The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Richard W Pastor - One of the best experts on this subject based on the ideXlab platform.
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surface shear viscosity and interleaflet friction from nonequilibrium simulations of Lipid Bilayers
Journal of Chemical Theory and Computation, 2019Co-Authors: Andrew Zgorski, Richard W Pastor, Edward LymanAbstract:Nonequilibrium simulation protocols based on shear deformations are applied to determine the surface viscosity and interleaflet friction of Lipid Bilayers. At high shear rates, a non-Newtonian shea...
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mechanical properties of Lipid Bilayers from molecular dynamics simulation
Chemistry and Physics of Lipids, 2015Co-Authors: Richard M Venable, Frank L H Brown, Richard W PastorAbstract:Lipid areas (Al), bilayer area compressibilities (KA), bilayer bending constants (KC), and monolayer spontaneous curvatures (c0) from simulations using the CHARMM36 force field are reported for 12 representative homogenous Lipid Bilayers. Al (or their surrogate, the average deuterium order parameter in the "plateau region" of the chain) agree very well with experiment, as do the KA. Simulated KC are in near quantitative agreement with vesicle flicker experiments, but are somewhat larger than KC from X-ray, pipette aspiration, and neutron spin echo for saturated Lipids. Spontaneous curvatures of bilayer leaflets from the simulations are approximately 30% smaller than experimental values of monolayers in the inverse hexagonal phase.
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the molecular structure of the liquid ordered phase of Lipid Bilayers
Journal of the American Chemical Society, 2014Co-Authors: Alexander J Sodt, Klaus Gawrisch, Michael Sandar, Richard W Pastor, Edward LymanAbstract:Molecular dynamics simulations reveal substructures within the liquid-ordered phase of Lipid Bilayers. These substructures, identified in a 10 μs all-atom trajectory of liquid-ordered/liquid-disordered coexistence (Lo/Ld) are composed of saturated hydrocarbon chains packed with local hexagonal order and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the Lo phase are in excellent agreement with 2H NMR measurements; the local hexagonal packing is also consistent with 1H-MAS NMR spectra of the Lo phase, NMR diffusion experiments, and small-angle X-ray and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the Lo regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways.
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the molecular structure of the liquid ordered phase of Lipid Bilayers
Journal of the American Chemical Society, 2014Co-Authors: Alexander J Sodt, Klaus Gawrisch, Michael Sandar, Richard W Pastor, Edward LymanAbstract:Molecular dynamics simulations reveal substructures within the liquid-ordered phase of Lipid Bilayers. These substructures, identified in a 10 μs all-atom trajectory of liquid-ordered/liquid-disord...
Edward Lyman - One of the best experts on this subject based on the ideXlab platform.
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surface shear viscosity and interleaflet friction from nonequilibrium simulations of Lipid Bilayers
Journal of Chemical Theory and Computation, 2019Co-Authors: Andrew Zgorski, Richard W Pastor, Edward LymanAbstract:Nonequilibrium simulation protocols based on shear deformations are applied to determine the surface viscosity and interleaflet friction of Lipid Bilayers. At high shear rates, a non-Newtonian shea...
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the molecular structure of the liquid ordered phase of Lipid Bilayers
Journal of the American Chemical Society, 2014Co-Authors: Alexander J Sodt, Klaus Gawrisch, Michael Sandar, Richard W Pastor, Edward LymanAbstract:Molecular dynamics simulations reveal substructures within the liquid-ordered phase of Lipid Bilayers. These substructures, identified in a 10 μs all-atom trajectory of liquid-ordered/liquid-disordered coexistence (Lo/Ld) are composed of saturated hydrocarbon chains packed with local hexagonal order and separated by interstitial regions enriched in cholesterol and unsaturated chains. Lipid hydrocarbon chain order parameters calculated from the Lo phase are in excellent agreement with 2H NMR measurements; the local hexagonal packing is also consistent with 1H-MAS NMR spectra of the Lo phase, NMR diffusion experiments, and small-angle X-ray and neutron scattering. The balance of cholesterol-rich to local hexagonal order is proposed to control the partitioning of membrane components into the Lo regions. The latter have been frequently associated with formation of so-called rafts, platforms in the plasma membranes of cells that facilitate interaction between components of signaling pathways.
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the molecular structure of the liquid ordered phase of Lipid Bilayers
Journal of the American Chemical Society, 2014Co-Authors: Alexander J Sodt, Klaus Gawrisch, Michael Sandar, Richard W Pastor, Edward LymanAbstract:Molecular dynamics simulations reveal substructures within the liquid-ordered phase of Lipid Bilayers. These substructures, identified in a 10 μs all-atom trajectory of liquid-ordered/liquid-disord...
Zhifeng Shao - One of the best experts on this subject based on the ideXlab platform.
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The vacuolating toxin from Helicobacter pylori forms hexameric pores in Lipid Bilayers at low pH (gastritisyulcersyAB toxinsyVacAymembrane protein)
2006Co-Authors: Daniel M. Czajkowsky, Hideki Iwamoto, Timothy L. Cover, Zhifeng ShaoAbstract:Pathogenic strains of Helicobacter pylori se- crete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predomi- nantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH '5, VacA associates with anionic Lipid Bilayers to form hexameric membrane-associated com- plexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into mem- brane-spanning hexamers. The surface contour of the mem- brane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measure- ments indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar Lipid Bilayers. This low pH- triggered pore formation is likely a critical step in VacA activity. associated complexes. In addition, electrophysiological mea- surements demonstrate that under these conditions, VacA forms pores in planar Lipid Bilayers. These results thus dem- onstrate that low pH indeed causes a critical change in the structure of the VacA oligomer, resulting in its interaction with a selected Lipid species. The pores formed by VacA oligomers in target membranes are likely to be directly related to the toxic effects of VacA on host cells.
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The vacuolating toxin from Helicobacter pylori forms hexameric pores in Lipid Bilayers at low pH
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Daniel M. Czajkowsky, Hideki Iwamoto, Timothy L. Cover, Zhifeng ShaoAbstract:Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH ≈5, VacA associates with anionic Lipid Bilayers to form hexameric membrane-associated complexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar Lipid Bilayers. This low pH-triggered pore formation is likely a critical step in VacA activity.
Alain Brisson - One of the best experts on this subject based on the ideXlab platform.
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formation of solid supported Lipid Bilayers an integrated view
Langmuir, 2006Co-Authors: Ralf P Richter, Remi Berat, Alain BrissonAbstract:Supported Lipid Bilayers (SLBs) are popular models of cell membranes with potential bio-technological applications. A qualitative understanding of the process of SLB formation after exposure of small Lipid vesicles to a hydrophilic support is now emerging. Recent studies have revealed a stunning variety of effects that can take place during this self-organization process. The ensemble of results in our group has revealed unprecedented insight into intermediates of the SLB-formation process and has helped to identify a number of parameters that are determinant for the Lipid deposition on solid supports. The pathway of Lipid deposition can be tuned by electrostatic interactions and by the presence of calcium. We emphasize the importance of the solid support in the SLB-formation process. Our results suggest that the molecular-level interaction between Lipids and the solid support needs to be considered explicitly, to understand the rupture of vesicles and the formation of SLBs as well as to predict the properties of the resulting SLB. The impact of the SLB-formation process on the quality and the physical properties of the resulting SLB as well as implications for other types of surface-confined Lipid Bilayers are discussed.
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The formation of supported Lipid Bilayers on silica nanoparticles revealed by cryoelectron microscopy
Nano Letters, 2005Co-Authors: Stéphane Mornet, Olivier Lambert, Etienne Duguet, Alain BrissonAbstract:The controlled fabrication of biocompatible devices made of Lipid Bilayers deposited onto flat solid supports presents interest as models of cell membranes as well as for their biotechnological applications. We report here on the formation of supported Lipid Bilayers on silica nanoparticles (nanoSLBs). The successive steps of the adsorption of Lipid vesicles on nanoparticles and the formation of nanoSLBs are revealed in detail by cryotransmission electron microscopy (cryo-EM). The formation of nanoSLBs was achieved for liposomes with positive, neutral, and low net negative charge, while liposomes with a high net negative charge adsorbed to silica nanoparticles but did not rupture. The nanoSLBs were found to follow faithfully the surface contours of the particles, information yet unavailable for SLB formation on planar solid substrates.
Daniel M. Czajkowsky - One of the best experts on this subject based on the ideXlab platform.
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The vacuolating toxin from Helicobacter pylori forms hexameric pores in Lipid Bilayers at low pH (gastritisyulcersyAB toxinsyVacAymembrane protein)
2006Co-Authors: Daniel M. Czajkowsky, Hideki Iwamoto, Timothy L. Cover, Zhifeng ShaoAbstract:Pathogenic strains of Helicobacter pylori se- crete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predomi- nantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH '5, VacA associates with anionic Lipid Bilayers to form hexameric membrane-associated com- plexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into mem- brane-spanning hexamers. The surface contour of the mem- brane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measure- ments indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar Lipid Bilayers. This low pH- triggered pore formation is likely a critical step in VacA activity. associated complexes. In addition, electrophysiological mea- surements demonstrate that under these conditions, VacA forms pores in planar Lipid Bilayers. These results thus dem- onstrate that low pH indeed causes a critical change in the structure of the VacA oligomer, resulting in its interaction with a selected Lipid species. The pores formed by VacA oligomers in target membranes are likely to be directly related to the toxic effects of VacA on host cells.
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The vacuolating toxin from Helicobacter pylori forms hexameric pores in Lipid Bilayers at low pH
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Daniel M. Czajkowsky, Hideki Iwamoto, Timothy L. Cover, Zhifeng ShaoAbstract:Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH ≈5, VacA associates with anionic Lipid Bilayers to form hexameric membrane-associated complexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar Lipid Bilayers. This low pH-triggered pore formation is likely a critical step in VacA activity.