scholarly journals On Physical Properties of Tetraether Lipid Membranes: Effects of Cyclopentane Rings

Archaea ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Parkson Lee-Gau Chong ◽  
Umme Ayesa ◽  
Varsha Prakash Daswani ◽  
Ellah Chay Hur
Keyword(s):  
Physical Properties ◽  
Computer Simulations ◽  
Significant Influence ◽  
Lipid Membranes ◽  
Membrane Properties ◽  
Membrane Thickness ◽  
Naturally Occurring ◽  
Tetraether Lipid ◽  
Tetraether Lipids ◽  
Lipid Conformation

This paper reviews the recent findings related to the physical properties of tetraether lipid membranes, with special attention to the effects of the number, position, and configuration of cyclopentane rings on membrane properties. We discuss the findings obtained from liposomes and monolayers, composed of naturally occurring archaeal tetraether lipids and synthetic tetraethers as well as the results from computer simulations. It appears that the number, position, and stereochemistry of cyclopentane rings in the dibiphytanyl chains of tetraether lipids have significant influence on packing tightness, lipid conformation, membrane thickness and organization, and headgroup hydration/orientation.

scholarly journals Sulfolobus acidocaldarius Microvesicles Exhibit Unusually Tight Packing Properties as Revealed by Optical Spectroscopy

2019 ◽  
Vol 20 (21) ◽  
pp. 5308 ◽  
Author(s):  
Alexander Bonanno ◽  
Robert C. Blake ◽  
Parkson Lee-Gau Chong
Keyword(s):  
Optical Spectroscopy ◽  
Lipid Membranes ◽  
Sulfolobus Acidocaldarius ◽  
Lipid Phase ◽  
Protein Fluorescence ◽  
Intrinsic Protein ◽  
Emission Maximum ◽  
Tetraether Lipid ◽  
Tetraether Lipids ◽  
Intrinsic Protein Fluorescence

In this study, we used optical spectroscopy to characterize the physical properties of microvesicles released from the thermoacidophilic archaeon Sulfolobus acidocaldarius (Sa-MVs). The most abundant proteins in Sa-MVs are the S-layer proteins, which self-assemble on the vesicle surface forming an array of crystalline structures. Lipids in Sa-MVs are exclusively bipolar tetraethers. We found that when excited at 275 nm, intrinsic protein fluorescence of Sa-MVs at 23 °C has an emission maximum at 303 nm (or 296 nm measured at 75 °C), which is unusually low for protein samples containing multiple tryptophans and tyrosines. In the presence of 10–11 mM of the surfactant n-tetradecyl-β-d-maltoside (TDM), Sa-MVs were disintegrated, the emission maximum of intrinsic protein fluorescence was shifted to 312 nm, and the excitation maximum was changed from 288 nm to 280.5 nm, in conjunction with a significant decrease (>2 times) in excitation band sharpness. These data suggest that most of the fluorescent amino acid residues in native Sa-MVs are in a tightly packed protein matrix and that the S-layer proteins may form J-aggregates. The membranes in Sa-MVs, as well as those of unilamellar vesicles (LUVs) made of the polar lipid fraction E (PLFE) tetraether lipids isolated from S. acidocaldarius (LUVPLFE), LUVs reconstituted from the tetraether lipids extracted from Sa-MVs (LUVMV) and LUVs made of the diester lipids, were investigated using the probe 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan). The generalized polarization (GP) values of Laurdan in tightly packed Sa-MVs, LUVMV, and LUVPLFE were found to be much lower than those obtained from less tightly packed DPPC gel state, which echoes the previous finding that the GP values from tetraether lipid membranes cannot be directly compared with the GP values from diester lipid membranes, due to differences in probe disposition. Laurdan’s GP and red-edge excitation shift (REES) values in Sa-MVs and LUVMV decrease with increasing temperature monotonically with no sign for lipid phase transition. Laurdan’s REES values are high (9.3–18.9 nm) in the tetraether lipid membrane systems (i.e., Sa-MVs, LUVMV and LUVPLFE) and low (0.4–5.0 nm) in diester liposomes. The high REES and low GP values suggest that Laurdan in tetraether lipid membranes, especially in the membrane of Sa-MVs, is in a very motionally restricted environment, bound water molecules and the polar moieties in the tetraether lipid headgroups strongly interact with Laurdan’s excited state dipole moment, and “solvent” reorientation around Laurdan’s chromophore in tetraether lipid membranes occurs very slowly compared to Laurdan’s lifetime.

Interactions of surfactants with lipid membranes

2008 ◽  
Vol 41 (3-4) ◽  
pp. 205-264 ◽  
Author(s):  
Heiko Heerklotz
Keyword(s):  
Lipid Membranes ◽  
Critical Concentration ◽  
Water Soluble ◽  
Membrane Properties ◽  
Published Data ◽  
Amphiphilic Peptides ◽  
Naturally Occurring ◽  
Amphiphilic Compounds ◽  
Water Partitioning ◽  
Surface Active

AbstractSurfactants are surface-active, amphiphilic compounds that are water-soluble in the micro- to millimolar range, and self-assemble to form micelles or other aggregates above a critical concentration. This definition comprises synthetic detergents as well as amphiphilic peptides and lipopeptides, bile salts and many other compounds. This paper reviews the biophysics of the interactions of surfactants with membranes of insoluble, naturally occurring lipids. It discusses structural, thermodynamic and kinetic aspects of membrane–water partitioning, changes in membrane properties induced by surfactants, membrane solubilisation to micelles and other phases formed by lipid–surfactant systems. Each section defines and derives key parameters, mentions experimental methods for their measurement and compiles and discusses published data. Additionally, a brief overview is given of surfactant-like effects in biological systems, technical applications of surfactants that involve membrane interactions, and surfactant-based protocols to study biological membranes.

scholarly journals Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

2014 ◽  
Vol 141 (19) ◽  
pp. 194902 ◽  
Author(s):  
I. A. Barragán Vidal ◽  
C. M. Rosetti ◽  
C. Pastorino ◽  
M. Müller
Keyword(s):  
Computer Simulations ◽  
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 Characterization of Ion Exchange Membranes with Special Surface Structure

2017 ◽  
Author(s):  
Eliška Stránská ◽  
Kristýna Weinertová ◽  
David Neděla ◽  
Jan Křivčík
Keyword(s):  
Ion Exchange ◽  
Physical Properties ◽  
Surface Structure ◽  
Flat Surface ◽  
Ion Exchange Membrane ◽  
Membrane Properties ◽  
Ion Exchange Membranes ◽  
Geometrical Structures ◽  
Special Surface ◽  
Exchange Membrane

This article focuses on the preparation of the heterogeneous ion exchange membrane with a special surface structure made with three types of knitted fabric. The special surface structure of ion exchange membranes can be useful for the intensification of mass transfer processes in electrodialysis.Three types of structured ion exchange membranes were prepared together with a membrane with a flat surface to compare the influence of geometrical structures on the behaviour of ion exchange membrane properties. Electrochemical, mechanical and physical properties were determined. Structured membranes exhibited comparable electrochemical and physical properties to the flat ion exchange membrane. Some transport parameters were measured in an electrodialysis stack with two concentrations of solution. Two electrodialysis stacks with different sizes of active area were used for comparison. Improving efficiency and mass flux was not confirmed. It was not demonstrated that structured IEMs were not better than IEMs with the flat surface.

scholarly journals Effect of composition on physical properties of food powders

2016 ◽  
Vol 30 (2) ◽  
pp. 237-243 ◽  
Author(s):  
Karolina Szulc ◽  
Andrzej Lenart
Keyword(s):  
Particle Size ◽  
Physical Properties ◽  
Bulk Density ◽  
Technological Process ◽  
Apparent Density ◽  
Significant Influence ◽  
Material Composition ◽  
Raw Material ◽  
Food Powders

Abstract The paper presents an influence of raw material composition and technological process applied on selected physical properties of food powders. Powdered multi-component nutrients were subjected to the process of mixing, agglomeration, coating, and drying. Wetting liquids ie water and a 15% water lactose solution, were used in agglomeration and coating. The analyzed food powders were characterized by differentiated physical properties, including especially: particle size, bulk density, wettability, and dispersibility. The raw material composition of the studied nutrients exerted a statistically significant influence on their physical properties. Agglomeration as well as coating of food powders caused a significant increase in particle size, decreased bulk density, increased apparent density and porosity, and deterioration in flowability in comparison with non-agglomerated nutrients.

Adhesion of Lipid Membranes Mediated by Electrostatic and Specific Interactions

1997 ◽  
Vol 489 ◽  
Author(s):  
Christian W. Maier ◽  
Almuth Behrisch ◽  
Annette Kloboucek ◽  
Rudolf Merkel
Keyword(s):  
Lipid Membranes ◽  
Cell Adhesion Molecule ◽  
Lipid Vesicles ◽  
Membrane Properties ◽  
Specific Cell ◽  
Receptor Aggregation ◽  
Host Membrane ◽  
Aspiration Technique ◽  
Membrane Adhesion ◽  
Positively Charged

AbstractWe used the micropipet aspiration technique for a study of biomembrane adhesion. Adhesion was caused by contact site A, a highly specific cell adhesion molecule, reconstituted in lipid vesicles of DOPC with 5 %(mol/mol) DOPE-PEG2000. We found adhesion and subsequent receptor aggregation in the contact zone. Additionally, electrostatic modulation of membrane adhesion was studied. Whereas addition of the negatively charged lipid SOPS to the lecithin (SOPC) host membrane suppressed adhesion due to electrostatic repulsion, a positively charged lipid (DOTAP) was surprisingly ineffective. This might be due to either phase separation of the mixture or DOTAP changing other membrane properties as bending stiffness and the Hamaker constant.

scholarly journals Large and Giant Unilamellar Vesicle(s) Obtained by Self-Assembly of Poly(dimethylsiloxane)-b-poly(ethylene oxide) Diblock Copolymers, Membrane Properties and Preliminary Investigation of Their Ability to Form Hybrid Polymer/Lipid Vesicles

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2013 ◽  
Author(s):  
Martin Fauquignon ◽  
Emmanuel Ibarboure ◽  
Stéphane Carlotti ◽  
Annie Brûlet ◽  
Marc Schmutz ◽  
...  
Keyword(s):  
Light Scattering ◽  
Ethylene Oxide ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Lipid Vesicles ◽  
Membrane Properties ◽  
Membrane Thickness ◽  
Hybrid Polymer ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

In the emerging field of hybrid polymer/lipid vesicles, relatively few copolymers have been evaluated regarding their ability to form these structures and the resulting membrane properties have been scarcely studied. Here, we present the synthesis and self-assembly in solution of poly(dimethylsiloxane)-block-poly(ethylene oxide) diblock copolymers (PDMS-b-PEO). A library of different PDMS-b-PEO diblock copolymers was synthesized using ring-opening polymerization of hexamethylcyclotrisiloxane (D3) and further coupling with PEO chains via click chemistry. Self-assembly of the copolymers in water was studied using Dynamic Light Scattering (DLS), Static Light Scattering (SLS), Small Angle Neutron Scattering (SANS), and Cryo-Transmission Electron Microscopy (Cryo-TEM). Giant polymersomes obtained by electroformation present high toughness compared to those obtained from triblock copolymer in previous studies, for similar membrane thickness. Interestingly, these copolymers can be associated to phospholipids to form Giant Hybrid Unilamellar Vesicles (GHUV); preliminary investigations of their mechanical properties show that tough hybrid vesicles can be obtained.

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