Critical Fluctuations in Plasma Membrane Vesicles

Veatch, Sarah L.; Cicuta, Pietro; Sengupta, Prabuddha; Honerkamp‐Smith, Aurelia R.; Holowka, David; Baird, Barbara

doi:10.1021/cb800012x

Cited by 452 publications

(564 citation statements)

References 35 publications

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“…S5A), the vesicles probably contain pre-existing nanoscopic domains in a microscopically uniform phase as previously suggested by Baumgart et al and others (25,42). Indeed, recent reports propose that GPMVs have a composition close to a critical point at which a decrease in temperature coalesces pre-existing nano-domains into a microscopic phase (43).…”

Section: Analysis Of Phase Separation In Plasma Membranessupporting

confidence: 72%

Order of lipid phases in model and plasma membranes

Kaiser

Lingwood

Levental

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

425

396

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Lipid rafts are nanoscopic assemblies of sphingolipids, cholesterol, and specific membrane proteins that contribute to lateral heterogeneity in eukaryotic membranes. Separation of artificial membranes into liquid-ordered (Lo) and liquid-disordered phases is regarded as a common model for this compartmentalization. However, tight lipid packing in Lo phases seems to conflict with efficient partitioning of raft-associated transmembrane (TM) proteins. To assess membrane order as a component of raft organization, we performed fluorescence spectroscopy and microscopy with the membrane probes Laurdan and C-laurdan. First, we assessed lipid packing in model membranes of various compositions and found cholesterol and acyl chain dependence of membrane order. Then we probed cell membranes by using two novel systems that exhibit inducible phase separation: giant plasma membrane vesicles [Baumgart et al. (2007) Proc Natl Acad Sci USA 104:3165-3170] and plasma membrane spheres. Notably, only the latter support selective inclusion of raft TM proteins with the ganglioside GM1 into one phase. We measured comparable small differences in order between the separated phases of both biomembranes. Lateral packing in the ordered phase of giant plasma membrane vesicles resembled the Lo domain of model membranes, whereas the GM1 phase in plasma membrane spheres exhibited considerably lower order, consistent with different partitioning of lipid and TM protein markers. Thus, lipid-mediated coalescence of the GM1 raft domain seems to be distinct from the formation of a Lo phase, suggesting additional interactions between proteins and lipids to be effective.generalized polarization value ͉ giant unilamellar vesicle ͉ membrane organization ͉ lipid sorting ͉ lipid raft T he lipid raft hypothesis postulates that selective interactions among sphingolipids, cholesterol, and membrane proteins contribute to lateral membrane heterogeneity (1). A tenet of the model is that small, dynamic cholesterol-sphingolipid-enriched assemblies can be induced to coalesce into larger, more stable structures through clustering of domain components (2). Although experimental data support cholesterol-dependent nano-scale membrane heterogeneity (3-8) and selective domain formation upon raft cross-linking (9-12), the mechanisms that govern such associations in cell membranes remain unclear.On the molecular level, a key feature that is thought to contribute to raft assembly is the propensity of cholesterol to pack tightly with saturated acyl chains of lipids causing them to adopt an extended conformation (13,14). In multi-component model membranes (n Ͼ 2), this interaction can lead to microscopically separate fluid membrane phases: the liquid-ordered (Lo) phase, enriched in saturated (sphingo-)lipids and cholesterol in a highly condensed state, and the liquid-disordered (Ld) phase, enriched in unsaturated glycerophospholipid in a disordered state (15)(16)(17).Several features of the Lo phase in model membranes correspond to the predicted properties of lipid rafts in cel...

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Section: Analysis Of Phase Separation In Plasma Membranessupporting

confidence: 72%

Order of lipid phases in model and plasma membranes

Kaiser

Lingwood

Levental

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

425

396

View full text Add to dashboard Cite

show abstract

“…Some researchers claim that the biomembrane is a 2D near-critical fluid mixture. [14][15][16] The influence of the near-criticality on the relaxation of the concentration fluctuation has been studied theoretically [17][18][19][20] and experimentally. 21) The author was recently involved in calculating the drag coefficient of a rigid spherical particle in a 3D near-critical binary fluid mixture, which is not very close to the critical point and is in the homogeneous phase far from the particle.…”

Section: Introductionmentioning

confidence: 99%

Drag Coefficient of a Raftlike Domain Embedded in a Fluid Membrane Being a Near-Critical Binary Mixture

Fujitani

2013

J. Phys. Soc. Jpn.

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We consider a circular liquid domain in a flat fluid membrane surrounded by three-dimensional fluids, and assume that the membrane outside the domain is a two-dimensional near-critical binary fluid mixture. The membrane viscosity outside the domain is assumed to be uniform, irrespective of the local composition, and to be the same as that of the domain. Using the Gaussian free-energy functional, we show that the drag coefficient of the domain can be decreased by the preferential attraction between the domain and a component of the mixture, unlike that of a rigid sphere in a three-dimensional near-critical binary fluid mixture studied recently.

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“…[1][2][3] Using an artificial multicomponent membrane with a vesicle shape of several microns in size, i.e., as large as a typical cell, some experimentalists studied the line tension below the critical point and the concentration fluctuation above it. 4) They suggested that the critical concentration fluctuation be involved with the raft formation; 5) a larger correlation length near the critical point could explain the restricted raft size in the biomembrane. Concentration fluctuation also influences the deuterium nuclear magnetic relaxation.…”

Section: Introductionmentioning

confidence: 99%

“…3, while our calculation procedure and results are shown in Sect. 4. Its last subsection gives numerical results and discussion on them.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Effect on Concentration Fluctuation in a Two-Component Fluid Membrane with a Spherical Shape

Fujitani

2013

J. Phys. Soc. Jpn.

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To the Gaussian model of a two-component fluid membrane with a spherical shape, we apply the mode coupling theory to study the hydrodynamic effect on the relaxation coefficient of concentration fluctuation in the homogeneous phase close to the critical point. In particular, when the viscosities of the three-dimensional fluids are the same inside and outside the vesicle, we obtain a concise analytical expression representing the hydrodynamic effect on the smallest wave-number mode. We derive its approximate expressions in various parameter regions to discuss the size effect of the vesicle. Much larger wave-number modes are studied numerically by means of our theoretical result. It is suggested that the hydrodynamic effect be diffusion-like, irrespective of the vesicle size, as long as the wavelength is much longer than the correlation length.

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Critical Fluctuations in Plasma Membrane Vesicles

Cited by 452 publications

References 35 publications

Order of lipid phases in model and plasma membranes

Order of lipid phases in model and plasma membranes

Drag Coefficient of a Raftlike Domain Embedded in a Fluid Membrane Being a Near-Critical Binary Mixture

Hydrodynamic Effect on Concentration Fluctuation in a Two-Component Fluid Membrane with a Spherical Shape

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