolf Merkel
- Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany
| | - Kheya Sengupta
- Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France.
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12
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Kollmitzer B, Heftberger P, Podgornik R, Nagle JF, Pabst G. Bending Rigidities and Interdomain Forces in Membranes with Coexisting Lipid Domains. Biophys J 2016; 108:2833-42. [PMID: 26083923 PMCID: PMC4472082 DOI: 10.1016/j.bpj.2015.05.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 04/13/2015] [Accepted: 05/03/2015] [Indexed: 11/29/2022] Open
Abstract
To precisely quantify the fundamental interactions between heterogeneous lipid membranes with coexisting liquid-ordered (Lo) and liquid-disordered (Ld) domains, we performed detailed osmotic stress small-angle x-ray scattering experiments by exploiting the domain alignment in raft-mimicking lipid multibilayers. Performing a Monte Carlo-based analysis allowed us to determine with high reliability the magnitude and functional dependence of interdomain forces concurrently with the bending elasticity moduli. In contrast to previous methodologies, this approach enabled us to consider the entropic undulation repulsions on a fundamental level, without having to take recourse to crudely justified mean-field-like additivity assumptions. Our detailed Hamaker-coefficient calculations indicated only small differences in the van der Waals attractions of coexisting Lo and Ld phases. In contrast, the repulsive hydration and undulation interactions differed significantly, with the latter dominating the overall repulsions in the Ld phase. Thus, alignment of like domains in multibilayers appears to originate from both, hydration and undulation repulsions.
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Affiliation(s)
- Benjamin Kollmitzer
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria
| | - Peter Heftberger
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria
| | - Rudolf Podgornik
- Department of Theoretical Physics, Jožef Stefan Institute, Ljubljana, Slovenia; Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia; Department of Physics, University of Massachusetts, Amherst, Massachusetts
| | - John F Nagle
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria.
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13
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Ahmadpoor F, Sharma P. Thermal fluctuations of vesicles and nonlinear curvature elasticity--implications for size-dependent renormalized bending rigidity and vesicle size distribution. SOFT MATTER 2016; 12:2523-36. [PMID: 26739194 DOI: 10.1039/c5sm02769a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Both closed and open biological membranes noticeably undulate at physiological temperatures. These thermal fluctuations influence a broad range of biophysical phenomena, ranging from self-assembly to adhesion. In particular, the experimentally measured thermal fluctuation spectra also provide a facile route to the assessment of mechanical and certain other physical properties of biological membranes. The theoretical assessment of thermal fluctuations, be it for closed vesicles or the simpler case of flat open lipid bilayers, is predicated upon assuming that the elastic curvature energy is a quadratic functional of the curvature tensor. However, a qualitatively correct description of several phenomena such as binding-unbinding transition, vesicle-to-bicelle transition, appearance of hats and saddles among others, appears to require consideration of constitutively nonlinear elasticity that includes fourth order curvature contributions rather than just quadratic. In particular, such nonlinear considerations are relevant in the context of large-curvature or small-sized vesicles. In this work we discuss the statistical mechanics of closed membranes (vesicles) incorporating both constitutive and geometrical nonlinearities. We derive results for the renormalized bending rigidity of small vesicles and show that significant stiffening may occur for sub-20 nm vesicle sizes. Our closed-form results may also be used to determine nonlinear curvature elasticity properties from either experimentally measured fluctuation spectra or microscopic calculations such as molecular dynamics. Finally, in the context of our results on thermal fluctuations of vesicles and nonlinear curvature elasticity, we reexamine the problem of determining the size distribution of vesicles and obtain results that reconcile well with experimental observations. However, our results are somewhat paradoxical. Specifically, the molecular dynamics predictions for the thermo-mechanical behavior of small vesicles of prior studies appear to be inconsistent with the nonlinear elastic properties that we estimate by fitting to the experimentally determined vesicle size-distribution trends and data.
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Affiliation(s)
- Fatemeh Ahmadpoor
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA.
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14
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Marquardt D, Heberle FA, Nickels JD, Pabst G, Katsaras J. On scattered waves and lipid domains: detecting membrane rafts with X-rays and neutrons. SOFT MATTER 2015; 11:9055-72. [PMID: 26428538 PMCID: PMC4719199 DOI: 10.1039/c5sm01807b] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/21/2015] [Indexed: 05/28/2023]
Abstract
In order to understand the biological role of lipids in cell membranes, it is necessary to determine the mesoscopic structure of well-defined model membrane systems. Neutron and X-ray scattering are non-invasive, probe-free techniques that have been used extensively in such systems to probe length scales ranging from angstroms to microns, and dynamics occurring over picosecond to millisecond time scales. Recent developments in the area of phase separated lipid systems mimicking membrane rafts will be presented, and the underlying concepts of the different scattering techniques used to study them will be discussed in detail.
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Affiliation(s)
- Drew Marquardt
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, Graz, Austria. and BioTechMed-Graz, Graz, Austria
| | - Frederick A Heberle
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
| | - Jonathan D Nickels
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, Graz, Austria. and BioTechMed-Graz, Graz, Austria
| | - John Katsaras
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. and Joint Institute for Neutron Sciences, Oak Ridge, Tennessee 37831, USA
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15
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Lu BS, Podgornik R. Effective interactions between fluid membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:022112. [PMID: 26382349 DOI: 10.1103/physreve.92.022112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Indexed: 06/05/2023]
Abstract
A self-consistent theory is proposed for the general problem of interacting undulating fluid membranes subject to the constraint that they do not interpenetrate. We implement the steric constraint via an exact functional integral representation and, through the use of a saddle-point approximation, transform it into a novel effective steric potential. The steric potential is found to consist of two contributions: one generated by zero-mode fluctuations of the membranes and the other by thermal bending fluctuations. For membranes of cross-sectional area S, we find that the bending fluctuation part scales with the intermembrane separation d as d-2 for d≪√S but crosses over to d-4 scaling for d≫√S, whereas the zero-mode part of the steric potential always scales as d-2. For membranes interacting exclusively via the steric potential, we obtain closed-form expressions for the effective interaction potential and for the rms undulation amplitude σ, which becomes small at low temperatures T and/or large bending stiffnesses κ. Moreover, σ scales as d for d≪√S but saturates at √kBTS/κ for d≫√S. In addition, using variational Gaussian theory, we apply our self-consistent treatment to study intermembrane interactions subject to different types of potentials: (i) the Moreira-Netz potential for a pair of strongly charged membranes with an intervening solution of multivalent counterions, (ii) an attractive square well, (iii) the Morse potential, and (iv) a combination of hydration and van der Waals interactions.
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Affiliation(s)
- Bing-Sui Lu
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000 Ljubljana, Slovenia and Department of Theoretical Physics, J. Stefan Institute, 1000 Ljubljana, Slovenia
| | - Rudolf Podgornik
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000 Ljubljana, Slovenia and Department of Theoretical Physics, J. Stefan Institute, 1000 Ljubljana, Slovenia
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16
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Parikh AN. Medium Matters: Order through Fluctuations? Biophys J 2015; 108:2751-3. [PMID: 26083909 DOI: 10.1016/j.bpj.2015.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 05/11/2015] [Accepted: 05/11/2015] [Indexed: 11/24/2022] Open
Affiliation(s)
- Atul N Parikh
- Departments of Biomedical Engineering and Chemical Engineering & Materials Science, University of California, Davis, Davis, California; Centre for Biomimetic Sensor Science, School of Materials Science & Engineering, Nanyang Technological University, Singapore.
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17
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Johnson M, Seifert S, Petrache HI, Kimble-Hill AC. Phase coexistence in single-lipid membranes induced by buffering agents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9880-9885. [PMID: 25102340 PMCID: PMC4148158 DOI: 10.1021/la5018938] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 07/29/2014] [Indexed: 05/28/2023]
Abstract
Recent literature has shown that buffers affect the interaction between lipid bilayers through a mechanism that involves van der Waals forces, electrostatics, hydration forces and membrane bending rigidity. This letter shows an additional peculiar effect of buffers on the mixed chain 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayers, namely phase coexistence similar to what was reported by Rappolt et al. for alkali chlorides. The data presented suggest that one phase appears to dehydrate below the value in pure water, while the other phase swells as the concentration of buffer is increased. However, since the two phases must be in osmotic equilibrium with one another, this behavior challenges theoretical models of lipid interactions.
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Affiliation(s)
- Merrell
A. Johnson
- Department
of Physics, Indiana University−Purdue
University Indianapolis, LD 154, 402 North Blackford Street, Indianapolis, Indiana 46202, United States
| | - Soenke Seifert
- X-ray
Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Horia I. Petrache
- Department
of Physics, Indiana University−Purdue
University Indianapolis, LD 154, 402 North Blackford Street, Indianapolis, Indiana 46202, United States
| | - Ann C. Kimble-Hill
- Department
of Biochemistry and Molecular Biology, Indiana
University School of Medicine, MS 4053, 635 Barnhill Drive, Indianapolis, Indiana 46202, United States
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18
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Loubet B, Lomholt MA, Khandelia H. Tension moderation and fluctuation spectrum in simulated lipid membranes under an applied electric potential. J Chem Phys 2013; 139:164902. [DOI: 10.1063/1.4826462] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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19
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Solmaz ME, Sankhagowit S, Biswas R, Mejia CA, Povinelli ML, Malmstadt N. Optical stretching as a tool to investigate the mechanical properties of lipid bilayers. RSC Adv 2013; 3:10.1039/C3RA42510J. [PMID: 24244843 PMCID: PMC3827026 DOI: 10.1039/c3ra42510j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Measurements of lipid bilayer bending modulus by various techniques produce widely divergent results. We attempt to resolve some of this ambiguity by measuring bending modulus in a system that can rapidly process large numbers of samples, yielding population statistics. This system is based on optical stretching of giant unilamellar vesicles (GUVs) in a microfluidic dual-beam optical trap (DBOT). The microfluidic DBOT system is used here to measure three populations of GUVs with distinct lipid compositions. We find that gel-phase membranes are significantly stiffer than liquid-phase membranes, consistent with previous reports. We also find that the addition of cholesterol does not alter the bending modulus of membranes composed of a monounsaturated phospholipid.
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Affiliation(s)
- Mehmet E. Solmaz
- Ming Hsieh Department of Electrical Engineering, University of Southern California, 3737 Watt Way, PHE 614, Los Angeles, CA 90089-0271, USA
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 925 Bloom Walk, HED 216, Los Angeles, CA 90089-1211, USA
| | - Shalene Sankhagowit
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 925 Bloom Walk, HED 216, Los Angeles, CA 90089-1211, USA
| | - Roshni Biswas
- Ming Hsieh Department of Electrical Engineering, University of Southern California, 3737 Watt Way, PHE 614, Los Angeles, CA 90089-0271, USA
| | - Camilo A. Mejia
- Ming Hsieh Department of Electrical Engineering, University of Southern California, 3737 Watt Way, PHE 614, Los Angeles, CA 90089-0271, USA
| | - Michelle L. Povinelli
- Ming Hsieh Department of Electrical Engineering, University of Southern California, 3737 Watt Way, PHE 614, Los Angeles, CA 90089-0271, USA
| | - Noah Malmstadt
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 925 Bloom Walk, HED 216, Los Angeles, CA 90089-1211, USA
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20
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Benhamou M, Kaidi H. Unbinding transition from fluid membranes with associated polymers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:125. [PMID: 24162525 DOI: 10.1140/epje/i2013-13125-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 07/06/2013] [Accepted: 10/09/2013] [Indexed: 06/02/2023]
Abstract
We consider two neighboring fluid membranes that are associated with long flexible polymers (proteins or other macromolecules). We are interested in two physical systems consisting of i) two adjacent membranes with end-grafted (or adsorbed) polymers (system I), or ii) two membranes confining a polymer solution (system II). In addition to the pure interactions between membranes, the presence of polymers gives rise to new induced mediated interactions, which are repulsive, for system I, and attractive, for system II. In fact, repulsive induced interactions are caused by the excluded-volume forces between grafted polymers, while attractive ones, by entropy loss, due to free motion of polymers between membranes. The main goal is a quantitative study of the unbinding transition thermodynamics that is drastically affected by the associated polymers. For system I, the repulsive polymer-mediated force delays this transition that can happen at low temperature. To investigate the unbinding phenomenon, we first present an exact mathematical analysis of the total potential that is the sum of the primitive and induced potentials. This mathematical study enables us to classify the total interaction potentials, in terms of all parameters of the problem. Second, use is made of the standard variational method to calculate the first moments of the membrane separation. Special attention is paid to the determination of the unbinding temperature. In particular, we discuss its dependence on the extra parameters related to the associated polymers, which are the surface coverage and the polymer layer thickness on each membrane (for system I) or the polymer density and the gyration radius of coils (for system II). Third, we compute the disjoining pressure upon membrane separation. Finally, we emphasize that the presence of polymers may be a mechanism to delay or to accentuate the appearance of the unbinding transition between fluid membranes.
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Affiliation(s)
- M Benhamou
- ENSAM, Moulay Ismail University, P.O. Box 25290, Al Mansour, Meknes, Morocco,
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21
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Hemmerle A, Malaquin L, Charitat T, Lecuyer S, Fragneto G, Daillant J. Controlling interactions in supported bilayers from weak electrostatic repulsion to high osmotic pressure. Proc Natl Acad Sci U S A 2012; 109:19938-42. [PMID: 23169650 PMCID: PMC3523853 DOI: 10.1073/pnas.1211669109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding interactions between membranes requires measurements on well-controlled systems close to natural conditions, in which fluctuations play an important role. We have determined, by grazing incidence X-ray scattering, the interaction potential between two lipid bilayers, one adsorbed on a solid surface and the other floating close by. We find that interactions in this highly hydrated model system are two orders of magnitude softer than in previously reported work on multilayer stacks. This is attributed to the weak electrostatic repulsion due to the small fraction of ionized lipids in supported bilayers with a lower number of defects. Our data are consistent with the Poisson-Boltzmann theory, in the regime where repulsion is dominated by the entropy of counter ions. We also have unique access to very weak entropic repulsion potentials, which allowed us to discriminate between the various models proposed in the literature. We further demonstrate that the interaction potential between supported bilayers can be tuned at will by applying osmotic pressure, providing a way to manipulate these model membranes, thus considerably enlarging the range of biological or physical problems that can be addressed.
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Affiliation(s)
- Arnaud Hemmerle
- Université de Strasbourg, Institut Charles Sadron, Unité Propre de Recherche 22, Centre National de la Recherche Scientifique (CNRS), 67034 Strasbourg Cedex 2, France
- Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS), Service Interdisciplinaire sur les Systémes Moléculaires et les Matériaux (SIS2M), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'Energie Atomique (CEA), Unité Mixte de Recherche 3299 CEA/CNRS, F-91191 Gif-sur-Yvette Cedex, France
| | - Linda Malaquin
- Université de Strasbourg, Institut Charles Sadron, Unité Propre de Recherche 22, Centre National de la Recherche Scientifique (CNRS), 67034 Strasbourg Cedex 2, France
- Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS), Service Interdisciplinaire sur les Systémes Moléculaires et les Matériaux (SIS2M), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'Energie Atomique (CEA), Unité Mixte de Recherche 3299 CEA/CNRS, F-91191 Gif-sur-Yvette Cedex, France
| | - Thierry Charitat
- Université de Strasbourg, Institut Charles Sadron, Unité Propre de Recherche 22, Centre National de la Recherche Scientifique (CNRS), 67034 Strasbourg Cedex 2, France
| | - Sigolène Lecuyer
- Université de Strasbourg, Institut Charles Sadron, Unité Propre de Recherche 22, Centre National de la Recherche Scientifique (CNRS), 67034 Strasbourg Cedex 2, France
| | | | - Jean Daillant
- Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS), Service Interdisciplinaire sur les Systémes Moléculaires et les Matériaux (SIS2M), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'Energie Atomique (CEA), Unité Mixte de Recherche 3299 CEA/CNRS, F-91191 Gif-sur-Yvette Cedex, France
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22
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Ahmed S, Savarala S, Chen Y, Bothun G, Wunder SL. Formation of lipid sheaths around nanoparticle-supported lipid bilayers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:1740-1751. [PMID: 22434657 DOI: 10.1002/smll.201101833] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Revised: 10/25/2011] [Indexed: 05/31/2023]
Abstract
High-surface-area nanoparticles often cluster, with unknown effects on their cellular uptake and environmental impact. In the presence of vesicles or cell membranes, lipid adsorption can occur on the nanoparticles, resulting in the formation of supported lipid bilayers (SLBs), which tend to resist cellular uptake. When the amount of lipid available is in excess compared with that required to form a single-SLB, large aggregates of SLBs enclosed by a close-fitting lipid bilayer sheath are shown to form. The proposed mechanism for this process is one where small unilamellar vesicles (SUVs) adsorb to aggregates of SLBs just above the gel-to-liquid phase transition temperature, T(m) , of the lipids (as observed by dynamic light scattering), and then fuse with each other (rather than to the underlying SLBs) upon cooling below T(m) . The sacks of SLB nanoparticles that are formed are encapsulated by the contiguous close-fitting lipid sheath, and precipitate below T(m) , due to reduced hydration repulsion and the absence of undulation/protrusion forces for the lipids attached to the solid support. The single-SLBs can be released above T(m) , where these forces are restored by the free lipid vesicles. This mechanism may be useful for encapsulation/release of drugs/DNA, and has implications for the toxic effects of nanoparticles, which may be mitigated by lipid sequestration.
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Affiliation(s)
- Selver Ahmed
- Department of Chemistry, Temple University, Philadelphia, PA 19317, USA
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23
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Water adsorption isotherms of lipids. Biophys J 2012; 101:2704-12. [PMID: 22261059 DOI: 10.1016/j.bpj.2011.10.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 09/26/2011] [Accepted: 10/12/2011] [Indexed: 11/21/2022] Open
Abstract
Hydration of bilayer lipids is a fundamental property of biological membranes. The available database of lipid hydration isotherms is fitted over the entire range of water activities by using a statistical mechanical approach that is an extension of the common Brunauer-Emmett-Teller model, to include differential energies of association for water molecules beyond the first strongly bound layer. Three-parameter fits are obtained that can be used to represent the experimental isotherms to a good degree of accuracy over the complete range of water-binding activities. Fits are also made in terms of the hydration pressure and correlation length of water ordering, by using the polarization theory of lipid hydration. The relationship of the latter approach to measurements of hydration forces between lipid bilayers is discussed.
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24
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Loubet B, Seifert U, Lomholt MA. Effective tension and fluctuations in active membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:031913. [PMID: 22587129 DOI: 10.1103/physreve.85.031913] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Indexed: 05/31/2023]
Abstract
We calculate the fluctuation spectrum of the shape of a lipid vesicle or cell exposed to a nonthermal source of noise. In particular, we take constraints on the membrane area and the volume of fluid that it encapsulates into account when obtaining expressions for the dependency of the membrane tension on the noise. We then investigate three possible origins of the nonthermal noise taken from the literature: A direct force, which models an external medium pushing on the membrane, a curvature force, which models a fluctuating spontaneous curvature, and a permeation force coming from an active transport of fluid through the membrane. For the direct force and curvature force cases, we compare our results to existing experiments on active membranes.
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Affiliation(s)
- Bastien Loubet
- Department of Physics, MEMPHYS-Center for Biomembrane Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark
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25
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Electrodynamics of lipid membrane interactions in the presence of zwitterionic buffers. Biophys J 2011; 101:362-9. [PMID: 21767488 DOI: 10.1016/j.bpj.2011.05.062] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 05/10/2011] [Accepted: 05/27/2011] [Indexed: 11/22/2022] Open
Abstract
Due to thermal motion and molecular polarizability, electrical interactions in biological systems have a dynamic character. Zwitterions are dipolar molecules that typically are highly polarizable and exhibit both a positive and a negative charge depending on the pH of the solution. We use multilamellar structures of common lipids to identify and quantify the effects of zwitterionic buffers that go beyond the control of pH. We use the fact that the repeat spacing of multilamellar lipid bilayers is a sensitive and accurate indicator of the force balance between membranes. We show that common buffers can in fact charge up neutral membranes. However, this electrostatic effect is not immediately recognized because of the concomitant modification of dispersion (van der Waals) forces. We show that although surface charging can be weak, electrostatic forces are significant even at large distances because of reduced ionic screening and reduced van der Waals attraction. The zwitterionic interactions that we identify are expected to be relevant for interfacial biological processes involving lipid bilayers, and for a wide range of biomaterials, including amino acids, detergents, and pharmaceutical drugs. An appreciation of zwitterionic electrodynamic character can lead to a better understanding of molecular interactions in biological systems and in soft materials in general.
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26
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Schneck E, Demé B, Gege C, Tanaka M. Membrane adhesion via homophilic saccharide-saccharide interactions investigated by neutron scattering. Biophys J 2011; 100:2151-9. [PMID: 21539782 DOI: 10.1016/j.bpj.2011.03.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 03/11/2011] [Accepted: 03/15/2011] [Indexed: 10/18/2022] Open
Abstract
Solid-supported membrane multilayers doped with membrane-anchored oligosaccharides bearing the LewisX motif (Le(X) lipid) were utilized as a model system of membrane adhesion mediated via homophilic carbohydrate-carbohydrate interactions. Specular and off-specular neutron scattering in bulk aqueous electrolytes allowed us to study multilayer structure and membrane mechanics at full hydration at various Ca(2+) concentrations, indicating that membrane-anchored Le(X) cross-links the adjacent membranes. To estimate forces and energies required for cross-linking, we theoretically modeled the interactions between phospholipid membranes and compared this model with our experimental results on membranes doped with Le(X) lipids. We demonstrated that the bending rigidity, extracted from the off-specular scattering signals, is not significantly influenced by the molar fraction of Le(X) lipids, while the vertical compression modulus (and thus the intermembrane confinement) increases with the molar fraction of Le(X) lipids.
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Affiliation(s)
- Emanuel Schneck
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg, Germany
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27
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Savarala S, Monson F, Ilies MA, Wunder SL. Supported lipid bilayer nanosystems: stabilization by undulatory-protrusion forces and destabilization by lipid bridging. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5850-5861. [PMID: 21500811 DOI: 10.1021/la200636k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Control of the stabilization/destabilization of supported lipid bilayers (SLBs) on nanoparticles is important for promotion of their organized assembly and for their use as delivery vehicles. At the same time, understanding the mechanism of these processes can yield insight into nanoparticle-cell interactions and nanoparticle toxicity. In this study, the suspension/precipitation process of zwitterionic lipid/SiO(2) nanosystems was analyzed as a function of ionic strength and as a function of the ratio of lipid/SiO(2) surface areas, at pH = 7.6. Salt is necessary to induce supported lipid bilayer (SLB) formation for zwitterionic lipids on silica (SiO(2)) (Seantier, B.; Kasemo, B., Influence of Mono- and Divalent Ions on the Formation of Supported Phospholipid Bilayers via Vesicle Adsorption. Langmuir 2009, 25 (10), 5767-5772). However, for zwitterionic SLBs on SiO(2) nanoparticles, addition of salt can cause precipitation of the SLBs, due to electrostatic shielding by both the lipid and the salt and to the suppression of thermal undulation/protrusion repulsive forces for lipids on solid surfaces. At ionic strengths that cause precipitation of SLBs, it was found that addition of excess SUVs, at ratios where there were equal populations of SUVs and SLBs, restored the undulation/protrusion repulsive forces and restabilized the suspensions. We suggest that SUVs separate SLBs in the suspension, as observed by TEM, and that SLB-SLB interactions are replaced by SLB-SUV interactions. Decreasing the relative amount of lipid, to the extent that there was less lipid available than the amount required for complete bilayer coverage of the SiO(2), resulted in precipitation of the nanosystem by a process of nanoparticle lipid bridging. For this case, we postulate a process in which lipid bilayer patches on one nanoparticle collide with bare silica patches on another SiO(2) nanoparticle, forming a single bilayer bridge between them. TEM data confirmed these findings, thus indicating that lipid bridges are composed of half bilayers on adjoining SiO(2) nanoparticles.
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Affiliation(s)
- Sushma Savarala
- Department of Chemistry, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, United States
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28
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Savarala S, Ahmed S, Ilies MA, Wunder SL. Stabilization of soft lipid colloids: competing effects of nanoparticle decoration and supported lipid bilayer formation. ACS NANO 2011; 5:2619-2628. [PMID: 21381770 DOI: 10.1021/nn1025884] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Stabilization against fusion of zwitterionic lipid small unilamellar vesicles (SUVs) by charged nanoparticles is essential to prevent premature inactivation and cargo unloading. In the present work, we examined the stabilization of DMPC and DPPC SUVs by monolithic silica (SiO(2)) nanoparticle envelopment, for SiO(2) with 4-6, 10-20, 20-30, and 40-50 nm nominal diameter. We found that for these soft colloids stabilization is critically dependent on whether fusion occurs between the charged nanoparticles and neutral SUVs to form supported lipid bilayers (SLBs), or whether the reverse occurs, namely, nanoparticle decoration of the SUVs. While SLB formation is accompanied by precipitation, nanoparticle decoration results in long-term stabilization of the SUVs. The fate of the nanosystem depends on the size of the nanoparticles and on the ionic strength of the medium. We found that, in the case of highly charged SiO(2) nanoparticles in water, there is no SUV fusion to SiO(2) for a specific range of nanoparticle sizes. Instead, the negatively charged SiO(2) nanoparticles surround the uncharged SUVs, resulting in electrostatic repulsion between the decorated SUVs, thus preventing their aggregation and precipitation. Addition of millimolar amounts of NaCl results in rapid SLB formation and precipitation. This study has great potential impact toward better understanding the interaction of nanoparticles with biological membranes and the factors affecting their use as drug carriers or sensors.
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Affiliation(s)
- Sushma Savarala
- Department of Chemistry, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA
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29
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Rodowicz KA, Francisco H, Layton B. Determination of the mechanical properties of DOPC:DOPS liposomes using an image procession algorithm and micropipette-aspiration techniques. Chem Phys Lipids 2010; 163:787-93. [PMID: 20863821 DOI: 10.1016/j.chemphyslip.2010.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 09/11/2010] [Accepted: 09/14/2010] [Indexed: 02/01/2023]
Abstract
Quantification of the mechanical properties of liposomes is critical in helping to predict their behavior during various applications such as targeted drug delivery, response to mechanical characterization or their interactions with isolated cytoskeletal elements. A numerical implementation of the Evans aspiration technique, and an image processing algorithm for measuring deformation of spherical DOPC:DOPS liposomes is presented. Liposomes were aspirated to pressures of -10mmHg (∼-1300Pa). The area expansion and Young's moduli of the liposomes were found to be 0.067Nm⁻¹ (67±4dyn/cm) and 15±1 MPa.
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Affiliation(s)
- Kathleen Allen Rodowicz
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104, USA
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30
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Effect of added monovalent electrolytes on the myelin formation from charged lipids. J Colloid Interface Sci 2010; 348:505-10. [PMID: 20553688 DOI: 10.1016/j.jcis.2010.05.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 05/03/2010] [Accepted: 05/04/2010] [Indexed: 11/21/2022]
Abstract
The effect of added monovalent electrolytes on the myelin formation of cardiolipin is investigated by optical microscopy observations. The results show that the myelin formation strongly depends on the concentration rather than the type of electrolytes. Myelin figures are observed only in a certain concentration range of electrolytes, and the diameter of the myelin figures decreases with increasing of the electrolyte concentration. Furthermore, the theoretical model of myelin formation for the neutral lipids developed by Huang-Zou-Witten [J.R. Huang, L.N. Zou, T.A. Witten, Eur. Phys. J. E. 18 (2005) 279-285] is extended to the charged membrane system by taking into account the electrostatic interaction to understand the mechanism of myelin formation. The theoretical results well produce our experimental results.
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31
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Ušaj M, Trontelj K, Miklavčič D, Kandušer M. Cell–Cell Electrofusion: Optimization of Electric Field Amplitude and Hypotonic Treatment for Mouse Melanoma (B16-F1) and Chinese Hamster Ovary (CHO) Cells. J Membr Biol 2010; 236:107-16. [DOI: 10.1007/s00232-010-9272-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 06/11/2010] [Indexed: 12/19/2022]
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32
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Abstract
Recent developments in the direct measurements of forces between surfaces in liquids at the ångstrom resolution level are reviewed. The results reveal a rich variety of interactions and interaction potentials that depend on the nature of the surfaces and intervening liquids. These results also shed new insights into liquid structure adjacent to surfaces and the interactions occurrig in complex systems, with implications in many different areas of chemical physics, biology, and technology. The origin of some important fundamental interactions, such as repulsive "hydration" forces and attractive "hydrophobic" forces, are still not understood and offer a challenge for experimental and theoretical work in this area.
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33
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Wetting properties of dioleoyl-phosphatidyl-choline bilayers in the presence of trehalose: an X-ray diffraction study. Chem Phys Lipids 2010; 163:601-6. [DOI: 10.1016/j.chemphyslip.2010.04.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 04/19/2010] [Accepted: 04/21/2010] [Indexed: 11/22/2022]
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34
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35
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Abstract
Highly aligned, substrate supported membranes have made it possible for physical techniques to extract unambiguous structural information previously not accessible from commonly available membrane dispersions, or so-called powder samples. This review will highlight some of the major breakthroughs in model membrane research that have taken place as a result of substrate supported samples.
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36
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Pabst G, Kucerka N, Nieh MP, Rheinstädter MC, Katsaras J. Applications of neutron and X-ray scattering to the study of biologically relevant model membranes. Chem Phys Lipids 2010; 163:460-79. [PMID: 20361949 DOI: 10.1016/j.chemphyslip.2010.03.010] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 03/23/2010] [Accepted: 03/24/2010] [Indexed: 11/19/2022]
Abstract
Scattering techniques, in particular electron, neutron and X-ray scattering have played a major role in elucidating the static and dynamic structure of biologically relevant membranes. Importantly, neutron and X-ray scattering have evolved to address new sample preparations that better mimic biological membranes. In this review, we will report on some of the latest model membrane results, and the neutron and X-ray techniques that were used to obtain them.
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Affiliation(s)
- G Pabst
- Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, A-8042 Graz, Austria
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37
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Manghi M, Destainville N. Statistical mechanics and dynamics of two supported stacked lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4057-4068. [PMID: 20000797 DOI: 10.1021/la903504n] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The statistical physics and dynamics of double supported bilayers are studied theoretically. The main goal in designing double supported lipid bilayers is to obtain model systems of biomembranes: the upper bilayer is meant to be almost freely floating, the substrate being screened by the lower bilayer. The fluctuation-induced repulsion between membranes and between the lower membrane and the wall are explicitly taken into account using a Gaussian variational approach. It is shown that the variational parameters, the "effective" adsorption strength, and the average distance to the substrate, depend strongly on temperature and membrane elastic moduli, the bending rigidity, and the microscopic surface tension, which is a signature of the crucial role played by membrane fluctuations. The range of stability of these supported membranes is studied, showing a complex dependence on bare adsorption strengths. In particular, the experimental conditions of having an upper membrane slightly perturbed by the lower one and still bound to the surface are found. Included in the theoretical calculation of the damping rates associated with membrane normal modes are hydrodynamic friction by the wall and hydrodynamic interactions between both membranes.
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Affiliation(s)
- Manoel Manghi
- Université de Toulouse, UPS, Laboratoire de Physique Thééorique (IRSAMC), F-31062 Toulouse, France.
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Khelashvili G, Harries D, Weinstein H. Modeling membrane deformations and lipid demixing upon protein-membrane interaction: the BAR dimer adsorption. Biophys J 2009; 97:1626-35. [PMID: 19751667 DOI: 10.1016/j.bpj.2009.07.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 07/02/2009] [Accepted: 07/07/2009] [Indexed: 12/13/2022] Open
Abstract
We use a self-consistent mean-field theory, designed to investigate membrane reshaping and lipid demixing upon interaction with proteins, to explore BAR domains interacting with large patches of lipid membranes of heterogeneous compositions. The computational model includes contributions to the system free energy from electrostatic interactions and elastic energies of the membrane, as well as salt and lipid mixing entropies. The results from our simulation of a single adsorbing Amphiphysin BAR dimer indicate that it is capable of stabilizing a significantly curved membrane. However, we predict that such deformations will occur only for membrane patches that have the inherent propensity for high curvature, reflected in the tendency to create local distortions that closely match the curvature of the BAR dimer itself. Such favorable preconditioning for BAR-membrane interaction may be the result of perturbations such as local lipid demixing induced by the interaction, or of a prior insertion of the BAR domain's amphiphatic N-helix. From our simulations it appears that local segregation of charged lipids under the influence of the BAR dimer cannot produce high enough asymmetry between bilayer leaflets to induce significant bending. In the absence of additional energy contributions that favor membrane asymmetry, the membrane will remain nearly flat upon single BAR dimer adsorption, relative to the undulation expected from thermal fluctuations. Thus, we conclude that the N-helix insertions have a critical mechanistic role in the local perturbation and curving of the membrane, which is then stabilized by the electrostatic interaction with the BAR dimer. We discuss how these results can be used to estimate the tendency of BARs to bend membranes in terms of a spatially nonisotropic spontaneous curvature.
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Affiliation(s)
- George Khelashvili
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York, USA.
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Sagar GH, Bellare JR. Estimation of Mechanical Strength of Unilamellar and Multilamellar AOT/Water Vesicles and Their Rupture Using Micropipet Aspiration. J Phys Chem B 2009; 113:13805-10. [DOI: 10.1021/jp902909z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- G. Hema Sagar
- Department of Chemical Engineering, School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai - 400076 India
| | - Jayesh R. Bellare
- Department of Chemical Engineering, School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai - 400076 India
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40
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Cell size dynamics and viability of cells exposed to hypotonic treatment and electroporation for electrofusion optimization. Radiol Oncol 2009. [DOI: 10.2478/v10019-009-0017-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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41
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Wheeler D, Bandaru VVR, Calabresi PA, Nath A, Haughey NJ. A defect of sphingolipid metabolism modifies the properties of normal appearing white matter in multiple sclerosis. ACTA ACUST UNITED AC 2008; 131:3092-102. [PMID: 18772223 PMCID: PMC2577809 DOI: 10.1093/brain/awn190] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Maintaining the appropriate complement and content of lipids in cellular membranes is critical for normal neural function. Accumulating evidence suggests that even subtle perturbations in the lipid content of neurons and myelin can disrupt their function and may contribute to myelin and axonal degradation. In this study, we determined the composition and quantified the content of lipids and sterols in normal appearing white matter (NAWM) and normal appearing grey matter (NAGM) from control and multiple sclerosis brain tissues by electrospray ionization tandem mass spectrometry. Our results suggest that in active-multiple sclerosis, there is a shift in the lipid composition of NAWM and NAGM to a higher phospholipid and lower sphingolipid content. We found that this disturbance in lipid composition was reduced in NAGM but not in NAWM of inactive-multiple sclerosis. The pattern of disturbance in lipid composition suggests a metabolic defect that causes sphingolipids to be shuttled to phospholipid production. Modelling the biophysical consequence of this change in lipid composition of NAWM indicated an increase in the repulsive force between opposing bilayers that could explain decompaction and disruption of myelin structure.
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Affiliation(s)
- David Wheeler
- Department of Neurology, Richard T Johnson Division of Neuroimmunology and Neurological Infections, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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Marsh D. Protein modulation of lipids, and vice-versa, in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1545-75. [DOI: 10.1016/j.bbamem.2008.01.015] [Citation(s) in RCA: 260] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 01/17/2008] [Accepted: 01/19/2008] [Indexed: 11/29/2022]
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Müller DJ, Wu N, Palczewski K. Vertebrate membrane proteins: structure, function, and insights from biophysical approaches. Pharmacol Rev 2008; 60:43-78. [PMID: 18321962 DOI: 10.1124/pr.107.07111] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Membrane proteins are key targets for pharmacological intervention because they are vital for cellular function. Here, we analyze recent progress made in the understanding of the structure and function of membrane proteins with a focus on rhodopsin and development of atomic force microscopy techniques to study biological membranes. Membrane proteins are compartmentalized to carry out extra- and intracellular processes. Biological membranes are densely populated with membrane proteins that occupy approximately 50% of their volume. In most cases membranes contain lipid rafts, protein patches, or paracrystalline formations that lack the higher-order symmetry that would allow them to be characterized by diffraction methods. Despite many technical difficulties, several crystal structures of membrane proteins that illustrate their internal structural organization have been determined. Moreover, high-resolution atomic force microscopy, near-field scanning optical microscopy, and other lower resolution techniques have been used to investigate these structures. Single-molecule force spectroscopy tracks interactions that stabilize membrane proteins and those that switch their functional state; this spectroscopy can be applied to locate a ligand-binding site. Recent development of this technique also reveals the energy landscape of a membrane protein, defining its folding, reaction pathways, and kinetics. Future development and application of novel approaches during the coming years should provide even greater insights to the understanding of biological membrane organization and function.
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Affiliation(s)
- Daniel J Müller
- Biotechnology Center, University of Technology, Dresden, Germany
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44
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Fluctuations of the red blood cell membrane: relation to mechanical properties and lack of ATP dependence. Biophys J 2008; 94:4134-44. [PMID: 18234829 DOI: 10.1529/biophysj.107.117952] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have analyzed the fluctuations of the red blood cell membrane in both the temporal ((omega(s(-1))) and spatial (q(m(-1))) frequency domains. The cells were examined over a range of osmolarities leading to cell volumes from 50% to 170% of that in the isotonic state. The fluctuations of the isotonic cell showed an approximately q(-3)-dependence, indicative of a motion dominated by bending, with an inferred bending modulus of approximately 9 x 10(-19) J. When the cells were osmotically swollen to just below the point of lysis (166% of physiological volume), a q(-1)-dependence of the fluctuations supervened, implying that the motion was now dominated by membrane tension; estimated as approximately 1.3 x 10(-4) nm(-1). When, on the other hand, the cells were osmotically dehydrated, the fluctuation amplitude progressively decreased. This was caused by a rise in internal viscosity, as shown by measurements on resealed ghosts containing a reduced hemoglobin concentration, which displayed no such effect. We examined, in addition, cells depleted of ATP, before the onset of echinocytosis, and could observe no change in fluctuation amplitude. We conclude that the membrane fluctuations of the red cell are governed by bending modulus, membrane tension, and cytosolic viscosity, with little or no dependence on the presence or absence of ATP.
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Rehfeldt F, Engler AJ, Eckhardt A, Ahmed F, Discher DE. Cell responses to the mechanochemical microenvironment--implications for regenerative medicine and drug delivery. Adv Drug Deliv Rev 2007; 59:1329-39. [PMID: 17900747 PMCID: PMC4124491 DOI: 10.1016/j.addr.2007.08.007] [Citation(s) in RCA: 259] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Accepted: 08/01/2007] [Indexed: 02/05/2023]
Abstract
Soft-tissue cells are surprisingly sensitive to the elasticity of their microenvironment, suggesting that traditional culture plastic and glass are less relevant to tissue regeneration and chemotherapeutics than might be achieved. Cells grown on gels that mimic the elasticity of tissue reveal a significant influence of matrix elasticity on adhesion, cytoskeletal organization, and even the differentiation of human adult derived stem cells. Cellular forces and feedback are keys to how cells feel their mechanical microenvironment, but detailed molecular mechanisms are still being elucidated. This review summarizes our initial findings for multipotent stem cells and also the elasticity-coupled effects of drugs on cancer cells and smooth muscle cells. The drugs include the contractility inhibitor blebbistatin, the proliferation inhibitor mitomycin C, an apoptotis-inducing antibody against CD47, and the translation inhibitor cycloheximide. The differential effects not only lend insight into mechano-sensing of the substrate by cells, but also have important implications for regeneration and molecular therapies.
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Affiliation(s)
- Florian Rehfeldt
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Adam J. Engler
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Adam Eckhardt
- Institute of Physiology, Czech Academy of Science, Prague, Czech Republic
| | - Fariyal Ahmed
- Department of Bioengineering, University of Pennsylvania, Philadelphia PA 19104, USA
| | - Dennis E. Discher
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia PA 19104, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia PA 19104, USA
- Graduate Group of Physics & Astronomy, University of Pennsylvania, Philadelphia PA 19104, USA
- Corresponding author. Molecular & Cell Biophysics and NanoBio-Polymers Lab, University of Pennsylvania, Philadelphia PA 19104, USA. Tel.: +1 215 898 4809
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Harries D, Podgornik R, Parsegian VA, Mar-Or E, Andelman D. Ion induced lamellar-lamellar phase transition in charged surfactant systems. J Chem Phys 2007; 124:224702. [PMID: 16784296 DOI: 10.1063/1.2198534] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a model for the liquid-liquid (L(alpha)-->L(alpha(') )) phase transition observed in osmotic pressure measurements of certain charged lamellae-forming amphiphiles. The model free energy combines mean-field electrostatic and phenomenological nonelectrostatic interactions, while the number of dissociated counterions is treated as a variable degree of freedom that is determined self-consistently. The model, therefore, joins two well-known theories: the Poisson-Boltzmann theory for ionic solutions between charged lamellae and the Langmuir-Frumkin-Davies adsorption isotherm modified to account for charged adsorbing species. Minimizing the appropriate free energy for each interlamellar spacing, we find the ionic density profiles and the resulting osmotic pressure. While in the simple Poisson-Boltzmann theory the osmotic pressure isotherms are always smooth, we observe a discontinuous liquid-liquid phase transition when the Poisson-Boltzmann theory is self-consistently augmented by the Langmuir-Frumkin-Davies adsorption. This phase transition depends on the area per amphiphilic head group, as well as on nonelectrostatic interactions of the counterions with the lamellae and interactions between counterion-bound and counterion-dissociated surfactants. Coupling the lateral phase transition in the bilayer plane with electrostatic interactions in the bulk, our results offer a qualitative explanation for the existence of the L(alpha)-->L(alpha(') ) phase transition of didodecyldimethylammonium bromide (DDABr), but the transition's apparent absence for the chloride and the iodide homologs. More quantitative comparisons with experiment require better understanding of the microscopic basis of the phenomenological model parameters.
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Affiliation(s)
- Daniel Harries
- Laboratory of Physical and Structural Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-0924, USA.
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47
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Fa N, Lins L, Courtoy PJ, Dufrêne Y, Van Der Smissen P, Brasseur R, Tyteca D, Mingeot-Leclercq MP. Decrease of elastic moduli of DOPC bilayers induced by a macrolide antibiotic, azithromycin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1830-8. [PMID: 17537401 DOI: 10.1016/j.bbamem.2007.04.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Revised: 04/06/2007] [Accepted: 04/10/2007] [Indexed: 10/23/2022]
Abstract
The elastic properties of membrane bilayers are key parameters that control its deformation and can be affected by pharmacological agents. Our previous atomic force microscopy studies revealed that the macrolide antibiotic, azithromycin, leads to erosion of DPPC domains in a fluid DOPC matrix [A. Berquand, M. P. Mingeot-Leclercq, Y. F. Dufrene, Real-time imaging of drug-membrane interactions by atomic force microscopy, Biochim. Biophys. Acta 1664 (2004) 198-205.]. Since this observation could be due to an effect on DOPC cohesion, we investigated the effect of azithromycin on elastic properties of DOPC giant unilamellar vesicles (GUVs). Microcinematographic and morphometric analyses revealed that azithromycin addition enhanced lipid membranes fluctuations, leading to eventual disruption of the largest GUVs. These effects were related to change of elastic moduli of DOPC, quantified by the micropipette aspiration technique. Azithromycin decreased both the bending modulus (k(c), from 23.1+/-3.5 to 10.6+/-4.5 k(B)T) and the apparent area compressibility modulus (K(app), from 176+/-35 to 113+/-25 mN/m). These data suggested that insertion of azithromycin into the DOPC bilayer reduced the requirement level of both the energy for thermal fluctuations and the stress to stretch the bilayer. Computer modeling of azithromycin interaction with DOPC bilayer, based on minimal energy, independently predicted that azithromycin (i) inserts at the interface of phospholipid bilayers, (ii) decreases the energy of interaction between DOPC molecules, and (iii) increases the mean surface occupied by each phospholipid molecule. We conclude that azithromycin inserts into the DOPC lipid bilayer, so as to decrease its cohesion and to facilitate the merging of DPPC into the DOPC fluid matrix, as observed by atomic force microscopy. These investigations, based on three complementary approaches, provide the first biophysical evidence for the ability of an amphiphilic antibiotic to alter lipid elastic moduli. This may be an important determinant for drug: lipid interactions and cellular pharmacology.
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Affiliation(s)
- N Fa
- Université Catholique de Louvain, Unité de Pharmacologie Cellulaire et Moléculaire, Avenue E. Mounier 73, Bt 7370, B-1200 Brussels, Belgium
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48
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Leontidis E, Aroti A, Belloni L, Dubois M, Zemb T. Effects of monovalent anions of the hofmeister series on DPPC lipid bilayers Part II: modeling the perpendicular and lateral equation-of-state. Biophys J 2007; 93:1591-607. [PMID: 17496050 PMCID: PMC1948044 DOI: 10.1529/biophysj.107.109264] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The effects of Hofmeister anions on the perpendicular and lateral equation-of-state (EOS) of the dipalmitoylphosphatidylcholine lamellar phase discussed in the companion article are here examined using appropriate free energy models for the intra- and interbilayer interactions. Minimizing the free energy with respect to the two basic geometrical parameters of the lamellar phase, which are the interbilayer water thickness, d(w), and the lipid headgroup area, a(L), provides the perpendicular (osmotic pressure balance) and lateral EOS. Standard models were used for the hydration, undulation, and Van der Waals attractive force between the bilayers in the presence of electrolytes whereas two alternative treatments of electrostatic interactions were used to obtain "binding" or "partitioning" constants of anions to the lipid bilayers both in the absence and in the presence of sodium binding. The computed binding constants depend on anion type and follow the Hofmeister series, but were found to increase with electrolyte concentration, implying that the local binding approximation cannot fit bilayer repulsion data. The partitioning model was also found inadequate at high electrolyte concentrations. The fitting attempts revealed two additional features worthy of future investigation. First, at maximum swelling in the presence of electrolytes the osmotic pressure of the bilayer system cannot be set equal to zero. Second, at high salt concentrations an additional repulsion appears to come into effect in the presence of strongly adsorbing anions such as I(-) or SCN(-). Both these phenomena may reflect an inconsistent treatment of the ion-surface interactions, which have an impact on the osmotic pressure. Alternatively, they may arise from bulk solution nonidealities that cannot be handled by the classical Poisson-Boltzmann formalism. The inability of current models to explain the "lateral" EOS by fitting the area per lipid headgroup as a function of salt type and concentration shows that current understanding of phospholipid-ion interactions is still very incomplete.
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Affiliation(s)
- E Leontidis
- Department of Chemistry, University of Cyprus, Nicosia, Cyprus.
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49
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Manciu M, Ruckenstein E. On possible microscopic origins of the swelling of neutral lipid bilayers induced by simple salts. J Colloid Interface Sci 2007; 309:56-67. [PMID: 17331528 DOI: 10.1016/j.jcis.2007.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 01/18/2007] [Accepted: 02/01/2007] [Indexed: 11/17/2022]
Abstract
It was recently suggested that the swelling of neutral multilipid bilayers upon addition of a salt can be simply explained only by the electrolyte screening of the van der Waals attractions, while assuming that the hydration force and the repulsion due to thermal undulations of membranes are unaffected by the salt. While we agree that the screening of the van der Waals interactions plays a role, we suggest that the increase in the hydration force upon addition of a salt has also to be taken into account. In a statistical model, which accounts for the membrane undulations, parameters could be found to explain the multibilayer swelling even when the van der Waals attraction is considered unaffected by the electrolyte screening. These results point out that the decrease by a factor of three of the Hamaker constant upon addition of a salt, suggested recently to be responsible for the swelling of neutral multilipid bilayers, is perhaps too large, and a smaller decrease in Hamaker constant, coupled with the above mentioned effects might explain the swelling.
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Affiliation(s)
- Marian Manciu
- Physics Department, University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79968, USA.
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50
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Marsh D. Elastic curvature constants of lipid monolayers and bilayers. Chem Phys Lipids 2006; 144:146-59. [PMID: 17045578 DOI: 10.1016/j.chemphyslip.2006.08.004] [Citation(s) in RCA: 225] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 08/22/2006] [Accepted: 08/29/2006] [Indexed: 11/21/2022]
Abstract
Bending elasticity is an important property of lipid vesicles, non-lamellar lipid phases and biological membranes. Experimental values of the mean curvature moduli, k(c), of lipid bilayers and of the monolayer leaflets of inverted hexagonal (H(II)) phases of lipids are tabulated here for easy reference. Experimental estimates of the Gaussian curvature modulus, k (c), are also included. Consideration is given to the relation between the bending moduli of bilayers and the constituent monolayer leaflets. Useful mathematical relations involving the bending moduli and spontaneous curvature are summarized.
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Affiliation(s)
- Derek Marsh
- Max-Planck-Institut für biophysikalische Chemie, Dept. Spektroskopie, 37070 Göttingen, Germany.
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