Heterogeneity in Lateral Distribution of Polycations at the Surface of Lipid Membrane: From the Experimental Data to the Theoretical Model

Natural and synthetic polycations of different kinds attract substantial attention due to an increasing number of their applications in the biomedical industry and in pharmacology. The key characteristic determining the effectiveness of the majority of these applications is the number of macromolecules adsorbed on the surface of biological cells or their lipid models. Their study is complicated by a possible heterogeneity of polymer layer adsorbed on the membrane. Experimental methods reflecting the structure of the layer include the electrokinetic measurements in liposome suspension and the boundary potential of planar bilayer lipid membranes (BLM) and lipid monolayers with a mixed composition of lipids and the ionic media. In the review, we systematically analyze the methods of experimental registration and theoretical description of the laterally heterogeneous structures in the polymer layer published in the literature and in our previous studies. In particular, we consider a model based on classical theory of the electrical double layer, used to analyze the available data of the electrokinetic measurements in liposome suspension with polylysines of varying molecular mass. This model suggests a few parameters related to the heterogeneity of the polymer layer and allows determining the conditions for its appearance at the membrane surface. A further development of this theoretical approach is discussed.

Download Full-text

Anionic nanoparticle-lipid membrane interactions: the protonation of anionic ligands at the membrane surface reduces membrane disruption

RSC Advances ◽

10.1039/c9ra02462j ◽

2019 ◽

Vol 9 (25) ◽

pp. 13992-13997 ◽

Cited By ~ 4

Author(s):

Sebastian Salassi ◽

Ester Canepa ◽

Riccardo Ferrando ◽

Giulia Rossi

Keyword(s):

Lipid Membranes ◽

Au Nanoparticles ◽

Lipid Membrane ◽

Membrane Surface ◽

Membrane Disruption ◽

Membrane Interactions ◽

Carboxylate Groups ◽

Model Lipid Membranes ◽

Anionic Ligands

The interaction between anionic Au nanoparticles and model lipid membranes is facilitated by the spontaneous protonation of the NP ligand carboxylate groups, COO−˙ → COOH, in the lipid headgroup region.

Download Full-text

Electrochemical Properties of Lipid Membranes Self-Assembled from Bicelles

Membranes ◽

10.3390/membranes11010011 ◽

2020 ◽

Vol 11 (1) ◽

pp. 11

Author(s):

Damian Dziubak ◽

Kamil Strzelak ◽

Slawomir Sek

Keyword(s):

Electrochemical Properties ◽

Self Assembly ◽

Lipid Membranes ◽

Lipid Membrane ◽

Membrane Resistance ◽

Electrochemical Characteristics ◽

Freeze Thaw ◽

Lipid Films ◽

Supported Lipid Membranes

Supported lipid membranes are widely used platforms which serve as simplified models of cell membranes. Among numerous methods used for preparation of planar lipid films, self-assembly of bicelles appears to be promising strategy. Therefore, in this paper we have examined the mechanism of formation and the electrochemical properties of lipid films deposited onto thioglucose-modified gold electrodes from bicellar mixtures. It was found that adsorption of the bicelles occurs by replacement of interfacial water and it leads to formation of a double bilayer structure on the electrode surface. The resulting lipid assembly contains numerous defects and pinholes which affect the permeability of the membrane for ions and water. Significant improvement in morphology and electrochemical characteristics is achieved upon freeze–thaw treatment of the deposited membrane. The lipid assembly is rearranged to single bilayer configuration with locally occurring patches of the second bilayer, and the number of pinholes is substantially decreased. Electrochemical characterization of the lipid membrane after freeze–thaw treatment demonstrated that its permeability for ions and water is significantly reduced, which was manifested by the relatively high value of the membrane resistance.

Download Full-text

Interactions of Linear Analogues of Battacin with Negatively Charged Lipid Membranes

Membranes ◽

10.3390/membranes11030192 ◽

2021 ◽

Vol 11 (3) ◽

pp. 192

Author(s):

Kinga Burdach ◽

Dagmara Tymecka ◽

Aneta Urban ◽

Robert Lasek ◽

Dariusz Bartosik ◽

...

Keyword(s):

Lipid Membranes ◽

Liquid Crystalline ◽

Lipid Membrane ◽

Attenuated Total Reflection ◽

Gram Positive ◽

Insertion Depth ◽

Force Microscopy ◽

Acyl Chains ◽

Hydrophobic Portion ◽

Membrane Fluidization

The increasing resistance of bacteria to available antibiotics has stimulated the search for new antimicrobial compounds with less specific mechanisms of action. These include the ability to disrupt the structure of the cell membrane, which in turn leads to its damage. In this context, amphiphilic lipopeptides belong to the class of the compounds which may fulfill this requirement. In this paper, we describe two linear analogues of battacin with modified acyl chains to tune the balance between the hydrophilic and hydrophobic portion of lipopeptides. We demonstrate that both compounds display antimicrobial activity with the lowest values of minimum inhibitory concentrations found for Gram-positive pathogens. Therefore, their mechanism of action was evaluated on a molecular level using model lipid films mimicking the membrane of Gram-positive bacteria. The surface pressure measurements revealed that both lipopeptides show ability to bind and incorporate into the lipid monolayers, resulting in decreased ordering of lipids and membrane fluidization. Atomic force microscopy (AFM) imaging demonstrated that the exposure of the model bilayers to lipopeptides leads to a transition from the ordered gel phase to disordered liquid crystalline phase. This observation was confirmed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) results, which revealed that lipopeptide action causes a substantial increase in the average tilt angle of lipid acyl chains with respect to the surface normal to compensate for lipopeptide insertion into the membrane. Moreover, the peptide moieties in both molecules do not adopt any well-defined secondary structure upon binding with the lipid membrane. It was also observed that a small difference in the structure of a lipophilic chain, altering the balance between hydrophobic and hydrophilic portion of the molecules, results in different insertion depth of the active compounds.

Download Full-text

On biological signaling

Zeitschrift für Naturforschung A ◽

10.1515/zna-2020-0070 ◽

2020 ◽

Vol 75 (6) ◽

pp. 507-509 ◽

Cited By ~ 1

Author(s):

Günter Nimtz ◽

Horst Aichmann

Keyword(s):

Phase Transition ◽

Alternative Model ◽

Pulse Propagation ◽

Membrane Surface ◽

Bound Water ◽

Theoretical Description ◽

Lyotropic Liquid Crystal ◽

Local Phase ◽

Electric Action ◽

Nerve Pulse

AbstractPresently, nerve pulse propagation is understood to take place by electric action pulses. The theoretical description is given by the Hodgkin-Huxley model. Recently, an alternative model was proclaimed, where signaling is carried out by acoustic solitons. The solitons are built by a local phase transition in the lyotropic liquid crystal (LLC) of a biologic membrane. We argue that the crystal structure arranging hydrogen bonds at the membrane surface do not allow such an acoustic soliton model. The bound water is a component of the LLC and the assumed phase transition represents a negative entropy step.

Download Full-text

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

Antioxidants ◽

10.3390/antiox9050430 ◽

2020 ◽

Vol 9 (5) ◽

pp. 430 ◽

Cited By ~ 2

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.

Download Full-text

The interplay between lipids and dopamine on α-synuclein oligomerization and membrane binding

Bioscience Reports ◽

10.1042/bsr20130092 ◽

2013 ◽

Vol 33 (5) ◽

Cited By ~ 16

Author(s):

Chi L. L. Pham ◽

Roberto Cappai

Keyword(s):

Lipid Membranes ◽

Amyloid Fibrils ◽

Lipid Membrane ◽

Hydrophobic Interactions ◽

Membrane Integrity ◽

Lipid Vesicles ◽

Helical Conformation ◽

Unfolded Protein ◽

Natively Unfolded Protein ◽

Natively Unfolded

The deposition of α-syn (α-synuclein) as amyloid fibrils and the selective loss of DA (dopamine) containing neurons in the substantia nigra are two key features of PD (Parkinson's disease). α-syn is a natively unfolded protein and adopts an α-helical conformation upon binding to lipid membrane. Oligomeric species of α-syn have been proposed to be the pathogenic species associated with PD because they can bind lipid membranes and disrupt membrane integrity. DA is readily oxidized to generate reactive intermediates and ROS (reactive oxygen species) and in the presence of DA, α-syn form of SDS-resistant soluble oligomers. It is postulated that the formation of the α-syn:DA oligomers involves the cross-linking of DA-melanin with α-syn, via covalent linkage, hydrogen and hydrophobic interactions. We investigate the effect of lipids on DA-induced α-syn oligomerization and studied the ability of α-syn:DA oligomers to interact with lipids vesicles. Our results show that the interaction of α-syn with lipids inhibits the formation of DA-induced α-syn oligomers. Moreover, the α-syn:DA oligomer cannot interact with lipid vesicles or cause membrane permeability. Thus, the formation of α-syn:DA oligomers may alter the actions of α-syn which require membrane association, leading to disruption of its normal cellular function.

Download Full-text

Mechanistic Understanding from Molecular Dynamics in Pharmaceutical Research 2: Lipid Membrane in Drug Design

Pharmaceuticals ◽

10.3390/ph14101062 ◽

2021 ◽

Vol 14 (10) ◽

pp. 1062

Author(s):

Tomasz Róg ◽

Mykhailo Girych ◽

Alex Bunker

Keyword(s):

Molecular Dynamics ◽

Drug Design ◽

Active Site ◽

Lipid Membranes ◽

Md Simulation ◽

Lipid Membrane ◽

Pharmaceutical Research ◽

Specific Protein ◽

Design Tool ◽

Drug Molecules

We review the use of molecular dynamics (MD) simulation as a drug design tool in the context of the role that the lipid membrane can play in drug action, i.e., the interaction between candidate drug molecules and lipid membranes. In the standard “lock and key” paradigm, only the interaction between the drug and a specific active site of a specific protein is considered; the environment in which the drug acts is, from a biophysical perspective, far more complex than this. The possible mechanisms though which a drug can be designed to tinker with physiological processes are significantly broader than merely fitting to a single active site of a single protein. In this paper, we focus on the role of the lipid membrane, arguably the most important element outside the proteins themselves, as a case study. We discuss work that has been carried out, using MD simulation, concerning the transfection of drugs through membranes that act as biological barriers in the path of the drugs, the behavior of drug molecules within membranes, how their collective behavior can affect the structure and properties of the membrane and, finally, the role lipid membranes, to which the vast majority of drug target proteins are associated, can play in mediating the interaction between drug and target protein. This review paper is the second in a two-part series covering MD simulation as a tool in pharmaceutical research; both are designed as pedagogical review papers aimed at both pharmaceutical scientists interested in exploring how the tool of MD simulation can be applied to their research and computational scientists interested in exploring the possibility of a pharmaceutical context for their research.

Download Full-text

Self-Healing Bilayer Lipid Membranes Formed Over Synthetic Substrates

Smart Materials, Adaptive Structures and Intelligent Systems, Volume 2 ◽

10.1115/smasis2008-460 ◽

2008 ◽

Author(s):

M. Austin Creasy ◽

Donald J. Leo

Keyword(s):

Self Assembly ◽

Lipid Membranes ◽

Lipid Membrane ◽

Bilayer Lipid Membrane ◽

Unique Property ◽

Bilayer Lipid Membranes ◽

Self Healing ◽

Electrical Field ◽

Bilayer Lipid ◽

Recent Experimental Study

Biological systems demonstrate autonomous healing of damage and are an inspiration for developing self-healing materials. Our recent experimental study has demonstrated that a bilayer lipid membrane (BLM), also called a black lipid membrane, has the ability to self-heal after mechanical failure. These molecules have a unique property that they spontaneously self assembly into organized structures in an aqueous medium. The BLM forms an impervious barrier to ions and fluid between two volumes and strength of the barrier is dependent on the pressure and electrical field applied to the membrane. A BLM formed over an aperture on a silicon substrate is shown to self-heal for 5 pressurization failure cycles.

Download Full-text

Enhanced Stability of Lipid Structures by Dip-Pen Nanolithography on Block-Type MPC Copolymer

Molecules ◽

10.3390/molecules25122768 ◽

2020 ◽

Vol 25 (12) ◽

pp. 2768

Author(s):

Hui-Yu Liu ◽

Ravi Kumar ◽

Madoka Takai ◽

Michael Hirtz

Keyword(s):

Lipid Membranes ◽

Silicon Oxide ◽

Lipid Membrane ◽

Block Type ◽

Membrane Structures ◽

Solid Supports ◽

Biomedical Sensing ◽

The Stability ◽

Lipid Structures ◽

Dip Pen Nanolithography

Biomimetic lipid membranes on solid supports have been used in a plethora of applications, including as biosensors, in research on membrane proteins or as interfaces in cell experiments. For many of these applications, structured lipid membranes, e.g., in the form of arrays with features of different functionality, are highly desired. The stability of these features on a given substrate during storage and in incubation steps is key, while at the same time the substrate ideally should also exhibit antifouling properties. Here, we describe the highly beneficial properties of a 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer for the stability of supported lipid membrane structures generated by dip-pen nanolithography with phospholipids (L-DPN). The MPC copolymer substrates allow for more stable and higher membrane stack structures in comparison to other hydrophilic substrates, like glass or silicon oxide surfaces. The structures remain highly stable under immersion in liquid and subsequent incubation and washing steps. This allows multiplexed functionalization of lipid arrays with antibodies via microchannel cantilever spotting (µCS), without the need of orthogonal binding tags for each antibody type. The combined properties of the MPC copolymer substrate demonstrate a great potential for lipid-based biomedical sensing and diagnostic platforms.

Download Full-text