Critical point fluctuations in supported lipid membranes

Connell, Simon D.; Heath, George R.; Olmsted, Peter D.; Kisil, Anastasia V.

doi:10.1039/c2fd20119d

Cited by 57 publications

(108 citation statements)

References 39 publications

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“…The planar bilayer exposed to E107-3 does not contain transmembrane pores, but rather resembles the fluctuation-like structures observed in ternary lipid mixtures [52, 62]. A correlation length ξ was used to describe the length scale of the fluctuation-like structures [52, 62].…”

Section: Resultsmentioning

confidence: 99%

Modulation of lipid membrane structural and mechanical properties by a peptidomimetic derived from reduced amide scaffold

Khadka¹,

Teng²,

Cai³

et al. 2017

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Understanding how antimicrobial peptidomimetics interact with lipid membranes is important in battling multidrug resistant bacterial pathogens. We study the effects of a recently reported peptidomimetic on lipid bilayer structural and mechanical properties. The compound referred to as E107-3 is synthesized based on the acylated reduced amide scaffold and has been shown to exhibit good antimicrobial potency. Our vesicle leakage essay indicates that the compound increases lipid bilayer permeability. We use micropipette aspiration to explore the kinetic response of giant unilamellar vesicles (GUVs). Exposure to the compound causes the GUV protrusion length LP to spontaneously increase and then decrease, followed by GUV rupture. Solution atomic force microscopy (AFM) is used to visualize lipid bilayer structural modulation within a nanoscopic regime. Unlike melittin, which produces pore-like structures, the peptidomimetic compound is found to induce nanoscopic heterogeneous structures. Finally, we use AFM-based force spectroscopy to study the impact of the compound on lipid bilayer mechanical properties. We find that incremental addition of the compound to planar lipid bilayers results in a moderate decrease of the bilayer puncture force FP and a 39% decrease of the bilayer area compressibility modulus KA. To explain our experimental data, we propose a membrane interaction model encompassing disruption of lipid chain packing and extraction of lipid molecules. The later action mode is supported by our observation of a double-bilayer structure in the presence of fusogenic calcium ions.

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Section: Resultsmentioning

confidence: 99%

Modulation of lipid membrane structural and mechanical properties by a peptidomimetic derived from reduced amide scaffold

Khadka¹,

Teng²,

Cai³

et al. 2017

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…We choose the well-studied DOPC/eSM/Chol as the model system. 21, 30–31 The heterogeneous structure of DOPC/eSM/Chol 0.48/0.32/0.20 is shown in Fig. S8 (Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“…Such a transition has been reported before. 21, 30 In addition to domain shape and height contrast, the area fraction of the Lo phase becomes 0.37 at 32mol% Chol.…”

Section: Resultsmentioning

confidence: 99%

Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study

Pan

Khadka

2016

J. Phys. Chem. B

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Quantitative characterization of membrane defects (pores) is important for elucidating molecular basis of many membrane active peptides. We study kinetic defects induced by melittin in vesicular and planar lipid bilayers. Fluorescence spectroscopy measurements indicate that melittin induces time-dependent calcein leakage. Solution atomic force microscopy (AFM) is used to visualize melittin induced membrane defects. After initial equilibration, the most probable defect radius is ~3.8 nm in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) bilayers. Unexpectedly, defects become larger with longer incubation, accompanied by substantial shape transformation. The initial defect radius is ~4.7 nm in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. Addition of 30mol% cholesterol to DOPC bilayers suppresses defect kinetics, although the inhibitory impact is negated by longer incubation. Overall, the kinetic rate of defect development follows DLPC > DOPC > DOPC/cholesterol. Kinetic defects are also observed when anionic lipids are present. Based on the observation that defects can occupy as large as 40% of the bilayer surface, we propose a kinetic defect growth model. We also study the effect of melittin on the phase behavior of DOPC/egg-sphingomyelin/cholesterol bilayers. We find that melittin initially suppresses or eliminates liquid-ordered (Lo) domains; Lo domains gradually emerge and become the dominant species with longer incubation. Defects in phase coexisting bilayers have a most probable radius of ~5 nm, and are exclusively localized in the liquid-disordered (Ld) phase. Our experimental data highlight that melittin induced membrane defects are not static; conversely, spontaneous defect growth is intrinsically associated with membrane permeabilization exerted by melittin.

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“…Even at the high end, this differences is within 15% of T c , well within the range where 2D Ising model scaling laws apply. Experiments using AFM to probe supported membranes have shown the applicability of 2D Ising model predictions to nearly 10°C from T C by directly measuring correlation lengths of detected domains in supported membranes 99 . Experiments in both synthetic GUVs and isolated GPMVs also showed consistency with 2D Ising model predictions over a broader temperature range (up to >30°C above T C ), where an extended phase-like domain was stabilized through adhesion to a supported membrane 97 .…”

Section: Some Things Remain Universalmentioning

confidence: 99%

The Continuing Mystery of Lipid Rafts

Levental¹,

Veatch

2016

Journal of Molecular Biology

248

251

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Since its initial formalization nearly twenty years ago, the concept of lipid rafts has generated a tremendous amount of attention and interest, and nearly as much controversy. The controversy is perhaps surprising because the notion itself is intuitive: compartmentalization in time and space is a ubiquitous theme at all scales of biology, and therefore the partitioning of cellular membranes into lateral subdivision should be expected. Nevertheless, the physicochemical principles responsible for compartmentalization and the molecular mechanisms by which they are functionalized remain nearly as mysterious today as they were two decades ago. Herein, we review recent literature on this topic with a specific focus on the major open questions in the field, including: (1) what are the best tools to assay raft behavior in living membranes; (2) what is the function of the complex lipidome of mammalian cells with respect to membrane organization; (3) what are the mechanisms that drive raft formation and determine their properties; (4) how can rafts be modulated; (5) how is membrane compartmentalization integrated into cellular signaling. Despite decades of intensive research, this compelling field remains full of fundamental questions.

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Critical point fluctuations in supported lipid membranes

Cited by 57 publications

References 39 publications

Modulation of lipid membrane structural and mechanical properties by a peptidomimetic derived from reduced amide scaffold

Modulation of lipid membrane structural and mechanical properties by a peptidomimetic derived from reduced amide scaffold

Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study

The Continuing Mystery of Lipid Rafts

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