Dielectric Properties of Phosphatidylcholine Membranes and the Effect of Sugars

Simple carbohydrates are associated with the enhanced risk of cardiovascular disease and adverse changes in lipoproteins in the organism. Conversely, sugars are known to exert a stabilizing effect on biological membranes, and this effect is widely exploited in medicine and industry for cryopreservation of tissues and materials. In view of elucidating molecular mechanisms involved in the interaction of mono- and disaccharides with biomimetic lipid systems, we study the alteration of dielectric properties, the degree of hydration, and the rotational order parameter and dipole potential of lipid bilayers in the presence of sugars. Frequency-dependent deformation of cell-size unilamellar lipid vesicles in alternating electric fields and fast Fourier transform electrochemical impedance spectroscopy are applied to measure the specific capacitance of phosphatidylcholine lipid bilayers in sucrose, glucose and fructose aqueous solutions. Alteration of membrane specific capacitance is reported in sucrose solutions, while preservation of membrane dielectric properties is established in the presence of glucose and fructose. We address the effect of sugars on the hydration and the rotational order parameter for 1-palmitoyl-2-oleoyl-sn-glycero-3- phosphocholine (POPC) and 1-stearoyl-2-oleoyl-sn-glycero-3- phosphocholine (SOPC). An increased degree of lipid packing is reported in sucrose solutions. The obtained results provide evidence that some small carbohydrates are able to change membrane dielectric properties, structure, and order related to membrane homeostasis. The reported data are also relevant to future developments based on the response of lipid bilayers to external physical stimuli such as electric fields and temperature changes.

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Changes in membrane elasticity caused by the hydrophobic surfactant proteins correlate poorly with adsorption of lipid vesicles

Soft Matter ◽

10.1039/d0sm02223c ◽

2021 ◽

Author(s):

Ryan W. Loney ◽

Bret Brandner ◽

Maayan P. Dagan ◽

Paige N. Smith ◽

Megan Roche ◽

...

Keyword(s):

Lipid Bilayers ◽

Order Parameter ◽

Diffuse Scattering ◽

Lipid Vesicles ◽

Surfactant Proteins ◽

Membrane Elasticity ◽

X Ray ◽

Bending Modulus ◽

Air Water Interface ◽

Acyl Chains

We used X-ray diffuse scattering to determine the bending modulus of lipid bilayers and an order parameter of the acyl chains to establish how the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of lipids to an air/water interface.

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Dielectric properties and lamellarity of single liposomes measured by in-liquid scanning dielectric microscopy

Journal of Nanobiotechnology ◽

10.1186/s12951-021-00912-6 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Martina Di Muzio ◽

Ruben Millan-Solsona ◽

Aurora Dols-Perez ◽

Jordi H. Borrell ◽

Laura Fumagalli ◽

...

Keyword(s):

Dielectric Properties ◽

Specific Capacitance ◽

Lipid Bilayer ◽

Lipid Bilayers ◽

Cell Model ◽

Metal Electrode ◽

Model Systems ◽

Label Free ◽

Detection Mode ◽

Invasive Method

AbstractLiposomes are widely used as drug delivery carriers and as cell model systems. Here, we measure the dielectric properties of individual liposomes adsorbed on a metal electrode by in-liquid scanning dielectric microscopy in force detection mode. From the measurements the lamellarity of the liposomes, the separation between the lamellae and the specific capacitance of the lipid bilayer can be obtained. As application we considered the case of non-extruded DOPC liposomes with radii in the range ~ 100–800 nm. Uni-, bi- and tri-lamellar liposomes have been identified, with the largest population corresponding to bi-lamellar liposomes. The interlamellar separation in the bi-lamellar liposomes is found to be below ~ 10 nm in most instances. The specific capacitance of the DOPC lipid bilayer is found to be ~ 0.75 µF/cm2 in excellent agreement with the value determined on solid supported planar lipid bilayers. The lamellarity of the DOPC liposomes shows the usual correlation with the liposome's size. No correlation is found, instead, with the shape of the adsorbed liposomes. The proposed approach offers a powerful label-free and non-invasive method to determine the lamellarity and dielectric properties of single liposomes.

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Is the Membrane Lipid Matrix a Key Target for Action of Pharmacologically Active Plant Saponins?

International Journal of Molecular Sciences ◽

10.3390/ijms22063167 ◽

2021 ◽

Vol 22 (6) ◽

pp. 3167

Author(s):

Svetlana S. Efimova ◽

Olga S. Ostroumova

Keyword(s):

Lipid Bilayers ◽

Molecular Mechanisms ◽

Antimicrobial Agents ◽

Positive Curvature ◽

Lipid Vesicles ◽

Membrane Lipid ◽

Systematic Analysis ◽

Boundary Potential ◽

Model Lipid Membranes ◽

Pharmacologically Active

This study was focused on the molecular mechanisms of action of saponins and related compounds (sapogenins and alkaloids) on model lipid membranes. Steroids and triterpenes were tested. A systematic analysis of the effects of these chemicals on the physicochemical properties of the lipid bilayers and on the formation and functionality of the reconstituted ion channels induced by antimicrobial agents was performed. It was found that digitonin, tribulosin, and dioscin substantially reduced the boundary potential of the phosphatidylcholine membranes. We concluded that saponins might affect the membrane boundary potential by restructuring the membrane hydration layer. Moreover, an increase in the conductance and lifetime of gramicidin A channels in the presence of tribulosin was due to an alteration in the membrane dipole potential. Differential scanning microcalorimetry data indicated the key role of the sapogenin core structure (steroid or triterpenic) in affecting lipid melting and disordering. We showed that an alteration in pore forming activity of syringomycin E by dioscin might be due to amendments in the lipid packing. We also found that the ability of saponins to disengage the fluorescent marker calcein from lipid vesicles might be also determined by their ability to induce a positive curvature stress.

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3D-Visualization of Amyloid-β Oligomer and Fibril Interactions with Lipid Membranes by Cryo-Electron Tomography

10.1101/2020.07.21.214072 ◽

2020 ◽

Author(s):

Yao Tian ◽

Ruina Liang ◽

Amit Kumar ◽

Piotr Szwedziak ◽

John H. Viles

Keyword(s):

Lipid Bilayers ◽

Molecular Mechanisms ◽

Lipid Membrane ◽

Electron Tomography ◽

3D Visualization ◽

Membrane Integrity ◽

Amyloid Β ◽

Lipid Vesicles ◽

Aβ Oligomers ◽

Cryo Electron Tomography

ABSTRACTAmyloid-β (Aβ) monomers assemble into mature fibrils via a range of metastable oligomeric and protofibrillar intermediates. These Aβ assemblies have been shown to bind to lipid bilayers. This can disrupt membrane integrity and cause a loss of cellular homeostasis, that triggers a cascade of events leading to Alzheimer’s disease. However, molecular mechanisms of Aβ cytotoxicity and how the different assembly forms interact with the membrane remain enigmatic. Here we use cryo-electron tomography (cryoET) to obtain three-dimensional nano-scale images of various Aβ assembly types and their interaction with liposomes. Aβ oligomers bind extensively to the lipid vesicles, inserting and carpeting the upper-leaflet of the bilayer. Furthermore, curvilinear protofibrils also insert into the bilayer, orthogonally to the membrane surface. Aβ oligomers concentrate at the interface of vesicles and form a network of Aβ-linked liposomes. While crucially, monomeric and fibrillar Aβ have relatively little impact on the membrane. Changes to lipid membrane composition highlights a significant role for GM1-ganglioside in promoting Aβ-membrane interactions. The different effects of Aβ assembly forms observed align with the highlighted cytotoxicity reported for Aβ oligomers. The wide-scale incorporation of Aβ oligomers and curvilinear protofibrils into the lipid bilayer suggests a mechanism by which membrane integrity is lost.

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Ultra-fast electroporation of giant unilamellar vesicles — Experimental validation of a molecular model

10.1101/2020.01.01.890137 ◽

2020 ◽

Author(s):

Esin B. Sözer ◽

Sourav Haldar ◽

Paul S. Blank ◽

Federica Castellani ◽

P. Thomas Vernier ◽

...

Keyword(s):

Lipid Bilayers ◽

Electric Fields ◽

Electrical Breakdown ◽

Molecular Model ◽

Molecular Simulations ◽

Molecular Transport ◽

Lipid Vesicles ◽

Fluorescent Dye ◽

Lipid Vesicle ◽

Multiple Pulses

AbstractDelivery of molecules to cells via electropermeabilization (electroporation) is a common procedure in laboratories and clinics. However, despite a long history of theoretical effort, electroporation protocols are still based on trial and error because the biomolecular structures and mechanisms underlying this phenomenon have not been established. Electroporation models, developed to explain observations of electrical breakdown of lipid membranes, describe the electric field-driven formation of pores in lipid bilayers. These transient pore models are consistent with molecular dynamics simulations, where field-stabilized lipid pores form within a few nanoseconds and collapse within tens of nanoseconds after the field is removed. Here we experimentally validate this nanoscale restructuring of bio-membranes by measuring the kinetics of transport of the impermeant fluorescent dye calcein into lipid vesicles exposed to ultrashort electric fields (6 ns and 2 ns), and by comparing these results to molecular simulations. Molecular transport after vesicle permeabilization induced by multiple pulses is additive for interpulse intervals as short as 50 ns, while the additive property of transport is no longer observed when the interval is reduced to 0 ns, consistent with the lifetimes of lipid electropores in molecular simulations. These results show that lipid vesicle responses to pulsed electric fields are significantly different from those of living cells where, for similar pulse properties, the uptake of fluorescent dye continues for several minutes.Graphical abstract

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Effects of vesicle components on the electro-permeability of lipid bilayers of vesicles induced by pulsed electric fields (PEF) treatment

Journal of Food Engineering ◽

10.1016/j.jfoodeng.2016.02.003 ◽

2016 ◽

Vol 179 ◽

pp. 88-97 ◽

Cited By ~ 11

Author(s):

Zhi-Wei Liu ◽

Zhong Han ◽

Xin-An Zeng ◽

Da-Wen Sun ◽

Rana Muhammad Aadil

Keyword(s):

Lipid Bilayers ◽

Electric Fields ◽

Pulsed Electric Fields

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Surface roughness as rupture control factor of lipid vesicles

Microscopy and Microanalysis ◽

10.1017/s1431927613001153 ◽

2013 ◽

Vol 19 (S4) ◽

pp. 107-108 ◽

Cited By ~ 2

Author(s):

A.A. Duarte ◽

M. Raposo

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Biological Membrane ◽

Substrate Surface ◽

Lipid Vesicles ◽

Planar Lipid Bilayer ◽

Root Mean Square Roughness ◽

Control Factor ◽

Formation Mechanisms ◽

Adsorbed Amount

Liposomes or lipid vesicles are self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside, which may incorporate almost any molecule, namely proteins, hormones, enzymes, antibiotics, anticancer agents, antifungical agents, gene transfer agents, DNA, and whole viruses. Scientific evidences prove that unprotected liposomes containing drugs are easily released from the endoplasmic reticulum of the cell. To increase the vesicles lifetime and to activate a controlled drug release with an external stimulus, the vesicles immobilization on a surface and the factors which create conditions to the liposome rupture have to be analyzed. A number of studies have identified some of the critical stages of vesicle adsorption (adhesion), fusion, deformation, rupture, and spreading of the lipid bilayer. Nevertheless, the formation mechanisms of well-controlled continuous supported bilayers or adsorption of whole liposomes are still not fully understood. As yet it was demonstrated that a controlled adsorption of vesicles containing a small fraction of charged lipids occurs without rupture and their subsequent embedding in polyelectrolyte multilayer (PEM) films, meaning vesicles may be immobilized in an intact or slightly deformed state, which can act as drug reservoirs. Moreover, depending on the nature of the physicochemical conditions of the vesicle solution and the substrate surface, a flat lipid bilayer can be formed, known as supported lipid bilayers, which can incorporate membrane proteins and keep the native dynamics of the lipid bilayer mimicking a biological membrane. In this study, a layer of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DPPG) liposomes adsorbed onto PEMs cushions based on poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) polyelectrolytes was analyzed by atomic force microscopy (AFM) technique in non-contact mode and quartz crystal microbalance (QCM).Sequential heterostructures of Si/PEI(PSS/PAH)4 and Si/PAH, also designated cushions, were prepared onto silicon substrates using the layer-by-layer (LbL) technique with polyelectrolyte solutions of PEI, PSS and PAH of monomeric concentrations of 0.01M. Topographic images of 1×1μm2 area of Si/PAH/DPPG (Figure 1 a), and Si/PEI(PSS/PAH)4/DPPG (Figure 1 b) LbL films were acquired by AFM. The root mean square roughness (RMS) calculated from topographies data are listed in table I. As shown, when a DPPG layer is adsorbed onto Si/PAH the RMS keeps an approximately equal value meaning that the liposome disrupted and spread onto the surface forming a planar lipid bilayer. But when a DPPG layer is adsorbed onto Si/PEI(PSS/PAH)4 the RMS value doubled, indicating that the structural integrity of the liposomes is maintained, even though there has been any deformation during adsorption. The adsorbed amount of the two PEMs and DPPG-liposomes layers was measured using a QCM and is displayed in table I. The DPPG adsorbed amount obtained on the PAH cushion was approximately equal to a planar lipid bilayer, while the adsorption onto PEI(PSS/PAH)4 was higher than the predicted for a planar lipid bilayer. This behavior suggests that the DPPG liposomes on the second PEM remained intact during adsorption. Both confirm the AFM results. Therefore we conclude that the initial roughness of the surface is a primordial factor to determine the adsorption or not of intact vesicles.The authors acknowledge the “Fundação para a Ciência e Tecnologia” (FCT-MEC) by the post-graduate scholarship SFRH/BD/62229/2009 and the “Plurianual” funding.

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Computation of currents induced by ELF electric fields in anisotropic human tissues using the Finite Integration Technique (FIT)

Advances in Radio Science ◽

10.5194/ars-3-227-2005 ◽

2005 ◽

Vol 3 ◽

pp. 227-231 ◽

Cited By ~ 4

Author(s):

V. C. Motrescu ◽

U. van Rienen

Keyword(s):

Dielectric Properties ◽

Electromagnetic Fields ◽

Electric Fields ◽

Human Body ◽

Low Frequency ◽

Integration Technique ◽

Human Body Model ◽

Body Model ◽

Finite Integration Technique ◽

Muscle Tissues

Abstract. In the recent years, the task of estimating the currents induced within the human body by environmental electromagnetic fields has received increased attention from scientists around the world. While important progress was made in this direction, the unpredictable behaviour of living biological tissue made it difficult to quantify its reaction to electromagnetic fields and has kept the problem open. A successful alternative to the very difficult one of performing measurements is that of computing the fields within a human body model using numerical methods implemented in a software code. One of the difficulties is represented by the fact that some tissue types exhibit an anisotropic character with respect to their dielectric properties. Our work consists of computing currents induced by extremely low frequency (ELF) electric fields in anisotropic muscle tissues using in this respect, a human body model extended with muscle fibre orientations as well as an extended version of the Finite Integration Technique (FIT) able to compute fully anisotropic dielectric properties.

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Salt Concentration Effect on Electrical and Dielectric Properties of Solid Polymer Electrolytes based Carboxymethyl Cellulose for Lithium-ion Batteries

Biointerface Research in Applied Chemistry ◽

10.33263/briac125.61146123 ◽

2021 ◽

Vol 12 (5) ◽

pp. 6114-6123

Keyword(s):

Dielectric Properties ◽

Ionic Conductivity ◽

Polymer Electrolytes ◽

Carboxymethyl Cellulose ◽

Electrochemical Impedance ◽

Lithium Ion ◽

Lithium Perchlorate ◽

Linear Sweep Voltammetry ◽

Solid Polymer Electrolytes ◽

Solid Polymer

Solid polymer electrolytes (SPEs) based carboxymethyl cellulose (CMC) with lithium perchlorate (LiClO4) were prepared via solution drop-cast technique. The CMC host is complexed by different concentrations of LiClO4 salt. SPEs were characterized by Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) in coin cells with lithium metal electrodes. EIS performed unique results based on various ionic conductivity values and dielectric properties. The higher ionic conductivity (1.32 × 10-5 S/cm) was obtained by SPEs 2 following by short-range ionic transport results based on dielectric properties depending on frequency. SPEs with LiClO4 addition are electrochemically stable over 2 V in lithium battery coin cells from LSV results.

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