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Nagao M, Seto H. Neutron scattering studies on dynamics of lipid membranes. Biophys Rev (Melville) 2023; 4:021306. [PMID: 38504928 PMCID: PMC10903442 DOI: 10.1063/5.0144544] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/01/2023] [Indexed: 03/21/2024]
Abstract
Neutron scattering methods are powerful tools for the study of the structure and dynamics of lipid bilayers in length scales from sub Å to tens to hundreds nm and the time scales from sub ps to μs. These techniques also are nondestructive and, perhaps most importantly, require no additives to label samples. Because the neutron scattering intensities are very different for hydrogen- and deuterium-containing molecules, one can replace the hydrogen atoms in a molecule with deuterium to prepare on demand neutron scattering contrast without significantly altering the physical properties of the samples. Moreover, recent advances in neutron scattering techniques, membrane dynamics theories, analysis tools, and sample preparation technologies allow researchers to study various aspects of lipid bilayer dynamics. In this review, we focus on the dynamics of individual lipids and collective membrane dynamics as well as the dynamics of hydration water.
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Affiliation(s)
| | - Hideki Seto
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
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2
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Kelley EG, Frewein MPK, Czakkel O, Nagao M. Nanoscale Bending Dynamics in Mixed-Chain Lipid Membranes. Symmetry (Basel) 2023; 15:191. [DOI: 10.3390/sym15010191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Lipids that have two tails of different lengths are found throughout biomembranes in nature, yet the effects of this asymmetry on the membrane properties are not well understood, especially when it comes to the membrane dynamics. Here we study the nanoscale bending fluctuations in model mixed-chain 14:0–18:0 PC (MSPC) and 18:0–14:0 PC (SMPC) lipid bilayers using neutron spin echo (NSE) spectroscopy. We find that despite the partial interdigitation that is known to persist in the fluid phase of these membranes, the collective fluctuations are enhanced on timescales of tens of nanoseconds, and the chain-asymmetric lipid bilayers are softer than an analogous chain-symmetric lipid bilayer with the same average number of carbons in the acyl tails, di-16:0 PC (DPPC). Quantitative comparison of the NSE results suggests that the enhanced bending fluctuations at the nanosecond timescales are consistent with experimental and computational studies that showed the compressibility moduli of chain-asymmetric lipid membranes are 20% to 40% lower than chain-symmetric lipid membranes. These studies add to growing evidence that the partial interdigitation in mixed-chain lipid membranes is highly dynamic in the fluid phase and impacts membrane dynamic processes from the molecular to mesoscopic length scales without significantly changing the bilayer thickness or area per lipid.
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3
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Molaei M, Kandy SK, Graber ZT, Baumgart T, Radhakrishnan R, Crocker JC. Probing lipid membrane bending mechanics using gold nanorod tracking. Phys Rev Res 2022; 4:L012027. [PMID: 35373142 PMCID: PMC8975244 DOI: 10.1103/physrevresearch.4.l012027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Lipid bilayer membranes undergo rapid bending undulations with wavelengths from tens of nanometers to tens of microns due to thermal fluctuations. Here, we probe such undulations and the membranes' mechanics by measuring the time-varying orientation of single gold nanorods (GNRs) adhered to the membrane, using high-speed dark field microscopy. In a lipid vesicle, such measurements allow the determination of the membrane's viscosity, bending rigidity, and tension as well as the friction coefficient for sliding of the monolayers over one another. The in-plane rotation of the GNR is hindered by undulations in a tension dependent manner, consistent with simulations. The motion of single GNRs adhered to the plasma membrane of living cultured cells similarly reveals the membrane's complex physics and coupling to the cell's actomyosin cortex.
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Affiliation(s)
- Mehdi Molaei
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Sreeja Kutti Kandy
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Zachary T. Graber
- Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Tobias Baumgart
- Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Ravi Radhakrishnan
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - John C. Crocker
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Corresponding author:
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4
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Iriondo MN, Etxaniz A, Antón Z, Montes LR, Alonso A. Molecular and mesoscopic geometries in autophagosome generation. A review. Biochim Biophys Acta Biomembr 2021; 1863:183731. [PMID: 34419487 DOI: 10.1016/j.bbamem.2021.183731] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 08/12/2021] [Accepted: 08/15/2021] [Indexed: 01/18/2023]
Abstract
Autophagy is an essential process in cell self-repair and survival. The centre of the autophagic event is the generation of the so-called autophagosome (AP), a vesicle surrounded by a double membrane (two bilayers). The AP delivers its cargo to a lysosome, for degradation and re-use of the hydrolysis products as new building blocks. AP formation is a very complex event, requiring dozens of specific proteins, and involving numerous instances of membrane biogenesis and architecture, including membrane fusion and fission. Many stages of AP generation can be rationalised in terms of curvature, both the molecular geometry of lipids interpreted in terms of 'intrinsic curvature', and the overall mesoscopic curvature of the whole membrane, as observed with microscopy techniques. The present contribution intends to bring together the worlds of biophysics and cell biology of autophagy, in the hope that the resulting cross-pollination will generate abundant fruit.
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Affiliation(s)
- Marina N Iriondo
- Instituto Biofisika (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, 48940 Leioa, Spain
| | - Asier Etxaniz
- Instituto Biofisika (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, 48940 Leioa, Spain
| | - Zuriñe Antón
- Instituto Biofisika (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, 48940 Leioa, Spain
| | - L Ruth Montes
- Instituto Biofisika (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, 48940 Leioa, Spain
| | - Alicia Alonso
- Instituto Biofisika (CSIC, UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, 48940 Leioa, Spain.
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5
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Calin VL, Mihailescu M, Tarba N, Sandu AM, Scarlat E, Moisescu MG, Savopol T. Digital holographic microscopy evaluation of dynamic cell response to electroporation. Biomed Opt Express 2021; 12:2519-2530. [PMID: 33996245 PMCID: PMC8086444 DOI: 10.1364/boe.421959] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 03/25/2021] [Accepted: 03/25/2021] [Indexed: 05/30/2023]
Abstract
Phase-derived parameters and time autocorrelation functions were used to analyze the behavior of murine B16 cells exposed to different amplitudes of electroporation pulses. Cells were observed using an off-axis digital holographic microscope equipped with a fast camera. Series of quantitative phase images of cells were reconstructed and further processed using MATLAB codes. Projected area, dry mass density, and entropy proved to be predictors for permeabilized cells that swell or collapse. Autocorrelation functions of phase fluctuations in different regions of the cell showed a good correlation with the local effectiveness of permeabilization.
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Affiliation(s)
- Violeta L. Calin
- Biophysics and Cellular Biotechnology Department, Faculty of Medicine, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
- Excellence Center for Research in Biophysics and Cellular Biotechnology, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
| | - Mona Mihailescu
- Digital Holography Imaging and Processing Laboratory, Physics Department, Faculty of Applied Sciences, University “Politehnica” of Bucharest, 313 Splaiul Independentei, Bucharest, 060042, Romania
| | - Nicolae Tarba
- Physics Department, Faculty of Applied Sciences, Doctoral School of Automatic Control and Computers, University “Politehnica” of Bucharest, 313 Splaiul Independentei, Bucharest, 060042, Romania
| | - Ana Maria Sandu
- CAMPUS Research Center, Doctoral School of Electrical Engineering, University “Politehnica” of Bucharest, 313 Splaiul Independentei, Bucharest, 060042, Romania
| | - Eugen Scarlat
- Digital Holography Imaging and Processing Laboratory, Physics Department, Faculty of Applied Sciences, University “Politehnica” of Bucharest, 313 Splaiul Independentei, Bucharest, 060042, Romania
| | - Mihaela G. Moisescu
- Biophysics and Cellular Biotechnology Department, Faculty of Medicine, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
- Excellence Center for Research in Biophysics and Cellular Biotechnology, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
| | - Tudor Savopol
- Biophysics and Cellular Biotechnology Department, Faculty of Medicine, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
- Excellence Center for Research in Biophysics and Cellular Biotechnology, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., Bucharest, 050474, Romania
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Abstract
We present the derivation of a new model to describe neutron spin echo spectroscopy and quasi-elastic neutron scattering data on liposomes. We compare the new model with existing approaches and benchmark it with experimental data. The analysis indicates the importance of including all major contributions in the modeling of the intermediate scattering function. Simultaneous analysis of the experimental data on lipids with full contrast and tail contrast matched samples reveals highly confined lipid tail motion. A comparison of their dynamics demonstrates the statistical independence of tail-motion and height-height correlation of the membrane. A more detailed analysis indicates that the lipid tail relaxation is confined to a potential with cylindrical symmetry, in addition to the undulation and diffusive motion of the liposome. Despite substantial differences in the chemistry of the fatty acid tails, the observation indicates a universal behavior. The analysis of partially deuterated systems confirms the strong contribution of the lipid tail to the intermediate scattering function. Within the time range from 5 to 100 ns, the intermediate scattering function can be described by the height-height correlation function. The existence of the fast-localized tail motion and the contribution of slow translational diffusion of liposomes determine the intermediate scattering function for t < 5 ns and t > 100 ns, respectively. Taking into account the limited time window lowers the bending moduli by a factor of 1.3 (DOPC) to 2 (DMPC) compared to the full range.
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Affiliation(s)
- Sudipta Gupta
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Gerald J Schneider
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA. and Department of Physics & Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
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7
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Rickeard BW, Nguyen MHL, DiPasquale M, Yip CG, Baker H, Heberle FA, Zuo X, Kelley EG, Nagao M, Marquardt D. Transverse lipid organization dictates bending fluctuations in model plasma membranes. Nanoscale 2020; 12:1438-1447. [PMID: 31746906 DOI: 10.1039/c9nr07977g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Membrane undulations play a vital role in many biological processes, including the regulation of membrane protein activity. The asymmetric lipid composition of most biological membranes complicates theoretical description of these bending fluctuations, yet experimental data that would inform any such a theory is scarce. Here, we used neutron spin-echo (NSE) spectroscopy to measure the bending fluctuations of large unilamellar vesicles (LUV) having an asymmetric transbilayer distribution of high- and low-melting lipids. The asymmetric vesicles were prepared using cyclodextrin-mediated lipid exchange, and were composed of an outer leaflet enriched in egg sphingomyelin (ESM) and an inner leaflet enriched in 1-palmitoyl-2-oleoyl-phosphoethanolamine (POPE), which have main transition temperatures of 37 °C and 25 °C, respectively. The overall membrane bending rigidity was measured at three temperatures: 15 °C, where both lipids are in a gel state; 45 °C, where both lipids are in a fluid state; and 30 °C, where there is gel-fluid co-existence. Remarkably, the dynamics for the fluid asymmetric LUVs (aLUVs) at 30 °C and 45 °C do not follow trends predicted by their symmetric counterparts. At 30 °C, compositional asymmetry suppressed the bending fluctuations, with the asymmetric bilayer exhibiting a larger bending modulus than that of symmetric bilayers corresponding to either the outer or inner leaflet. We conclude that the compositional asymmetry and leaflet coupling influence the internal dissipation within the bilayer and result in membrane properties that cannot be directly predicted from corresponding symmetric bilayers.
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Affiliation(s)
- Brett W Rickeard
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada.
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8
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Bivas I, Tonchev NS. Membrane stretching elasticity and thermal shape fluctuations of nearly spherical lipid vesicles. Phys Rev E 2019; 100:022416. [PMID: 31574724 DOI: 10.1103/physreve.100.022416] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Indexed: 11/07/2022]
Abstract
One of the most widely used methods for determination of the bending elasticity modulus of model lipid membranes is the analysis of the shape fluctuations of nearly spherical lipid vesicles. The theoretical basis of this analysis is given by Milner and Safran [Phys. Rev. A 36, 4371 (1987)0556-279110.1103/PhysRevA.36.4371]. In their theory the stretching effects are not considered. In the present study we generalized their approach including the stretching effects deduced after application of the statistical mechanics to vesicles.
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Affiliation(s)
- Isak Bivas
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee blvd., Sofia 1784, Bulgaria
| | - Nicholay S Tonchev
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee blvd., Sofia 1784, Bulgaria
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9
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Sreij R, Dargel C, Geisler P, Hertle Y, Radulescu A, Pasini S, Perez J, Moleiro LH, Hellweg T. DMPC vesicle structure and dynamics in the presence of low amounts of the saponin aescin. Phys Chem Chem Phys 2018; 20:9070-9083. [DOI: 10.1039/c7cp08027a] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Vesicle shape and bilayer parameters are studied by small-angle X-ray (SAXS) and small-angle neutron (SANS) scattering in the presence of the saponin aescin. Bilayer dynamics is studied by neutron spin-echo (NSE) spectroscopy.
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Affiliation(s)
- Ramsia Sreij
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Carina Dargel
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Philippe Geisler
- Cognitronics and Sensor Systems
- CITEC
- Bielefeld University
- Bielefeld
- Germany
| | - Yvonne Hertle
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Aurel Radulescu
- Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum (MLZ)
- Forschungszentrum Jülich GmbH
- Garching
- Germany
| | - Stefano Pasini
- Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum (MLZ)
- Forschungszentrum Jülich GmbH
- Garching
- Germany
| | | | - Lara H. Moleiro
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
| | - Thomas Hellweg
- Physical and Biophysical Chemistry
- Bielefeld University
- Bielefeld
- Germany
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10
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Arriaga LR, Rodríguez-García R, Moleiro LH, Prévost S, López-Montero I, Hellweg T, Monroy F. Dissipative dynamics of fluid lipid membranes enriched in cholesterol. Adv Colloid Interface Sci 2017; 247:514-520. [PMID: 28755780 DOI: 10.1016/j.cis.2017.07.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 07/08/2017] [Accepted: 07/08/2017] [Indexed: 01/26/2023]
Abstract
Cholesterol is an intriguing component of fluid lipid membranes: It makes them stiffer but also more fluid. Despite the enormous biological significance of this complex dynamical behavior, which blends aspects of membrane elasticity with viscous friction, their mechanical bases remain however poorly understood. Here, we show that the incorporation of physiologically relevant contents of cholesterol in model fluid membranes produces a fourfold increase in the membrane bending modulus. However, the increase in the compression rigidity that we measure is only twofold; this indicates that cholesterol increases coupling between the two membrane leaflets. In addition, we show that although cholesterol makes each membrane leaflet more fluid, it increases the friction between the membrane leaflets. This dissipative dynamics causes opposite but advantageous effects over different membrane motions: It allows the membrane to rearrange quickly in the lateral dimension, and to simultaneously dissipate out-of-plane stresses through friction between the two membrane leaflets. Moreover, our results provide a clear correlation between coupling and friction of membrane leaflets. Furthermore, we show that these rigid membranes are optimal to resist slow deformations with minimum energy dissipation; their optimized stability might be exploited to design soft technological microsystems with an encoded mechanics, vesicles or capsules for instance, useful beyond classical applications as model biophysical systems.
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Affiliation(s)
- Laura R Arriaga
- Dpto. Química Física I, Universidad Complutense, E-28040 Madrid, Spain; Translational Biophysics Unit, Instituto de Investigacion Biomédica Hospital Doce de Octubre (i+12), E-28041 Madrid, Spain
| | | | - Lara H Moleiro
- Dpto. Química Física I, Universidad Complutense, E-28040 Madrid, Spain; Translational Biophysics Unit, Instituto de Investigacion Biomédica Hospital Doce de Octubre (i+12), E-28041 Madrid, Spain; Fakultät für Chemie Physikalische und Biophysikalische Chemie (PC III), Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany
| | - Sylvain Prévost
- Institut Laue-Langevin, 71 avenue des Martyrs, F-38042 Grenoble, France; Helmholtz-Center-Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany; Stranski-Laboratorium, Straße des 17. Juni 124, Technische Universität Berlin, D-10623 Berlin, Germany
| | | | - Thomas Hellweg
- Fakultät für Chemie Physikalische und Biophysikalische Chemie (PC III), Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany
| | - Francisco Monroy
- Dpto. Química Física I, Universidad Complutense, E-28040 Madrid, Spain; Translational Biophysics Unit, Instituto de Investigacion Biomédica Hospital Doce de Octubre (i+12), E-28041 Madrid, Spain.
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11
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Moleiro L, Mell M, Bocanegra R, López-Montero I, Fouquet P, Hellweg T, Carrascosa J, Monroy F. Permeability modes in fluctuating lipid membranes with DNA-translocating pores. Adv Colloid Interface Sci 2017; 247:543-554. [PMID: 28735883 DOI: 10.1016/j.cis.2017.07.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 07/10/2017] [Accepted: 07/10/2017] [Indexed: 10/19/2022]
Abstract
Membrane pores can significantly alter not only the permeation dynamics of biological membranes but also their elasticity. Large membrane pores able to transport macromolecular contents represent an interesting model to test theoretical predictions that assign active-like (non-equilibrium) behavior to the permeability contributions to the enhanced membrane fluctuations existing in permeable membranes [Maneville et al. Phys. Rev. Lett. 82, 4356 (1999)]. Such high-amplitude active contributions arise from the forced transport of solvent and solutes through the open pores, which becomes even dominant at large permeability. In this paper, we present a detailed experimental analysis of the active shape fluctuations that appear in highly permeable lipid vesicles with large macromolecular pores inserted in the lipid membrane, which are a consequence of transport permeability events occurred in an osmotic gradient. The experimental results are found in quantitative agreement with theory, showing a remarkable dependence with the density of membrane pores and giving account of mechanical compliances and permeability rates that are compatible with the large size of the membrane pore considered. The presence of individual permeation events has been detected in the fluctuation time-series, from which a stochastic distribution of the permeation events compatible with a shot-noise has been deduced. The non-equilibrium character of the membrane fluctuations in a permeation field, even if the membrane pores are mere passive transporters, is clearly demonstrated. Finally, a bio-nano-technology outlook of the proposed synthetic concept is given on the context of prospective uses as active membrane DNA-pores exploitable in gen-delivery applications based on lipid vesicles.
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12
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Sachin Krishnan TV, Okamoto R, Komura S. Relaxation dynamics of a compressible bilayer vesicle containing highly viscous fluid. Phys Rev E 2017; 94:062414. [PMID: 28085330 DOI: 10.1103/physreve.94.062414] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Indexed: 11/07/2022]
Abstract
We study the relaxation dynamics of a compressible bilayer vesicle with an asymmetry in the viscosity of the inner and outer fluid medium. First we explore the stability of the vesicle free energy which includes a coupling between the membrane curvature and the local density difference between the two monolayers. Two types of instabilities are identified: a small wavelength instability and a larger wavelength instability. Considering the bulk fluid viscosity and the inter-monolayer friction as the dissipation sources, we next employ Onsager's variational principle to derive the coupled equations both for the membrane and the bulk fluid. The three relaxation modes are coupled to each other due to the bilayer and the spherical structure of the vesicle. Most importantly, a higher fluid viscosity inside the vesicle shifts the crossover mode between the bending and the slipping to a larger value. As the vesicle parameters approach the unstable regions, the relaxation dynamics is dramatically slowed down, and the corresponding mode structure changes significantly. In some limiting cases, our general result reduces to the previously obtained relaxation rates.
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Affiliation(s)
- T V Sachin Krishnan
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan.,Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Ryuichi Okamoto
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Shigeyuki Komura
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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13
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Abstract
Using coarse-grained molecular dynamics simulations, we study the relaxation of bilayer vesicles, uniaxially compressed by an atomic force microscope cantilever. The relaxation time exhibits a strong force dependence. Force-compression curves are very similar to recent experiments wherein giant unilamellar vesicles were compressed in a nearly identical manner.
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Affiliation(s)
- Ben M Barlow
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
| | - Martine Bertrand
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
| | - Béla Joós
- Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5
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14
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Liu K, Hamilton C, Allard J, Lowengrub J, Li S. Wrinkling dynamics of fluctuating vesicles in time-dependent viscous flow. Soft Matter 2016; 12:5663-5675. [PMID: 27136977 PMCID: PMC4927358 DOI: 10.1039/c6sm00499g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We study the fully nonlinear, nonlocal dynamics of two-dimensional vesicles in a time-dependent, incompressible viscous flow at finite temperature. We focus on a transient instability that can be observed when the direction of applied flow is suddenly reversed, which induces compressive forces on the vesicle interface, and small-scale interface perturbations known as wrinkles develop. These wrinkles are driven by regions of negative elastic tension on the membrane. Using a stochastic immersed boundary method with a biophysically motivated choice of thermal fluctuations, we investigate the wrinkling dynamics numerically. Different from deterministic wrinkling dynamics, thermal fluctuations lead to symmetry-breaking wrinkling patterns by exciting higher order modes. This leads to more rapid and more realistic wrinkling dynamics. Our results are in excellent agreement with the experimental data by Kantsler et al. [Kantsler et al., Phys. Rev. Lett., 2007, 99, 17802]. We compare the nonlinear simulation results with perturbation theory, modified to account for thermal fluctuations. The strength of the applied flow strongly influences the most unstable wavelength characterizing the wrinkles, and there are significant differences between the results from perturbation theory and the fully nonlinear simulations, which suggests that the perturbation theory misses important nonlinear interactions. Strikingly, we find that thermal fluctuations actually have the ability to attenuate variability of the characteristic wavelength of wrinkling by exciting a wider range of modes than the deterministic case, which makes the evolution less constrained and enables the most unstable wavelength to emerge more readily. We further find that thermal noise helps prevent the vesicle from rotating if it is misaligned with the direction of the applied extensional flow.
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Affiliation(s)
- Kai Liu
- Department of Applied Mathematics, Illinois Institute of Technology, Chicago, USA. and Department of Mathematics, University of California in Irvine, Irvine, USA
| | - Caleb Hamilton
- Department of Mathematics, University of California in Irvine, Irvine, USA
| | - Jun Allard
- Department of Mathematics, University of California in Irvine, Irvine, USA and Department of Physics, University of California in Irvine, USA
| | - John Lowengrub
- Department of Mathematics, University of California in Irvine, Irvine, USA
| | - Shuwang Li
- Department of Applied Mathematics, Illinois Institute of Technology, Chicago, USA.
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15
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Okamoto R, Kanemori Y, Komura S, Fournier JB. Relaxation dynamics of two-component fluid bilayer membranes. Eur Phys J E Soft Matter 2016; 39:52. [PMID: 27145960 DOI: 10.1140/epje/i2016-16052-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 06/05/2023]
Abstract
We theoretically investigate the relaxation dynamics of a nearly flat binary lipid bilayer membrane by taking into account the membrane tension, hydrodynamics of the surrounding fluid, inter-monolayer friction and mutual diffusion. Mutual diffusion is the collective irreversible process that leads to homogenization of the density difference between the two lipid species. We find that two relaxation modes associated with the mutual diffusion appear in addition to the three previously discussed relaxation modes reflecting the bending and compression of the membrane. Because of the symmetry, only one of the two diffusive modes is coupled to the bending mode. The two diffusive modes are much slower than the bending and compression modes in the entire realistic wave number range. This means that the long time relaxation behavior is dominated by the mutual diffusion in binary membranes. The two diffusive modes become even slower in the vicinity of the unstable region towards phase separation, while the other modes are almost unchanged. In short time scales, on the other hand, the lipid composition heterogeneity induces in-plane compression and bending of the bilayer.
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Affiliation(s)
- Ryuichi Okamoto
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 192-0397, Tokyo, Japan.
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, F-75205, Paris, France.
| | - Yuichi Kanemori
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 192-0397, Tokyo, Japan
| | - Shigeyuki Komura
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 192-0397, Tokyo, Japan
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, F-75205, Paris, France
| | - Jean-Baptiste Fournier
- Université Paris Diderot, Sorbonne Paris Cité, Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, F-75205, Paris, France
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Pérez-Gil J, Monroy FP. Surfing the continuous and walking amongst molecules to unravel the mechanical properties of biomembranes. Chem Phys Lipids 2015; 185:1-2. [PMID: 25618480 DOI: 10.1016/j.chemphyslip.2014.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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