CRYO-Tem Measurements of Membrane Elasticity in Equilibrium Vesicle Systems: Two Distinct Mechanisms of Stability

2000 ◽  
Vol 6 (S2) ◽  
pp. 848-849
Author(s):  
B. Coldren ◽  
H.T. Jung ◽  
J. Zasadzinski
Keyword(s):  
Lipid Bilayers ◽  
Spontaneous Curvature ◽  
Aqueous Mixtures ◽  
Membrane Elasticity ◽  
Theoretical Concepts ◽  
Curvature Energy ◽  
Nanomaterials Synthesis ◽  
Equilibrium Phases ◽  
Image Position ◽  
New Applications

Aqueous mixtures of oppositely charged surfactants spontaneously form equilibrium phases of unilamellar vesicles.1 The wide variety of surfactants that display this behavior allows control over vesicle charge, size, and polydispersity. This may be useful for new applications in drug delivery, nanomaterials synthesis, and as tests of theoretical concepts of membrane organization and interactions.A subtle competition between the entropy of mixing and the elastic properties of surfactant and lipid bilayers determines their phase behavior and morphology. The curvature energy per unit area of bilayer, fc, iswhere R1 and R2 are the principle radii of curvature, K is the curvature modulus, and is the saddle-splay modulus. The spontaneous curvature, l/ro, is nonzero only if there is asymmetry between the two sides of the bilayer.

scholarly journals Poly(catecholamine) Coating and Biofunctionalization of CsPbBr3 Microcrystals

2021 ◽  
Author(s):  
Sangyeon Cho ◽  
Seok-Hyun Yun
Keyword(s):  
Lipid Bilayers ◽  
Environmental Stability ◽  
Live Cells ◽  
Functional Coatings ◽  
Common Strategy ◽  
Novel Method ◽  
Halide Perovskites ◽  
The Stability ◽  
New Applications

<p>Lead halide perovskites (LHP) microcrystals are promising materials for various optoelectronic applications. Surface coating on particles is a common strategy to improve their functionality and environmental stability, but LHP is not amenable to most coating chemistries because of its intrinsic weakness against polar solvents. Here, we describe a novel method of synthesizing LHP microcrystals in a super-saturated polar solvent using sonochemistry and applying various functional coatings on individual microcrystals <i>in situ</i>. We synthesize cesium lead bromine perovskite (CsPbBr<sub>3</sub>) microparticles capped with organic poly-norepinephrine (pNE) layers. The catechol group of pNE coordinates to bromine-deficient lead atoms, forming a defect-passivating and diffusion-blocking shell. The pNE layer enhances the stability of CsPbBr<sub>3</sub> in water by 2,000-folds, enabling bright luminescence and lasing from single microcrystals in water. Furthermore, the pNE shell permits biofunctionalization with proteins, small molecules, and lipid bilayers. Luminescence from CsPbBr<sub>3</sub> microcrystals is sustained in water over 1 hour and observed in live cells. The functionalization method may enable new applications of LHP particles in water-rich environments.<b></b></p>

scholarly journals Nanomaterials under stress: A new opportunity for nanomaterials synthesis and engineering

MRS Bulletin ◽  
2015 ◽  
Vol 40 (11) ◽  
pp. 961-970 ◽  
Author(s):  
Feng Bai ◽  
Kaifu Bian ◽  
Binsong Li ◽  
Huimeng Wu ◽  
Leanne J. Alarid ◽  
...  
Keyword(s):  
Nanomaterials Synthesis ◽  
Image Position

Abstract

On the role of lipid-bilayer elasticity for the lipid–protein interaction and the indirect protein–protein coupling

1984 ◽  
Vol 62 (8) ◽  
pp. 778-788 ◽  
Author(s):  
E. Sackmann ◽  
R. Kotulla ◽  
Franz-Josef Heiszler
Keyword(s):  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Protein Interaction ◽  
Experimental Studies ◽  
Membrane Elasticity ◽  
Protein Protein Interaction ◽  
Lipid Protein Interaction ◽  
Elastic Distortion ◽  
Enzyme Complexes

The present paper deals with the curvature (or splay) elasticity of lipid bilayers and its possible consequences for the microscopic organization of membranes. Experimental studies of the microstructure of lipid–lipid and lipid–protein mixtures are reported and discussed in terms of this type of membrane elasticity. In particular, evidence is provided that the elastic distortion of lipid bilayers caused by the incorporation of proteins can lead to mechanisms of the indirect protein–protein interaction. Finally the question is discussed whether these mechanisms could also play a role for the formation of enzyme complexes in biological membranes.

scholarly journals Fusion Pore Diameter Regulation by Cations Modulating Local Membrane Anisotropy

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Doron Kabaso ◽  
Ana I. Calejo ◽  
Jernej Jorgačevski ◽  
Marko Kreft ◽  
Robert Zorec ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Continuum Model ◽  
Pore Diameter ◽  
Fusion Pore ◽  
Spontaneous Curvature ◽  
Local Concentration ◽  
Vesicle Membrane ◽  
Membrane Elasticity ◽  
Opening And Closing ◽  
Pore Dynamics

The fusion pore is an aqueous channel that is formed upon the fusion of the vesicle membrane with the plasma membrane. Once the pore is open, it may close again (transient fusion) or widen completely (full fusion) to permit vesicle cargo discharge. While repetitive transient fusion pore openings of the vesicle with the plasma membrane have been observed in the absence of stimulation, their frequency can be further increased using a cAMP-increasing agent that drives the opening of nonspecific cation channels. Our model hypothesis is that the openings and closings of the fusion pore are driven by changes in the local concentration of cations in the connected vesicle. The proposed mechanism of fusion pore dynamics is considered as follows: when the fusion pore is closed or is extremely narrow, the accumulation of cations in the vesicle (increased cation concentration) likely leads to lipid demixing at the fusion pore. This process may affect local membrane anisotropy, which reduces the spontaneous curvature and thus leads to the opening of the fusion pore. Based on the theory of membrane elasticity, we used a continuum model to explain the rhythmic opening and closing of the fusion pore.

scholarly journals Poly(catecholamine) coated CsPbBr3 perovskite microlasers: lasing in water and biofunctionalization

2021 ◽  
Author(s):  
Sangyeon Cho ◽  
Seok-Hyun Yun
Keyword(s):  
Lipid Bilayers ◽  
Environmental Stability ◽  
Live Cells ◽  
Functional Coatings ◽  
Common Strategy ◽  
Novel Method ◽  
Halide Perovskites ◽  
The Stability ◽  
New Applications

<p>Lead halide perovskites (LHP) microcrystals are promising materials for various optoelectronic applications. Surface coating on particles is a common strategy to improve their functionality and environmental stability, but LHP is not amenable to most coating chemistries because of its intrinsic weakness against polar solvents. Here, we describe a novel method of synthesizing LHP microcrystals in a super-saturated polar solvent using sonochemistry and applying various functional coatings on individual microcrystals <i>in situ</i>. We synthesize cesium lead bromine perovskite (CsPbBr<sub>3</sub>) microparticles capped with organic poly-norepinephrine (pNE) layers. The catechol group of pNE coordinates to bromine-deficient lead atoms, forming a defect-passivating and diffusion-blocking shell. The pNE layer enhances the stability of CsPbBr<sub>3</sub> in water by 2,000-folds, enabling bright luminescence and lasing from single microcrystals in water. Furthermore, the pNE shell permits biofunctionalization with proteins, small molecules, and lipid bilayers. Luminescence from CsPbBr<sub>3</sub> microcrystals is sustained in water over 1 hour and observed in live cells. The functionalization method may enable new applications of LHP particles in water-rich environments.<b></b></p>

scholarly journals Local sensitivity analysis of the ‘Membrane shape equation’ derived from the Helfrich energy

2020 ◽  
Author(s):  
P. Rangamani ◽  
A. Behzadan ◽  
M. Holst
Keyword(s):  
Differential Equations ◽  
Lipid Bilayers ◽  
Numerical Study ◽  
Membrane Vesicles ◽  
Energy Functional ◽  
Specific Model ◽  
Model Systems ◽  
Spontaneous Curvature ◽  
Membrane Mechanics ◽  
Curvature Term

AbstractThe Helfrich energy is commonly used to model the elastic bending energy of lipid bilayers in membrane mechanics. The governing differential equations for certain geometric characteristics of the shape of the membrane can be obtained by applying variational methods (minimization principles) to the Helfrich energy functional and are well-studied in the axisymmetric framework. However, the Helfrich energy functional and the resulting differential equations involve a number of parameters, and there is little explanation of the choice of parameters in the literature, particularly with respect to the choice of the “spontaneous curvature” term that appears in the functional. In this paper, we present a careful analytical and numerical study of certain aspects of parametric sensitivity of Helfrich’s model. Using simulations of specific model systems, we demonstrate the application of our scheme to the formation of spherical buds and pearled shapes in membrane vesicles.

scholarly journals Local sensitivity analysis of the “membrane shape equation” derived from the Helfrich energy

2020 ◽  
pp. 108128652095388
Author(s):  
P Rangamani ◽  
A Behzadan ◽  
M Holst
Keyword(s):  
Differential Equations ◽  
Lipid Bilayers ◽  
Numerical Study ◽  
Membrane Vesicles ◽  
Energy Functional ◽  
Specific Model ◽  
Model Systems ◽  
Spontaneous Curvature ◽  
Membrane Mechanics ◽  
Curvature Term

The Helfrich energy is commonly used to model the elastic bending energy of lipid bilayers in membrane mechanics. The governing differential equations for certain geometric characteristics of the shape of the membrane can be obtained by applying variational methods (minimization principles) to the Helfrich energy functional and are well studied in the axisymmetric framework. However, the Helfrich energy functional and the resulting differential equations involve a number of parameters, and there is little explanation of the choice of parameters in the literature, particularly with respect to the choice of the “spontaneous curvature” term that appears in the functional. In this paper, we present a careful analytical and numerical study of certain aspects of parametric sensitivity of Helfrich’s model. Using simulations of specific model systems, we demonstrate the application of our scheme to the formation of spherical buds and pearled shapes in membrane vesicles.

The Clifford Paterson Lecture, 1984 - Microwaves: the art and the science

1985 ◽  
Vol 398 (1814) ◽  
pp. 1-22
Keyword(s):  
Automatic Measurement ◽  
Wide Band ◽  
Theoretical Concepts ◽  
Satellite Systems ◽  
Microcomputer Control ◽  
Frequency Independent ◽  
Essential Contribution ◽  
Microwave Techniques ◽  
New Applications ◽  
Single Instrument

All engineering, although obviously science-based, contains a vital element: the art of engineering. In this lecture I hope to trace the development of microwaves during the past four decades or so, and to illustrate in this context the essential contribution that this second element has made. During this period, microwave techniques have been developed for many new applications, ranging from satellite systems and atomic clocks to intruder alarms and microwave ovens. The usable frequency range has been greatly extended, as has the instantaneous bandwidth available, typified by the invention of ‘frequency independent’ antennae and wide-band waveguides such as microstrip. Coupled with all of this has been the parallel development of microwave measurements, not only in the accuracy obtainable and in the rage of frequencies covered by a single instrument, but also by the possibility of automatic measurement with microcomputer control. The practical achievements are remarkable, but I hope above all to bring out the elegance of the theoretical concepts on which they are based.

scholarly journals Numerical Study of Membrane Configurations

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Luka Mesarec ◽  
Miha Fošnarič ◽  
Samo Penič ◽  
Veronika Kralj Iglič ◽  
Samo Kralj ◽  
...  
Keyword(s):  
Numerical Study ◽  
Thin Sheet ◽  
Topological Defects ◽  
Spontaneous Curvature ◽  
Minimal Models ◽  
Nematic Ordering ◽  
Curvature Energy ◽  
Spherical Topology ◽  
Numerical Minimization ◽  
Orientational Ordering

We studied biological membranes of spherical topology within the framework of the spontaneous curvature model. Both Monte Carlo simulations and the numerical minimization of the curvature energy were used to obtain the shapes of the vesicles. The shapes of the vesicles and their energy were calculated for different values of the reduced volume. The vesicles which exhibit in-plane ordering were also studied. Minimal models have been developed in order to study the orientational ordering in colloids coated with a thin sheet of nematic liquid crystal (nematic shells). The topological defects are always present on the surfaces with the topology of a sphere. The location of the topological defects depends strongly on the curvature of the surface. We studied the nematic ordering and the formation of topological defects on vesicles obtained by the minimization of the spontaneous curvature energy.

Changes in membrane elasticity caused by the hydrophobic surfactant proteins correlate poorly with adsorption of lipid vesicles

Soft Matter ◽  
2021 ◽  
Author(s):  
Ryan W. Loney ◽  
Bret Brandner ◽  
Maayan P. Dagan ◽  
Paige N. Smith ◽  
Megan Roche ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Order Parameter ◽  
Diffuse Scattering ◽  
Lipid Vesicles ◽  
Surfactant Proteins ◽  
Membrane Elasticity ◽  
X Ray ◽  
Bending Modulus ◽  
Air Water Interface ◽  
Acyl Chains

We used X-ray diffuse scattering to determine the bending modulus of lipid bilayers and an order parameter of the acyl chains to establish how the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of lipids to an air/water interface.

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