scholarly journals Accumulation of styrene oligomers alters lipid membrane phase order and miscibility

2021 ◽  
Vol 118 (4) ◽  
pp. e2016037118
Author(s):  
Mattia I. Morandi ◽  
Monika Kluzek ◽  
Jean Wolff ◽  
André Schroder ◽  
Fabrice Thalmann ◽  
...  
Keyword(s):  
Phase Behavior ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Spatial Modulation ◽  
Plastic Materials ◽  
Polymeric Species ◽  
Cell Components ◽  
Membrane Models ◽  
Membrane Mechanical Properties

Growth of plastic waste in the natural environment, and in particular in the oceans, has raised the accumulation of polystyrene and other polymeric species in eukyarotic cells to the level of a credible and systemic threat. Oligomers, the smallest products of polymer degradation or incomplete polymerization reactions, are the first species to leach out of macroscopic or nanoscopic plastic materials. However, the fundamental mechanisms of interaction between oligomers and polymers with the different cell components are yet to be elucidated. Simulations performed on lipid bilayers showed changes in membrane mechanical properties induced by polystyrene, but experimental results performed on cell membranes or on cell membrane models are still missing. We focus here on understanding how embedded styrene oligomers affect the phase behavior of model membranes using a combination of scattering, fluorescence, and calorimetric techniques. Our results show that styrene oligomers disrupt the phase behavior of lipid membranes, modifying the thermodynamics of the transition through a spatial modulation of lipid composition.

scholarly journals Mimicking the Mammalian Plasma Membrane: An Overview of Lipid Membrane Models for Biophysical Studies

Biomimetics ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 3
Author(s):  
Alessandra Luchini ◽  
Giuseppe Vitiello
Keyword(s):  
Plasma Membrane ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Cell Membranes ◽  
Lipid Membrane ◽  
Lipid Phase ◽  
Chemical Information ◽  
Lipid Species ◽  
Membrane Models ◽  
The Impact

Cell membranes are very complex biological systems including a large variety of lipids and proteins. Therefore, they are difficult to extract and directly investigate with biophysical methods. For many decades, the characterization of simpler biomimetic lipid membranes, which contain only a few lipid species, provided important physico-chemical information on the most abundant lipid species in cell membranes. These studies described physical and chemical properties that are most likely similar to those of real cell membranes. Indeed, biomimetic lipid membranes can be easily prepared in the lab and are compatible with multiple biophysical techniques. Lipid phase transitions, the bilayer structure, the impact of cholesterol on the structure and dynamics of lipid bilayers, and the selective recognition of target lipids by proteins, peptides, and drugs are all examples of the detailed information about cell membranes obtained by the investigation of biomimetic lipid membranes. This review focuses specifically on the advances that were achieved during the last decade in the field of biomimetic lipid membranes mimicking the mammalian plasma membrane. In particular, we provide a description of the most common types of lipid membrane models used for biophysical characterization, i.e., lipid membranes in solution and on surfaces, as well as recent examples of their applications for the investigation of protein-lipid and drug-lipid interactions. Altogether, promising directions for future developments of biomimetic lipid membranes are the further implementation of natural lipid mixtures for the development of more biologically relevant lipid membranes, as well as the development of sample preparation protocols that enable the incorporation of membrane proteins in the biomimetic lipid membranes.

scholarly journals The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation

Antioxidants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 430 ◽  
Author(s):  
Anja Sadžak ◽  
Janez Mravljak ◽  
Nadica Maltar-Strmečki ◽  
Zoran Arsov ◽  
Goran Baranović ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Structural Changes ◽  
Structural Integrity ◽  
Lipid Membrane ◽  
Membrane Properties ◽  
Structural Reorganization ◽  
Unsaturated Lipids ◽  
Oxidative Attack

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

scholarly journals Theoretical and computational modeling of peptide-lipid bilayer interaction studied by dynamic force spectroscopy

2019 ◽  
Author(s):  
◽  
Milica Utjesanovic
Keyword(s):  
Computational Modeling ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Conformational Dynamics ◽  
Quantitative Description ◽  
Md Simulations ◽  
Dynamic Force ◽  
Detachment Rate

This thesis consists of three interrelated theoretical and computational modeling projects that investigate different aspects of peptide-lipid membrane interactions. (1) A general theoretical approach is formulated for the quantitative description of the detachment force distribution, P(F), and the corresponding force dependent detachment rate, k(F), of a peptide from a lipid bilayer, by assuming that peptide detachment from lipid membranes occurs stochastically along a few dominant diffusive pathways. Besides providing a consistent interpretation of the experimental data, the new method also predicts that k(F) exhibits catch-bond behavior (when, counter intuitively, the detachment rate decreases with increasing force). (2) The proposed multiple detachment pathways method is tested and validated for a particular peptide (SecA2-11) interacting with both zwitterionic POPC lipid and polar E. Coli membranes. Furthermore, molecular dynamics (MD) simulations are used to explored the conformational dynamics of SecA2-11 during its interaction with both POPC and anionic POPG lipid bilayers. (3) Finally, MD simulations are used to explore the conformational dynamics and energetics of the peptide melittin (MWT) and its diastereomer (MD4) interacting with POPC and POPG lipid bilayers. The obtained results provide further insight into the role of secondary structure in peptide-lipid bilayer interactions.

scholarly journals Structure, Formation, and Biological Interactions of Supported Lipid Bilayers (SLB) Incorporating Lipopolysaccharide

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 981
Author(s):  
Palak Sondhi ◽  
Dhanbir Lingden ◽  
Keith J. Stine
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Biologically Active ◽  
Supported Lipid Bilayers ◽  
Biological Interactions ◽  
Relevant Model ◽  
Biologically Relevant ◽  
Model Lipid Membranes ◽  
Biomimetic Membrane

Biomimetic membrane systems play a crucial role in the field of biosensor engineering. Over the years, significant progress has been achieved creating artificial membranes by various strategies from vesicle fusion to Langmuir transfer approaches to meet an ever-growing demand for supported lipid bilayers on various substrates such as glass, mica, gold, polymer cushions, and many more. This paper reviews the diversity seen in the preparation of biologically relevant model lipid membranes which includes monolayers and bilayers of phospholipid and other crucial components such as proteins, characterization techniques, changes in the physical properties of the membranes during molecular interactions and the dynamics of the lipid membrane with biologically active molecules with special emphasis on lipopolysaccharides (LPS).

scholarly journals Calcium-triggered fusion of lipid membranes is enabled by amphiphilic nanoparticles

2020 ◽  
Vol 117 (31) ◽  
pp. 18470-18476 ◽  
Author(s):  
Mukarram A. Tahir ◽  
Zekiye P. Guven ◽  
Laura R. Arriaga ◽  
Berta Tinao ◽  
Yu-Sang Sabrina Yang ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Biomedical Applications ◽  
Lipid Membrane ◽  
Fusion Pore ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Kinetic Barriers

Lipid membrane fusion is an essential process for a number of critical biological functions. The overall process is thermodynamically favorable but faces multiple kinetic barriers along the way. Inspired by nature’s engineered proteins such as SNAP receptor [soluble N-ethylmale-imide-sensitive factor-attachment protein receptor (SNARE)] complexes or viral fusogenic proteins that actively promote the development of membrane proximity, nucleation of a stalk, and triggered expansion of the fusion pore, here we introduce a synthetic fusogen that can modulate membrane fusion and equivalently prime lipid membranes for calcium-triggered fusion. Our fusogen consists of a gold nanoparticle functionalized with an amphiphilic monolayer of alkanethiol ligands that had previously been shown to fuse with lipid bilayers. While previous efforts to develop synthetic fusogens have only replicated the initial steps of the fusion cascade, we use molecular simulations and complementary experimental techniques to demonstrate that these nanoparticles can induce the formation of a lipid stalk and also drive its expansion into a fusion pore upon the addition of excess calcium. These results have important implications in general understanding of stimuli-triggered fusion and the development of synthetic fusogens for biomedical applications.

Microfluidic Emulsion Generation and Trapping Enabling Droplet-Interfaced Bilayer Lipid Membrane Arrays

2009 ◽  
Author(s):  
C. Shao ◽  
D. L. DeVoe
Keyword(s):  
Lipid Bilayers ◽  
Single Molecule ◽  
Protein Interactions ◽  
Lipid Membranes ◽  
High Throughput Screening ◽  
Lipid Membrane ◽  
Bilayer Lipid Membrane ◽  
Single Molecule Level ◽  
Bilayer Lipid ◽  
Ion Translocation

Freestanding bilayer lipid membranes provide an exceptional platform for measurements of lipid/protein interactions and ion translocation events at the single molecule level. For drug screening applications, large arrays of individual bilayer supports are required. However, an effective method for generating, stabilizing, and monitoring arrays of lipid bilayers remains elusive. Here we investigate a novel approach towards the facile generation of bilayer arrays for high throughput screening. The approach takes advantage of fundamental microfluidic capabilities by combining an emulsion generator with droplet-interfaced membrane formation, allowing for fully-automated production of membrane arrays whose density is, in principle, unlimited.

scholarly journals Non-linear Conductance, Rectification, and Mechanosensitive Channel Formation of Lipid Membranes

2021 ◽  
Vol 8 ◽  
Author(s):  
Karis Amata Zecchi ◽  
Thomas Heimburg
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Electrical Response ◽  
Spontaneous Curvature ◽  
Pressure Gradients ◽  
Channel Formation ◽  
Voltage Gated ◽  
Non Linear ◽  
Different Depths

There is mounting evidence that lipid bilayers display conductive properties. However, when interpreting the electrical response of biological membranes to voltage changes, they are commonly considered as inert insulators. Lipid bilayers under voltage-clamp conditions display current traces with discrete conduction-steps, which are indistinguishable from those attributed to the presence of protein channels. In current-voltage (I-V) plots they may also display outward rectification, i.e., voltage-gating. Surprisingly, this has even been observed in chemically symmetric lipid bilayers. Here, we investigate this phenomenon using a theoretical framework that models the electrostrictive effect of voltage on lipid membranes in the presence of a spontaneous polarization, which can be recognized by a voltage offset in electrical measurements. It can arise from an asymmetry of the membrane, for example from a non-zero spontaneous curvature of the membrane. This curvature can be caused by voltage via the flexoelectric effect, or by hydrostatic pressure differences across the membrane. Here, we describe I-V relations for lipid membranes formed at the tip of patch pipettes situated close to an aqueous surface. We measured at different depths relative to air/water surface, resulting in different pressure gradients across the membrane. Both linear and non-linear I-V profiles were observed. Non-linear conduction consistently takes the form of outward rectified currents. We explain the conductance properties by two mechanisms: One leak current with constant conductance without pores, and a second process that is due to voltage-gated pore opening correlating with the appearance of channel-like conduction steps. In some instances, these non-linear I-V relations display a voltage regime in which dI/dV is negative. This has also been previously observed in the presence of sodium channels. Experiments at different depths reveal channel formation that depends on pressure gradients. Therefore, we find that the channels in the lipid membrane are both voltage-gated and mechanosensitive. We also report measurements on black lipid membranes that also display rectification. In contrast to the patch experiments they are always symmetric and do not display a voltage offset.

scholarly journals Orientation of Laurdan in Phospholipid Bilayers Influences Its Fluorescence: Quantum Mechanics and Classical Molecular Dynamics Study

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1707 ◽  
Author(s):  
Mirza Wasif Baig ◽  
Marek Pederzoli ◽  
Piotr Jurkiewicz ◽  
Lukasz Cwiklik ◽  
Jiri Pittner
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Liquid Crystalline ◽  
Lipid Membrane ◽  
Emission Spectra ◽  
Crystalline Phases ◽  
Classical Molecular Dynamics ◽  
Liquid Crystalline Phases ◽  
Lipid Environment

Fluidity of lipid membranes is known to play an important role in the functioning of living organisms. The fluorescent probe Laurdan embedded in a lipid membrane is typically used to assess the fluidity state of lipid bilayers by utilizing the sensitivity of Laurdan emission to the properties of its lipid environment. In particular, Laurdan fluorescence is sensitive to gel vs liquid–crystalline phases of lipids, which is demonstrated in different emission of the dye in these two phases. Still, the exact mechanism of the environment effects on Laurdan emission is not understood. Herein, we utilize dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) lipid bilayers, which at room temperature represent gel and liquid–crystalline phases, respectively. We simulate absorption and emission spectra of Laurdan in both DOPC and DPPC bilayers with quantum chemical and classical molecular dynamics methods. We demonstrate that Laurdan is incorporated in heterogeneous fashion in both DOPC and DPPC bilayers, and that its fluorescence depends on the details of this embedding.

High-Pressure Effects on the Structure and Phase Behavior of Model Membrane Systems

1996 ◽  
Author(s):  
Roland Winter ◽  
Anne Landwehr
Keyword(s):  
High Pressure ◽  
Phase Behavior ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Membrane Lipids ◽  
Pressure Effects ◽  
Scanning Calorimetry ◽  
Hydrocarbon Chains ◽  
Temperature And Pressure ◽  
Lipid Conformation

Phospholipids, which provide valuable model systems for lipid membranes, display a variety of polymorphic phases, depending on their molecular structure and on environmental conditions. High hydrostatic pressure has been used as a physical parameter to study the thermodynamic properties and phase behavior of these systems. High pressure is also a characteristic feature of certain natural membrane environments. In the first part of this article, we review our recent work on the temperature- and pressure-dependent phase behavior of phospholipid systems differing in lipid conformation and headgroup structure. In the second part, we report on the determination of the (T, x, p) phase diagrams of binary phospholipid mixtures. An additional section deals with effects of incorporating ions, small amphiphilic molecules, and steroids into the bilayer on the experimental temperature- and pressure-dependent phase behavior of lipid systems. Finally, we discuss lamellar to nonlamellar thermotropic and barotropic phase transformations, which occur for a number of lipids, such as phosphatidylethanolamines, monoacylglycerides, and lipid mixtures. It has been suggested that nonlamellar lipid structures might play an important role as transient and local intermediates in a number of biochemical processes. High-pressure smallangle x-ray (SAXS) and neutron (SANS) scattering, differential scanning calorimetry (DSC), high-pressure differential thermal analysis (DTA), and p, V, T measurements have been used as experimental methods for the investigation of these systems. Lipid bilayer dispersions, in particular the phosphatidylcholines and phosphatidylethanolamines, are the workhorses for the investigation of biophysical properties of membrane lipids because they constitute the basic structural component of biological membranes. They exhibit a rich lyotropic and thermotropic phase behavior (Cevc & Marsh, 1987; Marsh, 1991; Yeagle, 1992). Most fully hydrated saturated phospholipid bilayers exhibit two principal thermotropic lamellar phase transitions, corresponding to a gel to gel (Lβ′–Pβ′) transition and a gel to liquid-crystalline (Pβ′–Lα) main transition at a temperature Tm. In the fluid-like La phase, the hydrocarbon chains of the lipid bilayers are conformationally disordered, whereas in the gel phases the hydrocarbon chains are more extended and relatively ordered.

scholarly journals Theoretical and computational modeling of the dynamics of multicellular and lipid membrane systems

2016 ◽  
Author(s):  
◽  
Matthew McCune
Keyword(s):  
Computational Modeling ◽  
Neutron Scattering ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Drug Testing ◽  
Lipid Membrane ◽  
Dynamic Properties ◽  
Practical Implication ◽  
Free Standing ◽  
Silica Substrate

This dissertation presents two research projects that apply theoretical and computational modeling to (1) describe and predict the formation and shape evolution of three-dimensional (3D) bioprinted tissue constructs, and (2) investigate the effect of a silica substrate on the structural and dynamic properties of a single fully hydrated lipid bilayer. (1) Bioprinting, a novel tissue engineering technique, has the ultimate goal of using 3D printers with bioink made from a person’s own cells to create tissues in the laboratory for transplantation or drug testing. The outcome of the post-bioprinting process, where the bioink particles fuse to form the desired 3D tissue construct, is difficult to predict and experimental techniques have generally been optimized through trial and error. To address this shortcoming, by employing theoretical modeling and computer simulations, we have developed and implemented an effective procedure that is capable of describing and predicting the shape dynamics during post-printing structure formation in 3D bioprinting. In particular, we have explained and demonstrated that the post-printing fusion process is considerably faster when using cylindrical instead of spheroidal bioink particles, a result that has considerable practical implication for extrusion bioprinting. (2) The study of lipid bilayers using neutron scattering experiments requires samples that contain a large stack of membranes. The analysis and computer simulation of such systems is challenging mainly due to the unknown amount of water separating the membranes. To overcome this difficulty, more recent experiments place single lipid membranes onto a support and stack about a hundred of them together. In this project we use molecular dynamics simulations of both free-standing and hydrated single-supported lipid bilayers to investigate the effect of the silica substrate on the structural and dynamical properties of the lipids and hydration waters. Our results may provide useful information in interpreting some recent neutron scattering experiments.

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