Dynamics and Rheology of Actin Solutions

Isambert, Hervé; Maggs, A. C.

doi:10.1021/ma946418x

Cited by 199 publications

(279 citation statements)

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“…The generally accepted theory for the concentration dependence of the plateau modulus of entangled WLCs is based on the free energy change F of confining a polymer to a tube of diameter d [7,8] …”

Section: Prl 99 048101 (2007) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

“…Significant progress has also been made towards the description of the collective properties of WLCs, for example, in the form of entangled solutions. One of the hallmarks of this development is the scaling of the plateau shear modulus with concentration G c 7=5 [7][8][9], which is well established experimentally [10,11].Another important emerging class of semiflexible polymers consists of bundles of WLCs [12,13]. Semiflexible polymer bundles consisting of F-actin or microtubules are ubiquitous in biology [14] and have unique mechanical properties that may well be exploited in the design of nanomaterials [13].…”

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confidence: 99%

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Statistical Mechanics of Semiflexible Bundles of Wormlike Polymer Chains

2007

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We demonstrate that a semiflexible bundle of wormlike chains exhibits a state-dependent bending stiffness that alters fundamentally its scaling behavior with respect to the standard wormlike chain. We explore the equilibrium conformational and mechanical behavior of wormlike bundles in isolation, in cross-linked networks, and in solution. DOI: 10.1103/PhysRevLett.99.048101 PACS numbers: 87.16.Ka, 82.35.Lr, 83.10.ÿy, 87.15.La In recent decades, the wormlike chain (WLC) has emerged as the standard model for the description of semiflexible polymers [1]. The defining property of a WLC is a mechanical bending stiffness f that is an intrinsic material constant of the polymer. Within this framework, numerous correlation and response functions have been calculated, providing a comprehensive picture of the equilibrium and dynamical properties of WLCs [2 -4]. A number of experimental studies have demonstrated the applicability of the WLC model to DNA [5] and F-actin [6], among other biological and synthetic polymers. Significant progress has also been made towards the description of the collective properties of WLCs, for example, in the form of entangled solutions. One of the hallmarks of this development is the scaling of the plateau shear modulus with concentration G c 7=5 [7][8][9], which is well established experimentally [10,11].Another important emerging class of semiflexible polymers consists of bundles of WLCs [12,13]. Semiflexible polymer bundles consisting of F-actin or microtubules are ubiquitous in biology [14] and have unique mechanical properties that may well be exploited in the design of nanomaterials [13]. As shown by Bathe et al. [15,16], wormlike bundles (WLBs) have a state-dependent bending stiffness B that derives from a generic interplay between the high stiffness of individual filaments and their rather soft relative sliding motion. In this Letter, we demonstrate that this state dependence gives rise to fundamentally new behavior that cannot be reproduced trivially using existing relations for WLCs. We explore the consequences of a state-dependent bending stiffness on the statistical mechanics of isolated WLBs, as well as on the scaling behavior of their entangled solutions and cross-linked networks.We consider the bending of ordered bundles with an isotropic cross section. A bundle consists of N filaments of length L and bending stiffness f . Filaments are irreversibly cross-linked to their nearest neighbors by discrete cross-links with mean axial spacing . Cross-links are modeled to be compliant in shear along the bundle axis with finite shear stiffness k and to be inextensible transverse to the bundle axis, thus fixing the interfilament distance b [17]. Bundle deformations are characterized by the transverse deflection r ? s of the bundle neutral surface at axial position s along the backbone and by the stretching deformation u i s of filament i. The torsional stiffness of the bundle is assumed to be of the same order as the bending stiffness. Thus, as long as transverse deflections remain sm...

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Section: Prl 99 048101 (2007) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

mentioning

confidence: 99%

Statistical Mechanics of Semiflexible Bundles of Wormlike Polymer Chains

2007

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“…While the study of confined DNA is interesting from a physics perspective, it is also critical for device design, potentially leading to new applications of nanoconfinement (for example, the use of nanochannels to prestretch and stabilize DNA before threading through a nanopore [5]). Moreover, available models [7][8][9][10][11] and simulations [12,13] are unable to account for the effect of varying confinement over the entire range of scales used in nanodevices. The theory gives asymptotic results valid only in limits that are not necessarily compatible with device requirements [1].…”

mentioning

confidence: 99%

“…Physically, this time scale arises from the diffusion of contour along the tube [10]. [We note that there is a controversy in the literature over the correct scaling of the relaxation time with width [11].…”

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Statics and Dynamics of Single DNA Molecules Confined in Nanochannels

et al. 2005

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The successful design of nanofluidic devices for the manipulation of biopolymers requires an understanding of how the predictions of soft condensed matter physics scale with device dimensions. Here we present measurements of DNA extended in nanochannels and show that below a critical width roughly twice the persistence length there is a crossover in the polymer physics. DOI: 10.1103/PhysRevLett.94.196101 PACS numbers: 81.16.Nd, 82.35.Lr, 82.39.Pj Top-down approaches to nanotechnology have the potential to revolutionize biology by making possible the construction of chip-based devices that can not only detect and separate single DNA molecules by size [1-4] but also-it is hoped in the future-actually sequence at the single molecule level [5]. While a number of top-down approaches have been proposed, all these approaches have in common the confinement of DNA to nanometer scales, typically 5-200 nm. Confinement alters the statistical mechanical properties of DNA. A DNA molecule in a nanochannel will extend along the channel axis to a substantial fraction of its full contour length [1,6]. Moreover, confinement is expected to alter the Brownian dynamics of the confined molecule [1]. While the study of confined DNA is interesting from a physics perspective, it is also critical for device design, potentially leading to new applications of nanoconfinement (for example, the use of nanochannels to prestretch and stabilize DNA before threading through a nanopore [5]). Moreover, available models [7][8][9][10][11] and simulations [12,13] are unable to account for the effect of varying confinement over the entire range of scales used in nanodevices. The theory gives asymptotic results valid only in limits that are not necessarily compatible with device requirements [1].Consider a DNA molecule of contour length L, width w, and persistence length P confined to a nanochannel of width D with D less than the radius of gyration of the molecule. When D P, the molecule is free to coil in the nanochannel and the elongation is due entirely to excluded volume interactions between segments of the polymer greatly separated in position along the backbone (see Fig. 1). de Gennes developed a scaling argument for the average extension of a confined self-avoiding polymer [8,12] which was later generalized by Schaefer and Pincus to the case of a persistent self-avoiding polymer [14]. The de Gennes theory predicts an extension r that scales with D in the following way:If the aspect ratio of the channel is not unity, i.e., the width D D 1 does not equal the depth D 2 , then Eq. (1) is still valid provided that D is replaced by the geometric average of the dimensions. As the channel width drops below the persistence length, the physics is dominated not by excluded volume but by the interplay of confinement and intrinsic DNA elasticity. In the strong confinement limit D P, backfolding is energetically unfavorable and contour length is stored exclusively in deflections made by the polymer with the walls. These deflections occur on average over th...

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From Bioreactor to Bulk Rheology: Achieving Scalable Production of Highly Concentrated Circular DNA

Paiva,

Alakwe,

Marfai

et al. 2024

Advanced Materials

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DNA serves as a model system in polymer physics due to its ability to be obtained as a uniform polymer with controllable topology and nonequilibrium behavior. Currently, a major obstacle in the widespread adoption of DNA is obtaining it on a scale and cost basis that accommodates bulk rheology and high‐throughput screening. To address this, recent advancements in bioreactor‐based plasmid DNA production is coupled with anion exchange chromatography producing a unified approach to generating gram‐scale quantities of monodisperse DNA. With this method, 1.1 grams of DNA is obtained per batch to generate solutions with concentrations up to 116 mg mL−1. This solution of uniform supercoiled and relaxed circular plasmid DNA, is roughly 69 times greater than the overlap concentration. The utility of this method is demonstrated by performing bulk rheology measurements at sample volumes up to 1 mL on DNA of different lengths, topologies, and concentrations. The measured elastic moduli are orders of magnitude larger than those previously reported for DNA and allowed for the construction of a time‐concentration superposition curve that spans 12 decades of frequency. Ultimately, these results can provide important insights into the dynamics of ring polymers and the nature of highly condensed DNA dynamics.

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Dynamics and Rheology of Actin Solutions

Cited by 199 publications

References 21 publications

Statistical Mechanics of Semiflexible Bundles of Wormlike Polymer Chains

Statistical Mechanics of Semiflexible Bundles of Wormlike Polymer Chains

Statics and Dynamics of Single DNA Molecules Confined in Nanochannels

From Bioreactor to Bulk Rheology: Achieving Scalable Production of Highly Concentrated Circular DNA

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