Shape fluctuations and elastic properties of two-component bilayer membranes

Research on giant vesicles is becoming increasingly popular. Giant vesicles provide model biomembrane systems for systematic measurements of mechanical and rheological properties of bilayers as a function of membrane composition and temperature, as well as hydrodynamic interactions. Membrane response to external factors (for example electric fields, ions and amphiphilic molecules) can be directly visualized under the microscope. In this paper we review our current understanding of lipid bilayers as obtained from studies on giant unilamellar vesicles. Because research on giant vesicles increasingly attracts the interest of scientists from various backgrounds, we also try to provide a concise introduction for newcomers in the field. Finally, we summarize some recent developments on curvature effects induced by polymers, domain formation in membranes and shape transitions induced by electric fields.

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“…Both tensions have been recently measured in molecular dynamics simulations and were found to be different in magnitude (Imparato et al 2005).…”

Section: Bending Rigidity Stretching Elasticity and Spontaneous Curvmentioning

confidence: 92%

A practical guide to giant vesicles. Probing the membrane nanoregime via optical microscopy

Dimova

Aranda

Bezlyepkina

et al. 2006

J. Phys.: Condens. Matter

297

329

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“…The temperature of the system is maintained at k B T/ε = 0.22 by employing the Nose-Hoover thermostat. The model was implemented in the NAT ensemble [56,77,78]. Given that the diameter of the lipid particles is The timestep of the simulation is selected to be Δt = 0.01t s .…”

Section: Model and Simulation Methodsmentioning

confidence: 99%

Vesiculation of healthy and defective red blood cells

Lykotrafitis

2015

Phys. Rev. E

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Vesiculation of mature red blood cells (RBCs) contributes to removal of defective patches of the erythrocyte membrane. In blood disorders, which are related to defects in proteins of the RBC membrane, vesiculation of the plasma membrane is intensified. Several hypotheses have been proposed to explain RBC vesiculation but the exact underlying mechanisms and what determines the sizes of the vesicles are still not completely understood. In this work, we apply a twocomponent coarse-grained molecular dynamics (CGMD) RBC membrane model to study how RBC vesiculation is controlled by the membrane spontaneous curvature and by lateral compression of the membrane. Our simulation results show that the formation of small homogeneous vesicles with a diameter less than 40 nm can be attributed to a large spontaneous curvature of membrane domains. On the other hand, compression on the membrane can cause the formation of vesicles with heterogeneous composition and with sizes comparable with the size of the cytoskeleton corral. When spontaneous curvature and lateral compression are simultaneously considered, the compression on the membrane tends to facilitate formation of vesicles originated from curved membrane domains. We also simulate vesiculation of RBCs with membrane defects connected to hereditary elliptocytosis (HE) and to hereditary spherocytosis (HS). When the vertical connectivity between the lipid bilayer and the membrane skeleton is elevated, as is in normal RBCs, multiple vesicles are shed from the compressed membrane with diameters similar to the cytoskeleton corral size. In HS RBC, where the connectivity between the lipid bilayer and the cytoskeleton is reduced, larger size vesicles are released under the same compression ratio as in normal RBCs. Lastly, we find that vesicles released from HE RBCs can contain cytoskeletal filaments due to fragmentation of the membrane skeleton while vesicles released from the HS RBCs are depleted of cytoskeletal filaments.

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“…Hence, a more accurate determination of the true bilayer area is necessary to calculate area compressibility in large bilayer patches. Using a similar model for amphiphilic molecules (single-chain), Imparato et al [77] have shown that the bending rigidity of a two-component bilayer, in which the two amphiphiles differ only in tail length, exhibits a nonmonotonous behavior as function of bilayer composition. A similar functional dependence was found by Brannigan and Brown [56] using an implicit solvent, particle-based model.…”

Section: Empirical Coarse-grained Modelsmentioning

confidence: 99%

“…It is however important to note that, if the bilayer undergoes large fluctuations and undulations, the value of the area per lipid computed in this way is underestimated (see e.g. [77]). …”

Section: A2 Structural Properties Of Lipid Bilayersmentioning

confidence: 99%

Mesoscopic models of biological membranes

Venturoli¹,

et al. 2006

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Phospholipids are the main components of biological membranes and dissolved in water these molecules self-assemble into closed structures, of which bilayers are the most relevant from a biological point of view. Lipid bilayers are often used, both in experimental and by theoretical investigations, as model systems to understand the fundamental properties of biomembranes. The properties of lipid bilayers can be studied at different time and length scales. For some properties it is sufficient to envision a membrane as an elastic sheet, while for others it is important to take into account the details of the individual atoms. In this review, we focus on an intermediate level, where groups of atoms are lumped into pseudo-particles to arrive at a coarse-grained, or mesoscopic, description of a bilayer, which is subsequently studied using molecular simulation.The aim of this review is to compare various strategies to coarse grain a biological membrane. The conclusion of this comparison is that there can be many valid different strategies, but that the results obtained by the various mesoscopic models are surprisingly consistent. A second objective of this review is to illustrate how mesoscopic models can be used to obtain a better understanding of experimental systems. The advantage of coarse-grained models is that these can be simulated very efficiently, so that phenomena involving large systems, or requiring a large number of simulations, can be studied in detail. This is illustrated with the study of the relation between the phase behavior of a membrane and the structure of the phospholipids, and the membrane structural changes due to molecules (such as alcohols, cholesterol and anesthetics) adsorbed to the membrane. We then discuss the effect of transmembrane peptides on the local structure of a membrane and the mechanism of vesicle fusion and fission.

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Shape fluctuations and elastic properties of two-component bilayer membranes

Cited by 54 publications

References 36 publications

A practical guide to giant vesicles. Probing the membrane nanoregime via optical microscopy

A practical guide to giant vesicles. Probing the membrane nanoregime via optical microscopy

Vesiculation of healthy and defective red blood cells

Mesoscopic models of biological membranes

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