Molecular packing in sphingomyelin bilayers and sphingomyelin/phospholid mixtures

Byström, Tomas; Lindblom, Göran

doi:10.1016/s1386-1425(03)00014-3

Cited by 7 publications

(4 citation statements)

References 18 publications

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“…We incorporate this hypothesis into our model by adding to the free energy of the flat bilayer a bending energy. Because absolute values of the spontaneous curvatures of SM, PC, and PS are an order of magnitude smaller than that of PE (18,(31)(32)(33), we consider the curvature only of the latter and write the bending energy as…”

Section: Addition Of the Bending Energymentioning

confidence: 99%

How Cholesterol Could Be Drawn to the Cytoplasmic Leaf of the Plasma Membrane by Phosphatidylethanolamine

Giang

Schick

2014

Biophysical Journal

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In the mammalian plasma membrane, cholesterol can translocate rapidly between the exoplasmic and cytoplasmic leaves, so that its distribution between them should be given by the equality of its chemical potential in the leaves. Due to its favorable interaction with sphingomyelin, which is almost entirely in the outer leaf, one expects the great majority of cholesterol to be there also. Experimental results do not support this, implying that there is some mechanism attracting cholesterol to the inner leaf. We hypothesize that it is drawn there to reduce the bending free energy of the membrane caused by the presence of PE (phosphatidylethanolamine). It does this in two ways: first by simply diluting the amount of PE in the inner leaf, and second by ordering the tails of the PE to reduce its spontaneous curvature. Incorporating this mechanism into a model free energy for the bilayer, we find that between 50 and 60% of the total cholesterol should be in the inner leaf of human erythrocytes.

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Section: Addition Of the Bending Energymentioning

confidence: 99%

How Cholesterol Could Be Drawn to the Cytoplasmic Leaf of the Plasma Membrane by Phosphatidylethanolamine

Giang

Schick

2014

Biophysical Journal

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“…The mol fractions of these two lipids are~0.42 and 0.40 (18). The spontaneous curvature of these two lipids are similar, with that of SM being smaller than that of PC (32). Thus, it is not to be expected that fluctuation in their relative composition will couple strongly to fluctuations in bilayer curvature.…”

Section: Introductionmentioning

confidence: 99%

Model of a Raft in Both Leaves of an Asymmetric Lipid Bilayer

Shlomovitz

Schick

2013

Biophysical Journal

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We present a theory of inhomogeneities in the plasma membrane, or rafts, that can exist in both leaves of the plasma membrane. We note that although neither of the major phospholipid components of the outer leaf, sphingomyelin (SM) nor phosphatidylcholine (PC), evinces a tendency to form phases characterized by nonzero curvature, one of the major components of the inner leaf, phosphatidylethanolamine (PE), displays a strong tendency to do so whereas the other, phosphatidylserine (PS), does not. Therefore, we posit that the concentration difference of PS and PE couples to height fluctuations of the plasma membrane bilayer. This brings about a microemulsion in the inner leaf. Coupling of the concentration difference between PS and PE in the inner leaf and SM and PC in the outer leaf propagates the microemulsion to that leaf as well. The characteristic size of the inhomogeneities is equal to the square-root of the ratio of the bending modulus of the bilayer to its surface tension, a size which is ~100 nm for the plasma membrane. If the coupling between leaves were to be provided by the interchange of cholesterol, then our model raft would consist of SM and cholesterol in the outer leaf and PS and cholesterol in the inner leaf floating in a sea of PC and PE in both leaves.

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“…In the case of lipids with a cylindrical geometry, such as DOPC, POPC, and SM [29-31], l d -domains become sensitive to fluidization as compared to ordered domains, since partitioning of modifiers into the ld -domains seems to be impeded in the context of tightly packed lipids. This scenario is schematically illustrated in Fig .…”

Section: Resultsmentioning

confidence: 99%

Dipole Modifiers Regulate Lipid Lateral Heterogeneity in Model Membranes

Efimova¹,

Ostroumova²

2017

Acta Naturae

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In this study we report on experimental observations of giant unilamellar liposomes composed of ternary mixtures of cholesterol (Chol), phospholipids with relatively low Tmelt (DOPC, POPC, or DPoPC) and high Tmelt (sphingomyelin (SM), or tetramyristoyl cardiolipin (TMCL)) and their phase behaviors in the presence and absence of dipole modifiers. It was shown that the ratios of liposomes exhibiting noticeable phase separation decrease in the series POPC, DOPC, DPoPC regardless of any high-Tmelt lipid. Substitution of SM for TMCL led to increased lipid phase segregation. Taking into account the fact that the first and second cases corresponded to a reduction in the thickness of the lipid domains enriched in low- and high-Tmelt lipids, respectively, our findings indicate that the phase behavior depends on thickness mismatch between the ordered and disordered domains. The dipole modifiers, flavonoids and styrylpyridinium dyes, reduced the phase segregation of membranes composed of SM, Chol, and POPC (or DOPC). The other ternary lipid mixtures tested were not affected by the addition of dipole modifiers. It is suggested that dipole modifiers address the hydrophobic mismatch through fluidization of the ordered and disordered domains. The ability of a modifier to partition into the membrane and fluidize the domains was dictated by the hydrophobicity of modifier molecules, their geometric shape, and the packing density of domain-forming lipids. Phloretin, RH 421, and RH 237 proved the most potent among all the modifiers examined.

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Molecular packing in sphingomyelin bilayers and sphingomyelin/phospholid mixtures

Cited by 7 publications

References 18 publications

How Cholesterol Could Be Drawn to the Cytoplasmic Leaf of the Plasma Membrane by Phosphatidylethanolamine

How Cholesterol Could Be Drawn to the Cytoplasmic Leaf of the Plasma Membrane by Phosphatidylethanolamine

Model of a Raft in Both Leaves of an Asymmetric Lipid Bilayer

Dipole Modifiers Regulate Lipid Lateral Heterogeneity in Model Membranes

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