Investigation of Shape Transformations of Vesicles, Induced by Their Adhesion to Flat Substrates Characterized by Different Adhesion Strength (original) (raw)

Shape Transformations of Vesicles Induced by Their Adhesion to Flat Surfaces

ACS omega, 2020

The shape transformations of lipid vesicles induced by the adhesion to a flat surface is investigated. We perform the calculations within the framework of the Helfrich spontaneous curvature model. The calculations were performed for a few values of the reduced volume and the spontaneous curvature. The range of stability for different shapes (oblate, prolate, and stomatocyte) of adhered vesicles is determined. New physical phenomena such as budding induced by the adhesion of vesicles are reported.

Geometry of Lipid Vesicle Adhesion

Physical Review E, 2002

The adhesion of a lipid membrane vesicle to a fixed substrate is examined from a geometrical point of view. This vesicle is described by the Helfrich hamiltonian quadratic in the mean curvature; it interacts by contact with the substrate, with an interaction energy proportional to the area of contact. We identify the constraints on the geometry at the boundary of the shared surface. The result is interpreted in terms of the balance of the force normal to this boundary. No assumptions are made either on the symmetry of the vesicle or on that of the substrate. The strong bonding limit as well as the effect of curvature asymmetry on the boundary are discussed.

Characteristics of phospholipid vesicles enhanced by adhesion on an annular region

Physical Review E, 2019

Phospholipid vesicle membranes are simple models used to study the mechanical properties of cell membranes. The shapes of flaccid vesicles can exhibit very diverse forms. When researching very flaccid vesicles, axisymmetrical vesicles with the membranes adhered to an annular region can also be observed. A phase diagram of such shapes was studied for different values of the vesicle parameters, i.e., the adhesion constant, the vesicle volume-to-membrane ratio, the volume ratio between the polar and the equatorial parts, and the equilibrium difference between the membrane monolayers. The energies of the annular shapes with respect to the vesicle parameters were closely examined and compared with the energies of the discocyte and stomatocyte shapes. The requirements for the existence of such annular shapes were also given for adhesion-free vesicle membranes. The results show that the adhesion between the lipid bilayers stabilizes the observed shapes, which belong to the locally stable branch of the annular vesicles. The value obtained for the adhesion constant of the SOPC membrane is 3 × 10 −9 J/m 2 .

Two-dimensional model of vesicle adhesion on curved substrates

Acta Mechanica Sinica, 2006

We develop a two dimensional model of a vesicle adhered on a curved substrate via long-range molecular interactions while subjected to a detachment force. The relationship between the force and displacement of the vesicle is investigated as a function of the substrate shape. It is shown that both the forcedisplacement relationship and the maximum force at pull-off are significantly dependent on the substrate shape. The results suggest that probes with different tip shapes may be designed for cell manipulation. For example, we demonstrate that a vesicle can be pulled off a flat surface using a probe with a curved tip.

Adhesion of fluid vesicles at chemically structured substrates

The European Physical Journal E, 2007

The adhesion of fluid vesicles at chemically structured substrates is studied theoretically via Monte Carlo simulations. The substrate surface is planar and repels the vesicle membrane apart from a single surface domain γ, which strongly attracts this membrane. If the vesicle is larger than the attractive γ domain, the spreading of the vesicle onto the substrate is restricted by the size of this surface domain. Once the contact line of the adhering vesicle has reached the boundaries of the γ domain, further deflation of the vesicle leads to a regime of low membrane tension with pronounced shape fluctuations, which are now governed by the bending rigidity. For a circular γ domain and a small bending rigidity, the membrane oscillates strongly around an average spherical cap shape. If such a vesicle is deflated, the contact area increases or decreases with increasing osmotic pressure, depending on the relative size of the vesicle and the circular γ domain. The lateral localization of the vesicle's center of mass by such a domain is optimal for a certain domain radius, which is found to be rather independent of adhesion strength and bending rigidity. For vesicles adhering to stripe-shaped surface domains, the width of the contact area perpendicular to the stripe varies nonmonotonically with the adhesion strength.

Deformations of Lipid Vesicles Induced by Attached Spherical Particles

Langmuir, 2007

Wrapping of a spherical colloidal particle, located inside and outside a lipid vesicle, by the membrane which forms the wall of the vesicle is investigated. The process is studied for vesicles of different geometries: prolate, oblate, stomatocytes. We focus on the bending energy change and shape transformations induced by binding the membrane to the spherical particles. The ground-state shapes of vesicles are calculated within the framework of a Helfrich curvature energy functional.

Determination of the strength of adhesion between lipid vesicles

TheScientificWorldJournal, 2012

A commonly used method to determine the strength of adhesion between adhering lipid vesicles is measuring their effective contact angle from experimental images. The aim of this paper is to estimate the interobserver variations in vesicles effective contact angle measurements and to propose a new method for estimating the strength of membrane vesicle adhesion. Theoretical model shows for the old and for the new measure a monotonic dependence on the strength of adhesion. Results obtained by both measuring techniques show statistically significant correlation and high interobserver reliability for both methods. Therefore the conventional method of measuring the effective contact angle gives qualitatively relevant results as the measure of the lipid vesicle adhesion. However, the new measuring technique provides a lower variation of the measured values than the conventional measures using the effective contact angle. Moreover, obtaining the adhesion angle can be automatized more easily...

Influence of Spontaneous Curvature and Microtubules on the Conformations of Lipid Vesicles

Journal of Physical Chemistry B, 2005

The conformations of vesicles deformed by microtubules are studied within the framework of the curvature energy. The phenomenon in which the destruction of a microtubule is followed by the formation of peristaltic shapes on a protrusion created by the microtubule is investigated. The influence of the spontaneous curvature on the conformations of vesicles is examined, and the results are compared to existing experiments. The elastic properties of a vesicle deformed by the microtubule are studied.

SHAPE TRANSFORMATIONS OF VESICLES BUILT OF AMPHIPHILIC MOLECULES

Biophysical Reviews and Letters, 2008

We review our recent work on the shape transformations of vesicles subject to external stimuli. Possible shape transformations resulting from the change of the spontaneous curvature, volume, or composition of the components on the surface of a vesicle are examined within the framework of the spontaneus curvature model. The influence of encapsulated or adhered rigid object such as microtubules or colloidal particles on the shape transformation is also investigated. A few cases of shape transformations encountered in experiments are described.

Deformation of injected vesicles adhering onto flat rigid substrates

Computers & Mathematics with Applications, 2012

This study is concerned with the determination of the mechanical behaviour of closed fluid lipid bilayer membranes (vesicles) under a uniform hydrostatic pressure, pressed against and adhering onto a flat homogeneous rigid substrate. Assuming that the initial and deformed shapes of the vesicle are axisymmetric, a variational statement of the problem is developed on the ground of the so-called spontaneous curvature model. In this setting, the vesicle is regarded as a closed surface in the three-dimensional Euclidean space and its equilibrium shapes are supposed to provide stationary values of the bending energy functional under the constraint of fixed total area. The corresponding Euler-Lagrange equations and natural boundary conditions are derived, the work done by the pressure being taken into account, and used to determine the forces and moments in the membrane. Several examples of surfaces representing possible equilibrium shapes of so loaded membranes are determined numerically.