scholarly journals Charge-induced phase separation in lipid membranes

Soft Matter ◽  
2014 ◽  
Vol 10 (40) ◽  
pp. 7959-7967 ◽  
Author(s):  
Hiroki Himeno ◽  
Naofumi Shimokawa ◽  
Shigeyuki Komura ◽  
David Andelman ◽  
Tsutomu Hamada ◽  
...  
Keyword(s):  
Phase Separation ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Membrane Phase ◽  
Lipid Mixtures ◽  
The Stability

Phase separation in lipid bilayers is examined. We observed phase-separated structures in various lipid mixtures and determined membrane miscibility temperatures. It was found that a combination of negatively-charged heads and saturation of hydrocarbon tails is dominant for the stability of membrane phase separation.

Deposition of Lipid Bilayers with Atomic Force Microscopy

2005 ◽  
Vol 11 (S03) ◽  
pp. 44-47 ◽  
Author(s):  
G. D. Tavares ◽  
M. C. de Oliveira ◽  
J. M. C. Vilela ◽  
M. S. Andrade
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Flat Substrate ◽  
Atomic Force ◽  
Lipid Mixtures ◽  
A Cell ◽  
Integral Proteins ◽  
Spherical Vesicles

Biological membranes are constituted of lipids organized as a two dimensional bilayer supporting peripheral and integral proteins, providing a barrier between the inside and the outside of a cell [1]. Similar membranes can be prepared from the lipid mixtures forming liposomes. The liposomes are multi or unilamellar spherical vesicles in which an aqueous volume is enclosed and can be used to encapsulate some drugs [2]. In order to better expose the details of their structure, these membranes are generally deposited on the surface of a flat substrate. These supported planar lipid membranes can also provide a model system for investigating the properties and functions of the complex cell membrane and membrane mediated processes such as recognition events and biological signal transduction. Various methods have been used to create artificial lipid membranes supported on a solid surface, being the most used the Langmuir-Blodgett monolayers formation [3], the vesicle fusion or liposome adsorption [4] and the solution spreading [5].

scholarly journals Imaging phase separation in model lipid membranes through the use of BODIPY based molecular rotors

2015 ◽  
Vol 17 (28) ◽  
pp. 18393-18402 ◽  
Author(s):  
Michael R. Dent ◽  
Ismael López-Duarte ◽  
Callum J. Dickson ◽  
Niall D. Geoghegan ◽  
Jonathan M. Cooper ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Phase Separation ◽  
Fluorescence Spectroscopy ◽  
Molecular Dynamics Simulations ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Molecular Rotors ◽  
Model Lipid Membranes ◽  
Dynamics Simulations

Viscosity in the phase-separated lipid bilayers is investigated through the use of fluorescence spectroscopy and molecular dynamics simulations.

scholarly journals Amphiphilic gold nanoparticles perturb phase separation in multidomain lipid membranes

Nanoscale ◽  
2020 ◽  
Vol 12 (38) ◽  
pp. 19746-19759
Author(s):  
Ester Canepa ◽  
Sebastian Salassi ◽  
Anna Lucia de Marco ◽  
Chiara Lambruschini ◽  
Davide Odino ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Phase Separation ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Amphiphilic Nanoparticles

Experiments and simulations reveal that amphiphilic nanoparticles suppress phase separation in neuronal-like lipid bilayers and form bilayer-embedded ordered aggregates.

scholarly journals Effect of cholesterol on permeability of carbon dioxide across lipid membranes

2020 ◽  
Author(s):  
M.C. Blosser ◽  
J. So ◽  
M.S. Madani ◽  
N. Malmstadt
Keyword(s):  
Carbon Dioxide ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Gas Transport ◽  
Gas Diffusion ◽  
Physiological Processes ◽  
Lipid Mixtures ◽  
Model Lipid Membranes ◽  
Order Of Magnitude ◽  
Membrane Components

AbstractDetermining the permeability of lipid membranes to gases is important for understanding the biological mechanisms of gas transport. Experiments on model membranes have been used to determine the permeability of lipid bilayers in the absence of proteins. Previous measurements have used a number of different methods and obtained widely varying results. We have developed a microfluidic based microscopy assay that measures the rate of CO2 permeation in Giant Unilamellar Vesicles (GUVs), and we report permeability data for the POPC-cholesterol system. We find that cholesterol has a strong effect on permeability; bilayers containing high levels of cholesterol are an order of magnitude less permeable than bilayers without cholesterol, 9.9 ± 1.0 x 10−4 cm/s vs. 9.6 ± 1.4 x 10−3 cm/s.Statement of SignificanceDiffusion of dissolved gasses such as carbon dioxide through cell membranes is an important step in physiological processes. Key to understanding the behavior in cells is the measurement of gas diffusion through model lipid membranes, which isolates the effect of the lipids from other membrane components and allows for control of the composition. Previous measurements have yielded different results for the magnitude of gas transport, and have disagreed on the amount that cholesterol affects transport. The present study presents new data on gas transport across lipid mixtures containing cholesterol, and develops a microfluidic assay for gas transport that will enable further work.

scholarly journals How arginine derivatives alter the stability of lipid membranes: dissecting the roles of side chains, backbone and termini

2021 ◽  
Vol 50 (2) ◽  
pp. 127-142 ◽  
Author(s):  
Sarah F. Verbeek ◽  
Neha Awasthi ◽  
Nikolas K. Teiwes ◽  
Ingo Mey ◽  
Jochen S. Hub ◽  
...  
Keyword(s):  
Free Energy ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Pore Formation ◽  
Line Tension ◽  
Md Simulations ◽  
Substantial Effect ◽  
Cell Penetrating Peptides ◽  
Free Energy Calculations ◽  
The Stability

AbstractArginine (R)-rich peptides constitute the most relevant class of cell-penetrating peptides and other membrane-active peptides that can translocate across the cell membrane or generate defects in lipid bilayers such as water-filled pores. The mode of action of R-rich peptides remains a topic of controversy, mainly because a quantitative and energetic understanding of arginine effects on membrane stability is lacking. Here, we explore the ability of several oligo-arginines R$$_n$$ n and of an arginine side chain mimic R$$_\mathrm {Side}$$ Side to induce pore formation in lipid bilayers employing MD simulations, free-energy calculations, breakthrough force spectroscopy and leakage assays. Our experiments reveal that R$$_\mathrm {Side}$$ Side but not R$$_n$$ n reduces the line tension of a membrane with anionic lipids. While R$$_n$$ n peptides form a layer on top of a partly negatively charged lipid bilayer, R$$_\mathrm {Side}$$ Side leads to its disintegration. Complementary, our simulations show R$$_\mathrm {Side}$$ Side causes membrane thinning and area per lipid increase beside lowering the pore nucleation free energy. Model polyarginine R$$_8$$ 8 similarly promoted pore formation in simulations, but without overall bilayer destabilization. We conclude that while the guanidine moiety is intrinsically membrane-disruptive, poly-arginines favor pore formation in negatively charged membranes via a different mechanism. Pore formation by R-rich peptides seems to be counteracted by lipids with PC headgroups. We found that long R$$_n$$ n and R$$_\mathrm {Side}$$ Side but not short R$$_n$$ n reduce the free energy of nucleating a pore. In short R$$_n$$ n , the substantial effect of the charged termini prevent their membrane activity, rationalizing why only longer $$\mathrm {R}_{n}$$ R n are membrane-active.

Observation of Concanavalin-A receptors on hydrated planar erythrocyte membrane film by in situ electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 608-609
Author(s):  
Neng-Bo He ◽  
S.W. Hui
Keyword(s):  
Lipid Bilayers ◽  
Erythrocyte Membrane ◽  
Lipid Membranes ◽  
Surface Film ◽  
Biological Membranes ◽  
Electron Microscopic Observation ◽  
Electron Microscopic ◽  
Black Lipid Membranes ◽  
Fine Mesh ◽  
Planar Films

Monolayers and planar "black" lipid membranes have been widely used as models for studying the structure and properties of biological membranes. Because of the lack of a suitable method to prepare these membranes for electron microscopic observation, their ultrastructure is so far not well understood. A method of forming molecular bilayers over the holes of fine mesh grids was developed by Hui et al. to study hydrated and unsupported lipid bilayers by electron diffraction, and to image phase separated domains by diffraction contrast. We now adapted the method of Pattus et al. of spreading biological membranes vesicles on the air-water interfaces to reconstitute biological membranes into unsupported planar films for electron microscopic study. hemoglobin-free human erythrocyte membrane stroma was prepared by hemolysis. The membranes were spreaded at 20°C on balanced salt solution in a Langmuir trough until a surface pressure of 20 dyne/cm was reached. The surface film was repeatedly washed by passing to adjacent troughs over shallow partitions (fig. 1).

scholarly journals Cardiolipin-Containing Lipid Membranes Attract the Bacterial Cell Division Protein DivIVA

2021 ◽  
Vol 22 (15) ◽  
pp. 8350
Author(s):  
Naďa Labajová ◽  
Natalia Baranova ◽  
Miroslav Jurásek ◽  
Robert Vácha ◽  
Martin Loose ◽  
...  
Keyword(s):  
Cell Division ◽  
Lipid Bilayers ◽  
Bacterial Cell ◽  
Lipid Membranes ◽  
Model Organism ◽  
Active Role ◽  
Membrane Curvature ◽  
Bacterial Cell Division ◽  
Division Site ◽  
Clostridioides Difficile

DivIVA is a protein initially identified as a spatial regulator of cell division in the model organism Bacillus subtilis, but its homologues are present in many other Gram-positive bacteria, including Clostridia species. Besides its role as topological regulator of the Min system during bacterial cell division, DivIVA is involved in chromosome segregation during sporulation, genetic competence, and cell wall synthesis. DivIVA localizes to regions of high membrane curvature, such as the cell poles and cell division site, where it recruits distinct binding partners. Previously, it was suggested that negative curvature sensing is the main mechanism by which DivIVA binds to these specific regions. Here, we show that Clostridioides difficile DivIVA binds preferably to membranes containing negatively charged phospholipids, especially cardiolipin. Strikingly, we observed that upon binding, DivIVA modifies the lipid distribution and induces changes to lipid bilayers containing cardiolipin. Our observations indicate that DivIVA might play a more complex and so far unknown active role during the formation of the cell division septal membrane.

scholarly journals The Use of Tethered Bilayer Lipid Membranes to Identify the Mechanisms of Antimicrobial Peptide Interactions with Lipid Bilayers

Antibiotics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 12 ◽  
Author(s):  
Amani Alghalayini ◽  
Alvaro Garcia ◽  
Thomas Berry ◽  
Charles Cranfield
Keyword(s):  
New Zealand ◽  
Patch Clamp ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Antimicrobial Agents ◽  
Bilayer Lipid Membranes ◽  
Bilayer Lipid ◽  
Black Lipid Membranes ◽  
Peptide Interactions ◽  
New Research

This review identifies the ways in which tethered bilayer lipid membranes (tBLMs) can be used for the identification of the actions of antimicrobials against lipid bilayers. Much of the new research in this area has originated, or included researchers from, the southern hemisphere, Australia and New Zealand in particular. More and more, tBLMs are replacing liposome release assays, black lipid membranes and patch-clamp electrophysiological techniques because they use fewer reagents, are able to obtain results far more quickly and can provide a uniformity of responses with fewer artefacts. In this work, we describe how tBLM technology can and has been used to identify the actions of numerous antimicrobial agents.

scholarly journals Dynamics of Phase Separation in Lipid Membranes

2010 ◽  
Vol 98 (3) ◽  
pp. 664a
Author(s):  
Brian Camley ◽  
Frank L.H. Brown
Keyword(s):  
Phase Separation ◽  
Lipid Membranes
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