Membrane bending energy and shape determination of phospholipid vesicles and red blood cells

Svetina, S.; Žekš, B.

doi:10.1007/bf00257107

Cited by 350 publications

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“…Its phase diagram, now explored in considerable detail, comprises a broad spectrum of shapes such as stomatocytes, discocytes, dumbbells, pears, torocytes, starfish, rackets, etc. (2)(3)(4)(5). A large majority of the predicted shapes has been observed experimentally (6), and some of them correspond very closely to the different normal and abnormal forms of a mammalian erythrocyte, a simple anucleate eukaryotic cell.…”

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“…Another parameter that codefines vesicle shapes is the difference between the areas of the outer and inner monolayers, which is given by ⌬A ϭ h Ͷ (C 1 ϩ C 2 )dA; here, h is the separation of the monolayers' neutral surfaces. Minimizing the bending energy at a fixed vesicle area, volume, and ⌬A gives the complete set of possible stationary shapes of a free vesicle (2,3); the stability of each shape also depends on its nonlocal bending energy, corresponding to the relative stretching of lipid monolayers and conventionally written as k r (⌬A Ϫ ⌬A 0 ) 2 /2h 2 A 0 , where k r is the nonlocal bending constant [2k c to 3k c in vesicles (24) as well as in erythrocytes (23)], A 0 is the vesicle area, and ⌬A 0 is the relaxed monolayer area difference of a free vesicle (25). The bending energy and the nonlocal bending energy together constitute the area-difference-elasticity (ADE) model (25,26), and the set of stable shapes predicted by this model is controlled by the ratio of the two bending constants, k r /k c .…”

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confidence: 99%

“…¶ In this introductory study of nonaxisymmetric vesicle aggregates, we would like to identify the main qualitative features of the possible morphologies. To this end, we focus on two limiting cases of the ADE model and analyze (i) shapes characterized by a given area, volume, and ⌬A, which correspond to the bilayercouple model (2), and (ii) shapes with unconstrained ⌬A. Within this framework, the energy of a doublet is a sum of the vesicles' bending energies, W b,1 and W b,2 , and the adhesion energy assumed to be proportional to the contact area A c ,…”

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confidence: 99%

“…We first have concentrated on vesicles of a reduced volume of v ϭ 0.6 and ⌬a ϭ 1.04. These values of the parameters correspond to the discocyte shape of a normal human erythrocyte (2,32). If ␥ is small but larger than the threshold for adhesion at a flat substrate (8,9), the contact zone is planar and circular as if each of the vesicles would stick to a wall (10), the shapes of the two vesicles are the same, and the doublet thus belongs to the C ϱh symmetry class.…”

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Flat and sigmoidally curved contact zones in vesicle–vesicle adhesion

Ziherl

Svetina

2007

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

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Using the membrane-bending elasticity theory and a simple effective model of adhesion, we study the morphology of lipid vesicle doublets. In the weak adhesion regime, we find flat-contact axisymmetric doublets, whereas at large adhesion strengths, the vesicle aggregates are nonaxisymmetric and characterized by a sigmoidally curved, S-shaped contact zone with a single invagination and a complementary evagination on each vesicle. The sigmoid-contact doublets agree very well with the experimentally observed shapes of erythrocyte aggregates. Our results show that in identical vesicles with large to moderate surface-to-volume ratio, the sigmoid-contact shape is the only bound morphology. We also discuss the role of sigmoid contacts in the formation of multicellular aggregates such as erythrocyte rouleaux.lipid vesicle ͉ vesicle doublet ͉ sigmoid-contact doublet ͉ rouleau E lastic theory of shapes of phospholipid vesicles (1) is a very successful model. Its phase diagram, now explored in considerable detail, comprises a broad spectrum of shapes such as stomatocytes, discocytes, dumbbells, pears, torocytes, starfish, rackets, etc. (2-5). A large majority of the predicted shapes has been observed experimentally (6), and some of them correspond very closely to the different normal and abnormal forms of a mammalian erythrocyte, a simple anucleate eukaryotic cell. If the theory is extended to include the shear elasticity of the membrane skeleton, the agreement between the calculated and the actual shapes is truly striking, even in very deformed erythrocytes such as echinocytes (7).These results give hope that the approach can be extended to describe not only single vesicles but also their aggregates. With some exceptions, theoretical studies of aggregates rely on the simplest model of the intermembrane attraction where the adhesion energy is proportional to the contact area (8-10). In the first analyses of erythrocyte doublets and rouleaux, the contact zone was assumed to be flat (10-12), but at large adhesion strengths, this hypothesis was found to disagree with experiments (10); so far no explanation of the observed shapes has been available.Here we fill this gap by studying vesicle-vesicle adhesion within a fully numerical model free of all symmetry constraints, and we focus on vesicle doublets as the most elementary aggregates. Our central result is a doublet morphology with a sigmoid shape of the contact zone, which closely reproduces the large-scale features of erythrocyte doublets (10-16). In vesicles of volume and area of a human erythrocyte, this doublet is the stable shape at large enough adhesion strengths, whereas immediately beyond the aggregation threshold, a flat-contact doublet is found. We show that with increasing surface-to-volume ratio, the range of adhesion strengths corresponding to the flat-contact doublet should diminish and eventually vanish, leaving the sigmoid-contact doublet as the only stable bound morphology. These findings also provide an insight into the mechanics of aggregates of more than ...

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Flat and sigmoidally curved contact zones in vesicle–vesicle adhesion

Ziherl

Svetina

2007

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

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“…The fact that vesicle shapes, that are compositions of spheres, may have only two different radii is taken into account [25].…”

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Budding of giant unilamellar vesicles induced by an amphitropic protein β2-glycoprotein I

Kovačič

Božić

Svetina

2010

Biophysical Chemistry

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Please cite this article as: Jasna Kovačič, Bojan Božič, Saša Svetina, Budding of giant unilamellar vesicles induced by an amphitropic protein β 2 -glycoprotein I, Biophysical Chemistry (2010Chemistry ( ), doi: 10.1016Chemistry ( /j.bpc.2010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

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Membrane Properties of Archæal Macrocyclic Diether Phospholipids

et al. 2000

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Several biophysical properties of four synthetic archaeal phospholipids [one polyprenyl macrocyclic lipid A and three polyprenyl double-chain lipids (B, C, D) bearing zero, one or four double bonds in each chain] were studied using differential scanning calorimetry, electron and optical microscopies, stopped-flow/light scattering and solid-state 2H-NMR techniques. These phospholipids gave a variety of self-organized structures in water, in particular vesicles and tubules. These assemblies change in response to simple thermal convection. Some specific membrane properties of these archaeal phospholipids were observed: They are in a liquid-crystalline state over a wide temperature range; the dynamics of their polyprenyl chains is higher than that of n-acyl chains; the water permeability of the membranes is lower than that of n-acyl phospholipid membranes. It was also found that macrocyclization remarkably improves the barrier properties to water and the membrane stability. This may be related to the adaptation of Methanococcus jannaschii to the extreme conditions of the deep-sea hydrothermal vents.

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Membrane bending energy and shape determination of phospholipid vesicles and red blood cells

Cited by 350 publications

References 19 publications

Flat and sigmoidally curved contact zones in vesicle–vesicle adhesion

Flat and sigmoidally curved contact zones in vesicle–vesicle adhesion

Budding of giant unilamellar vesicles induced by an amphitropic protein β2-glycoprotein I

Membrane Properties of Archæal Macrocyclic Diether Phospholipids

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