Complex Tracer Diffusion Dynamics in Polymer Solutions

Vagias, Apostolos; Raccis, Riccardo; Koynov, Kaloian; Jonas, Ulrich; Butt, Hans‐Jürgen; Fytas, George; Košovan, Peter; Lenz, Olaf; Holm, Christian

doi:10.1103/physrevlett.111.088301

Cited by 54 publications

(69 citation statements)

References 33 publications

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“…Careful analysis of the ACFs (as described in our previous work on this system 16 ) showed that the existence of a prolonged interaction between the streptavidin and the dextran can be ruled out. Indeed, if tracer/polymer complexes are stable enough to diffuse through the observation volume without dissociating, a second separate diffusion term should appear in the ACF, as indeed observed in systems where specific interactions exist between the tracer and the polymer 103 . No such term is observed in the case of streptavidin and dextran.…”

Section: The Anomalous Yet Brownian Motion Of Proteins In Crowded Dementioning

confidence: 99%

“…This does not immediately exclude, however, a more dynamic interaction scenario, where tracer molecules may bind and unbind during their passage through the detection volume. The duration of the tracer/polymer interaction would then introduce a characteristic timescale in the system, which, if similar to the characteristic residence time of the tracer in the FCS observation volume, might produce a deformation of individual ACFs undistinguishable from that caused by FBM 103 . An analytical form for the ACF can be derived in the case of rapid binding and unbinding to a single type of immobile "traps" ("stickand-diffuse" model, used to explain the mobility of synaptic vesicles 34 and transcription factors 104 ).…”

Section: The Anomalous Yet Brownian Motion Of Proteins In Crowded Dementioning

confidence: 99%

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Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy

et al. 2016

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The diffusion of macromolecules in cells and in complex fluids is often found to deviate from simple Fickian diffusion. One explanation offered for this behavior is that molecular crowding renders diffusion anomalous, where the mean-squared displacement of the particles scales as r 2 ∝ t α with α < 1. Unfortunately, methods such as fluorescence correlation spectroscopy (FCS) or fluorescence recovery after photobleaching (FRAP) probe diffusion only over a narrow range of lengthscales and cannot directly test the dependence of the mean-squared displacement (MSD) on time. Here we show that variable-lengthscale FCS (VLS-FCS), where the volume of observation is varied over several orders of magnitude, combined with a numerical inversion procedure of the correlation data, allows retrieving the MSD for up to five decades in time, bridging the gap between diffusion experiments performed at different lengthscales. In addition, we show that VLS-FCS provides a way to assess whether the propagator associated with the diffusion is Gaussian or non-Gaussian. We used VLS-FCS to investigate two systems where anomalous diffusion had been previously reported. In the case of dense cross-linked agarose gels, the measured MSD confirmed that the diffusion of small beads was anomalous at short lengthscales, with a cross-over to simple diffusion around ≈ 1 µm, consistent with a caged diffusion process. On the other hand, for solutions crowded with marginally entangled dextran molecules, we uncovered an apparent discrepancy between the MSD, found to be linear, and the propagators at short lengthscales, found to be non-Gaussian. These contradicting features call to mind the "anomalous, yet Brownian" diffusion observed in several biological systems, and the recently proposed "diffusing diffusivity" model.

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Section: The Anomalous Yet Brownian Motion Of Proteins In Crowded Dementioning

confidence: 99%

Section: The Anomalous Yet Brownian Motion Of Proteins In Crowded Dementioning

confidence: 99%

Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy

et al. 2016

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“…We used a terylenediimide derivative (TDI) as fluorescent tracer, which is well soluble in the used organic solvents. All autocorrelation curves recorded in both gel systems (Figure S8a,b, Supporting Information) could be adequately fitted by an analytical model equation, suggesting single component Fickian diffusion (no specific interactions between TDI tracers and the gels) . In the gels, the tracer diffusion rates (represented by their diffusion coefficient D ; see the Supporting Information for details) decrease as a consequence of the confinement effect of the polymer network.…”

Section: Resultsmentioning

confidence: 78%

Redox‐Responsive and Thermoresponsive Supramolecular Nanosheet Gels with High Young's Moduli

Zheng

Wang

Cui

et al. 2018

Macromol. Rapid Commun.

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Supramolecular gels made from 2D building blocks are emerging as one of the novel multifunctional soft materials for various applications. This study reports on a class of supramolecular nanosheet gels formed through a reversible self-assembly process involving both intramolecular folding and intermolecular self-assembly of poly[oligo(ethylene glycol)-co-(phenyl-capped bithiophenes)]. Such hierarchical self-assembled structure allows the gels to switch between sol and gel states under either redox or thermostimulus. Moreover, the gels illustrate high Young's moduli, compared to their controls that are made from the same oligo(ethylene glycol) and phenyl-capped bithiophenes blocks but have highly covalent-crosslinked structures. The example might open a window for emerging supramolecular 2D materials to develop mechanically robust and stimuli-responsive soft materials without compromising their intrinsic functions.

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“…Ultimately, the issue with the diffusion law is that it collapses the rich information contained in the shape of the ACF into a single value, τ 1/2 . In contrast, analysis of the detailed shape of the ACFs obtained at different w can give a lot of information about the underlying process (as shown for obstructed diffusion (22), two-component diffusion (38,39) or diffusion in phase separated membranes (50)). However, it is model-dependent.…”

Section: Discussionmentioning

confidence: 99%

“…We then considered the general case, where particles can switch back and forth between two simple diffusion modes with Poisson statistics (k on = k off = 500 s −1 ). In this scenario (one of the few considered before in the context of VLS-FCS (38,39)), we expect a cross-over around the relaxation time, τ c = 1/(k on + k off ). In the "fast diffusion" regime (τ τ c ) tracers remains in the same state while crossing the observation volume and behave as two separate populations.…”

Section: Two-component Diffusionmentioning

confidence: 93%

Anomalous diffusion in inverted variable-lengthscale fluorescence correlation spectroscopy

Fradin¹,

Stolle²

2018

Preprint

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Using fluorescence correlation spectroscopy (FCS) to distinguish between different types of diffusion processes is often a perilous undertaking, as the analysis of the resulting autocorrelation data is model-dependant. Two recently introduced strategies, however, can help move towards a model-independent interpretation of FCS experiments: 1) the obtention of correlation data at different length-scales and 2) its inversion to retrieve the mean-squared displacement associated with the process under study. We use computer simulations to examine the signature of several biologically relevant diffusion processes (simple diffusion, continuous-time random walk, caged diffusion, obstructed diffusion, two-state diffusion and diffusing diffusivity) in variable-lengthscale FCS. We show that, when used in concert, lengthscale variation and data inversion permit to identify non-Gaussian processes and, regardless of Gaussianity, to retrieve their mean-squared displacement over several orders of magnitude in time. This makes unbiased discrimination between different classes of diffusion models possible.Received for publication xxx and in final form xxx.

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Complex Tracer Diffusion Dynamics in Polymer Solutions

Cited by 54 publications

References 33 publications

Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy

Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy

Redox‐Responsive and Thermoresponsive Supramolecular Nanosheet Gels with High Young's Moduli

Anomalous diffusion in inverted variable-lengthscale fluorescence correlation spectroscopy

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