The depletion attraction: an underappreciated force driving cellular organization

Marenduzzo, Davide; Finan, Kieran; Cook, Peter R.

doi:10.1083/jcb.200609066

Cited by 343 publications

(319 citation statements)

References 62 publications

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“…These systems are of particular interest because they serve as a convenient model to study depletion interactions, which also play a considerable role in biological settings, contributing to protein folding, fiber bundling, and the formation of supramolecules [2][3][4][5]. Depletion arises as two or more confining surfaces approach one another and exclude a region between them where the depletant, in this case polymer, can no longer exist.…”

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confidence: 99%

Structure of phase-separated athermal colloid-polymer systems in the protein limit

2013

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Structural features of phase separated athermal colloid-polymer mixtures in the so-called "protein limit," where polymer chain dimensions exceed those of the colloid, are investigated using grand canonical Monte Carlo simulations on a fine lattice. Previous work [N. A. Mahynski, et al. Phys. Rev. E 85, 051402 (2012)] has shown that this model accurately captures the phase behavior of experimental systems, and that colloids with sufficiently small diameters, σc, relative to that of the monomeric segments, σs, phase separate more readily than their large-diameter counterparts. In the present study, we directly connect colloid and polymer structure with their phase behavior by investigating these solutions along their binodal curves; we also explore the role of colloid surface curvature in destabilizing such solutions. Our findings suggest that simple consideration of an additional depletion radius, on the order of the σs, leads to a quantitatively accurate prediction of the division between stable and unstable ranges of d = σs/σc. We compare these results to continuum models with different bonding potentials between monomer segments in order to elucidate the significance of the lattice model's bond fluctuations and inherently coarse colloid surface. In a number of cases, the continuum models deviate both qualitatively and quantitatively from the lattice results, but the binodals of the continuum models are presently not known, making a strong conclusion about these differences impossible.

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Structure of phase-separated athermal colloid-polymer systems in the protein limit

2013

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“…In contrast to the case of thermotropic LC- 45 CNT composites, one thus always starts by preparing an isotropic low-surfactant-concentration suspension of CNTs, and then this is made liquid crystalline by adding more surfactant [24][25][26] or it is added to an already prepared lyotropic liquid crystal sample 51,55 . Adding dry CNT powder directly to 50 a preformed lyotropic liquid crystal phase works poorly 55 , as it is difficult to break up the large CNT aggregates of a dry CNT sample in such a viscous host.…”

Section: Cnts In Lyotropic Liquid Crystalsmentioning

confidence: 99%

“…However, as the amount of surfactant is increased in a CNT suspension, one must take the important phenomenon of depletion attraction into account 49,50 . When much more of a certain surfactant is present than what is 60 necessary for covering the CNT surfaces, the surplus surfactant molecules organize into small empty micelles.…”

Section: Introductionmentioning

confidence: 99%

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Carbon Nanotubes in Liquid Crystals

Lagerwall

Scalia

2014

Handbook of Liquid Crystals

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We review the research on carbon nanotube (CNT) dispersion in liquid crystals (LCs), focusing mainly on the approaches where the aim is to align CNTs along the LC director field, but covering briefly also the proposed possibility to enhance thermotropic LCs by CNT-doping. All relevant LC types are considered: thermotropic LC hosts allowing dynamic CNT realignment, lyotropic LC hosts allowing very high concentration of CNTs uniformly aligned over macroscopic areas and 10 consequent removal of the LC, and LC phases formed by CNTs themselves, used in spinning highquality carbon nanotube fibres. We also discuss the issue of CNT dispersion with some detail, since successful nanotube separation is imperative for success in this field regardless of the type of LC that is considered. We end by defining a few major challenges for the development of the field over the next few years, critical for reaching the stage where industrially viable protocols for LC-15 based CNT alignment can be defined.

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“…Indeed, entropic depletion should exist for all polymers, leading to macromolecular ''crowding'' that can accelerate associative biochemical reactions within cells (8) (reviewed in ref. 9). However, the long persistence length of F-actin should make depletion dramatic.…”

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Filament rigidity causes F-actin depletion from nonbinding surfaces

Fisher¹,

Kuo

2009

Proc. Natl. Acad. Sci. U.S.A.

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Proximity to membranes is required of actin networks for many key cell functions, including mechanics and motility. However, F-actin rigidity should hinder a filament's approach to surfaces. Using confocal microscopy, we monitor the distribution of fluorescent actin near nonadherent glass surfaces. Initially uniform, monomers polymerize to create a depletion zone where F-actin is absent at the surface but increases monotonically with distance from the surface. At its largest, depletion effects can extend >35 m, comparable with the average, mass-weighted filament length. Increasing the rigidity of actin filaments with phalloidin increases the extent of depletion, whereas shortening filaments by using capping protein reduces it proportionally. In addition, depletion kinetics are faster with higher actin concentrations, consistent with faster polymerization and faster Brownian-ratchet-driven motion. Conversely, the extent of depletion decreases with actin concentration, suggesting that entropy is the thermodynamic driving force. Quantitatively, depletion kinetics and extent match existing actin kinetics, rigidity, and lengths. However, explaining depletion profiles and concentration dependence (power-law of ؊1) requires modifying the rigid rod model. Within cells, surface depletion should slow membrane-associated F-actin reactions another Ϸ10-fold beyond hydrodynamically slowed diffusion of filaments (Ϸ10-fold). In addition, surface depletion should cause membranes to bend spontaneously toward filaments. Such depletion principles underlie the thermodynamics of all surface-associated reactions with mechanical structures, ranging from DNA to filaments to networks. For various functions, cells must actively resist the thermodynamics of depletion.confocal microscopy ͉ cytoskeleton ͉ fluorescence ͉ polymer physics ͉ polymer depletion

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The depletion attraction: an underappreciated force driving cellular organization

Cited by 343 publications

References 62 publications

Structure of phase-separated athermal colloid-polymer systems in the protein limit

Structure of phase-separated athermal colloid-polymer systems in the protein limit

Carbon Nanotubes in Liquid Crystals

Filament rigidity causes F-actin depletion from nonbinding surfaces

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