An application of the optical microscopy to the determination of the curvature elastic modulus of biological and model membranes

Bivas, I.; Hanusse, P.; Bothorel, P.; Lalanne, J. R.; Aguerre-Chariol, Olivier

doi:10.1051/jphys:01987004805085500

Cited by 112 publications

(65 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Schneider et al [30] studied the amplitudes and spectra of membrane fluctuations at manually selected vesicle contour points. Bivas et al [4] experimentally determined k c by describing the vesicle contour with points that were located in the middle between the maximal and minimal image intensities and by analyzing the angular autocorrelation of the vesicle contour fluctuations. On the other hand, Engelhardt et al [12] determined k c by describing the vesicle contour with points of minimal image intensity represented by a Fourier series.…”

Section: Introductionmentioning

confidence: 99%

Automated tracking and analysis of phospholipid vesicle contours in phase contrast microscopy images

Usenik

Vrtovec

Pernuš

et al. 2011

Med Biol Eng Comput

View full text Add to dashboard Cite

In this article, we propose a method for automated tracking and analysis of vesicle contours in video sequences acquired by phase contrast microscopy. The contour is determined in each frame of the selected video sequence by detecting the transition between the interior and exterior of the vesicle that is reflected in the image intensity gradients. The resulting contour points are represented in the polar coordinate system, i.e., with uniform angular sampling and with coordinates that originate from the vesicle center of mass, enabling the analysis of the vesicle shape and its membrane fluctuations. By analyzing artificial images with known ground-truth contours, the accuracy and precision of the proposed method was estimated to be 34.1 and 26.9 nm for image signal-to-noise ratio of 23 dB and pixel size of 35 nm, respectively. The proposed method was evaluated on quasi-spherical vesicles made up of different proportions of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol and exposed to different temperatures. The results show that the method is robust and efficient in terms of speed and quantitative description of vesicle fluctuations. The magnitude of vesicle membrane fluctuations increased with temperature, while the bending rigidity of the membrane was increasing for temperatures up to 20 °C and decreasing for higher temperatures irrespective of the vesicle molecular structure.

show abstract

Section: Introductionmentioning

confidence: 99%

Automated tracking and analysis of phospholipid vesicle contours in phase contrast microscopy images

Usenik

Vrtovec

Pernuš

et al. 2011

Med Biol Eng Comput

View full text Add to dashboard Cite

show abstract

“…The bending rigidity of amphiphilic bilayers has been measured in many experiments: while phospholipid membranes [4,8,[20][21][22] are characterized by a bending rigidity of the order of tens of k B T , lamellar and fluid microemulsion phases composed of single chain surfactants, short chain alcohols, oil and water [23][24][25][26] exhibit a bending rigidity of the order of k B T . The bilayer studied in our Molecular Dynamics simulations are composed of single-chain amphiphiles and have bending rigidities which are of the same order of magnitude as those studied in the second group of experiments.…”

mentioning

confidence: 99%

Shape fluctuations and elastic properties of two-component bilayer membranes

2005

View full text Add to dashboard Cite

Abstract. -The elastic properties of two-component bilayer membranes are studied using a coarse grain model for amphiphilic molecules. The two species of amphiphiles considered here differ only in their length. Molecular Dynamics simulations are performed in order to analyze the shape fluctuations of the two-component bilayer membranes and to determine their bending rigidity. Both the bending rigidity and its inverse are found to be nonmonotonic functions of the mole fraction xB of the shorter B-amphiphiles and, thus, do not satisfy a simple lever rule. The intrinsic area of the bilayer also exhibits a nonmonotonic dependence on xB and a maximum close to xB ≃ 1/2.Biological membranes are multicomponent systems consisting of mixtures of many different lipids and proteins. Because the composition of lipid bilayers affects their physical properties and biological functions, this composition varies from one organism to the other and between organelles in the same cell [1]. Biological membranes contain a fluid bilayer which is highly flexible and, thus, can easily change its shape. Typical examples are provided by the plasma membranes of red and white blood cells which are so flexible that they can move through rather small capillaries. This flexibility is also responsible for the thermally excited shape fluctuations of biomembranes in physiological conditions, the amplitude of which depends on temperature, membrane composition and mechanical constraints. One important example is provided by mixed membranes containing phospholipids and cholesterol which exhibit a strong increase in rigidity with increasing amount of cholesterol [2][3][4]. In erythrocytes, on the other hand, the amplitude of the shape fluctuations is influenced by the spectrin-ankyrin network which is coupled to the interior of the plasma membrane [5,6]. The study of these fluctuations can thus provide information on the elastic properties of the bilayer membrane and on how these properties depend on membrane composition. One important elastic parameter is the bending rigidity [7], which describes the resistance of the membrane to bending, and which can be obtained from the spectrum of the shape fluctuations [8].

show abstract

“…Direct measurements of the wavelength.<Jependent relaxation times of single bilayers by video microscopy of vesicle fluctuations have been restricted to wavelengths larger than half a micrometer [9,10]. Even though we expect to see deviations from the asymptotic low-q behavior.…”

mentioning

confidence: 99%

Viscous Modes of Fluid Bilayer Membranes

1993

View full text Add to dashboard Cite

PACS. 68.10 -Fluid surfaces and interfaces with fluids (inc. surface tension, capillarity, wetting and related phenomena). FACS. 68.80 -Dynamics of solid surfaces and interface vibrations.Abstract. -We detennine the dispersion relation for a fluid bilayer membrane, taking into account the coupling between bending and the local density of the two monolayers. Apart from important corrections to the conventional bending mode, we obtain a second slow mode which is essentially a fluctuation in the density difference of the two monolayers, damped by inter-monolayer friction. Estimates for a stack of membranes show reasonable agreement with a recent spin-echo study of membrane undulations.The traditional model for fluid phospholipid membranes treats them as a single incompressible sheet with bending rigidity [1). Actually, of course, they consist of a pair of slightly compressible monolayers bound tightly together. This bilayer structure implies that bending a membrane necessarily leads to a stretching of one monolayer and a compression of the other. Since the membrane is fluid, density inhomogeneities can relax within each monolayer by lateral lipid flow. For the investigation of static equilibrium phenomena, one ean therefore assume that the lipid density within each monolayer is homogeneous. The only effect of the bilayer structure is to add a global term to the energy, the area difference elasticity [2-4), which is important for calculating the phase diagram of vesicle shapes.Evans and Yeung [5, 6) recently stressed that for the dynamics of conformational changes of membranes the coupling between bending and relative compression is crucial, and demonstrated this in the analysis of a tether fonnation experiment. The purpose of this paper is, first, to analyse this coupling for the much simpler but paradigmatic case of the dynamical equilibrium fluctuations of an almost planar bilayer embedded in a viscous medium and then, briefly, to discuss these fluctuations for the experimentally relevant case of membrane stacks.The standard treatment [7) of the fluctuating single membrane leads to a relaxation rate y, = "q'/4~ for a plane wave excitation with wave number q within the membrane. The bending rigidity" provides the driving force, while the viscosity ~ of the surrounding liquid provides the dissipation. Does this relation hold for a bilayer in which the lipids can

show abstract

An application of the optical microscopy to the determination of the curvature elastic modulus of biological and model membranes

Cited by 112 publications

References 17 publications

Automated tracking and analysis of phospholipid vesicle contours in phase contrast microscopy images

Automated tracking and analysis of phospholipid vesicle contours in phase contrast microscopy images

Shape fluctuations and elastic properties of two-component bilayer membranes

Viscous Modes of Fluid Bilayer Membranes

Contact Info

Product

Resources

About