The Experts below are selected from a list of 10272 Experts worldwide ranked by ideXlab platform
Gerald W. Feigenson - One of the best experts on this subject based on the ideXlab platform.
-
lowering line tension with high cholesterol content induces a transition from macroscopic to nanoscopic phase domains in model biomembranes
Biochimica et Biophysica Acta, 2019Co-Authors: Wenchyan Tsai, Gerald W. FeigensonAbstract:Abstract Chemically simplified lipid mixtures are used here as models of the cell plasma membrane exoplasmic leaflet. In such models, phase separation and morphology transitions controlled by line tension in the liquid-disordered (Ld) + liquid-ordered (Lo) coexistence regime have been described [1]. Here, we study two four-component lipid mixtures at different cholesterol fractions: brain sphingomyelin (BSM) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). On giant unilamellar vesicles (GUVs) display a nanoscopic-to-macroscopic transition of Ld + Lo phase domains as POPC is replaced by DOPC, and this transition also depends on the cholesterol fraction. Line tension decreases with increasing cholesterol mole fractions in both lipid mixtures. For the ternary BSM/DOPC/Chol mixture, the published phase diagram [19] requires a modification to show that when cholesterol mole fraction is >~0.33, coexisting phase domains become nanoscopic.
-
FRET Detects the Size of Nanodomains for Coexisting Liquid-Disordered and Liquid-Ordered Phases.
Biophysical Journal, 2018Co-Authors: Thais A. Enoki, Frederick A. Heberle, Gerald W. FeigensonAbstract:Abstract Biomembranes with as few as three lipid components can form coexisting liquid-disordered (Ld) and liquid-ordered (Lo) phases. In the coexistence region of Ld and Lo phases, the lipid mixtures 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/chol or brain sphingomyelin (bSM)/DOPC/chol form micron-scale domains that are easily visualized with light microscopy. Although large domains are not observed in the mixtures DSPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/chol and bSM/POPC/chol, lateral heterogeneity is nevertheless detected using techniques with nanometer-scale spatial resolution. We propose a simple and accessible method to measure domain sizes below optical resolution (∼200 nm). We measured nanodomain size for the latter two mixtures by combining experimental Forster resonance energy transfer data with a Monte-Carlo-based analysis. We found a domain radius of 7.5−10 nm for DSPC/POPC/chol, similar to values obtained previously by neutron scattering, and ∼5 nm for bSM/POPC/chol, slightly smaller than measurable by neutron scattering. These analyses also detect the domain-size transition that is observed by fluorescence microscopy in the four-component lipid mixture bSM/DOPC/POPC/chol. Accurate measurements of fluorescent-probe partition coefficients are especially important for the analysis; therefore, we exploit three different methods to measure the partition coefficient of fluorescent molecules between Ld and Lo phases.
-
phase diagram of a 4 component lipid mixture dspc dopc POPC chol
Biochimica et Biophysica Acta, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Gerald W. FeigensonAbstract:Abstract We report the first 4-component phase diagram for the lipid bilayer mixture, DSPC/DOPC/POPC/chol (distearoylphosphatidylcholine/dioleoylphosphatidylcholine/1-palmitoyl, 2-oleoylphosphatidylcholine/cholesterol). This phase diagram, which has macroscopic Ld + Lo phase domains, clearly shows that all phase boundaries determined for the 3-component mixture containing DOPC transition smoothly into the boundaries for the 3-component mixture containing POPC, which has nanoscopic phase domains of Ld + Lo. Our studies start from two published ternary phase diagrams, and show how these can be combined into a quaternary phase diagram by study of a few hundred samples of intermediate compositions.
-
Phase diagram of a 4-component lipid mixture: DSPC/DOPC/POPC/chol.
Biochimica et biophysica acta, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Gerald W. FeigensonAbstract:Abstract We report the first 4-component phase diagram for the lipid bilayer mixture, DSPC/DOPC/POPC/chol (distearoylphosphatidylcholine/dioleoylphosphatidylcholine/1-palmitoyl, 2-oleoylphosphatidylcholine/cholesterol). This phase diagram, which has macroscopic Ld + Lo phase domains, clearly shows that all phase boundaries determined for the 3-component mixture containing DOPC transition smoothly into the boundaries for the 3-component mixture containing POPC, which has nanoscopic phase domains of Ld + Lo. Our studies start from two published ternary phase diagrams, and show how these can be combined into a quaternary phase diagram by study of a few hundred samples of intermediate compositions.
-
Toward a better raft model: modulated phases in the four-component bilayer, DSPC/DOPC/POPC/CHOL.
Biophysical journal, 2013Co-Authors: Shih Lin Goh, Jonathan J. Amazon, Gerald W. FeigensonAbstract:The liquid-liquid (Ld + Lo) coexistence region within a distearoyl-phosphatidylcholine/dioleoyl-phosphatidylcholine/palmitoyl-oleoyl-phosphatidylcholine/cholesterol (DSPC/DOPC/POPC/CHOL) mixture displays a nanoscopic-to-macroscopic transition of phase domains as POPC is replaced by DOPC. Previously, we showed that the transition goes through a modulated phase regime during this replacement, in which patterned liquid phase morphologies are observed on giant unilamellar vesicles (GUVs). Here, we describe a more detailed investigation of the modulated phase regime along two different thermodynamic tielines within the Ld + Lo region of this four-component mixture. Using fluorescence microscopy of GUVs, we found that the modulated phase regime occurs at relatively narrow DOPC/(DOPC+POPC) ratios. This modulated phase window shifts to higher values of DOPC/(DOPC+POPC) when CHOL concentration is increased, and coexisting phases become closer in properties. Monte Carlo simulations reproduced the patterns observed on GUVs, using a competing interactions model of line tension and curvature energies. Sufficiently low line tension and high bending moduli are required to generate stable modulated phases. Altogether, our studies indicate that by tuning the lipid composition, both the domain size and morphology can be altered drastically within a narrow composition space. This lends insight into a possible mechanism whereby cells can reorganize plasma membrane compartmentalization simply by tuning the local membrane composition or line tension.
Paulo F. Almeida - One of the best experts on this subject based on the ideXlab platform.
-
investigation of domain formation in sphingomyelin cholesterol POPC mixtures by fluorescence resonance energy transfer and monte carlo simulations
Biophysical Journal, 2007Co-Authors: Monica L. Frazier, Antje Pokorny, Jenny R. Wright, Paulo F. AlmeidaAbstract:We have recently proposed a phase diagram for mixtures of porcine brain sphingomyelin (BSM), cholesterol (Chol), and 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) on the basis of kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin. Although that study indicated the existence of domains, phase separations in the micrometer scale have not been observed by fluorescence microscopy in BSM/Chol/POPC mixtures, though they have for some other sphingomyelins (SM). Here we examine the same BSM/Chol/POPC system by a combination of fluorescence resonance energy transfer (FRET) and Monte Carlo simulations. The results clearly demonstrate that domains are formed in this system. Comparison of the FRET experimental data with the computer simulations allows the estimate of lipid-lipid interaction Gibbs energies between SM/Chol, SM/POPC, and Chol/POPC. The latter two interactions are weakly repulsive, but the interaction between SM and Chol is favorable. Furthermore, those three unlike lipid interaction parameters between the three possible lipid pairs are sufficient for the existence of a closed loop in the ternary phase diagram, without the need to involve multibody interactions. The calculations also indicate that the largest POPC domains contain several thousand lipids, corresponding to linear sizes of the order of a few hundred nanometers.
-
Investigation of domain formation in sphingomyelin/cholesterol/POPC mixtures by fluorescence resonance energy transfer and monte carlo simulations
Biophysical journal, 2007Co-Authors: Monica L. Frazier, Antje Pokorny, Jenny R. Wright, Paulo F. AlmeidaAbstract:We have recently proposed a phase diagram for mixtures of porcine brain sphingomyelin (BSM), cholesterol (Chol), and 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) on the basis of kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin. Although that study indicated the existence of domains, phase separations in the micrometer scale have not been observed by fluorescence microscopy in BSM/Chol/POPC mixtures, though they have for some other sphingomyelins (SM). Here we examine the same BSM/Chol/POPC system by a combination of fluorescence resonance energy transfer (FRET) and Monte Carlo simulations. The results clearly demonstrate that domains are formed in this system. Comparison of the FRET experimental data with the computer simulations allows the estimate of lipid-lipid interaction Gibbs energies between SM/Chol, SM/POPC, and Chol/POPC. The latter two interactions are weakly repulsive, but the interaction between SM and Chol is favorable. Furthermore, those three unlike lipid interaction parameters between the three possible lipid pairs are sufficient for the existence of a closed loop in the ternary phase diagram, without the need to involve multibody interactions. The calculations also indicate that the largest POPC domains contain several thousand lipids, corresponding to linear sizes of the order of a few hundred nanometers.
-
temperature and composition dependence of the interaction of δ lysin with ternary mixtures of sphingomyelin cholesterol POPC
Biophysical Journal, 2006Co-Authors: Antje Pokorny, Lindsay E. Yandek, Adekunle Elegbede, Anne Hinderliter, Paulo F. AlmeidaAbstract:The kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin from vesicles of porcine brain sphingomyelin (BSM), 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and cholesterol (Chol) were investigated as a function of temperature and composition. Sphingomyelin (SM)/Chol mixtures form a liquid-ordered (Lo) phase whereas POPC exists in the liquid-disordered (Ld) phase at ambient temperature. δ-Lysin binds strongly to Ld and poorly to Lo phase. In BSM/Chol/POPC vesicles the rate of carboxyfluorescein efflux induced by δ-lysin increases as the POPC content decreases. This is explained by the increase of δ-lysin concentration in Ld domains, which enhances membrane perturbation by the peptide. Phase separations in the micrometer scale have been observed by fluorescence microscopy in SM/Chol/POPC mixtures for some SM, though not for BSM. Thus, δ-lysin must detect heterogeneities (domains) in BSM/Chol/POPC on a much smaller scale. Advantage was taken of the inverse variation of the efflux rate with the Ld content of BSM/Chol/POPC vesicles to estimate the Ld fraction in those mixtures. These results were combined with differential scanning calorimetry to obtain the BSM/Chol/POPC phase diagram as a function of temperature.
-
Temperature and Composition Dependence of the Interaction of δ-Lysin with Ternary Mixtures of Sphingomyelin/Cholesterol/POPC
Biophysical journal, 2006Co-Authors: Antje Pokorny, Lindsay E. Yandek, Adekunle Elegbede, Anne Hinderliter, Paulo F. AlmeidaAbstract:The kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin from vesicles of porcine brain sphingomyelin (BSM), 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and cholesterol (Chol) were investigated as a function of temperature and composition. Sphingomyelin (SM)/Chol mixtures form a liquid-ordered (Lo) phase whereas POPC exists in the liquid-disordered (Ld) phase at ambient temperature. δ-Lysin binds strongly to Ld and poorly to Lo phase. In BSM/Chol/POPC vesicles the rate of carboxyfluorescein efflux induced by δ-lysin increases as the POPC content decreases. This is explained by the increase of δ-lysin concentration in Ld domains, which enhances membrane perturbation by the peptide. Phase separations in the micrometer scale have been observed by fluorescence microscopy in SM/Chol/POPC mixtures for some SM, though not for BSM. Thus, δ-lysin must detect heterogeneities (domains) in BSM/Chol/POPC on a much smaller scale. Advantage was taken of the inverse variation of the efflux rate with the Ld content of BSM/Chol/POPC vesicles to estimate the Ld fraction in those mixtures. These results were combined with differential scanning calorimetry to obtain the BSM/Chol/POPC phase diagram as a function of temperature.
Antje Pokorny - One of the best experts on this subject based on the ideXlab platform.
-
investigation of domain formation in sphingomyelin cholesterol POPC mixtures by fluorescence resonance energy transfer and monte carlo simulations
Biophysical Journal, 2007Co-Authors: Monica L. Frazier, Antje Pokorny, Jenny R. Wright, Paulo F. AlmeidaAbstract:We have recently proposed a phase diagram for mixtures of porcine brain sphingomyelin (BSM), cholesterol (Chol), and 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) on the basis of kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin. Although that study indicated the existence of domains, phase separations in the micrometer scale have not been observed by fluorescence microscopy in BSM/Chol/POPC mixtures, though they have for some other sphingomyelins (SM). Here we examine the same BSM/Chol/POPC system by a combination of fluorescence resonance energy transfer (FRET) and Monte Carlo simulations. The results clearly demonstrate that domains are formed in this system. Comparison of the FRET experimental data with the computer simulations allows the estimate of lipid-lipid interaction Gibbs energies between SM/Chol, SM/POPC, and Chol/POPC. The latter two interactions are weakly repulsive, but the interaction between SM and Chol is favorable. Furthermore, those three unlike lipid interaction parameters between the three possible lipid pairs are sufficient for the existence of a closed loop in the ternary phase diagram, without the need to involve multibody interactions. The calculations also indicate that the largest POPC domains contain several thousand lipids, corresponding to linear sizes of the order of a few hundred nanometers.
-
Investigation of domain formation in sphingomyelin/cholesterol/POPC mixtures by fluorescence resonance energy transfer and monte carlo simulations
Biophysical journal, 2007Co-Authors: Monica L. Frazier, Antje Pokorny, Jenny R. Wright, Paulo F. AlmeidaAbstract:We have recently proposed a phase diagram for mixtures of porcine brain sphingomyelin (BSM), cholesterol (Chol), and 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) on the basis of kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin. Although that study indicated the existence of domains, phase separations in the micrometer scale have not been observed by fluorescence microscopy in BSM/Chol/POPC mixtures, though they have for some other sphingomyelins (SM). Here we examine the same BSM/Chol/POPC system by a combination of fluorescence resonance energy transfer (FRET) and Monte Carlo simulations. The results clearly demonstrate that domains are formed in this system. Comparison of the FRET experimental data with the computer simulations allows the estimate of lipid-lipid interaction Gibbs energies between SM/Chol, SM/POPC, and Chol/POPC. The latter two interactions are weakly repulsive, but the interaction between SM and Chol is favorable. Furthermore, those three unlike lipid interaction parameters between the three possible lipid pairs are sufficient for the existence of a closed loop in the ternary phase diagram, without the need to involve multibody interactions. The calculations also indicate that the largest POPC domains contain several thousand lipids, corresponding to linear sizes of the order of a few hundred nanometers.
-
temperature and composition dependence of the interaction of δ lysin with ternary mixtures of sphingomyelin cholesterol POPC
Biophysical Journal, 2006Co-Authors: Antje Pokorny, Lindsay E. Yandek, Adekunle Elegbede, Anne Hinderliter, Paulo F. AlmeidaAbstract:The kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin from vesicles of porcine brain sphingomyelin (BSM), 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and cholesterol (Chol) were investigated as a function of temperature and composition. Sphingomyelin (SM)/Chol mixtures form a liquid-ordered (Lo) phase whereas POPC exists in the liquid-disordered (Ld) phase at ambient temperature. δ-Lysin binds strongly to Ld and poorly to Lo phase. In BSM/Chol/POPC vesicles the rate of carboxyfluorescein efflux induced by δ-lysin increases as the POPC content decreases. This is explained by the increase of δ-lysin concentration in Ld domains, which enhances membrane perturbation by the peptide. Phase separations in the micrometer scale have been observed by fluorescence microscopy in SM/Chol/POPC mixtures for some SM, though not for BSM. Thus, δ-lysin must detect heterogeneities (domains) in BSM/Chol/POPC on a much smaller scale. Advantage was taken of the inverse variation of the efflux rate with the Ld content of BSM/Chol/POPC vesicles to estimate the Ld fraction in those mixtures. These results were combined with differential scanning calorimetry to obtain the BSM/Chol/POPC phase diagram as a function of temperature.
-
Temperature and Composition Dependence of the Interaction of δ-Lysin with Ternary Mixtures of Sphingomyelin/Cholesterol/POPC
Biophysical journal, 2006Co-Authors: Antje Pokorny, Lindsay E. Yandek, Adekunle Elegbede, Anne Hinderliter, Paulo F. AlmeidaAbstract:The kinetics of carboxyfluorescein efflux induced by the amphipathic peptide δ-lysin from vesicles of porcine brain sphingomyelin (BSM), 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and cholesterol (Chol) were investigated as a function of temperature and composition. Sphingomyelin (SM)/Chol mixtures form a liquid-ordered (Lo) phase whereas POPC exists in the liquid-disordered (Ld) phase at ambient temperature. δ-Lysin binds strongly to Ld and poorly to Lo phase. In BSM/Chol/POPC vesicles the rate of carboxyfluorescein efflux induced by δ-lysin increases as the POPC content decreases. This is explained by the increase of δ-lysin concentration in Ld domains, which enhances membrane perturbation by the peptide. Phase separations in the micrometer scale have been observed by fluorescence microscopy in SM/Chol/POPC mixtures for some SM, though not for BSM. Thus, δ-lysin must detect heterogeneities (domains) in BSM/Chol/POPC on a much smaller scale. Advantage was taken of the inverse variation of the efflux rate with the Ld content of BSM/Chol/POPC vesicles to estimate the Ld fraction in those mixtures. These results were combined with differential scanning calorimetry to obtain the BSM/Chol/POPC phase diagram as a function of temperature.
Jenifer Thewalt - One of the best experts on this subject based on the ideXlab platform.
-
Phase Coexistence in Ternary Lipid Mixtures Containing POPC and Phytosterols, Ergosterol or 7-Dehydrocholesterol
Biophysical Journal, 2014Co-Authors: Mehran Shaghaghi, Martin J Zuckermann, Ya-wei Hsueh, Ming-yen Kuo, Jenifer ThewaltAbstract:2H-NMR spectroscopy was used to investigate the occurrence of phase coexistence in multilamellar vesicles of DPPC and POPC (33mol%: 33mol%) with either stigmasterol, brassicasterol, ergosterol or 7-DHC (each 33mol%). In all cases, the sn-1 chains of DPPC and POPC were deuterated in turn, and 2H-NMR spectra were measured for both lipid components as a function of temperature between 5 oC and 48 oC. The chain order of DPPC was found to be greater than that of POPC in all the above mixtures. An equimolar DPPC/POPC membrane exhibits a clear solid-ordered (so)-liquid disordered (ld) transition between 5 oC and about 33 oC as observed for each lipid by a fairly steep reduction in the average spectral width. Adding sterol generally results in a more gradual change in average spectral width over this temperature range. Depending on the particular sterol, NMR spectra taken in this temperature range either appeared poorly resolved (“blurry”) or displayed coexisting liquid ordered (lo) and ld spectra. Liquid-liquid phase coexistence is observed in DPPC/POPC/ergosterol mixtures. The spectra for DPPC/POPC/ brassicasterol only exhibited liquid-liquid coexistence when a small concentration (0.02 mol%) of the fluorescent lipid dye TR-DHPE was added to the system. Only one liquid phase was observed for either DPPC/POPC/7DHC or DPPC/POPC/stigmasterol. In summary, our interest was to study how liquid phase coexistence in DPPC/POPC/sterol is modified by small changes in the sterol structure. These studies show that ergosterol is the most effective sterol in fostering phase coexistence. Note that in comparison to cholesterol, which does not cause micron scale phase coexistence in DPPC/POPC, ergosterol has an extra double in the fused ring, as well as a double bond at C22. Possible connections between the detailed sterol structures and these observations will be discussed.
-
A 2h-nmr Study Of POPC/sterol Membranes: Some Exciting Anomalies
Biophysical Journal, 2009Co-Authors: Mehran Shaghaghi, Martin J Zuckermann, Jenifer ThewaltAbstract:In a recent article [1], Y-W Hsueh et al showed that the 2H-NMR order parameter, M1, of 1-[2H31]palmitoyl, 2-oleoyl, sn-glycero-3-phosphocholine (POPC)/ergosterol multi-bilayers at 25oC increased linearly as a function of ergosterol concentration to 25 mol%, but did not increase further when more ergosterol was added. By contrast, M1 for POPC/cholesterol bilayers increases linearly to at least 50% sterol. Now the structural difference between cholesterol and ergosterol is that ergosterol has an additional double bond in its fused ring (C7-8) and a trans double bond (C22-23) plus a methyl group (at C24) in its alkyl chain. The question then arises as to which of these structural changes is responsible for the observed saturation of the order parameter in POPC/ergosterol bilayers. In [1] it was shown that the M1 of POPC/7-dehydrocholesterol (7-DHC) multilayers behaves similarly to that of POPC/cholesterol, increasing linearly with [7-DHC]. Note that 7-DHC has an ergosterol fused ring structure but a cholesterol alkyl tail. To further explore this phenomenon, we determined the sterol concentration dependence of POPC containing brassicasterol, a phytosterol that has the same fused ring structure as cholesterol with the alkyl tail of ergosterol [2]. We found that POPC/brassicasterol bilayers exhibit the same saturation behavior in M1 at 25oC as POPC/ergosterol bilayers, but at a lower value of M1. We are in the process of examining POPC-campesterol bilayers to evaluate the role of the C22-23 trans double bond in the saturation effect. Other sterols are also being investigated in order to understand the sensitivity of POPC/sterol membranes to the sterol's alkyl tail structure.[1] Y-W Hsueh et al., (2007) Biophys. J. 92:1606-1615.[2] We are most grateful to Till Boecking for suggesting brassicasterol for this study.
-
Ergosterol in POPC Membranes: Physical Properties and Comparison with Structurally Similar Sterols
Biophysical journal, 2006Co-Authors: Ya-wei Hsueh, Martin J Zuckermann, Mei-ting Chen, Philipus J. Patty, Christian Code, John T.j. Cheng, Barbara J. Frisken, Jenifer ThewaltAbstract:The physical properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/ergosterol bilayers in the liquid-crystalline phase were determined using deuterium nuclear magnetic resonance (2H NMR) and vesicle extrusion. For the 2H NMR experiments, the sn-1 chain of POPC was perdeuterated, and spectra were taken as a function of ergosterol concentration and temperature. Analysis of the liquid-crystalline spectra provides clear evidence that two types of liquid-crystalline domains, neither of which is a liquid-ordered phase, having distinct average chain conformations coexist in 80:20 and 75:25 POPC/ergosterol membranes over a wide temperature range (from −2 to at least 31°C). Adding ergosterol to a concentration of 25 mol % increases POPC-d31 chain ordering as measured by the NMR spectral first moment M1 and also increases the membrane lysis tension, obtained from vesicle extrusion. Further addition of ergosterol had no effect on either chain order or lysis tension. This behavior is in marked contrast to the effect of cholesterol on POPC membranes: POPC/cholesterol membranes have a linear dependence of chain order on sterol concentration to at least 40 mol %. To investigate further we compared the dependence on sterol structure and concentration of the NMR spectra and lysis tension for several POPC/sterol membranes at 25°C. For all POPC/sterol membranes investigated in this study, we observed a universal linear relation between lysis tension and M1. This suggests that changes in acyl chain ordering directly affect the tensile properties of the membrane.
Tatyana M. Konyakhina - One of the best experts on this subject based on the ideXlab platform.
-
phase diagram of a 4 component lipid mixture dspc dopc POPC chol
Biochimica et Biophysica Acta, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Gerald W. FeigensonAbstract:Abstract We report the first 4-component phase diagram for the lipid bilayer mixture, DSPC/DOPC/POPC/chol (distearoylphosphatidylcholine/dioleoylphosphatidylcholine/1-palmitoyl, 2-oleoylphosphatidylcholine/cholesterol). This phase diagram, which has macroscopic Ld + Lo phase domains, clearly shows that all phase boundaries determined for the 3-component mixture containing DOPC transition smoothly into the boundaries for the 3-component mixture containing POPC, which has nanoscopic phase domains of Ld + Lo. Our studies start from two published ternary phase diagrams, and show how these can be combined into a quaternary phase diagram by study of a few hundred samples of intermediate compositions.
-
Phase diagram of a 4-component lipid mixture: DSPC/DOPC/POPC/chol.
Biochimica et biophysica acta, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Gerald W. FeigensonAbstract:Abstract We report the first 4-component phase diagram for the lipid bilayer mixture, DSPC/DOPC/POPC/chol (distearoylphosphatidylcholine/dioleoylphosphatidylcholine/1-palmitoyl, 2-oleoylphosphatidylcholine/cholesterol). This phase diagram, which has macroscopic Ld + Lo phase domains, clearly shows that all phase boundaries determined for the 3-component mixture containing DOPC transition smoothly into the boundaries for the 3-component mixture containing POPC, which has nanoscopic phase domains of Ld + Lo. Our studies start from two published ternary phase diagrams, and show how these can be combined into a quaternary phase diagram by study of a few hundred samples of intermediate compositions.
-
four component phase diagrams for dspc dopc POPC chol and dspc dopc sopc chol bilayer mixtures
Biophysical Journal, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Thomas Torng, Gerald W. FeigensonAbstract:We report the phase diagram for the four-component DSPC/DOPC/POPC/Chol mixture and compare it to our recent findings for the DSPC/DOPC/SOPC/Chol mixture. Four-component mixtures allow exploring the transition from macroscopic-to-nanoscopic domains. We have found modulated phase morphology in a particular region of composition within the liquid-ordered (Lo) and liquid-disordered (Ld) coexistence region in DSPC/DOPC/POPC/Chol and DSPC/DOPC/SOPC/Chol mixtures. Overall, we conclude the following: (1) Phase diagrams are very similar with shifts observed in phase boundaries; (2) Comparing the phase behavior of the two mixtures, the striking difference is in the compositional location where modulated phases are seen: the SOPC-containing mixture requires much higher DOPC concentration to form modulated phases. This observation is consistent with lower line tension in the SOPC-containing mixtures as compared to the POPC-containing mixtures; (3) By controlling lipid composition, we observe distinct types of modulated liquid-liquid phase morphologies, including linear, irregular, and angular features in GUVs. These studies show that both the size and morphology of membrane rafts are controlled by the mixture composition and the type of low-melting lipid in mixtures with high-melting lipid and cholesterol.View Large Image | View Hi-Res Image | Download PowerPoint Slide
-
Four-Component Phase Diagrams for DSPC/DOPC/POPC/CHOL and DSPC/DOPC/SOPC/CHOL Bilayer Mixtures
Biophysical Journal, 2013Co-Authors: Tatyana M. Konyakhina, Frederick A. Heberle, James D. Mastroianni, Thomas Torng, Gerald W. FeigensonAbstract:We report the phase diagram for the four-component DSPC/DOPC/POPC/Chol mixture and compare it to our recent findings for the DSPC/DOPC/SOPC/Chol mixture. Four-component mixtures allow exploring the transition from macroscopic-to-nanoscopic domains. We have found modulated phase morphology in a particular region of composition within the liquid-ordered (Lo) and liquid-disordered (Ld) coexistence region in DSPC/DOPC/POPC/Chol and DSPC/DOPC/SOPC/Chol mixtures. Overall, we conclude the following: (1) Phase diagrams are very similar with shifts observed in phase boundaries; (2) Comparing the phase behavior of the two mixtures, the striking difference is in the compositional location where modulated phases are seen: the SOPC-containing mixture requires much higher DOPC concentration to form modulated phases. This observation is consistent with lower line tension in the SOPC-containing mixtures as compared to the POPC-containing mixtures; (3) By controlling lipid composition, we observe distinct types of modulated liquid-liquid phase morphologies, including linear, irregular, and angular features in GUVs. These studies show that both the size and morphology of membrane rafts are controlled by the mixture composition and the type of low-melting lipid in mixtures with high-melting lipid and cholesterol.View Large Image | View Hi-Res Image | Download PowerPoint Slide
-
The Phase Diagram for the Four-Component DSPC/DOPC/POPC/CHOL Mixture
Biophysical Journal, 2012Co-Authors: Tatyana M. Konyakhina, James D. Mastroianni, Gerald W. FeigensonAbstract:When liquid-ordered (Lo) and liquid-disordered (Ld) phases coexist in mixtures of DSPC/DOPC/Chol, phase domains appear as large round domains in giant unilamellar vesicles (GUVs) examined by fluorescence microscopy. However, when liquid-ordered and liquid-disordered phases coexist in DSPC/POPC/Chol mixtures, domain size is too small to be detected by fluorescence microscopy. The phase diagram of the four-component DSPC/DOPC/POPC/Chol mixture allows for the exploration of the transition from macroscopic-to-nanoscopic domains. We have found complex shapes (modulated phase morphology) in a particular region of composition within the liquid-ordered and liquid-disordered coexistence region in DSPC/DOPC/POPC/Chol mixtures. By controlling lipid composition, we see distinct types of modulated liquid-liquid phase morphologies, including linear, irregular, and angular features in GUVs. These studies show that both the size and morphology of membrane rafts can be controlled by adjusting the composition and the type of low-melting lipid in mixtures with high-melting lipid and cholesterol.
