Passive or Active Fluctuations in Membranes Containing Proteins

Girard, Philippe; Prost, Jacques; Bassereau, Patricia

doi:10.1103/physrevlett.94.088102

Cited by 129 publications

(135 citation statements)

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“…This leads to a reduction of the bending stiffness of the membrane. In fact, this has been measured for conical-shaped transmembrane proteins such as calcium ATP-ase (Girard et al 2005), whereas no reduction of the bending stiffness was measured for the cylindrical shaped protein pump bacteriorhodopsin (Manneville et al 1999). Confocal microscopy of membrane nanotubes has also revealed the sorting of the curvaturesensitive GTP-ase ArfGap1 (Ambroggio et al 2010).…”

Section: Protein Binding Enhances Lipid Sortingmentioning

confidence: 99%

Curvature-Driven Lipid Sorting in Biomembranes

Callan-Jones¹,

Sorre²,

Bassereau³

2011

Cold Spring Harbor Perspectives in Biology

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It has often been suggested that the high curvature of transport intermediates in cells may be a sufficient means to segregate different lipid populations based on the relative energy costs of forming bent membranes. In this review, we present in vitro experiments that highlight the essential physics of lipid sorting at thermal equilibrium: It is driven by a trade-off between bending energy, mixing entropy, and interactions between species. We collect evidence that lipid sorting depends strongly on lipid -lipid and protein-lipid interactions, and hence on the underlying composition of the membrane and on the presence of bound proteins.

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Section: Protein Binding Enhances Lipid Sortingmentioning

confidence: 99%

Curvature-Driven Lipid Sorting in Biomembranes

Callan-Jones¹,

Sorre²,

Bassereau³

2011

Cold Spring Harbor Perspectives in Biology

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128

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“…The importance of active processes has been demonstrated in an experiment showing that the fluctuations in the shape of red blood cells depend on the viscosity of the environment and on ATP concentrations [4]. In in vitro experiments, nonequilibrium forces arising from ion pumps embedded in a membrane are shown to enhance its fluctuations [5,6,7]. There are currently two theoretical models for active membranes [3].…”

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confidence: 99%

Dynamics of active membranes with internal noise

Lacoste¹,

Lau²

2005

Europhys. Lett.

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Subcellular structure and processes. PACS. 05.40.-a -Fluctuation phenomena, random processes, noise, and Brownian motion. PACS. 05.70.Np -Interface and surface thermodynamics.Abstract. -We study the time-dependent height fluctuations of an active membrane containing energy-dissipating pumps that drive the membrane out of equilibrium. Unlike previous investigations based on models that neglect either curvature couplings or random fluctuations in pump activities, our formulation explores two new models that take both of these effects into account. In the first model, the magnitude of the nonequilibrium forces generated by the pumps is allowed to fluctuate temporally. In the second model, the pumps are allowed to switch between "on" and "off" states. We compute the mean squared displacement of a membrane point for both models, and show that they exhibit distinct dynamical behaviors from previous models, and in particular, a superdiffusive regime specifically arising from the shot noise.Introduction. -While the physics of biomembranes in equilibrium is fairly developed [1], recent studies focus on active membranes that contain proteins, such as ion channels, ion pumps, and photo-active proteins like bacteriorhodopsin. These proteins consume the chemical energy of ATP, dissipate it into the medium, and thus drive the membrane out of equilibrium [2,3]. The importance of active processes has been demonstrated in an experiment showing that the fluctuations in the shape of red blood cells depend on the viscosity of the environment and on ATP concentrations [4]. In in vitro experiments, nonequilibrium forces arising from ion pumps embedded in a membrane are shown to enhance its fluctuations [5,6,7]. There are currently two theoretical models for active membranes [3]. The Prost-Bruinsma (PB) model takes nonequilibrium forces in the form of active noises that include diffusion and the stochastic nature (shot noise) of the pumps, but ignores the coupling between the pumps and membrane curvature [8,9,10]. The other model proposed by Ramaswamy, Toner and Prost (RTP) incorporates this coupling but ignores the random nature of the protein activity [11,12]. For steady state measurements of active membranes, the RTP model agrees quite well with experiments [6,7]. In this Letter, we further explore the dynamical properties of the RTP model, argue that it is important to include the shot noise for dynamical measurements, and present two new models that include both curvature effects and pump stochasticity. In the first model, which may be an appropriate description for light-activated pumps such as

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“…In [4,6] a factor two to three increase of T eff in micropipette experiments on active membranes were reported. This increase was assigned to the averaged forcedipole activity represented by F (2) in Equation (69).…”

Section: Micropipette Experimentsmentioning

confidence: 99%

“…Lipid membranes in their fluid phase are flexible structures undergoing thermally excited shape fluctuations that can be observed directly by video microscopy [2]. Indirect studies of the fluctuations, using micromanipulation techniques to measure the amount of membrane excess area stored in the fluctuations, have already given evidence that activated proteins incorporated in lipid membranes enhance these fluctuations [3,4]. Efforts are being put into extending these studies to use video microscopy to obtain the fluctuation spectrum directly [5].…”

Section: Introductionmentioning

confidence: 99%

Fluctuation spectrum of quasispherical membranes with force-dipole activity

Lomholt¹

2006

Phys. Rev. E

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The fluctuation spectrum of a quasi-spherical vesicle with active membrane proteins is calculated. The activity of the proteins is modeled as the proteins pushing on their surroundings giving rise to non-local force distributions. Both the contributions from the thermal fluctuations of the active protein densities and the temporal noise in the individual active force distributions of the proteins are taken into account. The noise in the individual force distributions is found to become significant at short wavelengths.

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Passive or Active Fluctuations in Membranes Containing Proteins

Cited by 129 publications

References 24 publications

Curvature-Driven Lipid Sorting in Biomembranes

Curvature-Driven Lipid Sorting in Biomembranes

Dynamics of active membranes with internal noise

Fluctuation spectrum of quasispherical membranes with force-dipole activity

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