Methods of Digital Video Microscopy for Colloidal Studies

Crocker, John C.; Grier, David G.

doi:10.1006/jcis.1996.0217

Cited by 3,438 publications

(3,287 citation statements)

References 15 publications

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“…12 The colloidal clusters were imaged by a CCD camera connected to a microscope and the beads were traced individually using standard routines. 48 The frame rate of the camera was chosen to be in the range 8-12.5 Hz, high enough to capture the diffusive behaviour of the particles. 1,2,49 For our analysis, clusters with different particle numbers and in different external connement were realized.…”

Section: Methodsmentioning

confidence: 99%

Effect of confinement on the mode dynamics of dipole clusters

et al. 2015

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Dynamical properties of colloidal clusters composed of paramagnetic beads are presented. The clusters were trapped either in a parabolic trough or in a hard-wall confinement. In order to access the dynamics of the ensembles, the instantaneous normal mode (INM) approach is utilized, which uses cluster configurations as an input. The peaks in the mode spectra weaken when the system size is increased and when the coupling strength is lowered. The short-time diffusive properties of the clusters are deduced using the INM technique. It is found that angular diffusion is always larger than radial diffusion regardless of the shape of the external trap. Further, short-time diffusion seems to be almost independent of the coupling strength in the solid regime, but decreases with increasing packing fraction and size of the ensembles. In general, it is found that diffusion is larger for parabolically confined than for hard-wall trapped clusters.

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Section: Methodsmentioning

confidence: 99%

Effect of confinement on the mode dynamics of dipole clusters

et al. 2015

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“…Fiducial motion was imaged using wide-field fluorescence microscopy, and particle displacement was calculated using particle-tracking velocimetry based on algorithms presented in (29). Particle displacement was interpolated into a regularized grid corresponding to the approximate substrate displacement.…”

Section: Traction Force Microscopymentioning

confidence: 99%

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Kovari

Wei

Chang

et al. 2016

Biophysical Journal

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Conventional studies of dynamic phagocytic behavior have been limited in terms of spatial and temporal resolution due to the inherent three-dimensionality and small features of phagocytosis. To overcome these issues, we use a series of frustrated phagocytosis assays to quantitatively characterize phagocytic spreading dynamics. Our investigation reveals that frustrated phagocytic spreading occurs in phases and is punctuated by a distinct period of contraction. The spreading duration and peak contact areas are independent of the surface opsonin density, although the opsonin density does affect the likelihood that a cell will spread. This reinforces the idea that phagocytosis dynamics are primarily dictated by cytoskeletal activity. Structured illumination microscopy reveals that F-actin is reorganized during the course of frustrated phagocytosis. F-actin in early stages is consistent with that observed in lamellipodial protrusions. During the contraction phase, it is bundled into fibers that surround the cell and is reminiscent of a contractile belt. Using traction force microscopy, we show that cells exert significant strain on the underlying substrate during the contraction phase but little strain during the spreading phase, demonstrating that phagocytes actively constrict during late-stage phagocytosis. We also find that latestage contraction initiates after the cell surface area increases by 225%, which is consistent with the point at which cortical tension begins to rise. Moreover, reducing tension by exposing cells to hypertonic buffer shifts the onset of contraction to occur in larger contact areas. Together, these findings provide further evidence that tension plays a significant role in signaling late-stage phagocytic activity.

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“…Particle positions were tracked in 2D snapshots using image analysis software. 19 For all systems, at least six images were analyzed containing altogether more than 600 particles.…”

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confidence: 99%

Dipolar Structures in Colloidal Dispersions of PbSe and CdSe Quantum Dots

et al. 2007

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We show by cryogenic transmission electron microscopy that PbSe and CdSe nanocrystals of various shapes in a liquid colloidal dispersion self-assemble into equilibrium structures that have a pronounced dipolar character, to an extent that depends on particle concentration and size. Analyzing the cluster-size distributions with a one-dimensional (1D) aggregation model yields a dipolar pair attraction of 8−10 k B T at room temperature. This accounts for the long-range alignment of the crystal planes of individual nanocrystals in self-assembled superstructures and for anisotropic nanostructures grown via oriented attachment.

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Methods of Digital Video Microscopy for Colloidal Studies

Cited by 3,438 publications

References 15 publications

Effect of confinement on the mode dynamics of dipole clusters

Effect of confinement on the mode dynamics of dipole clusters

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Dipolar Structures in Colloidal Dispersions of PbSe and CdSe Quantum Dots

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