The role of optical projection in the analysis of membrane fluctuations

Rautu, S. Alex; Orsi, Davide; Michele, Lorenzo Di; Rowlands, G.; Cicuta, Pietro; Turner, Matthew S.

doi:10.1039/c7sm00108h

Cited by 33 publications

(38 citation statements)

References 53 publications

(76 reference statements)

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“…e)-(f ) we test the effect of changing membrane bending modulus κ. In the range of values we tested, centred around the experimental bending modulus of DOPC bilayersκ ≈ 19k B T ,[71][72][73] we observe little effect on the patch size and thereby on the configurational free energy. This evidence confirms that contributions arising from the elastic deformation and the suppression of membrane thermal fluctuations are overwhelmed by the entropic terms related to bridge formation 62,63.…”

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confidence: 82%

Melting transition in lipid vesicles functionalised by mobile DNA linkers

et al. 2016

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We study phase behaviour of lipid-bilayer vesicles functionalised by ligand-receptor complexes made of synthetic DNA by introducing a modelling framework and a dedicated experimental platform. In particular, we perform Monte Carlo simulations that combine a coarse grained description of the lipid bilayer with state of art analytical models for multivalent ligand-receptor interactions. Using density of state calculations, we derive the partition function in pairs of vesicles and compute the number of ligand-receptor bonds as a function of temperature. Numerical results are compared to microscopy and fluorimetry experiments on large unilamellar vesicles decorated by DNA linkers carrying complementary overhangs. We find that vesicle aggregation is suppressed when the total number of linkers falls below a threshold value. Within the model proposed here, this is due to the higher configurational costs required to form inter-vesicle bridges as compared to intra-vesicle loops, which are in turn related to membrane deformability. Our findings and our numerical/experimental methodologies are applicable to the rational design of liposomes used as functional materials and drug delivery applications, as well as to study inter-membrane interactions in living systems, such as cell adhesion.

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confidence: 82%

Melting transition in lipid vesicles functionalised by mobile DNA linkers

et al. 2016

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“…Note that the relaxation time given by Eq. 2 in Rautu et al [25] has incorrect dependence on the viscosities of the enclosed and suspending solutions. The simulated contours were analyzed by our code and the extracted bending rigidity and tension were compared to the input values to confirm accuracy of the contour detection, Fourier decomposition and data fitting algorithms.…”

Section: Equilibrium Fluctuations Of a Quasi-spherical Vesiclementioning

confidence: 97%

“…The fluctuating amplitudes have variance dependent on the membrane bending rigidity and tension. Imaging is most commonly done by phase contrast microscopy [1,7,15,[17][18][19][20][21][22] but other methods such as confocal [23][24][25] and light sheet microscopy [26] have also been employed. The increased variety of imaging methods raises the question if they all yield the same results.…”

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confidence: 99%

“…Recently, Rautu et al [25] pointed out that in phase contrast imaging, projections of out-of-focus fluctuations may contribute to the contour statistics leading to systematic overestimation of the bending rigidity value when compared to other methods such as micropipette aspiration and X-ray scattering. Their analysis claimed to resolve the discrepancies and confocal microscopy was suggested as a better imaging technique due to the precise control over the focal depth.…”

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confidence: 99%

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Fluctuation spectroscopy of giant unilamellar vesicles using confocal and phase contrast microscopy

Faizi¹,

Reeves

Georgiev

et al. 2020

Preprint

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A widely used method to measure the bending rigidity of bilayer membranes is fluctuation spectroscopy, which analyses the thermally-driven membrane undulations of giant unilamellar vesicles recorded with either phase-contrast or confocal microscopy. Here, we analyze the fluctuations of the same vesicle using both techniques and obtain consistent values for the bending modulus. We discuss the factors that may lead to discrepancies.

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“…GUV membrane tension is quantified by flicker spectroscopy. [31][32][33] This technique analyses the power spectrum of membrane undulations (mean square undulation amplitude 〈| ( )| 2 〉 versus wavenumber from image analysis of a confocal microscopy time series taken at the midpoint (equator) of the GUV. 1000 frames are taken per GUV at 1024x1024 pixel resolution, frame rate and pixel size varied on a case by case basis as the maximum magnification that could accommodate the whole GUV is used to maximize scan speed and these factors are accounted for in the MATLAB analysis software.…”

Section: Flicker Spectroscopymentioning

confidence: 99%

In vitro membrane remodelling by ESCRT-II/ESCRT-III is regulated by negative feedback from membrane tension

Booth

Ciani

et al. 2018

Preprint

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Artificial cells can shed new light on the molecular basis for life and hold potential for new chemical technologies. Inspired by how nature dynamically regulates its membrane compartments, we aim to repurpose the endosomal sorting complex required for transport (ESCRT) to generate complex membrane architectures as suitable scaffolds for artificial cells.Purified ESCRT-III components perform topological transformations on giant unilamellar vesicles (GUVs) to create complex "vesicles-within-a-vesicle" architectures resembling the compartmentalisation in eukaryotic cells. Thus far, the proposed mechanisms for this activity are based on how assembly and disassembly of ESCRT-III on the membrane drives deformation. Here we demonstrate the existence of a negative feedback mechanism from membrane mechanics that regulates ESCRT-III activity. ILV formation removes excess membrane area, increasing tension, which in turn suppresses downstream ILV formation.This mechanism for in vitro regulation of ESCRT-III activity may also have important implications for its in vivo functions.

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The role of optical projection in the analysis of membrane fluctuations

Cited by 33 publications

References 53 publications

Melting transition in lipid vesicles functionalised by mobile DNA linkers

Melting transition in lipid vesicles functionalised by mobile DNA linkers

Fluctuation spectroscopy of giant unilamellar vesicles using confocal and phase contrast microscopy

In vitro membrane remodelling by ESCRT-II/ESCRT-III is regulated by negative feedback from membrane tension

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