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Maria M. Santore - One of the best experts on this subject based on the ideXlab platform.
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1 2 dipalmitoyl sn glycero 3 phosphocholine dppc rich Domain Formation in binary phospholipid vesicle membranes two dimensional nucleation and growth
Langmuir, 2014Co-Authors: Dong Chen, Maria M. SantoreAbstract:Decades of study have probed phase transitions in model phospholipid bilayers and vesicles, especially in the context of the equilibrium phase diagram. Critical to the response of vesicles to environmental triggers, to the ultimate Domain morphology, and to the approach to equilibrium (or not), we present here a study of Domain Formation in vesicles, focusing on a mechanism by which the cooling rate, tension, and composition affect the first appearance (nucleation) and subsequent growth of solid membrane Domains. Employing a popular mixed membrane model based on DOPC and DPPC (1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, respectively), we examined phase separation in giant two-component vesicles that were cooled from the one-phase fluid (Lα) region of the phase diagram into a region of fluid (Lα)–solid coexistence. At moderate and low membrane tensions, cooling produced solid DPPC-rich Domains appearing as compact patches or irregular hexagons and likely with a...
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1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-Rich Domain Formation in Binary Phospholipid Vesicle Membranes: Two-Dimensional Nucleation and Growth
2014Co-Authors: Dong Chen, Maria M. SantoreAbstract:Decades of study have probed phase transitions in model phospholipid bilayers and vesicles, especially in the context of the equilibrium phase diagram. Critical to the response of vesicles to environmental triggers, to the ultimate Domain morphology, and to the approach to equilibrium (or not), we present here a study of Domain Formation in vesicles, focusing on a mechanism by which the cooling rate, tension, and composition affect the first appearance (nucleation) and subsequent growth of solid membrane Domains. Employing a popular mixed membrane model based on DOPC and DPPC (1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, respectively), we examined phase separation in giant two-component vesicles that were cooled from the one-phase fluid (Lα) region of the phase diagram into a region of fluid (Lα)–solid coexistence. At moderate and low membrane tensions, cooling produced solid DPPC-rich Domains appearing as compact patches or irregular hexagons and likely with a Pβ′ (ripple) arrangement. (The compact solid Domains in this study differed distinctly from striped Domains in vesicles of the same composition, in terms of molecular organization and conditions of first appearance during cooling.) The amounts of these solid Domains were shown to adhere to the lever arm rule for a tie line on the phase diagram, with a solid composition near 95 mol % DPPC. The nucleation of the compact solid Domains occurred in a short period, followed by rapid addition of ordered molecules to the nucleated Domains, excluding tracer dye. The two-dimensional nucleation density of these compact solid Domains (in the range of 10–2–10–1 μm–2) was found to increase with the cooling rate (equivalent to the quench depth) with a greater than linear dependence. The 2-D nucleation density was also seen to decrease with membrane tension, presumably because membrane tension increases the line tension around a Domain that opposes nucleation. A sigmoidal dependence of the nucleation density on the DPPC concentration was also found. With cooling rates in excess of ∼1 °C/min, solid Domains persisted down to room temperature, likely passing from a preferred equilibrium to a local equilibrium with continued cooling. As a result of the persistence of the originally nucleated Domains and the conservation of DPPC in the membrane, we observed an increasingly greater number of smaller Domains with increased cooling rates. The Domains in these vesicles were compact or hexagonal-shaped in contrast to flower-shaped dendritic Domains in the same membrane system in a supported membrane configuration
Preston R Mason - One of the best experts on this subject based on the ideXlab platform.
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rosmarinic acid and its esters inhibit membrane cholesterol Domain Formation through an antioxidant mechanism based in nonlinear fashion on alkyl chain length
Biochimica et Biophysica Acta, 2019Co-Authors: Samuel C R Sherratt, Pierre Villeneuve, Erwann Durand, Preston R MasonAbstract:Abstract Background Under conditions of oxidative stress, cholesterol aggregates into discrete membrane bilayer Domains that precipitate the Formation of extracellular crystals, a feature of advanced atheroma in cardiovascular disease. Therapeutic interventions using membrane-directed antioxidants, such as polyphenolic esters, may reduce cholesterol Domains and crystal Formation. In this study, the effects of rosmarinic acid (RC0) and rosmarinic esters, with alkyl chain lengths ranging from 4 to 16‑carbons (RC4-RC16), on membrane lipid oxidation and cholesterol Domain Formation were investigated. Methods Model membranes were prepared with 1,2-dilinoleoyl-sn-glycero-3-phosphocholine and cholesterol at different cholesterol-to-phospholipid mole ratios (0.3:1, 0.9:1, and 1.2:1), in the absence or presence of each molecule and exposed to 72 h of oxidation. Changes in lipid hydroperoxide (LOOH) and cholesterol Domain Formation were measured using iodometric and small angle x-ray diffraction approaches, respectively. Results Rosmarinic acid and its esters had differential effects on LOOH Formation based on alkyl chain length. RC8 exhibited the greatest antioxidant effect, reducing LOOH levels by 82%, and inhibited cholesterol Domain Formation. By contrast, RC0 and RC16 failed to inhibit either LOOH Formation or cholesterol Domain Formation. Conclusion These data indicate that the membrane antioxidant and cholesterol Domain inhibition activities of rosmarinic acid esters are dependent, nonlinearly, on alkyl chain length. The mechanism for this effect is attributed to the influence of alkyl chain length on the optimal depth of the polyphenols into the lipid bilayer for trapping free radicals. General significance These findings provide insight into novel atheroprotective benefits of polyphenol esters that are dependent on their membrane location.
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eicosapentaenoic acid reduces membrane fluidity inhibits cholesterol Domain Formation and normalizes bilayer width in atherosclerotic like model membranes
Biochimica et Biophysica Acta, 2016Co-Authors: Preston R Mason, Robert F Jacob, Sandeep Shrivastava, Samuel C R Sherratt, Amitabha ChattopadhyayAbstract:Abstract Cholesterol crystalline Domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol Domain Formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol Domain Formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing Domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol Domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol Domain Formation were dose-dependent. In membranes with 1:1 C/P (predisposing Domain Formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol Domain Formation without affecting temperature-induced changes in–bilayer unit cell periodicity relative to controls (d-space; 57 A–55 A over 15–30 °C). Together, these data suggest simultaneous Formation of distinct cholesterol-rich ordered Domains and cholesterol-poor disordered Domains in the presence of DHA. By contrast, EPA had no effect on cholesterol Domain Formation and produced larger d-space values relative to controls (60 A–57 A; p
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eicosapentaenoic acid reduces membrane fluidity inhibits cholesterol Domain Formation and normalizes bilayer width in atherosclerotic like model membranes
Biochimica et Biophysica Acta, 2016Co-Authors: Preston R Mason, Robert F Jacob, Sandeep Shrivastava, Samuel C R Sherratt, Amitabha ChattopadhyayAbstract:Cholesterol crystalline Domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol Domain Formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol Domain Formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing Domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol Domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol Domain Formation were dose-dependent. In membranes with 1:1 C/P (predisposing Domain Formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol Domain Formation without affecting temperature-induced changes in–bilayer unit cell periodicity relative to controls (d-space; 57 A–55 A over 15–30 °C). Together, these data suggest simultaneous Formation of distinct cholesterol-rich ordered Domains and cholesterol-poor disordered Domains in the presence of DHA. By contrast, EPA had no effect on cholesterol Domain Formation and produced larger d-space values relative to controls (60 A–57 A; p < 0.05) over the same temperature range, suggesting a more uniform maintenance of lipid dynamics despite the presence of cholesterol. These data indicate that EPA and DHA had different effects on membrane bilayer width, membrane fluidity, and cholesterol crystalline Domain Formation; suggesting omega-3 fatty acids with differing chain length or unsaturation may differentially influence membrane lipid dynamics and structural organization as a result of distinct phospholipid/sterol interactions.
Walter Hofstetter - One of the best experts on this subject based on the ideXlab platform.
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magnetism and Domain Formation in su 3 symmetric multi species fermi mixtures
New Journal of Physics, 2011Co-Authors: Irakli Titvinidze, Antonio Privitera, S Y Chang, Sebastian Diehl, M A Baranov, Andrew J Daley, Walter HofstetterAbstract:We study the phase diagram of an SU(3)-symmetric mixture of three-component ultracold fermions with attractive interactions in an optical lattice, including the additional effect on the mixture of an effective three-body constraint induced by three-body losses. We address the properties of the system in D≥2 by using dynamical mean-field theory and variational Monte Carlo techniques. The phase diagram of the model shows a strong interplay between magnetism and superfluidity. In the absence of the three-body constraint (no losses), the system undergoes a phase transition from a color superfluid (c-SF) phase to a trionic phase, which shows additional particle density modulations at half-filling. Away from the particle–hole symmetric point the c-SF phase is always spontaneously magnetized, leading to the Formation of different c-SF Domains in systems where the total number of particles of each species is conserved. This can be seen as the SU(3) symmetric realization of a more general tendency for phase separation in three-component Fermi mixtures. The three-body constraint strongly disfavors the trionic phase, stabilizing a (fully magnetized) c-SF also at strong coupling. With increasing temperature we observe a transition to a non-magnetized SU(3) Fermi liquid phase.
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magnetism and Domain Formation in su 3 symmetric multi species fermi mixtures
arXiv: Quantum Gases, 2010Co-Authors: Irakli Titvinidze, Antonio Privitera, S Y Chang, Sebastian Diehl, M A Baranov, Andrew J Daley, Walter HofstetterAbstract:We study the phase diagram of an SU(3)-symmetric mixture of three-component ultracold fermions with attractive interactions in an optical lattice, including the additional effect on the mixture of an effective three-body constraint induced by three-body losses. We address the properties of the system in $D \geq 2$ by using dynamical mean-field theory and variational Monte Carlo techniques. The phase diagram of the model shows a strong interplay between magnetism and superfluidity. In the absence of the three-body constraint (no losses), the system undergoes a phase transition from a color superfluid phase to a trionic phase, which shows additional particle density modulations at half-filling. Away from the particle-hole symmetric point the color superfluid phase is always spontaneously magnetized, leading to the Formation of different color superfluid Domains in systems where the total number of particles of each species is conserved. This can be seen as the SU(3) symmetric realization of a more general tendency to phase-separation in three-component Fermi mixtures. The three-body constraint strongly disfavors the trionic phase, stabilizing a (fully magnetized) color superfluid also at strong coupling. With increasing temperature we observe a transition to a non-magnetized SU(3) Fermi liquid phase.
Dong Chen - One of the best experts on this subject based on the ideXlab platform.
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1 2 dipalmitoyl sn glycero 3 phosphocholine dppc rich Domain Formation in binary phospholipid vesicle membranes two dimensional nucleation and growth
Langmuir, 2014Co-Authors: Dong Chen, Maria M. SantoreAbstract:Decades of study have probed phase transitions in model phospholipid bilayers and vesicles, especially in the context of the equilibrium phase diagram. Critical to the response of vesicles to environmental triggers, to the ultimate Domain morphology, and to the approach to equilibrium (or not), we present here a study of Domain Formation in vesicles, focusing on a mechanism by which the cooling rate, tension, and composition affect the first appearance (nucleation) and subsequent growth of solid membrane Domains. Employing a popular mixed membrane model based on DOPC and DPPC (1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, respectively), we examined phase separation in giant two-component vesicles that were cooled from the one-phase fluid (Lα) region of the phase diagram into a region of fluid (Lα)–solid coexistence. At moderate and low membrane tensions, cooling produced solid DPPC-rich Domains appearing as compact patches or irregular hexagons and likely with a...
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1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-Rich Domain Formation in Binary Phospholipid Vesicle Membranes: Two-Dimensional Nucleation and Growth
2014Co-Authors: Dong Chen, Maria M. SantoreAbstract:Decades of study have probed phase transitions in model phospholipid bilayers and vesicles, especially in the context of the equilibrium phase diagram. Critical to the response of vesicles to environmental triggers, to the ultimate Domain morphology, and to the approach to equilibrium (or not), we present here a study of Domain Formation in vesicles, focusing on a mechanism by which the cooling rate, tension, and composition affect the first appearance (nucleation) and subsequent growth of solid membrane Domains. Employing a popular mixed membrane model based on DOPC and DPPC (1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, respectively), we examined phase separation in giant two-component vesicles that were cooled from the one-phase fluid (Lα) region of the phase diagram into a region of fluid (Lα)–solid coexistence. At moderate and low membrane tensions, cooling produced solid DPPC-rich Domains appearing as compact patches or irregular hexagons and likely with a Pβ′ (ripple) arrangement. (The compact solid Domains in this study differed distinctly from striped Domains in vesicles of the same composition, in terms of molecular organization and conditions of first appearance during cooling.) The amounts of these solid Domains were shown to adhere to the lever arm rule for a tie line on the phase diagram, with a solid composition near 95 mol % DPPC. The nucleation of the compact solid Domains occurred in a short period, followed by rapid addition of ordered molecules to the nucleated Domains, excluding tracer dye. The two-dimensional nucleation density of these compact solid Domains (in the range of 10–2–10–1 μm–2) was found to increase with the cooling rate (equivalent to the quench depth) with a greater than linear dependence. The 2-D nucleation density was also seen to decrease with membrane tension, presumably because membrane tension increases the line tension around a Domain that opposes nucleation. A sigmoidal dependence of the nucleation density on the DPPC concentration was also found. With cooling rates in excess of ∼1 °C/min, solid Domains persisted down to room temperature, likely passing from a preferred equilibrium to a local equilibrium with continued cooling. As a result of the persistence of the originally nucleated Domains and the conservation of DPPC in the membrane, we observed an increasingly greater number of smaller Domains with increased cooling rates. The Domains in these vesicles were compact or hexagonal-shaped in contrast to flower-shaped dendritic Domains in the same membrane system in a supported membrane configuration
Amitabha Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.
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eicosapentaenoic acid reduces membrane fluidity inhibits cholesterol Domain Formation and normalizes bilayer width in atherosclerotic like model membranes
Biochimica et Biophysica Acta, 2016Co-Authors: Preston R Mason, Robert F Jacob, Sandeep Shrivastava, Samuel C R Sherratt, Amitabha ChattopadhyayAbstract:Abstract Cholesterol crystalline Domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol Domain Formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol Domain Formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing Domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol Domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol Domain Formation were dose-dependent. In membranes with 1:1 C/P (predisposing Domain Formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol Domain Formation without affecting temperature-induced changes in–bilayer unit cell periodicity relative to controls (d-space; 57 A–55 A over 15–30 °C). Together, these data suggest simultaneous Formation of distinct cholesterol-rich ordered Domains and cholesterol-poor disordered Domains in the presence of DHA. By contrast, EPA had no effect on cholesterol Domain Formation and produced larger d-space values relative to controls (60 A–57 A; p
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eicosapentaenoic acid reduces membrane fluidity inhibits cholesterol Domain Formation and normalizes bilayer width in atherosclerotic like model membranes
Biochimica et Biophysica Acta, 2016Co-Authors: Preston R Mason, Robert F Jacob, Sandeep Shrivastava, Samuel C R Sherratt, Amitabha ChattopadhyayAbstract:Cholesterol crystalline Domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol Domain Formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol Domain Formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing Domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol Domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol Domain Formation were dose-dependent. In membranes with 1:1 C/P (predisposing Domain Formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol Domain Formation without affecting temperature-induced changes in–bilayer unit cell periodicity relative to controls (d-space; 57 A–55 A over 15–30 °C). Together, these data suggest simultaneous Formation of distinct cholesterol-rich ordered Domains and cholesterol-poor disordered Domains in the presence of DHA. By contrast, EPA had no effect on cholesterol Domain Formation and produced larger d-space values relative to controls (60 A–57 A; p < 0.05) over the same temperature range, suggesting a more uniform maintenance of lipid dynamics despite the presence of cholesterol. These data indicate that EPA and DHA had different effects on membrane bilayer width, membrane fluidity, and cholesterol crystalline Domain Formation; suggesting omega-3 fatty acids with differing chain length or unsaturation may differentially influence membrane lipid dynamics and structural organization as a result of distinct phospholipid/sterol interactions.