scholarly journals The effect of hexadecaprenol on molecular organisation and transport properties of model membranes.

2000 ◽  
Vol 47 (3) ◽  
pp. 661-673 ◽  
Author(s):  
T Janas ◽  
K Nowotarski ◽  
W I Gruszecki ◽  
T Janas
Keyword(s):  
Activation Energy ◽  
Membrane Permeability ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Permeability Coefficient ◽  
Membrane Conductance ◽  
Chloride Ions ◽  
Molecular Area ◽  
Model Lipid Membranes ◽  
Molecular Organisation

The Langmuir monolayer technique and voltammetric analysis were used to investigate the properties of model lipid membranes prepared from dioleoylphosphatidylcholine (DOPC), hexadecaprenol (C80), and their mixtures. Surface pressure-molecular area isotherms, current-voltage characteristics, and membrane conductance-temperature were measured. Molecular area isobars, specific molecular areas, excess free energy of mixing, collapse pressure and collapse area were determined for lipid monolayers. Membrane conductance, activation energy of ion migration across the membrane, and membrane permeability coefficient for chloride ions were determined for lipid bilayers. Hexadecaprenol decreases the activation energy and increases membrane conductance and membrane permeability coefficient. The results of monolayer and bilayer investigations show that some electrical, transport and packing properties of lipid membranes change under the influence of hexadecaprenol. The results indicate that hexadecaprenol modulates the molecular organisation of the membrane and that the specific molecular area of polyprenol molecules depends on the relative concentration of polyprenols in membranes. We suggest that hexadecaprenol modifies lipid membranes by the formation of fluid microdomains. The results also indicate that electrical transmembrane potential can accelerate the formation of pores in lipid bilayers modified by long chain polyprenols.

scholarly journals The effect of undecaprenol on bilayer lipid membranes.

1994 ◽  
Vol 41 (3) ◽  
pp. 351-358 ◽  
Author(s):  
T Janas ◽  
T Chojnacki ◽  
E Swiezewska ◽  
T Janas
Keyword(s):  
Activation Energy ◽  
Lipid Membranes ◽  
Electrical Potential ◽  
Membrane Conductance ◽  
Transference Numbers ◽  
Bilayer Lipid Membranes ◽  
Ion Migration ◽  
Bilayer Lipid ◽  
Membrane Breakdown ◽  
Transmembrane Electrical Potential

The influence of undecaprenol on phosphatidylcholine macrovesicular bilayer lipid membranes has been studied by electrophysiological techniques. The current-voltage characteristics, ionic transference numbers, the membrane conductance-temperature relationships and the membrane breakdown voltage were measured. The permeability coefficients for Na+ and Cl- ions, the activation energy of ion migration across the membrane, the membrane hydrophobic thickness and the membrane Young's modulus were determined. Undecaprenol increases membrane conductance, membrane capacitance, membrane ionic permeability and membrane elastic deformability, decreases the activation energy, membrane hydrophobic thickness and membrane electromechanical stability, and does not change membrane selectivity. The formation by undecaprenyl molecules of fluid microdomains modulating membrane hydrophobic thickness is postulated. The data suggest that the behaviour of undecaprenol in membranes is regulated by transmembrane electrical potential.

scholarly journals Characterization and Antimicrobial Activity of Amphiphilic Peptide AP3 and Derivative Sequences

Antibiotics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 20 ◽  
Author(s):  
Christina Chrom ◽  
Lindsay Renn ◽  
Gregory Caputo
Keyword(s):  
Antimicrobial Activity ◽  
Fluorescence Spectroscopy ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Cd Spectroscopy ◽  
Membrane Permeabilization ◽  
Bacterial Membrane ◽  
Bacterial Strains ◽  
Bacterial Membranes ◽  
Model Lipid Membranes

The continued emergence of new antibiotic resistant bacterial strains has resulted in great interest in the development of new antimicrobial treatments. Antimicrobial peptides (AMPs) are one of many potential classes of molecules to help meet this emerging need. AMPs are naturally derived sequences, which act as part of the innate immune system of organisms ranging from insects through humans. We investigated the antimicrobial peptide AP3, which is originally isolated from the winter flounder Pleuronectes americanus. This peptide is of specific interest because it does not exhibit the canonical facially amphiphilic orientation of side chains when in a helical orientation. Different analogs of AP3 were synthesized in which length, charge identity, and Trp position were varied to investigate the sequence-structure and activity relationship. We performed biophysical and microbiological characterization using fluorescence spectroscopy, CD spectroscopy, vesicle leakage assays, bacterial membrane permeabilization assays, and minimal inhibitory concentration (MIC) assays. Fluorescence spectroscopy showed that the peptides bind to lipid bilayers to similar extents, while CD spectra show the peptides adopt helical conformations. All five peptides tested in this study exhibited binding to model lipid membranes, while the truncated peptides showed no measurable antimicrobial activity. The most active peptide proved to be the parent peptide AP3 with the highest degree of leakage and bacterial membrane permeabilization. Moreover, it was found that the ability to permeabilize model and bacterial membranes correlated most closely with the ability to predict antimicrobial activity.

scholarly journals The Water and Nonelectrolyte Permeability Induced in Thin Lipid Membranes by the Polyene Antibiotics Nystatin and Amphotericin B

1970 ◽  
Vol 56 (1) ◽  
pp. 125-145 ◽  
Author(s):  
Ronald Holz ◽  
Alan Finkelstein
Keyword(s):  
Amphotericin B ◽  
Lipid Membranes ◽  
Permeability Coefficient ◽  
Membrane Conductance ◽  
Red Cell Membrane ◽  
Water Permeability Coefficient ◽  
Permeability Increase ◽  
Hydrophilic Solutes ◽  
Human Red Cell Membrane ◽  
Nonelectrolyte Permeability

Nystatin and amphotericin B increase the permeability of thin (<100 A) lipid membranes to ions, water, and nonelectrolytes. Water and nonelectrolyte permeability increase linearly with membrane conductance (i.e., ion permeability). In the unmodified membrane, the osmotic permeability coefficient, Pf, is equal to the tagged water permeability coefficient, (Pd)w; in the nystatin- or amphotericin B-treated membrane, Pf/(Pd)w ≈ 3. The unmodified membrane is virtually impermeable to small hydrophilic solutes, such as urea, ethylene glycol, and glycerol; the nystatin- or amphotericin B-treated membrane displays a graded permeability to these solutes on the basis of size. This graded permeability is manifest both in the tracer permeabilities, Pd, and in the reflection coefficients, σ (Table I). The "cutoff" in permeability occurs with molecules about the size of glucose (Stokes-Einstein radius ≊ 4 A). We conclude that nystatin and amphotericin B create aqueous pores in thin lipid membranes; the effective radius of these pores is approximately 4 A. There is a marked similarity between the permeability of a nystatin- or amphotericin B-treated membrane to water and small hydrophilic solutes and the permeability of the human red cell membrane to these same molecules.

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 Molecular Dynamics Simulation of the Interaction Between Benzanthrone Dye and Model Lipid Membranes

2020 ◽  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Fluorescent Dyes ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Membrane Composition ◽  
Model Lipid Membranes

The benzanthrone fluorescent dyes are known as environmentally-sensitive reporters for exploring the physicochemical properties and structural alterations of lipid membranes. In the present work the 100-ns molecular dynamics simulation (MD) was used to characterize the bilayer location and the nature of interactions between the benzanthrone fluorescent dye ABM and the model lipid membranes composed of the zwitterionic lipid phosphatidylcholine (PC) and its mixtures with the anionic lipid phosphatidylglycerol (PG20) and sterol cholesterol (Chol30). The MD simulations were performed in the CHARMM36m force field using the GROMACS package. The ABM molecule, which was initially placed at a distance of 30 Å from the midplane of the lipid bilayer, after 10 ns of simulation was found to be completely incorporated into the membrane interior and remained within the lipid bilayer for the rest of the simulation time. The analysis of the MD simulation results showed that the lipid bilayer location of the benzanthrone dye ABM depends on the membrane composition, with the distance from bilayer center being gradually shifted from 0.78 nm in the neat PC bilayer to 0.95 nm and 1.5 nm in the PG- and Chol-containing membranes, respectively. In addition, the partitioning of the ABM into the neat PC bilayer was followed by the probe translocation from the outer membrane leaflet to the inner one. A separate series of MD simulations was aimed at examining the ABM influence on the lipid bilayer structure. It was found that ABM partitioning into the lipid bilayers of various composition has no significant effect on the orientation of the fatty acid chains and leads only to a small increase of the deuterium order parameter for the carbon atoms 5-to-8 in the sn-2 acyl chains of the neat PC membranes. In addition, the interaction of the ABM with the model lipid membranes caused the slight decrease of the surface area per lipid pointing to the slight increase of the packing density of lipid molecules in the presence of ABM. The results obtained provide a basis for deeper understanding of the membrane interactions of benzanthrone dyes and may be useful for the design of the novel fluorescent probes for membrane studies.

scholarly journals Basic Methods for Preparation of Liposomes and Studying Their Interactions with Different Compounds, with the Emphasis on Polyphenols

2021 ◽  
Vol 22 (12) ◽  
pp. 6547
Author(s):  
Luka Šturm ◽  
Nataša Poklar Ulrih
Keyword(s):  
Lipid Bilayers ◽  
Bioactive Compounds ◽  
Lipid Membranes ◽  
Good Condition ◽  
Research Field ◽  
Bioactive Molecules ◽  
Model Lipid Membranes ◽  
Simple Lipid ◽  
Potential Inhibitors ◽  
Kinetics Of

Studying the interactions between lipid membranes and various bioactive molecules (e.g., polyphenols) is important for determining the effects they can have on the functionality of lipid bilayers. This knowledge allows us to use the chosen compounds as potential inhibitors of bacterial and cancer cells, for elimination of viruses, or simply for keeping our healthy cells in good condition. As studying those effect can be exceedingly difficult on living cells, model lipid membranes, such as liposomes, can be used instead. Liposomal bilayer systems represent the most basic platform for studying those interactions, as they are simple, quite easy to prepare and relatively stable. They are especially useful for investigating the effects of bioactive compounds on the structure and kinetics of simple lipid membranes. In this review, we have described the most basic methods available for preparation of liposomes, as well as the essential techniques for studying the effects of bioactive compounds on those liposomes. Additionally, we have provided details for an easy laboratory implementation of some of the described methods, which should prove useful especially to those relatively new on this research field.

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 Water-ion permselectivity of narrow-diameter carbon nanotubes

2020 ◽  
Vol 6 (38) ◽  
pp. eaba9966 ◽  
Author(s):  
Yuhao Li ◽  
Zhongwu Li ◽  
Fikret Aydin ◽  
Jana Quan ◽  
Xi Chen ◽  
...  
Keyword(s):  
Activation Energy ◽  
Water Transport ◽  
Lipid Membranes ◽  
High Performance ◽  
High Water ◽  
Chloride Ions ◽  
Experimental Conditions ◽  
Measured Activation Energy ◽  
Water Salt ◽  
Measured Activation

Carbon nanotube (CNT) pores, which mimic the structure of the aquaporin channels, support extremely high water transport rates that make them strong candidates for building artificial water channels and high-performance membranes. Here, we measure water and ion permeation through 0.8-nm-diameter CNT porins (CNTPs)—short CNT segments embedded in lipid membranes—under optimized experimental conditions. Measured activation energy of water transport through the CNTPs agrees with the barrier values typical for single-file water transport. Well-tempered metadynamics simulations of water transport in CNTPs also report similar activation energy values and provide molecular-scale details of the mechanism for water entry into these channels. CNTPs strongly reject chloride ions and show water-salt permselectivity values comparable to those of commercial desalination membranes.

scholarly journals Fluorescence Approaches for Characterizing Ion Channels in Synthetic Bilayers

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 857
Author(s):  
Md. Sirajul Islam ◽  
James P. Gaston ◽  
Matthew A. B. Baker
Keyword(s):  
Ion Channels ◽  
Membrane Proteins ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Protein Composition ◽  
Cellular Processes ◽  
Model Lipid Membranes ◽  
Wide Range ◽  
Lipid Environment

Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins into model lipid membranes. Such simpler, in vitro, systems offer the advantage of control over the membrane and protein composition and the lipid environment. Rhodopsin and rhodopsin-like ion channels are widely studied due to their light-interacting properties and are a natural candidate for investigation with fluorescence methods. Here we review techniques for synthesizing liposomes and for reconstituting membrane proteins into lipid bilayers. We then summarize fluorescence assays which can be used to verify the functionality of reconstituted membrane proteins in synthetic liposomes.

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