Small-volume extrusion apparatus for preparation of large, unilamellar vesicles

MacDonald, Robert C.; Menco, Bert Ph. M.; Takeshita, Keizo; Subbarao, Nanda K.; Hu, Lanrong

doi:10.1016/0005-2736(91)90295-j

Cited by 1,466 publications

(948 citation statements)

References 20 publications

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“…The tube was flushed with pure gaseous nitrogen and sealed with Parafilm M. Multilamellar liposomes were formed during vortex mixing and brief sonication in a bath sonicator. Unilamellar liposomes were prepared by extrusion of this dispersion through a polycarbonate filter (Nuclepore, Plesanton, USA) with pores of 50 nm diameter, using the LiposoFast Basic extruder (Avestin, Ottawa, Canada) fitted with two gas-tight Hamilton syringes (Hamilton, Reno, USA) as described by MacDonald et al (1991). The samples were subjected to 51 passes through the filter at a temperature above the main phase transition temperature of pure phospholipid.…”

Section: Methodsmentioning

confidence: 99%

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

et al. 2010

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Section: Methodsmentioning

confidence: 99%

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

et al. 2010

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“…Then, the material was extruded by 11 passages through 2 stacked Nuclepore TM polycarbonate membranes of 100 nm pore size in a homebuilt miniextruder (MacDonald et al 1991).…”

Section: Isothermal Titration Calorimetrymentioning

confidence: 99%

Leakage and lysis of lipid membranes induced by the lipopeptide surfactin

2006

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Surfactin is a lipopeptide produced by Bacillus subtilis which possesses antimicrobial activity. We have studied the leakage and lysis of POPC vesicles induced by surfactin using calcein fluorescence de-quenching, isothermal titration calorimetry and 31 P solid state NMR. Membrane leakage starts at a surfactin-to-lipid ratio in the membrane, R b % 0.05, and an aqueous surfactin concentration of C S w % 2 lM. The transient, graded nature of leakage and the apparent coupling with surfactin translocation to the inner leaflet of the vesicles, suggests that this low-concentration effect is due to a bilayer-couple mechanism. Different permeabilization behaviour is found at R b % 0.15 and attributed to surfactin-rich clusters, which can induce leaks and stabilize them by covering their hydrophobic edges. Membrane lysis or solubilization to micellar structures starts at R b sat = 0.22 and C S w = 9 lM and is completed at R m sol = 0.43 and C S w = 11 lM. The membrane-water partition coefficient of surfactin is obtained as K = 2 · 10 4 M -1 . These data resolve inconsistencies in the literature and shed light on the variety of effects often referred to as detergent-like effects of antibiotic peptides on membranes. The results are compared with published parameters characterizing the hemolytic and antibacterial activity.

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“…This assay uses brominated lipids and allows for sedimentation using a tabletop microfuge and avoids nonidealities introduced at higher centrifugal forces using nonbrominated lipids (25). Large unilamellar vesicles were made by extrusion as described previously (26) with a lipid composition of DOPC and DOPG (60:40) doped with 0.25% lissamine rhodamine B-labeled DOPE added to visualize the lipid fraction. For binding experiments, 10 μM protein was incubated with 2.5 mM lipid vesicles (P:L, 1:250) overnight at 25 °C as a function of pH using Perrin's constant-ionic strength (I = 0.05) buffers (27).…”

Section: Lipid Vesicle Sedimentation Assaymentioning

confidence: 99%

The N-Terminal Domain of Bcl-x_L Reversibly Binds Membranes in a pH-Dependent Manner

et al. 2006

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Bcl-x L regulates apoptosis by maintaining the integrity of the mitochondrial outer membrane by adopting both soluble and membrane-associated forms. The membrane-associated conformation does not require a conserved, C-terminal transmembrane domain and appears to be inserted into the bilayer of synthetic membranes as assessed by membrane permeabilization and critical surface pressure measurements. Membrane association is reversible and is regulated by the cooperative binding of approximately two protons to the protein. Two acidic residues, Glu153 and Asp156, that lie in a conserved hairpin of Bcl-x L ΔTM appear to be important in this process on the basis of a 16% increase in the level of membrane association of the double mutant E153Q/D156N. Contrary to that for the wild type, membrane permeabilization for the mutant is not correlated with membrane association. Monolayer surface pressure measurements suggest that this effect is primarily due to less membrane penetration. These results suggest that E153 and D156 are important for the Bclx L ΔTM conformational change and that membrane binding can be distinct from membrane permeabilization. Taken together, these studies support a model in which Bcl-x L activity is controlled by reversible insertion of its N-terminal domain into the mitochondrial outer membrane. Future studies with Bcl-x L mutants such as E153Q/D156N should allow determination of the relative contributions of membrane binding, insertion, and permeabilization to the regulation of apoptosis.Bcl-2 proteins act as checkpoints in the regulation of apoptosis by integrating intracellular signals to control the permeability and possibly the morphology of the mitochon-drion (1-9). For many Bcl-2 proteins, this checkpoint involves a change in localization from the cytosol to the mitochondrion (10-13). For example, Bcl-x L displays mixed localization to the cytosol and to organellar membranes, including the mitochondrion. After an apoptotic stimulus, Bcl-x L appears to localize primarily to the mitochondrial outer membrane where it may bind other apoptotic factors such as Bad (10,11,14) or form an ion channel thought to maintain the integrity of the mitochondrial membrane (11,(15)(16)(17). While mixed localization of Bcl-x L is well-established, the relative importance of cytosolic-and membranous-localized protein to the regulation of apoptosis is not. Intriguingly, the membrane activity of Bcl-x L may contribute more to its anti-apoptotic activity than its ability to sequester pro-apoptotic proteins: a mutant

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Small-volume extrusion apparatus for preparation of large, unilamellar vesicles

Cited by 1,466 publications

References 20 publications

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

Leakage and lysis of lipid membranes induced by the lipopeptide surfactin

The N-Terminal Domain of Bcl-x_L Reversibly Binds Membranes in a pH-Dependent Manner

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Small-volume extrusion apparatus for preparation of large, unilamellar vesicles

Cited by 1,466 publications

References 20 publications

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

Leakage and lysis of lipid membranes induced by the lipopeptide surfactin

The N-Terminal Domain of Bcl-xL Reversibly Binds Membranes in a pH-Dependent Manner

Contact Info

Product

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The N-Terminal Domain of Bcl-x_L Reversibly Binds Membranes in a pH-Dependent Manner