Advanced Flicker Spectroscopy of Fluid Membranes
Hans-Günther Döbereiner,Gerhard Gompper,Christopher K. Haluska,D. M. Kroll,Peter G. Petrov,Karin A. Riske +5 more
TL;DR: This work presents a new method, advanced flicker spectroscopy of giant nonspherical vesicles, which makes it possible to simultaneously measure both parameters for the first time, and makes it Possible to easily characterize membrane curvature as a function of environmental conditions.
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Abstract: The bending elasticity of a fluid membrane is characterized by its modulus and spontaneous curvature. We present a new method, advanced flicker spectroscopy of giant nonspherical vesicles, which makes it possible to simultaneously measure both parameters for the first time. Our analysis is based on the generation of a large set of reference data from Monte Carlo simulations of randomly triangulated surfaces. As an example of the potential of the procedure, we monitor thermal trajectories of vesicle shapes and discuss the elastic response of zwitterionic membranes to transmembrane pH gradients. Our technique makes it possible to easily characterize membrane curvature as a function of environmental conditions.
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Figures
![FIG. 4. Normalized histograms [ R p a da 1] of the elliptical shape fluctuations of a prolate SOPC vesicle (RA 5:2 m) with varying external pH of 7.7 (open circles), 8.1 (open squares), and 8.5 (open triangles) at constant internal pH 7.7. Gaussian fits are shown. With increasing pH gradient the vesicle develops a more elongated shape (larger a2) with decreasing fluctuations.](/figures/fig-4-normalized-histograms-r-p-a-da-1-of-the-elliptical-1ky54jcg.png)
FIG. 4. Normalized histograms [ R p a da 1] of the elliptical shape fluctuations of a prolate SOPC vesicle (RA 5:2 m) with varying external pH of 7.7 (open circles), 8.1 (open squares), and 8.5 (open triangles) at constant internal pH 7.7. Gaussian fits are shown. With increasing pH gradient the vesicle develops a more elongated shape (larger a2) with decreasing fluctuations. 
FIG. 3. Thermal trajectory of a prolate vesicle in c0; v parameter space with a radius RA 4:8 m and g 0:21. The experimental points correspond to temperatures T 25:0 C, 29:4 C, 34:2 C, and 38:8 C. The crossing points of a linear fit to the trajectory with the upper (budding) and lower spinodal (prolate-oblate transition) are indicated. For the bending modulus we find 35 5 kBT. 
FIG. 2. Simulated mean-square amplitude h a22i of shape fluctuations as a function of the effective spontaneous curvature c0. Note the peak at the prolate-to-oblate transition. Three different values of the reduced volume are shown, as indicated. The other parameters are =kBT 25, 0:90, and g 0:37. 
FIG. 5. Spontaneous curvature c0 as a function of external pH for g 0:8. Note that the reduced volume and bending modulus, which are given in brackets, v; , remain constant. v, c0, and are obtained simultaneously via comparison of the data shown in Fig. 4 to Monte Carlo simulations. 
FIG. 1. Experimental and theoretical vesicle shapes. (A) Phase contrast micrograph (v 0:828). The scale bar corresponds to 5 m, (B) simulation snapshot. The parameters in the simulations are v 0:825, =kBT 25, 0:90, c0
![FIG. 4. Normalized histograms [ R p a da 1] of the elliptical shape fluctuations of a prolate SOPC vesicle (RA 5:2 m) with varying external pH of 7.7 (open circles), 8.1 (open squares), and 8.5 (open triangles) at constant internal pH 7.7. Gaussian fits are shown. With increasing pH gradient the vesicle develops a more elongated shape (larger a2) with decreasing fluctuations.](/figures/fig-4-normalized-histograms-r-p-a-da-1-of-the-elliptical-1ky54jcg.webp)
Citations
Characterization of Red Blood Cells' Rheological and Physiological State Using Optical Flicker Spectroscopy
Vadim L. Kononenko
- 05 Apr 2011
TL;DR: The main aspects of cytometric application of optical flicker spectroscopy are presented and discussed and the main experimental results of flicker in erythrocytes are reviewed, and flicker interrelations between the physiological state and the membrane dynamics of a cell are considered.
2
Generalization of the swelling method to measure the intrinsic curvature of lipids
TL;DR: Via computer simulation of a coarse-grained model of two-component lipid bilayers, two methods of measuring the intrinsic curvatures of the constituting monolayers are compared and it is highlighted that the two-leaflet structure inherent to the latter method has the advantage of allowing measurements for mixed lipid systems up to their critical point of demixing.
2
•Dissertation
Mesure du spectre de fluctuations de vésicules géantes par analyse de contours ; applications aux membranes passives et actives
Jacques Pécréaux
- 01 Jan 2004
TL;DR: In this paper, a nouvelle technique de reconnaissance de contours of vesicules lipidiques geantes en microscopie is proposed, a technique that is based on the theory developpement sur des membranes planes.
2
Interpretation of Phase Boundary Fluctuation Spectra in Biological Membranes with Nanoscale Organization
TL;DR: The different q-regimes in the fluctuation spectra can be used to characterize mode dependent inter-facial tensions to understand the interfaces beyond the linear line tension calculations, which could be useful in interpretation of fluctuating boundaries in out-of-equilibrium in-vivo membrane systems.
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