Coiling of semiflexible paramagnetic colloidal chains.

Semiflexible filaments deform into a variety of configurations that dictate different phenomena manifesting at low Reynolds number. Harnessing the elasticity of these filaments to perform transport-related processes at the microfluidic scale requires structures that can be directly manipulated to attain controllable geometric features during their deformation. The configuration of semiflexible chains assembled from paramagnetic colloids can be readily controlled upon the application of external time-varying magnetic fields.

A small-volume microcapillary rheometer.

We demonstrate a capillary device used to measure the shear rate-dependent viscosity of microliter scale volumes. Liquid samples are driven pneumatically through a microcapillary and partially fill a larger glass capillary. The glass capillary is mounted on an optical linear sensor to track the air-liquid meniscus in real time and trigger the reversal of flow direction by switching a pneumatic valve.

Mechanical and functional properties of epothilone-stabilized microtubules.

Using a suite of biophysical tools, we assess the mechanical, structural, and functional properties of microtubules (MTs) stabilized by the chemotherapeutic compounds epothilone-A, epothilone-B, and taxol in vitro. We demonstrate that MTs stabilized by epothilone-A or epothilone-B are competent to bind tau proteins and support kinesin translocation. Kinesin speed is sensitive not only to the type of small molecule stabilizer used but also to the presence of the essential MT-associated protein tau.

Spectral analysis methods for the robust measurement of the flexural rigidity of biopolymers.

The mechanical properties of biopolymers can be determined from a statistical analysis of the ensemble of shapes they exhibit when subjected to thermal forces. In practice, extracting information from fluorescence microscopy images can be challenging due to low signal/noise ratios and other artifacts. To address these issues, we develop a suite of tools for image processing and spectral data analysis that is based on a biopolymer contour representation expressed in a spectral basis of orthogonal polynomials.

Articular cartilage deformation following experimental synovitis in the rabbit hip.

The development of transient synovitis in the hips of young children occurs quite frequently. This experiment examined the effects of a model synovitis on the deformability of articular cartilage of the immature rabbit hip. At 1, 2, 3, and 4 weeks following synovitis, there was an increase of cartilage deformability on both the acetabular and femoral sides of the joint.