1
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Kumar H, Mandal S, Yadav R, Gupta S, Meena H, Kadu M, Kudawla R, Sharma P, Kaur IP, Maiti S, Ipsen JH, Bhatia T. Bottom-up approach to explore alpha-amylase assisted membrane remodelling. Chem Phys Lipids 2024; 259:105374. [PMID: 38176612 DOI: 10.1016/j.chemphyslip.2023.105374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/19/2023] [Accepted: 12/27/2023] [Indexed: 01/06/2024]
Abstract
Soluble alpha-amylases play an important role in the catabolism of polysaccharides. In this work, we show that the malt α -amylase can interact with the lipid membrane and further alter its mechanical properties. Vesicle fluctuation spectroscopy is used for quantitative measurement of the membrane bending rigidity of phosphatidylcholines lipid vesicles from the shape fluctuation based on the whole contour of Giant Unilamellar Vesicles (GUVs). The bending rigidity of the 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipid vesicles in water increases significantly with the presence of 0.14 micromolar alpha-amylase (AA) in the exterior solution. It appears that the enzyme present in the external solution interacts with the outer layer of the bilayer membrane, leading to an asymmetry of the solution on either side of the bilayer membrane and altering its elasticity. At AA concentration of 1.5 micromolars and above, changes in the morphology of the GUV membrane are observed. The interaction between AA in the external solution and the external leaflet causes the bilayer membrane to curve spontaneously, leading to the formation of outbuds, giving a positive spontaneous curvature of C0 ≤ 0.05 μm-1 at ≈ 1 mg / ml of the AA concentration. We validate and characterize its concentration-dependent role in stabilizing the membrane curvature. Our findings indicate that the involvement of the enzyme, depending on the concentration, can have a considerable effect on the mechanical characteristics of the membrane.
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Affiliation(s)
- Harshit Kumar
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Sayar Mandal
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Reena Yadav
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Suhasi Gupta
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Hemraj Meena
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Mayur Kadu
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Rajni Kudawla
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - Pratibha Sharma
- University Institute of Pharmaceutical Sciences, Punjab University, Sector 14, Chandigarh 160014, Punjab, India
| | - Indu Pal Kaur
- University Institute of Pharmaceutical Sciences, Punjab University, Sector 14, Chandigarh 160014, Punjab, India
| | - Subhabrata Maiti
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India
| | - John H Ipsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej, Odense, 5230 M, Denmark.
| | - Tripta Bhatia
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Knowledge City, Manauli, SAS Nagar, Punjab 140306, India.
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2
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Hossein A, Beaven AH, Sapp K, Sodt AJ. Softening in two-component lipid mixtures by spontaneous curvature variance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.12.571323. [PMID: 38168180 PMCID: PMC10760180 DOI: 10.1101/2023.12.12.571323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
The bending modulus of a lipid bilayer quantifies its mechanical resistance to curvature. It is typically understood in terms of thickness, e.g., thicker bilayers are stiffer. Here, we describe an additional and powerful molecular determinant of stiffness - the variance in the distribution of curvature sensitivity of lipids and lipid conformations. Zwitterionic choline and ethanolamine head-groups of glycero-phospholipids dynamically explore inter- and intra-species interactions, leading to transient clustering. We demonstrate that these clusters couple strongly to negative curvature, exciting undulatory membrane modes and reducing the apparent bending modulus. Three forcefields (Martini 2, Martini 3, and all-atom CHARMM C36) each show the effect to a different extent, with the coarse-grained Martini models showing the most clustering and thus the most softening. The theory is a guide to understanding the stiffness of biological membranes with their complex composition, as well as how choices of forcefield parameterization are translated into mechanical stiffness.
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Affiliation(s)
- Amirali Hossein
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, United States
| | - Andrew H Beaven
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, United States
- Postdoctoral Research Associate Program, National Institute of General Medical Sciences, Bethesda, MD 20892, United States
| | - Kayla Sapp
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, United States
| | - Alexander J Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, United States
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3
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Wang MT, Ma R, Wu CX. Membrane buckling and the determination of Gaussian curvature modulus. Phys Rev E 2023; 108:034802. [PMID: 37849138 DOI: 10.1103/physreve.108.034802] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 08/25/2023] [Indexed: 10/19/2023]
Abstract
Biological membranes can exhibit various morphology due to the fluidity of the lipid molecules within the monolayers. The shape transformation of membranes has been well described by the classical Helfrich theory, which consists only a few phenomenological parameters, including the mean and the Gaussian curvature modulus. Though various methods have been proposed to measure the mean curvature modulus, determining the Gaussian curvature modulus remains difficult both in experiments and in simulations. In this paper we study the buckling process of a rectangular membrane and a circular membrane subject to compressive stresses and under different boundary conditions. We find that the buckling of a rectangular membrane takes place continuously, while the buckling of a circular membrane can be discontinuous depending on the boundary conditions. Furthermore, our results show that the stress-strain relationship of a buckled circular membrane can be used to determine the Gaussian curvature modulus effectively.
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Affiliation(s)
- Mei-Ting Wang
- Fujian Provincial Key Laboratory for Soft Functional Materials Research, Research Institute for Biomimetics and Soft Matter, Department of Physics, College of Physical Science and Technology, Xiamen University, Xiamen 361005, People's Republic of China
| | - Rui Ma
- Fujian Provincial Key Laboratory for Soft Functional Materials Research, Research Institute for Biomimetics and Soft Matter, Department of Physics, College of Physical Science and Technology, Xiamen University, Xiamen 361005, People's Republic of China
| | - Chen-Xu Wu
- Fujian Provincial Key Laboratory for Soft Functional Materials Research, Research Institute for Biomimetics and Soft Matter, Department of Physics, College of Physical Science and Technology, Xiamen University, Xiamen 361005, People's Republic of China
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4
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Karaz S, Senses E. Liposomes Under Shear: Structure, Dynamics, and Drug Delivery Applications. ADVANCED NANOBIOMED RESEARCH 2023. [DOI: 10.1002/anbr.202200101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- Selcan Karaz
- Department of Chemical and Biological Engineering Koç University Istanbul 34450 Turkey
| | - Erkan Senses
- Department of Chemical and Biological Engineering Koç University Istanbul 34450 Turkey
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5
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Morvan E, Taib-Maamar N, Grélard A, Loquet A, Dufourc EJ. Bio-membranes: Picosecond to second dynamics and plasticity as deciphered by solid state NMR. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184097. [PMID: 36442647 DOI: 10.1016/j.bbamem.2022.184097] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/21/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Since the first membrane models in the 1970s, the concept of biological membranes has evolved considerably. The membrane is now seen as a very complex mixture whose dynamic behavior is even more complex. Solid-state NMR is well suited for such studies as it can probe the movements of the membrane from picoseconds to seconds. Two NMR observables can be used: motionally averaged spectra and relaxation times. They bring information on order parameters, phase transitions, correlation times, activation energies and membrane elasticity. Spectra are used to determine the nature of the membrane phase. The order parameters can be measured directly from spectra that are dominated by quadrupolar, dipolar and chemical shielding magnetic interactions and allow describing the lipid membrane as being very rigid at the glycerol and chain level and very fluid at its center and surface. Correlation times and activation energies can be measured for intramolecular motions (pico to nanoseconds), molecular motions (nano to 100 ns) and collective modes of membrane deformation (microseconds). Sterols modulate membrane phases, order parameters, correlation times and membrane elasticity. In general terms, sterols tend to act to reduce the impact of environmental changes on molecular order and dynamics. They can be described as regulators of membrane dynamics by keeping them in a state of dynamics that changes very little when the temperature or other factors change. The presence of such large-scale membrane dynamics is proposed as a means of adapting to evolutionary constraints.
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Affiliation(s)
- Estelle Morvan
- Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US01, Pessac, France
| | - Nada Taib-Maamar
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, 33600 Pessac, France
| | - Axelle Grélard
- Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US01, Pessac, France; Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, 33600 Pessac, France
| | - Antoine Loquet
- Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US01, Pessac, France; Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, 33600 Pessac, France
| | - Erick J Dufourc
- Institut Européen de Chimie et Biologie UAR3033 CNRS, University of Bordeaux, INSERM US01, Pessac, France; Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, University of Bordeaux, Bordeaux Polytechnic Institute, 33600 Pessac, France.
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6
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Zabala-Ferrera O, Liu P, Beltramo PJ. Determining the Bending Rigidity of Free-Standing Planar Phospholipid Bilayers. MEMBRANES 2023; 13:129. [PMID: 36837632 PMCID: PMC9959114 DOI: 10.3390/membranes13020129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/14/2023] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
We describe a method to determine membrane bending rigidity from capacitance measurements on large area, free-standing, planar, biomembranes. The bending rigidity of lipid membranes is an important biological mechanical property that is commonly optically measured in vesicles, but difficult to quantify in a planar, unsupported system. To accomplish this, we simultaneously image and apply an electric potential to free-standing, millimeter area, planar lipid bilayers composed of DOPC and DOPG phospholipids to measure the membrane Young's (elasticity) modulus. The bilayer is then modeled as two adjacent thin elastic films to calculate bending rigidity from the electromechanical response of the membrane to the applied field. Using DOPC, we show that bending rigidities determined by this approach are in good agreement with the existing work using neutron spin echo on vesicles, atomic force spectroscopy on supported lipid bilayers, and micropipette aspiration of giant unilamellar vesicles. We study the effect of asymmetric calcium concentration on symmetric DOPC and DOPG membranes and quantify the resulting changes in bending rigidity. This platform offers the ability to create planar bilayers of controlled lipid composition and aqueous ionic environment, with the ability to asymmetrically alter both. We aim to leverage this high degree of compositional and environmental control, along with the capacity to measure physical properties, in the study of various biological processes in the future.
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7
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Valorphins alter physicochemical characteristics of phosphatidylcholine membranes: datasets on lipid packing, bending rigidity, specific electrical capacitance, dipole potential, vesicle size. Data Brief 2022; 45:108716. [DOI: 10.1016/j.dib.2022.108716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
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8
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Pritzl SD, Morstein J, Kahler S, Konrad DB, Trauner D, Lohmüller T. Postsynthetic Photocontrol of Giant Liposomes via Fusion-Based Photolipid Doping. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11941-11949. [PMID: 36130117 PMCID: PMC9536078 DOI: 10.1021/acs.langmuir.2c01685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/06/2022] [Indexed: 06/15/2023]
Abstract
We report on photolipid doping of giant unilamellar vesicles (GUVs) via vesicle fusion with small unilamellar photolipid vesicles (pSUVs), which enables retroactive optical control of the membrane properties. We observe that vesicle fusion is light-dependent, if the phospholipids are neutral. Charge-mediated fusion involving anionic and cationic lipid molecules augments the overall fusion performance and doping efficiency, even in the absence of light exposure. Using phosphatidylcholine analogs with one or two azobenzene photoswitches (azo-PC and dazo-PC) affects domain formation, bending stiffness, and shape of the resulting vesicles in response to irradiation. Moreover, we show that optical membrane control can be extended to long wavelengths using red-absorbing photolipids (red-azo-PC). Combined, our findings present an attractive and practical method for the precise delivery of photolipids, which offers new prospects for the optical control of membrane function.
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Affiliation(s)
- Stefanie D. Pritzl
- Chair
for Photonics and Optoelectronics, Nano-Institute Munich, Department
of Physics, Ludwig-Maximilians-Universität
(LMU), 80539 Munich, Germany
| | - Johannes Morstein
- Department
of Chemistry, New York University, Silver Center, New York 10003, United States
- Department
of Cellular and Molecular Pharmacology, UCSF, San Francisco, California 94143, United States
| | - Sophia Kahler
- Department
of Chemistry, New York University, Silver Center, New York 10003, United States
| | - David B. Konrad
- Department
of Pharmacy, Ludwig-Maximilians-Universität
(LMU), 81377 Munich, Germany
| | - Dirk Trauner
- Department
of Chemistry, New York University, Silver Center, New York 10003, United States
| | - Theobald Lohmüller
- Chair
for Photonics and Optoelectronics, Nano-Institute Munich, Department
of Physics, Ludwig-Maximilians-Universität
(LMU), 80539 Munich, Germany
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9
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Unveiling the mono-rhamnolipid and di-rhamnolipid mechanisms of action upon plasma membrane models. J Colloid Interface Sci 2022; 624:579-592. [DOI: 10.1016/j.jcis.2022.05.145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/18/2022]
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10
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Appshaw P, Seddon AM, Hanna S. Scale-invariance in miniature coarse-grained red blood cells by fluctuation analysis. SOFT MATTER 2022; 18:1747-1756. [PMID: 34994752 DOI: 10.1039/d1sm01542g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
To accurately represent the morphological and elastic properties of a human red blood cell, Fu et al. [Fu et al., Lennard-Jones type pair-potential method for coarse-grained lipid bilayer membrane simulations in LAMMPS, 2017, 210, 193-203] recently developed a coarse-grained molecular dynamics model with particular detail in the membrane. However, such a model accrues an extremely high computational cost for whole-cell simulation when assuming an appropriate length scaling - that of the bilayer thickness. To date, the model has only simulated "miniature" cells in order to circumvent this, with the a priori assumption that these miniaturised cells correctly represent their full-sized counterparts. The present work assesses the validity of this approach, by testing the scale invariance of the model through simulating cells of various diameters; first qualitatively in their shape evolution, then quantitatively by measuring their bending rigidity through fluctuation analysis. Cells of diameter of at least 0.5 μm were able to form the characteristic biconcave shape of human red blood cells, though smaller cells instead equilibrated to bowl-shaped stomatocytes. Thermal fluctuation analysis showed the bending rigidity to be constant over all cell sizes tested, and consistent between measurements on the whole-cell and on a planar section of bilayer. This is as expected from the theory on both counts. Therefore, we confirm that the evaluated model is a good representation of a full-size RBC when the model diameter is ≥0.5 μm, in terms of the morphological and mechanical properties investigated.
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Affiliation(s)
- Paul Appshaw
- School of Physics, HH Wills Physics Laboratory, University of Bristol, BS8 1TL, UK.
| | - Annela M Seddon
- Bristol Centre for Functional Nanomaterials, HH Wills Physics Laboratory, University of Bristol, BS8 1TL, UK
| | - Simon Hanna
- School of Physics, HH Wills Physics Laboratory, University of Bristol, BS8 1TL, UK.
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11
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Pritzl SD, Konrad DB, Ober MF, Richter AF, Frank JA, Nickel B, Trauner D, Lohmüller T. Optical Membrane Control with Red Light Enabled by Red-Shifted Photolipids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:385-393. [PMID: 34969246 DOI: 10.1021/acs.langmuir.1c02745] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Photoswitchable phospholipids, or "photolipids", that harbor an azobenzene group in their lipid tails are versatile tools to manipulate and control lipid bilayer properties with light. So far, the limited ultraviolet-A/blue spectral range in which the photoisomerization of regular azobenzene operates has been a major obstacle for biophysical or photopharmaceutical applications. Here, we report on the synthesis of nano- and micrometer-sized liposomes from tetra-ortho-chloro azobenzene-substituted phosphatidylcholine (termed red-azo-PC) that undergoes photoisomerization on irradiation with tissue-penetrating red light (≥630 nm). Photoswitching strongly affects the fluidity and mechanical properties of lipid membranes, although small-angle X-ray scattering and dynamic light scattering measurements reveal only a minor influence on the overall bilayer thickness and area expansion. By controlling the photostationary state and the photoswitching efficiency of red-azo-PC for specific wavelengths, we demonstrate that shape transitions such as budding or pearling and the division of cell-sized vesicles can be achieved. These results emphasize the applicability of red-azo-PC as a nanophotonic tool in synthetic biology and for biomedical applications.
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Affiliation(s)
- Stefanie D Pritzl
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universtität (LMU), Königinstraße 10, 80539 Munich, Germany
| | - David B Konrad
- Department of Pharmacy, Ludwig-Maximilians-Universtität (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Martina F Ober
- Faculty of Physics and CeNS, Ludwig-Maximilians-Universtität (LMU), Geschwister-Scholl-Platz 1, 80539 München, Germany
| | - Alexander F Richter
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universtität (LMU), Königinstraße 10, 80539 Munich, Germany
| | - James A Frank
- Department of Chemical Physiology & Biochemistry, Vollum Institute, Oregon, Health & Science University, 3181 S.W. Sam Jackson Park Rd., Portland, Oregon 97239, United States
| | - Bert Nickel
- Faculty of Physics and CeNS, Ludwig-Maximilians-Universtität (LMU), Geschwister-Scholl-Platz 1, 80539 München, Germany
| | - Dirk Trauner
- Department of Chemistry, New York University, Silver Center, 100 Washington Square East, Room 712, New York, New York 10003, United States
| | - Theobald Lohmüller
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universtität (LMU), Königinstraße 10, 80539 Munich, Germany
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12
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Surface Properties of Synaptosomes in the Presence of L-Glutamic and Kainic Acids: In Vitro Alteration of the ATPase and Acetylcholinesterase Activities. MEMBRANES 2021; 11:membranes11120987. [PMID: 34940488 PMCID: PMC8708669 DOI: 10.3390/membranes11120987] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/12/2021] [Accepted: 12/14/2021] [Indexed: 11/23/2022]
Abstract
Morphologically and functionally identical to brain synapses, the nerve ending particles synaptosomes are biochemically derived membrane structures responsible for the transmission of neural information. Their surface and mechanical properties, measured in vitro, provide useful information about the functional activity of synapses in the brain in vivo. Glutamate and kainic acid are of particular interest because of their role in brain pathology (including causing seizure, migraine, ischemic stroke, aneurysmal subarachnoid hemorrhage, intracerebral hematoma, traumatic brain injury and stroke). The effects of the excitatory neurotransmitter L-glutamic acid and its agonist kainic acid are tested on Na+, K+-ATPase and Mg2+-ATPase activities in synaptic membranes prepared from the cerebral cortex of rat brain tissue. The surface parameters of synaptosome preparations from the cerebral cortex in the presence of L-glutamic and kainic acids are studied by microelectrophoresis for the first time. The studied neurotransmitters promote a significant increase in the electrophoretic mobility and surface electrical charge of synaptosomes at 1–4 h after isolation. The measured decrease in the bending modulus of model bimolecular membranes composed of monounsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine provides evidence for softer membranes in the presence of L-glutamate. Kainic acid does not affect membrane mechanical stability even at ten-fold higher concentrations. Both the L-glutamic and kainic acids reduce acetylcholinesterase activity and deviation from the normal functions of neurotransmission in synapses is presumed. The presented results regarding the modulation of the enzyme activity of synaptic membranes and surface properties of synaptosomes are expected by biochemical and biophysical studies to contribute to the elucidation of the molecular mechanisms of neurotransmitters/agonists’ action on membranes.
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13
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Abstract
Hierarchic self-assembly underpins much of the form and function seen in synthetic or biological soft materials. Lipids are paramount examples, building themselves in nature or synthetically in a variety of meso/nanostructures. Synthetic block copolymers capture many of lipid's structural and functional properties. Lipids are typically biocompatible and high molecular weight polymers are mechanically robust and chemically versatile. The development of new materials for applications like controlled drug/gene/protein delivery, biosensors, and artificial cells often requires the combination of lipids and polymers. The emergent composite material, a "polymer-lipid hybrid membrane", displays synergistic properties not seen in pure components. Specific examples include the observation that hybrid membranes undergo lateral phase separation that can correlate in registry across multiple layers into a three-dimensional phase-separated system with enhanced permeability of encapsulated drugs. It is timely to underpin these emergent properties in several categories of hybrid systems ranging from colloidal suspensions to supported hybrid films. In this review, we discuss the form and function of a vast number of polymer-lipid hybrid systems published to date. We rationalize the results to raise new fundamental understanding of hybrid self-assembling soft materials as well as to enable the design of new supramolecular systems and applications.
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Affiliation(s)
- Yoo Kyung Go
- Department of Materials Science and Engineering, University of Illinois at Urbana─Champaign, Urbana, Illinois 61801, 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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14
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Lopez Mora N, Findlay HE, Brooks NJ, Purushothaman S, Ces O, Booth PJ. The membrane transporter lactose permease increases lipid bilayer bending rigidity. Biophys J 2021; 120:3787-3794. [PMID: 34273316 PMCID: PMC8456183 DOI: 10.1016/j.bpj.2021.06.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 06/23/2021] [Accepted: 06/28/2021] [Indexed: 11/26/2022] Open
Abstract
Cellular life relies on membranes, which provide a resilient and adaptive cell boundary. Many essential processes depend upon the ease with which the membrane is able to deform and bend, features that can be characterized by the bending rigidity. Quantitative investigations of such mechanical properties of biological membranes have primarily been undertaken in solely lipid bilayers and frequently in the absence of buffers. In contrast, much less is known about the influence of integral membrane proteins on bending rigidity under physiological conditions. We focus on an exemplar member of the ubiquitous major facilitator superfamily of transporters and assess the influence of lactose permease on the bending rigidity of lipid bilayers. Fluctuation analysis of giant unilamellar vesicles (GUVs) is a useful means to measure bending rigidity. We find that using a hydrogel substrate produces GUVs that are well suited to fluctuation analysis. Moreover, the hydrogel method is amenable to both physiological salt concentrations and anionic lipids, which are important to mimic key aspects of the native lactose permease membrane. Varying the fraction of the anionic lipid in the lipid mixture DOPC/DOPE/DOPG allows us to assess the dependence of membrane bending rigidity on the topology and concentration of an integral membrane protein in the lipid bilayer of GUVs. The bending rigidity gradually increases with the incorporation of lactose permease, but there is no further increase with greater amounts of the protein in the membrane.
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Affiliation(s)
- Nestor Lopez Mora
- Department of Chemistry, Kings College London, London, United Kingdom
| | - Heather E Findlay
- Department of Chemistry, Kings College London, London, United Kingdom
| | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, London, United Kingdom
| | - Sowmya Purushothaman
- Department of Chemistry, Imperial College London, London, United Kingdom; Beyond Meat, El Segundo, California
| | - Oscar Ces
- Department of Chemistry, Imperial College London, London, United Kingdom
| | - Paula J Booth
- Department of Chemistry, Kings College London, London, United Kingdom.
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15
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Faizi HA, Dimova R, Vlahovska PM. Electromechanical characterization of biomimetic membranes using electrodeformation of vesicles. Electrophoresis 2021; 42:2027-2032. [PMID: 34297846 DOI: 10.1002/elps.202100091] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 07/01/2021] [Accepted: 07/09/2021] [Indexed: 11/08/2022]
Abstract
We describe a facile method to simultaneously measure the bending rigidity and capacitance of biomimetic lipid bilayers. Our approach utilizes the ellipsoidal deformation of quasi-spherical giant unilamellar vesicles induced by a uniform AC electric field. Vesicle shape depends on the electric field frequency and amplitude. Membrane bending rigidity can be obtained from the variation of the vesicle elongation on either field amplitude at fixed frequency or frequency at fixed field amplitude. Membrane capacitance is determined from the frequency at which the vesicle shape changes from prolate to oblate ellipsoid as the frequency is increased at a given field amplitude.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA
| | - Rumiana Dimova
- Department of Theory and Biosystems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam, Germany
| | - Petia M Vlahovska
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL, USA
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16
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Ergüder MF, Deserno M. Identifying systematic errors in a power spectral analysis of simulated lipid membranes. J Chem Phys 2021; 154:214103. [PMID: 34240970 DOI: 10.1063/5.0049448] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The elastic properties of lipid membranes can be measured by monitoring their thermal fluctuations. For instance, comparing the power spectra of membrane shape or lipid director fluctuations with predictions based on suitable continuum theories gives access to bending-, tilt-, and twist-moduli. However, to do so in a computer simulation, we must first define a continuum surface shape and lipid director field from the discrete configurations of lipid molecules in a typically fairly small box. Here, we show that the required mapping choices, as well as the details of the subsequent data analysis, can shift the measured values of these moduli by far more than their statistical uncertainties. We investigate the resulting systematic errors on the basis of atomistic simulation trajectories for 13 different lipids, previously published by Venable et al. [Chem. Phys. Lipids 192, 60-74 (2015)]. Specifically, we examine mapping choices for surface- and tilt-field definitions, normalizing and averaging lipid directors, accounting for wave vector dependent time autocorrelations, error propagation, and finding the right fitting range. We propose a set of criteria that may help to decide upon a particular combination of choices underlying the fluctuation analysis, and we make several recommendations based on these. While systematic shifts in observables that are extracted from large-wavelength limits vanish, in principle, for sufficiently large system size, no such exact limit exists for intrinsically local parameters, such as the twist modulus or the splay-tilt coupling, and so not all potential choices can be trivially verified.
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Affiliation(s)
- Muhammed F Ergüder
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
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17
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Liu K, Patteson AE, Banigan EJ, Schwarz JM. Dynamic Nuclear Structure Emerges from Chromatin Cross-Links and Motors. PHYSICAL REVIEW LETTERS 2021; 126:158101. [PMID: 33929233 DOI: 10.1103/physrevlett.126.158101] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 02/22/2021] [Indexed: 06/12/2023]
Abstract
The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin protein filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, cross-linked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity and cross-links. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, cross-linking, and chromosome-lamina binding. Therefore, complex chromosome dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.
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Affiliation(s)
- Kuang Liu
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
| | - Alison E Patteson
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
| | - Edward J Banigan
- Institute for Medical Engineering and Science and Department of Physics, MIT, Cambridge, Massachusetts 02139, USA
| | - J M Schwarz
- Department of Physics and BioInspired Syracuse, Syracuse University, Syracuse, New York 13244, USA
- Indian Creek Farm, Ithaca, New York 14850, USA
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18
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Aden S, Snoj T, Anderluh G. The use of giant unilamellar vesicles to study functional properties of pore-forming toxins. Methods Enzymol 2021; 649:219-251. [PMID: 33712188 DOI: 10.1016/bs.mie.2021.01.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Pore-forming toxins (PFTs) act upon lipid membranes and appropriate model systems are of great importance in researching these proteins. Giant unilamellar vesicles (GUVs) are an excellent model membrane system to study interactions between lipids and proteins. Their main advantage is the size comparable to cells, which means that GUVs can be observed directly under the light microscope. Many PFTs properties can be studied by using GUVs, such as binding specificity, membrane reorganization upon protein binding and oligomerization, pore properties and mechanism of pore formation. GUVs also represent a good model for biotechnological approaches, e.g., in applications in synthetic biology and medicine. Each research area has its own demands for GUVs properties, so several different approaches for GUVs preparations have been developed and will be discussed in this chapter.
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Affiliation(s)
- Saša Aden
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Tina Snoj
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Gregor Anderluh
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia.
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19
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Affiliation(s)
- Chandra Has
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
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20
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Pritzl SD, Urban P, Prasselsperger A, Konrad DB, Frank JA, Trauner D, Lohmüller T. Photolipid Bilayer Permeability is Controlled by Transient Pore Formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13509-13515. [PMID: 33143416 DOI: 10.1021/acs.langmuir.0c02229] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Controlling the release or uptake of (bio-) molecules and drugs from liposomes is critically important for a range of applications in bioengineering, synthetic biology, and drug delivery. In this paper, we report how the reversible photoswitching of synthetic lipid bilayer membranes made from azobenzene-containing phosphatidylcholine (azo-PC) molecules (photolipids) leads to increased membrane permeability. We show that cell-sized, giant unilamellar vesicles (GUVs) prepared from photolipids display leakage of fluorescent dyes after irradiation with UV-A and visible light. Langmuir-Blodgett and patch-clamp measurements show that the permeability is the result of transient pore formation. By comparing the trans-to-cis and cis-to-trans isomerization process, we find that this pore formation is the result of area fluctuations and a change of the area cross-section between both photolipid isomers.
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Affiliation(s)
- Stefanie D Pritzl
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
| | - Patrick Urban
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
| | - Alexander Prasselsperger
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
| | - David B Konrad
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Department of Pharmacy, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - James A Frank
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Dirk Trauner
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Department of Chemistry, New York University, Silver Center, 100 Washington Square East, Room 712, New York 10003, United States
| | - Theobald Lohmüller
- Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
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21
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Spanke HT, Style RW, François-Martin C, Feofilova M, Eisentraut M, Kress H, Agudo-Canalejo J, Dufresne ER. Wrapping of Microparticles by Floppy Lipid Vesicles. PHYSICAL REVIEW LETTERS 2020; 125:198102. [PMID: 33216584 DOI: 10.1103/physrevlett.125.198102] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/13/2020] [Indexed: 06/11/2023]
Abstract
Lipid membranes, the barrier defining living cells and many of their subcompartments, bind to a wide variety of nano- and micrometer sized objects. In the presence of strong adhesive forces, membranes can strongly deform and wrap the particles, an essential step in crossing the membrane for a variety of healthy and disease-related processes. A large body of theoretical and numerical work has focused on identifying the physical properties that underly wrapping. Using a model system of micron-sized colloidal particles and giant unilamellar lipid vesicles with tunable adhesive forces, we measure a wrapping phase diagram and make quantitative comparisons to theoretical models. Our data are consistent with a model of membrane-particle interactions accounting for the adhesive energy per unit area, membrane bending rigidity, particle size, and vesicle radius.
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Affiliation(s)
| | | | | | | | - Manuel Eisentraut
- Department of Physics, University of Bayreuth, 95447 Bayreuth, Germany
| | - Holger Kress
- Department of Physics, University of Bayreuth, 95447 Bayreuth, Germany
| | - Jaime Agudo-Canalejo
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), D-37077 Göttingen, Germany
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22
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23
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Faizi HA, Reeves CJ, Georgiev VN, Vlahovska PM, Dimova R. Fluctuation spectroscopy of giant unilamellar vesicles using confocal and phase contrast microscopy. SOFT MATTER 2020; 16:8996-9001. [PMID: 32966528 DOI: 10.1039/d0sm00943a] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A widely used method to measure the bending rigidity of bilayer membranes is fluctuation spectroscopy, which analyses the thermally-driven membrane undulations of giant unilamellar vesicles recorded with either phase-contrast or confocal microscopy. Here, we analyze the fluctuations of the same vesicle using both techniques and obtain consistent values for the bending modulus. We discuss the factors that may lead to discrepancies.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA. and Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
| | - Cody J Reeves
- Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA
| | - Vasil N Georgiev
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
| | - Petia M Vlahovska
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA. and Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, USA
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
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24
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Lamparter L, Galic M. Cellular Membranes, a Versatile Adaptive Composite Material. Front Cell Dev Biol 2020; 8:684. [PMID: 32850810 PMCID: PMC7419611 DOI: 10.3389/fcell.2020.00684] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 07/06/2020] [Indexed: 12/17/2022] Open
Abstract
Cellular membranes belong to the most vital yet least understood biomaterials of live matter. For instance, its biomechanical requirements substantially vary across species and subcellular sites, raising the question how membranes manage to adjust to such dramatic changes. Central to its adaptability at the cell surface is the interplay between the plasma membrane and the adjacent cell cortex, forming an adaptive composite material that dynamically adjusts its mechanical properties. Using a hypothetical composite material, we identify core challenges, and discuss how cellular membranes solved these tasks. We further muse how pathological changes in material properties affect membrane mechanics and cell function, before closing with open questions and future challenges arising when studying cellular membranes.
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Affiliation(s)
- Lucas Lamparter
- Institute of Medical Physics and Biophysics, Faculty of Medicine, University of Münster, Münster, Germany.,Cells in Motion Interfaculty Centre, University of Müenster, Münster, Germany
| | - Milos Galic
- Institute of Medical Physics and Biophysics, Faculty of Medicine, University of Münster, Münster, Germany.,Cells in Motion Interfaculty Centre, University of Müenster, Münster, Germany
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25
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Dazzoni R, Grélard A, Morvan E, Bouter A, Applebee CJ, Loquet A, Larijani B, Dufourc EJ. The unprecedented membrane deformation of the human nuclear envelope, in a magnetic field, indicates formation of nuclear membrane invaginations. Sci Rep 2020; 10:5147. [PMID: 32198481 PMCID: PMC7083927 DOI: 10.1038/s41598-020-61746-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/14/2020] [Indexed: 12/04/2022] Open
Abstract
Human nuclear membrane (hNM) invaginations are thought to be crucial in fusion, fission and remodeling of cells and present in many human diseases. There is however little knowledge, if any, about their lipid composition and dynamics. We therefore isolated nuclear envelope lipids from human kidney cells, analyzed their composition and determined the membrane dynamics after resuspension in buffer. The hNM lipid extract was composed of a complex mixture of phospholipids, with high amounts of phosphatidylcholines, phosphatidylinositols (PI) and cholesterol. hNM dynamics was determined by solid-state NMR and revealed that the lamellar gel-to-fluid phase transition occurs below 0 °C, reflecting the presence of elevated amounts of unsaturated fatty acid chains. Fluidity was higher than the plasma membrane, illustrating the dual action of Cholesterol (ordering) and PI lipids (disordering). The most striking result was the large magnetic field-induced membrane deformation allowing to determine the membrane bending elasticity, a property related to hydrodynamics of cells and organelles. Human Nuclear Lipid Membranes were at least two orders of magnitude more elastic than the classical plasma membrane suggesting a physical explanation for the formation of nuclear membrane invaginations.
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Affiliation(s)
- Régine Dazzoni
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, Université Bordeaux, INP-Bordeaux, F-33600, Pessac, France.,Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Instituto Biofísika (CSIC, UPV/EHU) and Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Axelle Grélard
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, Université Bordeaux, INP-Bordeaux, F-33600, Pessac, France
| | - Estelle Morvan
- Institut Européen de Chimie et Biologie, UMS3033, CNRS, Université Bordeaux, INSERM (US001), 2 rue Escarpit, Pessac, 33600, France
| | - Anthony Bouter
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, Université Bordeaux, INP-Bordeaux, F-33600, Pessac, France
| | - Christopher J Applebee
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Instituto Biofísika (CSIC, UPV/EHU) and Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa, Spain.,Cell Biophysics Laboratory, Centre for Therapeutic Innovation & Department of Pharmacy and Pharmacology, & Department of Physics, University of Bath, Bath, United Kingdom
| | - Antoine Loquet
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, Université Bordeaux, INP-Bordeaux, F-33600, Pessac, France
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Instituto Biofísika (CSIC, UPV/EHU) and Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa, Spain. .,Cell Biophysics Laboratory, Centre for Therapeutic Innovation & Department of Pharmacy and Pharmacology, & Department of Physics, University of Bath, Bath, United Kingdom.
| | - Erick J Dufourc
- Institute of Chemistry & Biology of Membranes & Nanoobjects, UMR5248, CNRS, Université Bordeaux, INP-Bordeaux, F-33600, Pessac, France.
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26
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Terzi MM, Ergüder MF, Deserno M. A consistent quadratic curvature-tilt theory for fluid lipid membranes. J Chem Phys 2019; 151:164108. [PMID: 31675861 DOI: 10.1063/1.5119683] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The tilt of a lipid molecule describes the deviation of its orientation away from the local normal of its embedding membrane. Tilt is the subleading degree of freedom after a membrane's geometry, and it becomes relevant at scales comparable to lipid bilayer thickness. Building on earlier work by Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)], who envisioned lipid membranes as thin prestressed fluid elastic films, and Terzi and Deserno [J. Chem. Phys. 147, 084702 (2017)], who discovered a new coupling term between splay and tilt divergence, we construct a theory of membrane elasticity that is quadratic in geometry and tilt and complete at order 1/length2. We show that a general and consistent treatment of both lateral and transverse depth-dependent shear stresses creates several contributions to the elastic energy density, of which only a subset had previously been identified. Apart from the well-known penalty of lipid twist (the curl of tilt), these terms generate no qualitatively new phenomenology, but they quantitatively revise the connections between the moduli of a tilt-curvature theory and its underlying microscopic foundation. In particular, we argue that the monolayer Gaussian curvature modulus κ¯m, widely believed to be equal to the second moment of the transmonolayer stress profile, acquires a second contribution from lipid twist, which is always negative. This could resolve the long-standing conundrum that many measured values of κ¯m appeared to have a sign that violates basic stability considerations. We also show that the previously discovered novel coupling between splay and tilt divergence is not simply proportional to κ¯m but acquires its own splay-tilt coupling modulus, κst,m. We explore the predictions of our theory for various elastic moduli and their mutual interrelations and use an extensive set of existing atomistic molecular dynamics simulations for 12 different lipid types to collectively reason about such predictions. We find that bending rigidities are captured fairly well by existing theories, while reliable predictions for local moduli, especially the splay-tilt coupling modulus, remain challenging.
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Affiliation(s)
- M Mert Terzi
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Muhammed F Ergüder
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
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27
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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] [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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28
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Xu R, Dehghan A, Shi AC, Zhou J. Elastic property of membranes self-assembled from diblock and triblock copolymers. Chem Phys Lipids 2019; 221:83-92. [PMID: 30926383 DOI: 10.1016/j.chemphyslip.2019.03.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 03/23/2019] [Accepted: 03/25/2019] [Indexed: 01/31/2023]
Abstract
The elastic property of membranes self-assembled from AB diblock and ABA triblock copolymers, as coarse-grained model of lipids and the bolalipids, are studied using the self-consistent field theory (SCFT). Specifically, solutions of the SCFT equations, corresponding to membranes in different geometries (planar, cylindrical, spherical, and pore) have been obtained for a model system composed of amphiphilic AB diblock copolymers and ABA triblock copolymers dissolved in A homopolymers. The free energy of the membranes with different geometries is then used to extract the bending modulus, Gaussian modulus, and line tension of the membranes. The results reveal that the bending modulus of the triblock membrane is greater than that of the diblock membrane. Furthermore, the Gaussian modulus and line tension of the triblock membrane indicate that the triblock membranes have higher pore formation energy than that of the diblock membranes. The equilibrium bridging and looping fractions of the triblock copolymers are also obtained. Implications of the theoretical results on the elastic properties of biologically equivalent lipid bilayers and the bolalipid membranes are discussed.
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Affiliation(s)
- Rui Xu
- Department of Physics & Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
| | - Ashkan Dehghan
- Department of Physics & Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
| | - An-Chang Shi
- Department of Physics & Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada.
| | - Jiajia Zhou
- Center of Soft Matter Physics and its Applications, Beihang University, Beijing 100191, China; School of Chemistry, Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing 100191, China.
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29
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Schroder AP, Crassous JJ, Marques CM, Olsson U. Rapid confocal imaging of vesicle-to-sponge phase droplet transition in dilute dispersions of the C 10E 3 surfactant. Sci Rep 2019; 9:2292. [PMID: 30783162 PMCID: PMC6381169 DOI: 10.1038/s41598-019-38620-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 12/15/2018] [Indexed: 11/09/2022] Open
Abstract
The lamellar-to-sponge phase transition of fluorescently labelled large unilamellar vesicles (LUVs) of the non-ionic surfactant triethylene glycol mono n-decyl ether (C10E3) was investigated in situ by confocal laser scanning microscopy (CLSM). Stable dispersions of micrometer-sized C10E3 LUVs were prepared at 20 °C and quickly heated at different temperatures close to the lamellar-to-sponge phase transition temperature. Phase transition of the strongly fluctuating individual vesicles into micrometre-sized sponge phase droplets was observed to occur via manyfold multilamellar morphologies with increasing membrane confinement through inter- and intra- lamellar fusion. The very low bending rigidity and lateral tension of the C10E3 bilayer were supported by quantitative image analysis of a stable fluctuating membrane using both flicker noise spectroscopy and spatial autocorrelation function.
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Affiliation(s)
- André Pierre Schroder
- Institut Charles Sadron, Université de Strasbourg, CNRS UP22, F-67200, Strasbourg, France.
| | - Jérôme Joseph Crassous
- Institute of Physical Chemistry, RWTH Aachen University, D-52074, Aachen, Germany.,Physical Chemistry, Department of Chemistry, Lund University, SE-22100, Lund, Sweden
| | - Carlos Manuel Marques
- Institut Charles Sadron, Université de Strasbourg, CNRS UP22, F-67200, Strasbourg, France
| | - Ulf Olsson
- Physical Chemistry, Department of Chemistry, Lund University, SE-22100, Lund, Sweden
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30
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Mell M, Monroy F. A gradient-based, GPU-accelerated, high-precision contour-segmentation algorithm with application to cell membrane fluctuation spectroscopy. PLoS One 2018; 13:e0207376. [PMID: 30521560 PMCID: PMC6283589 DOI: 10.1371/journal.pone.0207376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 10/30/2018] [Indexed: 11/25/2022] Open
Abstract
We present a novel intensity-gradient based algorithm specifically designed for nanometer-segmentation of cell membrane contours obtained with high-resolution optical microscopy combined with high-velocity digital imaging. The algorithm relies on the image oversampling performance and computational power of graphical processing units (GPUs). Both, synthetic and experimental data are used to quantify the sub-pixel precision of the algorithm, whose analytic performance results comparatively higher than in previous methods. Results from the synthetic data indicate that the spatial precision of the presented algorithm is only limited by the signal-to-noise ratio (SNR) of the contour image. We emphasize on the application of the new algorithm to membrane fluctuations (flickering) in eukaryotic cells, bacteria and giant vesicle models. The method shows promising applicability in several fields of cellular biology and medical imaging for nanometer-precise boundary-determination and mechanical fingerprinting of cellular membranes in optical microscopy images. Our implementation of this high-precision flicker spectroscopy contour tracking algorithm (HiPFSTA) is provided as open-source at www.github.com/michaelmell/hipfsta.
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Affiliation(s)
- Michael Mell
- Mechanics of Biological Membranes and Biorheology, Dpto. Química Física I, Universidad Complutense, Madrid, Spain
| | - Francisco Monroy
- Mechanics of Biological Membranes and Biorheology, Dpto. Química Física I, Universidad Complutense, Madrid, Spain
- Translational Biophysics, Instituto de Investigacion Biomédica Hospital Doce de Octubre (i+12), Madrid, Spain
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31
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Abstract
On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane's reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters. In the present paper, we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. This term arises because, as one moves along the membrane, the curvature-induced change of transverse distances contributes to the area strain-an effect that was believed to be small but nevertheless ends up contributing at the same (quadratic) order as all other terms in their Hamiltonian. We illustrate the consequences of this amendment by deriving the monolayer and bilayer Euler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations. A particularly curious aspect of our new term is that its associated coupling constant is the second moment of the lipid monolayer's lateral stress profile-which within this framework is equal to the monolayer Gaussian curvature modulus, κ¯m. On the one hand, this implies that many theoretical predictions now contain a parameter that is poorly known (because the Gauss-Bonnet theorem limits access to the integrated Gaussian curvature); on the other hand, the appearance of κ¯m outside of its Gaussian curvature provenance opens opportunities for measuring it by more conventional means, for instance by monitoring a membrane's undulation spectrum at short scales.
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Affiliation(s)
- M Mert Terzi
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213, USA
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32
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Doskocz J, Drabik D, Chodaczek G, Przybyło M, Langner M. Statistical Analysis of Bending Rigidity Coefficient Determined Using Fluorescence-Based Flicker-Noise Spectroscopy. J Membr Biol 2018; 251:601-608. [PMID: 29858612 DOI: 10.1007/s00232-018-0037-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
Abstract
Bending rigidity coefficient describes propensity of a lipid bilayer to deform. In order to measure the parameter experimentally using flickering noise spectroscopy, the microscopic imaging is required, which necessitates the application of giant unilamellar vesicles (GUV) lipid bilayer model. The major difficulty associated with the application of the model is the statistical character of GUV population with respect to their size and the homogeneity of lipid bilayer composition, if a mixture of lipids is used. In the paper, the bending rigidity coefficient was measured using the fluorescence-enhanced flicker-noise spectroscopy. In the paper, the bending rigidity coefficient was determined for large populations of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine vesicles. The quantity of obtained experimental data allows to perform statistical analysis aiming at the identification of the distribution, which is the most appropriate for the calculation of the value of the membrane bending rigidity coefficient. It has been demonstrated that the bending rigidity coefficient is characterized by an asymmetrical distribution, which is well approximated with the gamma distribution. Since there are no biophysical reasons for that we propose to use the difference between normal and gamma fits as a measure of the homogeneity of vesicle population. In addition, the effect of a fluorescent label and types of instrumental setups on determined values has been tested. Obtained results show that the value of the bending rigidity coefficient does not depend on the type of a fluorescent label nor on the type of microscope used.
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Affiliation(s)
- Joanna Doskocz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Pl. Grunwaldzki 13, 50-377, Wrocław, Poland.
| | - Dominik Drabik
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Pl. Grunwaldzki 13, 50-377, Wrocław, Poland
| | - Grzegorz Chodaczek
- Wroclaw Research Centre EIT+, ul. Stabłowicka 147, 54-066, Wrocław, Poland
| | - Magdalena Przybyło
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Pl. Grunwaldzki 13, 50-377, Wrocław, Poland.,Lipid Systems sp. z o.o., ul. Krzemieniecka 48C, 54-613, Wrocław, Poland
| | - Marek Langner
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Pl. Grunwaldzki 13, 50-377, Wrocław, Poland.,Lipid Systems sp. z o.o., ul. Krzemieniecka 48C, 54-613, Wrocław, Poland
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33
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Doktorova M, Harries D, Khelashvili G. Determination of bending rigidity and tilt modulus of lipid membranes from real-space fluctuation analysis of molecular dynamics simulations. Phys Chem Chem Phys 2018. [PMID: 28627570 DOI: 10.1039/c7cp01921a] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We have recently developed a novel computational methodology (termed RSF for Real-Space Fluctuations) to quantify the bending rigidity and tilt modulus of lipid membranes from real-space analysis of fluctuations in the tilt and splay degrees of freedom as sampled in molecular dynamics (MD) simulations. In this article, we present a comprehensive study that combines results from the application of the RSF method to a wide range of lipid bilayer systems that encompass membranes of different fluidities and sizes, including lipids with saturated and unsaturated lipid tails, single and multi-component lipid systems, as well as non-standard lipids such as the four-tailed cardiolipin. By comparing the material properties calculated with the RSF method to those obtained from experimental data and from other computational methodologies, we rigorously demonstrate the validity of our approach and show its robustness. This should allow for future applications of even more complex lipidic assemblies, whose material properties are not tractable by other computational techniques. In addition, we discuss the relationship between different definitions of the tilt modulus appearing in current literature to address some important unresolved discrepancies in the field.
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Affiliation(s)
- M Doktorova
- Tri-Institutional PhD Program in Computational Biology and Medicine, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA
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34
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Elsayed MMA, Ibrahim MM, Cevc G. The effect of membrane softeners on rigidity of lipid vesicle bilayers: Derivation from vesicle size changes. Chem Phys Lipids 2018; 210:98-108. [PMID: 29107604 DOI: 10.1016/j.chemphyslip.2017.10.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/14/2017] [Accepted: 10/25/2017] [Indexed: 12/26/2022]
Abstract
Deformability is not just a fundamentally interesting vesicle characteristic; it is also the key determinant of vesicle ability to cross the skin barrier; i.e. skin penetrability. Development of bilayer vesicles for drug and vaccine delivery across the skin should hence involve optimization of this property, which is controllable by the concentration of bilayer softeners in or near the vesicle bilayers. To this end, we propose a simple method for quantifying the effect of bilayer softeners on deformability of bilayer vesicles. The method derives the bending rigidity of vesicle bilayers from vesicle size dependence on softener concentration. To exemplify the method, we studied mixtures of soybean phosphatidylcholine with anionic sodium deoxycholate, non-ionic polyoxyethylene (20) sorbitan oleyl ester (polysorbate 80), or non-ionic polyoxyethylene (20) oleyl ether (C18:1EO20, Brij® 98). With each of the tested bilayer softeners, the bending rigidity of the resulting mixed-amphipat vesicle bilayers decreased quasi-exponentially as the concentration of the bilayer softener increased, as one would expect on theoretical ground. The bilayer bending rigidity reached low values, near the thermal stability limit, i.e. kBT, before vesicle transformation into non-vesicular aggregates began. For a soybean phosphatidylcholine concentration of 5.0mmolkg-1, the bilayer bending rigidity reached 1.5kBT at the total deoxycholate concentration of 4.1mmolkg-1 and 3.4kBT at the total polysorbate 80 concentration of 2.0mmolkg-1. In the case of C18:1EO20, the bilayer bending rigidity reached 1.5kBT at the bilayer surface occupancy α=0.1. The dependence of vesicle size on bilayer softener concentration thus reveals vesicle transformation into different aggregate structures (such as mixed micelles with poor skin penetrability) and practically valuable information on vesicle deformability. Our results compare favorably with results of literature measurements. We provide practical guidance on using the new analytical method to optimize deformable vesicle formulations.
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Affiliation(s)
- Mustafa M A Elsayed
- Department of Pharmaceutics, College of Pharmacy, University of Hail, Hail, Saudi Arabia; Department of Pharmaceutics, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt.
| | - Marwa M Ibrahim
- Department of Pharmaceutics, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt
| | - Gregor Cevc
- The Advanced Treatments Institute, Gauting, Germany
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35
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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] [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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36
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Zelisko M, Ahmadpoor F, Gao H, Sharma P. Determining the Gaussian Modulus and Edge Properties of 2D Materials: From Graphene to Lipid Bilayers. PHYSICAL REVIEW LETTERS 2017; 119:068002. [PMID: 28949621 DOI: 10.1103/physrevlett.119.068002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Indexed: 06/07/2023]
Abstract
The dominant deformation behavior of two-dimensional materials (bending) is primarily governed by just two parameters: bending rigidity and the Gaussian modulus. These properties also set the energy scale for various important physical and biological processes such as pore formation, cell fission and generally, any event accompanied by a topological change. Unlike the bending rigidity, the Gaussian modulus is, however, notoriously difficult to evaluate via either experiments or atomistic simulations. In this Letter, recognizing that the Gaussian modulus and edge tension play a nontrivial role in the fluctuations of a 2D material edge, we derive closed-form expressions for edge fluctuations. Combined with atomistic simulations, we use the developed approach to extract the Gaussian modulus and edge tension at finite temperatures for both graphene and various types of lipid bilayers. Our results possibly provide the first reliable estimate of this elusive property at finite temperatures and appear to suggest that earlier estimates must be revised. In particular, we show that, if previously estimated properties are employed, the graphene-free edge will exhibit unstable behavior at room temperature. Remarkably, in the case of graphene, we show that the Gaussian modulus and edge tension even change sign at finite temperatures.
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Affiliation(s)
- Matthew Zelisko
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
| | - Fatemeh Ahmadpoor
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Pradeep Sharma
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
- Department of Physics, University of Houston, Houston, Texas 77204, USA
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37
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Irajizad E, Walani N, Veatch SL, Liu AP, Agrawal A. Clathrin polymerization exhibits high mechano-geometric sensitivity. SOFT MATTER 2017; 13:1455-1462. [PMID: 28124714 PMCID: PMC5452080 DOI: 10.1039/c6sm02623k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
How tension modulates cellular transport has become a topic of interest in the recent past. However, the effect of tension on clathrin assembly and vesicle growth remains less understood. Here, we use the classical Helfrich theory to predict the energetic cost that clathrin is required to pay to remodel the membrane at different stages of vesicle formation. Our study reveals that this energetic cost is highly sensitive to not only the tension in the membrane but also to the instantaneous geometry of the membrane during shape evolution. Our study predicts a sharp reduction in clathrin coat size in the intermediate tension regime (0.01-0.1 mN m-1). Remarkably, the natural propensity of the membrane to undergo bending beyond the Ω shape causes a significant decrease in the energy needed from clathrin to drive vesicle growth. Our studies in mammalian cells confirm a reduction in clathrin coat size in an increased tension environment. In addition, our findings suggest that the two apparently distinct clathrin assembly modes, namely coated pits and coated plaques, observed in experimental investigations might be a consequence of varied tensions in the plasma membrane. Overall, the mechano-geometric sensitivity revealed in this study might also be at play during the polymerization of other membrane remodeling proteins.
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Affiliation(s)
- Ehsan Irajizad
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA
| | - Nikhil Walani
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA
| | - Sarah L Veatch
- Department of Biophysics, University of Michigan, Ann Arbor, MI, USA
| | - Allen P Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Ashutosh Agrawal
- Department of Mechanical Engineering, University of Houston, Houston, TX, USA.
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38
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Magarkar A, Jurkiewicz P, Allolio C, Hof M, Jungwirth P. Increased Binding of Calcium Ions at Positively Curved Phospholipid Membranes. J Phys Chem Lett 2017; 8:518-523. [PMID: 28067523 DOI: 10.1021/acs.jpclett.6b02818] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Calcium ion is the ubiquitous messenger in cells and plays a key role in neuronal signaling and fusion of synaptic vesicles. These vesicles are typically ∼20-50 nm in diameter, and thus their interaction with calcium ions cannot be modeled faithfully with a conventional flat membrane bilayer setup. Within our newly developed molecular dynamics simulations setup, we characterize here interactions of the calcium ion with curved membrane interfaces with atomistic detail. The present molecular dynamics simulations together with time-dependent fluorescence shift experiments suggest that the mode and strength of interaction of calcium ion with a phospholipid bilayer depends on its curvature. Potential of mean force calculations demonstrate that the binding of calcium ion to the positively curved side of the bilayer is significantly stronger compared with that to a flat membrane.
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Affiliation(s)
- Aniket Magarkar
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Faculty of Pharmacy, University of Helsinki , Viikinkaari 5E, Helsinki 00014, Finland
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic , v.v.i., Dolejškova 3, CZ-182 23 Prague, Czech Republic
| | - Christoph Allolio
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg , 93040 Regensburg, Germany
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic , v.v.i., Dolejškova 3, CZ-182 23 Prague, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Department of Physics, Tampere University of Technology , P.O. Box 692, FI-33101 Tampere, Finland
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39
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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] [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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40
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Mitkova D, Vitkova V. The aqueous surroundings alter the bending rigidity of lipid membranes. RUSS J ELECTROCHEM+ 2016. [DOI: 10.1134/s1023193516120090] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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41
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Caorsi V, Lemière J, Campillo C, Bussonnier M, Manzi J, Betz T, Plastino J, Carvalho K, Sykes C. Cell-sized liposome doublets reveal active tension build-up driven by acto-myosin dynamics. SOFT MATTER 2016; 12:6223-6231. [PMID: 27378156 DOI: 10.1039/c6sm00856a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Cells modulate their shape to fulfill specific functions, mediated by the cell cortex, a thin actin shell bound to the plasma membrane. Myosin motor activity, together with actin dynamics, contributes to cortical tension. Here, we examine the individual contributions of actin polymerization and myosin activity to tension increase with a non-invasive method. Cell-sized liposome doublets are covered with either a stabilized actin cortex of preformed actin filaments, or a dynamic branched actin network polymerizing at the membrane. The addition of myosin II minifilaments in both cases triggers a change in doublet shape that is unambiguously related to a tension increase. Preformed actin filaments allow us to evaluate the effect of myosin alone while, with dynamic actin cortices, we examine the synergy of actin polymerization and myosin motors in driving shape changes. Our assay paves the way for a quantification of tension changes triggered by various actin-associated proteins in a cell-sized system.
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Affiliation(s)
- V Caorsi
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
| | - J Lemière
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France and Univ Paris Diderot, Sorbonne Paris Cité, Paris, F-75205, France and Department of Molecular Biophysics and Biochemistry, Nanobiology Institute, Yale University, New Haven, CT, USA
| | - C Campillo
- Université Evry Val d'Essonne, LAMBE, Boulevard F Mitterrand, Evry 91025, France
| | - M Bussonnier
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France and Univ Paris Diderot, Sorbonne Paris Cité, Paris, F-75205, France
| | - J Manzi
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
| | - T Betz
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France and Institute of Cell Biology, Center for Molecular Biology of Inflammation, Cells-in-Motion Cluster of Excellence, Münster University, Von-Esmarch-Strasse 56, D-48149 Münster, Germany
| | - J Plastino
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
| | - K Carvalho
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
| | - C Sykes
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, UMR168, 75005, Paris, France and Sorbonne Universités, UPMC Univ Paris 06, 75005, Paris, France
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42
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West A, Brummel BE, Braun AR, Rhoades E, Sachs JN. Membrane remodeling and mechanics: Experiments and simulations of α-Synuclein. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1858:1594-609. [PMID: 26972046 PMCID: PMC5081225 DOI: 10.1016/j.bbamem.2016.03.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/05/2016] [Accepted: 03/07/2016] [Indexed: 01/24/2023]
Abstract
We review experimental and simulation approaches that have been used to determine curvature generation and remodeling of lipid bilayers by membrane-bending proteins. Particular emphasis is placed on the complementary approaches used to study α-Synuclein (αSyn), a major protein involved in Parkinson's disease (PD). Recent cellular and biophysical experiments have shown that the protein 1) deforms the native structure of mitochondrial and model membranes; and 2) inhibits vesicular fusion. Today's advanced experimental and computational technology has made it possible to quantify these protein-induced changes in membrane shape and material properties. Collectively, experiments, theory and multi-scale simulation techniques have established the key physical determinants of membrane remodeling and rigidity: protein binding energy, protein partition depth, protein density, and membrane tension. Despite the exciting and significant progress made in recent years in these areas, challenges remain in connecting biophysical insights to the cellular processes that lead to disease. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- Ana West
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA
| | - Benjamin E Brummel
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA
| | - Anthony R Braun
- Department of Neuroscience, University of Minnesota, 321 Church St. SE, Minneapolis, MN 55455, USA
| | - Elizabeth Rhoades
- Department of Chemistry, University of Pennsylvania, 231 S 34th St., Philadelphia, PA 19104, USA
| | - Jonathan N Sachs
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA.
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43
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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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44
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Wang X, Deserno M. Determining the Lipid Tilt Modulus by Simulating Membrane Buckles. J Phys Chem B 2016; 120:6061-73. [DOI: 10.1021/acs.jpcb.6b02016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Xin Wang
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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45
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Dahl JB, Narsimhan V, Gouveia B, Kumar S, Shaqfeh ESG, Muller SJ. Experimental observation of the asymmetric instability of intermediate-reduced-volume vesicles in extensional flow. SOFT MATTER 2016; 12:3787-96. [PMID: 26984509 PMCID: PMC4838492 DOI: 10.1039/c5sm03004h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Vesicles provide an attractive model system to understand the deformation of living cells in response to mechanical forces. These simple, enclosed lipid bilayer membranes are suitable for complementary theoretical, numerical, and experimental analysis. A recent study [Narsimhan, Spann, Shaqfeh, J. Fluid Mech., 2014, 750, 144] predicted that intermediate-aspect-ratio vesicles extend asymmetrically in extensional flow. Upon infinitesimal perturbation to the vesicle shape, the vesicle stretches into an asymmetric dumbbell with a cylindrical thread separating the two ends. While the symmetric stretching of high-aspect-ratio vesicles in extensional flow has been observed and characterized [Kantsler, Segre, Steinberg, Phys. Rev. Lett., 2008, 101, 048101] as well as recapitulated in numerical simulations by Narsimhan et al., experimental observation of the asymmetric stretching has not been reported. In this work, we present results from microfluidic cross-slot experiments observing this instability, along with careful characterization of the flow field, vesicle shape, and vesicle bending modulus. The onset of this shape transition depends on two non-dimensional parameters: reduced volume (a measure of vesicle asphericity) and capillary number (ratio of viscous to bending forces). We observed that every intermediate-reduced-volume vesicle that extends forms a dumbbell shape that is indeed asymmetric. For the subset of the intermediate-reduced-volume regime we could capture experimentally, we present an experimental phase diagram for asymmetric vesicle stretching that is consistent with the predictions of Narsimhan et al.
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Affiliation(s)
- Joanna B Dahl
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720-1460, USA.
| | - Vivek Narsimhan
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Bernardo Gouveia
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720-1460, USA.
| | - Sanjay Kumar
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720-1460, USA. and Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720-1762, USA
| | - Eric S G Shaqfeh
- Department of Chemical Engineering, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA and Institute of Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Susan J Muller
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720-1460, USA.
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46
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Rodríguez-García R, López-Montero I, Mell M, Egea G, Gov NS, Monroy F. Direct Cytoskeleton Forces Cause Membrane Softening in Red Blood Cells. Biophys J 2016; 108:2794-806. [PMID: 26083919 DOI: 10.1016/j.bpj.2015.05.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 04/29/2015] [Accepted: 05/11/2015] [Indexed: 10/23/2022] Open
Abstract
Erythrocytes are flexible cells specialized in the systemic transport of oxygen in vertebrates. This physiological function is connected to their outstanding ability to deform in passing through narrow capillaries. In recent years, there has been an influx of experimental evidence of enhanced cell-shape fluctuations related to metabolically driven activity of the erythroid membrane skeleton. However, no direct observation of the active cytoskeleton forces has yet been reported to our knowledge. Here, we show experimental evidence of the presence of temporally correlated forces superposed over the thermal fluctuations of the erythrocyte membrane. These forces are ATP-dependent and drive enhanced flickering motions in human erythrocytes. Theoretical analyses provide support for a direct force exerted on the membrane by the cytoskeleton nodes as pulses of well-defined average duration. In addition, such metabolically regulated active forces cause global membrane softening, a mechanical attribute related to the functional erythroid deformability.
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Affiliation(s)
- Ruddi Rodríguez-García
- Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain
| | - Iván López-Montero
- Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain
| | - Michael Mell
- Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain
| | - Gustavo Egea
- Departament of Cell Biology, Immunology and Neurosciences, University of Barcelona School of Medicine and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Nanociències i Nanotecnologia (IN(2)UB), Barcelona, Spain
| | - Nir S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Francisco Monroy
- Department of Physical Chemistry, Universidad Complutense. Ciudad Universitaria, Madrid, Spain; Instituto de Investigación Hospital Doce de Octubre (i+12), Madrid, Spain.
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47
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Bavi O, Vossoughi M, Naghdabadi R, Jamali Y. The Combined Effect of Hydrophobic Mismatch and Bilayer Local Bending on the Regulation of Mechanosensitive Ion Channels. PLoS One 2016; 11:e0150578. [PMID: 26958847 PMCID: PMC4784931 DOI: 10.1371/journal.pone.0150578] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 02/17/2016] [Indexed: 12/03/2022] Open
Abstract
The hydrophobic mismatch between the lipid bilayer and integral membrane proteins has well-defined effect on mechanosensitive (MS) ion channels. Also, membrane local bending is suggested to modulate MS channel activity. Although a number of studies have already shown the significance of each individual factor, the combined effect of these physical factors on MS channel activity have not been investigated. Here using finite element simulation, we study the combined effect of hydrophobic mismatch and local bending on the archetypal mechanosensitive channel MscL. First we show how the local curvature direction impacts on MS channel modulation. In the case of MscL, we show inward (cytoplasmic) bending can more effectively gate the channel compared to outward bending. Then we indicate that in response to a specific local curvature, MscL inserted in a bilayer with the same hydrophobic length is more expanded in the constriction pore region compared to when there is a protein-lipid hydrophobic mismatch. Interestingly in the presence of a negative mismatch (thicker lipids), MscL constriction pore is more expanded than in the presence of positive mismatch (thinner lipids) in response to an identical membrane curvature. These results were confirmed by a parametric energetic calculation provided for MscL gating. These findings have several biophysical consequences for understanding the function of MS channels in response to two major physical stimuli in mechanobiology, namely hydrophobic mismatch and local membrane curvature.
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Affiliation(s)
- Omid Bavi
- Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, Iran
| | - Manouchehr Vossoughi
- Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, Iran
- Biochemical & Bioenvironmental Research Center (BBRC), Tehran, Iran
| | - Reza Naghdabadi
- Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, Iran
- Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
| | - Yousef Jamali
- Department of Mathematics, Tarbiat Modares University, Tehran, Iran
- Computational physical Sciences Research Laboratory, School of Nano-Science, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
- * E-mail:
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48
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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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49
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Georgieva R, Mircheva K, Vitkova V, Balashev K, Ivanova T, Tessier C, Koumanov K, Nuss P, Momchilova A, Staneva G. Phospholipase A2-Induced Remodeling Processes on Liquid-Ordered/Liquid-Disordered Membranes Containing Docosahexaenoic or Oleic Acid: A Comparison Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1756-1770. [PMID: 26794691 DOI: 10.1021/acs.langmuir.5b03317] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Vesicle cycling, which is an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The capacity of PLA2 to trigger the budding and fission of liquid-ordered (L(o)) domains has been examined in palmitoyl-docosahexaenoylphosphatidylcholine (PDPC) and palmitoyl-oleoylphosphatidylcholine (POPC)/sphingomyelin/cholesterol membranes. They both exhibited a L(o)/liquid-disordered (L(d)) phase separation. We demonstrated that PLA2 was able to trigger budding in PDPC-containing vesicles but not POPC ones. The enzymatic activity, line tension, and elasticity of the membrane surrounding the L(o) domains are critical for budding. The higher line tension of Lo domains in PDPC mixtures was assigned to the greater difference in order parameters of the coexisting phases. The higher amount of lysophosphatidylcholine generated by PLA2 in the PDPC-containing mixtures led to a less-rigid membrane, compared to POPC. The more elastic L(d) membranes in PDPC mixtures exert a lower counteracting force against the L(o) domain bending.
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Affiliation(s)
- Rayna Georgieva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Kristina Mircheva
- Biophysical Chemistry Laboratory, Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, University of Sofia , 1 J. Bourchier Str., 1164 Sofia, Bulgaria
| | - Victoria Vitkova
- Institute of Solid State Physics, Bulgarian Academy of Sciences , 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria
| | - Konstantin Balashev
- Biophysical Chemistry Laboratory, Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, University of Sofia , 1 J. Bourchier Str., 1164 Sofia, Bulgaria
| | - Tzvetanka Ivanova
- Biophysical Chemistry Laboratory, Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, University of Sofia , 1 J. Bourchier Str., 1164 Sofia, Bulgaria
| | - Cedric Tessier
- Sorbonne Universites-UPMC Univ Paris 06, UMR 7203, INSERM ERL 1157, CHU St. Antoine, 27 rue Chaligny, 75012 Paris, France
- Department of Psychiatry, Hôpital Saint-Antoine, AP-HP , Paris, France
| | - Kamen Koumanov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Philippe Nuss
- Sorbonne Universites-UPMC Univ Paris 06, UMR 7203, INSERM ERL 1157, CHU St. Antoine, 27 rue Chaligny, 75012 Paris, France
- Department of Psychiatry, Hôpital Saint-Antoine, AP-HP , Paris, France
| | - Albena Momchilova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Galya Staneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences , Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
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50
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Nagle JF, Jablin MS, Tristram-Nagle S. Sugar does not affect the bending and tilt moduli of simple lipid bilayers. Chem Phys Lipids 2016; 196:76-80. [PMID: 26899248 DOI: 10.1016/j.chemphyslip.2016.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/25/2016] [Accepted: 01/29/2016] [Indexed: 11/17/2022]
Abstract
The diffuse X-ray scattering method has been applied to samples composed of SOPC, DOPC, DMPC, and POPC with added sugar, either sucrose, glucose, fructose, maltose, or trehalose. Several sugar concentrations in the range 200-500 mM were investigated for each of the lipid/sugar samples. We observed no systematic change in the bending modulus KC or in the tilt modulus Kθ with increasing sugar concentration. The average values of both these moduli were the same as those of the respective pure lipid controls within statistical uncertainty of 2%. These results are inconsistent with previous reports of sugar concentration dependent values of KC.
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Affiliation(s)
- John F Nagle
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 USA.
| | - Michael S Jablin
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 USA
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