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Giant liposomes obtained by electroformation and observed by phase-contrast video microscopy show spontaneous deformations originating from Brownian motion that are characterized, in the case of quasispherical vesicles, by two parameters only, the membrane tension sigma and the bending elasticity k(c). For liposomes containing dimyristoyl(More)
The analysis of shape fluctuations of giant nearly spherical lipid vesicles observed via optical microscopy is one of the widely used methods for the determination of the bending elasticity of lipid membranes. Although the method has been used already for three decades, the values of this material constant, obtained by different groups for membranes of the(More)
We investigate the bending elasticity of lipid membranes with the increase of the alamethicin concentrations in the membrane via analysis of the thermally induced shape fluctuations of quasi-spherical giant vesicles. Our experimental results prove the strong influence of alamethicin molecules on the bending elasticity of diphytanoyl phosphatidylcholine and(More)
2014 Thermal fluctuations of giant lipid vesicles have been investigated both theoretically and experimentally. At the theoretical level, the model developed here takes explicitly into account the conservation of vesicle volume and membrane area. Under these conditions, the amplitude of thermal fluctuations depends critically not only on the bending(More)
The bending elasticity modulus of lipid membranes is obtained by applying for the first time, to the best of our knowledge, a novel experimental technique based on digital holographic microscopy. The fluctuations of the radius with time were extracted by tracking and measuring the optical thickness at the vesicle poles. The temporal autocorrelation function(More)
The passive water permeability of a lipid vesicle membrane was studied, related to the hydrostatic (not osmotic) pressure difference between the inner and the outer side of the vesicle in a water environment without additives. Each pressure difference was created by sucking a vesicle into a micropipette at a given sucking pressure. The part of the membrane(More)
The static and dynamic behavior of a bilayer containing an additive is examined theoretically. We have proved that the amplitudes of the thermal shape fluctuations of a quasi spherical lipid vesicle depend on the value of the bending elasticity of the vesicle's membrane at free exchange of molecules between its constituent monolayers. The dependence is(More)
  • Isak Bivas
  • Physical review. E, Statistical, nonlinear, and…
  • 2010
It is known that the relaxation of the shape fluctuations of nearly spherical lipid vesicles is accompanied by a lateral displacement of the monolayers, comprising their bilayers. In this work a dissipation mechanism of the mechanical energy stored in the fluctuation is revealed that concerns the viscous friction of the flow in the liquid around the vesicle(More)
It is shown in this paper that the existing theories of the form fluctuations of quasispherical lipid vesicle give a too high mean stretching energy of its membrane. A more precise theory taking into account the area conservation of the membrane is proposed. The relation between the amplitudes of the form fluctuations and the curvature elastic modulus of(More)
2014 A new method is proposed to measure the curvature elastic modulus kc of a membrane, by observing the thermal induced fluctuations of the shape of a spherical vesicle. Observations of the liposomes were carried out under a microscospe working in the regime of Nomarski differential interference contrast. We show that the value of kc thus measured is the(More)