Diffusion of compact macromolecules through polymer meshes: mesh dynamics and probe dynamics

Biehl, Ralf; Guo, Xuhong; Prud'homme, Robert Krafft; Monkenbusch, M.; Allgeier, J.; Richter, D.

doi:10.1016/j.physb.2004.03.258

Cited by 6 publications

(7 citation statements)

References 3 publications

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“…Based on these values, a cubic lattice model that assumes mucins to be long rigid polymers predicts an average pore size of 40-100 nm. If mucins are instead assumed to be flexible polymers (29,30), the predicted pore size is approximately 15-50 nm (31). Therefore, the rapid diffusion of 500-nm PEG-coated nanoparticles indicates that individual mucin monomers must be condensed and/or bundled together into thick cables in CVM, markedly increasing the pore size.…”

Section: Resultsmentioning

confidence: 99%

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses

Lai

Wang²,

Hida³

et al. 2009

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

339

343

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The mechanisms by which mucus helps prevent viruses from infecting mucosal surfaces are not well understood. We engineered non-mucoadhesive nanoparticles of various sizes and used them as probes to determine the spacing between mucin fibers (pore sizes) in fresh undiluted human cervicovaginal mucus (CVM) obtained from volunteers with healthy vaginal microflora. We found that most pores in CVM have diameters significantly larger than human viruses (average pore size 340 ± 70 nm; range approximately 50–1800 nm). This mesh structure is substantially more open than the 15–100-nm spacing expected assuming mucus consists primarily of a random array of individual mucin fibers. Addition of a nonionic detergent to CVM caused the average pore size to decrease to 130 ± 50 nm. This suggests hydrophobic interactions between lipid-coated “naked” protein regions on mucins normally cause mucin fibers to self-condense and/or bundle with other fibers, creating mucin “cables” at least three times thicker than individual mucin fibers. Although the native mesh structure is not tight enough to trap most viruses, we found that herpes simplex virus (approximately 180 nm) was strongly trapped in CVM, moving at least 8,000-fold slower than non-mucoadhesive 200-nm nanoparticles. This work provides an accurate measurement of the pore structure of fresh, hydrated ex vivo CVM and demonstrates that mucoadhesion, rather than steric obstruction, may be a critical protective mechanism against a major sexually transmitted virus and perhaps other viruses.

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Section: Resultsmentioning

confidence: 99%

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses

Lai

Wang²,

Hida³

et al. 2009

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

339

343

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“…12a). In microrheological experiments with viscoelastic media such as gels, elastic trapping can usually be detected for diffusing particles by the appearance of a trapping plateau on shorter time scales, while on longer time scales, the particles break free and diffuse normally (Biehl et al 2004;Mason and Weitz 1995;Tseng et al 2004;Wong et al 2004). For our chromatin networks, no characteristic time scale for the transition from being trapped to free diffusion can be determined, suggesting that the self-diffusion of the chromatin network is too rapid to keep molecules trapped.…”

Section: Nuclear Elasticitymentioning

confidence: 99%

Chromosome dynamics, molecular crowding, and diffusion in the interphase cell nucleus: a Monte Carlo lattice simulation study

Fritsch

Langowski

2010

Chromosome Res

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Using Monte Carlo simulations, we have investigated the decondensation of chromosomes during interphase and the diffusive transport of spherical probe particles in the chromatin network. The chromatin fibers are modeled as semiflexible polymer chains on a fixed threedimensional grid, taking into account their flexibility and eventual chain crossing by the aid of topoisomerases. The network thus created will obstruct the diffusion of macromolecules. A result of our simulations is that crowding of diffusing molecules leaves the dynamics of the chromosomes and the behavior of other diffusing molecules qualitatively unaffected. Furthermore, the capability of the simulated chromatin network to trap diffusing molecules over long times is lower than that measured in microrheological experiments. Microrheology is a technique that allows to determine the viscoelastic properties of a material by the motion of embedded tracer particles. Long-time trapping requires a stiff network, as only such a network quickly responds to the diffusive fluctuations of tracers C. C. Fritsch · J. Langowski (B) Biophysics of Macromolecules, German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), Im Neuenheimer Feld 580, 69120 Heidelberg, Germany e-mail: joerg.langowski@dkfz-heidelberg.de and prevents them from squeezing through meshes. A high degree of crosslinking amplifies this effect. The presence of a flexible and uncrosslinked polymer simply increases the effective viscosity sensed by tracer particles. The diffusion of tracers in our simulations reveals rather viscous than elastic chromatin networks, suggesting that chromatin alone cannot account for the high elasticity of the cell nucleus.

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“…The relaxation rates agree quantitatively with the literature (Γ = 0.09-0.18 ns -1 at Q = 0.1 A ˚-1 ). 12,13 From our relaxation rates, we would estimate the effective viscosities of the surroundings to η S = 0.253Q 3 k B T/Γ = 0.016 and 0.0091 Pa s for the 4 and 8% samples. The higher polymer concentration leads to faster motions because the denser polymer is more rigid.…”

Section: T H Imentioning

confidence: 99%

“…This finding agrees qualitatively with the literature, 11 but not for pure gels. 12,13 The dynamics can be described in more detail by the original models of polymers. For solutions, there is the Zimm 24 model, and for melts, there is the Rouse 25 model.…”

Section: T H Imentioning

confidence: 99%

“…This is in qualitative agreement with sound velocities 11 but opposes pure polymer gels. 12,13 The connection of a constraint region near the clay particles and the overall dynamics observed by rheological experiments was proposed in ref 14. This article focuses on the dynamics of polymers adsorbed on clay platelets. The characterization was done by neutron spinecho spectroscopy.…”

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confidence: 99%

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Confined Polymer Dynamics on Clay Platelets

et al. 2010

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The structure and dynamics of poly(ethylene oxide) adsorbed on dispersed clay platelets are investigated by small-angle neutron scattering and neutron spin-echo spectroscopy. The intermediate scattering function has a mobile contribution described by the Zimm theory and an immobile contribution that is constant within the time window. The immobile fraction as a function of the scattering vector Q is described by a Lorentz function, from which a localization length is determined. The relaxation rates grow with polymer concentration in agreement with dielectric measurements but contrary to pure polymer gels.

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Diffusion of compact macromolecules through polymer meshes: mesh dynamics and probe dynamics

Cited by 6 publications

References 3 publications

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses

Chromosome dynamics, molecular crowding, and diffusion in the interphase cell nucleus: a Monte Carlo lattice simulation study

Confined Polymer Dynamics on Clay Platelets

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