Mechanical Stability of Micropipet-Aspirated Giant Vesicles with Fluid Phase Coexistence

Das, Sovan Lal; Tian, Aiwei; Baumgart, Tobias

doi:10.1021/jp800029u

Cited by 15 publications

(11 citation statements)

References 29 publications

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“…4 and 7, in light of the concepts previously introduced in Refs. [18,38], can be tested by a carefully conducted experiment such as the one recently reported in Ref. [10].…”

Section: Discussionmentioning

confidence: 99%

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Structure of a micropipette-aspirated vesicle determined from the bending-energy model

Chen

2012

Phys. Rev. E

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The structure of the system consisting of an aspirating pipette and an aspirated vesicle is investigated with fixed total vesicle volume, total vesicle surface area, and aspirated volume fraction, based on the bending-energy model. Through an energetic consideration, the usage of an aspirated volume fraction can be converted to the aspirating pressure for the determination of a phase diagram; the procedure identifies a first-order transition, between a weakly aspirated state and the strongly aspirated state, as the pressure increases. The physical properties of the system are obtained from minimization of the bending energy by an implementation of the simulated annealing Monte Carlo procedure, which searches for a minimum in a multivariable space. An analysis of the hysteresis effects indicates that the experimentally observed aspirating and releasing critical pressures are related to the location of the spinodal points.

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“…4 and 7, in light of the concepts previously introduced in Refs. [18,38], can be tested by a carefully conducted experiment such as the one recently reported in Ref. [10].…”

Section: Discussionmentioning

confidence: 99%

“…Some of the concepts introduced in this work are similar to those demonstrated in Ref. [38], where the authors considered a simple toy model for the vesicle, neglecting the bending rigidity.…”

Section: Introductionmentioning

confidence: 92%

Structure of a micropipette-aspirated vesicle determined from the bending-energy model

Chen

2012

Phys. Rev. E

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“…Besides being an attractive mathematical problem, the stability of a uniform spherical membrane is of practical importance. Many experiments on multicomponent vesicles have demonstrated a complex landscape of morphologies with a spherical (or quasi-spherical) membrane shape [2,3,6,34]. Moreover, the starting point of these experiments is often spherical and uniform vesicles, which respond to an external stimulation, such as changes in temperature or in osmotic pressure, by altering their composition, landscape, and shape.…”

Section: Linear Stabilitymentioning

confidence: 99%

“…On the other hand, phosphatidylethanolamine molecules have a small headgroup and are cone-shaped, while in lysophosphatidylcholine the hydrophobic part occupies a relatively smaller surface area and the molecule has the shape of an inverted cone [30]. The mixture of cylindrical lipids and conical lipids will have a spontaneous curvature that depends on the concentration of the conical lipids [6]. In addition, the two phases can have different mechanical properties.…”

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confidence: 99%

Stability of MultiComponent Biological Membranes

Givli¹,

Giang²,

Bhattacharya³

2012

SIAM J. Appl. Math.

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Abstract. Equilibrium equations and stability conditions are derived for a general class of multicomponent biological membranes. The analysis is based on a generalized Helfrich energy that accounts for geometry through the stretch and curvature, the composition, and the interaction between geometry and composition. The use of nonclassical differential operators and related integral theorems in conjunction with appropriate composition and mass conserving variations simplify the derivations. We show that instabilities of multicomponent membranes are significantly different from those in single component membranes, as well as those in systems undergoing spinodal decomposition in flat spaces. This is due to the intricate coupling between composition and shape as well as the nonuniform tension in the membrane. Specifically, critical modes have high frequencies unlike single component vesicles and stability depends on system size unlike in systems undergoing spinodal decomposition in flat space. An important implication is that small perturbations may nucleate localized but very large deformations. We show that the predictions of the analysis are in qualitative agreement with experimental observations. Key words. stability, membrane, biological, spherical, heterogeneous AMS subject classifications. 74K25, 92C05, 49Q10 DOI. 10.1137/110831301 1. Introduction. Biological membranes (BMs) are fundamental building blocks of cell walls, mitochondria, and other organelles. They protect the cell by providing a barrier, and control almost all interaction with the surroundings, including transport, signaling, transduction, and adhesion. A key to this diverse functionality is the coupling between mechanical signals carried by the BM and biochemical events in the cell [13,24,31,37,47] and the rich phenomena that this coupling creates; see, e.g., [3,16,34,28,36]. For example, gated mechano-sensitive ion channels open to form a large conductance pore in response to membrane stretching [14,17,18,33,38,25].BMs are primarily made of a lipid bilayer, but also contain proteins, rigid cholesterol molecules, and other functional molecules [9]. Moreover, for the same lipid, various phases may be found, such as gels, liquid disordered phases, and liquid ordered phases. These phases differ in their mechanical properties, which makes the BM a heterogeneous mechanical structure. Moreover, BMs are dynamic structures whose molecular arrangements can change with conditions. Depending on the type of lipids and the functional molecules involved, as well as the external conditions like osmotic pressure and temperature, the BM can remain homogeneous or segregate into different phases/domains. The latter changes the stress distribution in the BM and either absorbs or releases energy. Therefore, just like other heterogeneous materials, deformation of the BM is dictated by composition. However, unlike standard mechanical structures, composition is modulated by the shape of the BM [26].

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“…On the other hand, phosphatidylethanolamine molecules have a small headgroup and are cone-shaped, while in lysophosphatidylcholine the hydrophobic part occupies a relatively smaller surface area and the molecule has the shape of an inverted cone (Sprong et al, 2001). The mixture of cylindrical lipids and conical lipids will have a spontaneous curvature that depends on the concentration of the conical lipids (Das et al, 2008). For simplicity, we assume here that the spontaneous curvature has a linear dependence with concentration, i.e.,…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Biological membranes from the perspective of smart materials – A theoretical study

Atia

Givli

2012

International Journal of Solids and Structures

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a b s t r a c tThe unique properties and diverse functionality of biological membranes make them excellent candidates for nano-scale applications, such as sensors and actuators. Taking the view of biological membranes as smart bio-materials, we study the behavior of a simply supported beam made from a biological membrane-like material. Equilibrium configurations are derived by calculating the first variation of a generalized Helfrich energy, and their stability is examined by means of the second variation. Our numerical results demonstrate the richness of phenomena exhibited by these structures, in accordance with experimental observation of multi-component vesicles. Further, we demonstrate that the intriguing behavior of biological membrane beams, which is fundamentally different from standard beams and from standard Cahn Hilliard systems, can be utilized for actuation and sensing. For example, temperature and also pressure difference across the membrane can be indirectly measured by gauging the fluorescence intensity of the membrane components.

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Mechanical Stability of Micropipet-Aspirated Giant Vesicles with Fluid Phase Coexistence

Cited by 15 publications

References 29 publications

Structure of a micropipette-aspirated vesicle determined from the bending-energy model

Structure of a micropipette-aspirated vesicle determined from the bending-energy model

Stability of MultiComponent Biological Membranes

Biological membranes from the perspective of smart materials – A theoretical study

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