Coupling between Lateral and Transverse Organization in Three-Component Lipid Mixtures Investigated with Asymmetric GUVs Prepared by Hemifusion

Recently, a new approach to measure the bending stiffness (curvature elastic modulus) of lipid bilayer membrane was developed (Biophys. J., Vol. 55; pp. 509–517, 1989). The method involves the formation of cylindrical membrane strands (tethers) from bilayer vesicles. The bending stiffness (B) can be calculated from measurements of the tether radius (Rt) as a function of the axial force (f) on the tether: B =f·Rt/2π. In the present report, we apply this method to determine the bending stiffness of bilayer membranes composed of mixtures of SOPC (1-stearoyl-2-oleoyl phosphatidyl choline) and POPS (1-palmitoyl-2-oleoyl phosphatidyl serine). Three different mixtures were tested: pure SOPC, SOPC plus 2 percent (mol/mol) POPS, and SOPC plus 16 percent POPS. The bending stiffness determined for these three different lipid mixtures were not significantly different (1.6–1.8×10-12 ergs). Because POPS carries a net negative charge, these results indicate that changes in the density of the membrane surface charge have no effect on the intrinsic rigidity of the membrane. The values we obtain are consistent with published values for the bending stiffness of other membranes determined by different methods. Measurements of the aspiration pressure, the tether radius and the tether force were used to verify a theoretical relationship among these quantities at equilibrium. The ratio of the theoretical force to the measured force was 1.12 ± 0.17.

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Formation mechanism of self-assembled unilamellar vesiclesSpecial issue on Neutron Scattering in Canada

Canadian Journal of Physics ◽

10.1139/p10-014 ◽

2010 ◽

Vol 88 (10) ◽

pp. 735-740 ◽

Cited By ~ 5

Author(s):

Mu-Ping Nieh ◽

Norbert Kučerka ◽

John Katsaras

Keyword(s):

Neutron Scattering ◽

Hydrocarbon Chain ◽

Lipid Concentration ◽

Uniform Size ◽

Lipid Mixtures ◽

Hydrocarbon Chain Length ◽

Membrane Rigidity ◽

Self Assembled ◽

Best Fit ◽

Sans Data

Uniform size self-assembled unilamellar vesicles (ULVs) can be produced from mixtures of weakly charged short- and long-chain phospholipids. These lipid mixtures self-assemble into bilayered micelles (so-called bicelles), and a bicelle to ULV transition has been previously reported. Here, we discuss the effect of various parameters (i.e., lipid concentration, charge density, membrane rigidity, lipid composition, and lipid hydrocarbon chain length) on ULV radius as determined by small angle neutron scattering (SANS). SANS data were best fit using a core-shell disk and a spherical-shell model to obtain the size of bicelles and ULVs, respectively. From the present experiments we conclude that a previously proposed mechanism of ULV formation, where bicelles coalesce into large precursor and self-fold into ULVs, is able to explain the present SANS data.

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An Approach for Analysis of Protein Toxins Based on Thin Films of Lipid Mixtures in an Optical Biosensor

Analytical Chemistry ◽

10.1021/ac000619j ◽

2001 ◽

Vol 73 (1) ◽

pp. 72-79 ◽

Cited By ~ 25

Author(s):

Gertrud Puu

Keyword(s):

Thin Films ◽

Optical Biosensor ◽

Lipid Mixtures ◽

Protein Toxins

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The thermodynamic properties of mixed phospholipid bilayers: a theoretical analysis

Canadian Journal of Biochemistry and Cell Biology ◽

10.1139/o84-101 ◽

1984 ◽

Vol 62 (8) ◽

pp. 796-802 ◽

Cited By ~ 6

Author(s):

Maryse Mondat ◽

A. Georgallas ◽

D. A. Pink ◽

M. J. Zuckermann

Keyword(s):

Experimental Data ◽

Thermodynamic Properties ◽

Reasonable Agreement ◽

Phospholipid Bilayers ◽

Scanning Calorimetry ◽

Phase Separations ◽

Lipid Mixtures ◽

Wide Range ◽

Acyl Chains ◽

Gel Phase

A theoretical model is presented with the intention of describing lateral phase separations in binary lipid mixtures in which the acyl chains of the components differ in their length. The model includes explicitly interactions between the acyl chains and between polar heads of the lipid molecules. Phase diagrams and thermodynamic properties of binary lipid mixtures were calculated using a wide range of interaction parameters. It is shown that the occurrence of immiscibility in the gel phase is related to the interactions between the polar heads of the lipid molecules. The calculated results for binary lipid mixtures are compared with the available experimental data. In particular, the calculated specific heat for dilauroyl phosphatidylcholine – distearoyl phosphatidylcholine is in reasonable agreement with experimental results obtained from differential scanning calorimetry measurements.

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Structural Characterization of Natural Yeast Phosphatidylcholine and Bacterial Phosphatidylglycerol Lipid Multilayers by Neutron Diffraction

Frontiers in Chemistry ◽

10.3389/fchem.2021.628186 ◽

2021 ◽

Vol 9 ◽

Author(s):

Alessandra Luchini ◽

Giacomo Corucci ◽

Krishna Chaithanya Batchu ◽

Valerie Laux ◽

Michael Haertlein ◽

...

Keyword(s):

Neutron Diffraction ◽

Acyl Chain ◽

Model Systems ◽

Head Group ◽

Single Class ◽

Lipid Mixtures ◽

Chain Composition ◽

Acyl Chain Composition ◽

The Impact

Eukaryotic and prokaryotic cell membranes are difficult to characterize directly with biophysical methods. Membrane model systems, that include fewer molecular species, are therefore often used to reproduce their fundamental chemical and physical properties. In this context, natural lipid mixtures directly extracted from cells are a valuable resource to produce advanced models of biological membranes for biophysical investigations and for the development of drug testing platforms. In this study we focused on single phospholipid classes, i.e. Pichia pastoris phosphatidylcholine (PC) and Escherichia coli phosphatidylglycerol (PG) lipids. These lipids were characterized by a different distribution of their respective acyl chain lengths and number of unsaturations. We produced both hydrogenous and deuterated lipid mixtures. Neutron diffraction experiments at different relative humidities were performed to characterize multilayers from these lipids and investigate the impact of the acyl chain composition on the structural organization. The novelty of this work resides in the use of natural extracts with a single class head-group and a mixture of chain compositions coming from yeast or bacterial cells. The characterization of the PC and PG multilayers showed that, as a consequence of the heterogeneity of their acyl chain composition, different lamellar phases are formed.

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Viability of the microencapsulation of a casein hydrolysate in lipid microparticles of cupuacu butter and stearic acid

International Journal of Food Studies ◽

10.7455/ijfs.v2i1.125 ◽

2013 ◽

Vol 2 (1) ◽

Author(s):

Samantha Cristina Pinho ◽

Janaina Costa Da Silva

Keyword(s):

Stearic Acid ◽

Room Temperature ◽

Casein Hydrolysate ◽

Polysorbate 80 ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Initial Amount ◽

X Ray ◽

Lipid Mixtures ◽

Lipid Microparticles

Solid lipid microparticles produced with a mixture of cupuacu butter and stearic acid were used to microencapsulate a commercial casein hydrolysate (Hyprol 8052). The composition of the lipid matrix used for the production of the lipid microparticles was chosen according to data on the wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) of bulk lipid mixtures, which indicated that the presence of 10 % cupuacu butter was sufficient to significantly change the crystalline arrangement of pure stearic acid. Preliminary tests indicated that a minimum proportion of 4 % of surfactant (polysorbate 80) was necessary to produce empty spherical lipid particles with average diameters below 10 mm. The lipid microparticles were produced using 20 % cupuacu butter and 80 % stearic acid and then stabilized with 4 % of polysorbate 80, exhibiting an encapsulation efficiency of approximately 74 % of the casein hydrolysate. The melting temperature of the casein hydrolysate-loaded lipid microparticles was detected at 65.2 °C, demonstrating that the particles were solid at room temperature as expected and indicating that the incorporation of peptides had not affected their thermal behavior. After 25 days of storage, however, there was a release of approximately 30 % of the initial amount of encapsulated casein hydrolysate. This release was not thought to have been caused by the liberation of encapsulated casein hydrolysate. Instead, it was attributed to the possible desorption of the adsorbed peptides present on the surface of the lipid microparticles.

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