Colloidal probe study of short time local and long time reptational motion of semiflexible macromolecules in entangled networks

Dichtl, Marius A.; Sackmann, E.

doi:10.1088/1367-2630/1/1/318

Cited by 37 publications

(60 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…j Þ. This is the case for probabilities <0:1, corresponding to a constraining potential of $2k B T or more, a regime not probed in prior studies [9]. At other actin concentrations, the distribution was similar except that it broadened as concentration decreased.…”

mentioning

confidence: 61%

“…In addition to the voluminous literature comparing models to measurements of mechanical properties and diffusion [6,8], which is indirect, we call attention to the direct measurements. The pioneering work of Sackmann confirmed anisotropy of diffusion for the system that we study here [9], semiflexible filaments of F-actin, but was limited by colloidal bead markers attached to actin. Force measurements were made by dragging DNA through other similar DNA molecules [10] but nonlinear flows complicated interpretation.…”

mentioning

confidence: 61%

See 1 more Smart Citation

Confining Potential when a Biopolymer Filament Reptates

et al. 2010

View full text Add to dashboard Cite

Using single-molecule fluorescence imaging, we track Brownian motion perpendicular to the contour of tightly entangled F-actin filaments and extract the confining potential. The chain localization presents a small-displacement Hookean regime followed by a large amplitude regime where the effective restoring force is independent of displacement. The implied heterogeneity characterized by a distribution of tube width is modeled.

show abstract

mentioning

confidence: 61%

mentioning

confidence: 61%

Confining Potential when a Biopolymer Filament Reptates

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The latter have been measured rheometrically for biopolymers such as actin [11][12][13][14] and pectin [15], as well as for self-assembling synthetic networks [16,17]. While theoretical approaches so far have employed a homogeneity (or mean-field) assumption, treating the tube radius as a constant, experiments [5][6][7]18,19] indicate substantial heterogeneities, which recently also have been found in simulations [9].…”

mentioning

confidence: 99%

Tube Width Fluctuations in F-Actin Solutions

et al. 2010

View full text Add to dashboard Cite

We determine the statistics of the local tube width in F-actin solutions, beyond the usually reported mean value. Our experimental observations are explained by a segment fluid theory based on the binary collision approximation. In this systematic generalization of the standard mean-field approach, effective polymer segments interact via a potential representing the topological constraints. The analytically predicted universal tube width distribution with a stretched tail is in good agreement with the data.

show abstract

“…Therefore, the conformational dynamics and motion of single filaments embedded in networks may be visualized and analyzed by fluorescence microscopy (16) or by labeling with colloidal probes (17). In previous work, the latter possibility was used to relate macroscopic viscoelastic impedance spectra to thermally driven single-filament motion.…”

mentioning

confidence: 99%

Microrheometry of semiflexible actin networks through enforced single-filament reptation: Frictional coupling and heterogeneities in entangled networks

Dichtl

Sackmann

2002

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

View full text Add to dashboard Cite

Magnetic tweezers are applied to study the enforced motion of single actin filaments in entangled actin networks to gain insight into friction-mediated entanglement in semiflexible macromolecular networks. Magnetic beads are coupled to one chain end of test filaments, which are pulled by 5 to 20 pN force pulses through entangled solutions of nonlabeled actin, the test filaments thus acting as linear force probes of the network. The transient filament motion is analyzed by microfluorescence, and the deflectionversus-time curves of the beads are evaluated in terms of a mechanical equivalent circuit to determine viscoelastic parameters, which are then interpreted in terms of viscoelastic moduli of the network. We demonstrate that the frictional coefficient characterizing the hydrodynamic coupling of the filaments to the surrounding network is much higher than predicted by the tube model, suggesting that friction-mediated interfilament coupling plays an important role in the entanglement of non-cross-linked actin networks. Furthermore, the local tube width along the filament contour (measured in terms of the root-mean-square displacement characterizing the lateral Brownian motion of the test filament) reveals strong fluctuations that can lead to transient local pinching of filaments. N etworks of filamentous actin (F-actin) are of great interest from the point of view of both cell biology and polymer physics and have thus been the subject of intense experimental and theoretical studies. On the one hand, actin is a major structural component of the intracellular scaffold (the cytoskeleton) and plays a key role in various cellular processes, such as cell locomotion (1, 2), the transport processes within cells (3), or the control of cell adhesion on surfaces (4). To fulfill this multiplicity of tasks, nature uses a large number of helper proteins. These include severing proteins by which the length of actin filaments can be manipulated, monomer-sequestering proteins that allow the control of the polymer concentration, and finally a manifold of cross-linker proteins enabling the generation of randomly organized gels or arrangements of bundles acting as cell-stabilizing fibers or cables for intracellular transport (5).On the other hand, F-actin is a prototype of a semiflexible polymer. Highly versatile models of entangled and cross-linked networks of semiflexible macromolecules can be designed by controlling the structure through the manifold of manipulating proteins to study the distinct physical properties of this particular class of polymer networks. Such semiflexible polymer networks exhibit outstanding viscoelastic features, which are determined by a subtle interplay of entropic and enthalpic contributions to the elastic free energy of the individual filament (6-12).One distinct advantage of actin as model polymer is the large contour length (typically in the 10-m range) (13) and persistence length (L p Ӎ17 m) (10, 14, 15) enabling the design of networks with mesh sizes in the optical wavelength regime. Therefore, t...

show abstract

Colloidal probe study of short time local and long time reptational motion of semiflexible macromolecules in entangled networks

Cited by 37 publications

References 16 publications

Confining Potential when a Biopolymer Filament Reptates

Confining Potential when a Biopolymer Filament Reptates

Tube Width Fluctuations in F-Actin Solutions

Microrheometry of semiflexible actin networks through enforced single-filament reptation: Frictional coupling and heterogeneities in entangled networks

Contact Info

Product

Resources

About