Dynamics of Single Actin Filaments and Bundles in Flow

Actin filaments, aside from their biological renown as providing the `skeleton' of cells, also proffer an ideal platform from which to study -- more generally -- the properties of semi-flexible polymers. Microfluidic devices made using soft-lithography are easily adapted in dimension and geometry to create well-defined flow environments. Actin filaments are visualized in continuous flow in a microfluidic channel by stroboscopic laser light illumination. A detailed analysis of filament orientation, center-of-mass distribution, and thermal fluctuations as a function of flow rate and channel geometry is reported. In addition, the non-equilibrium bundling behavior of actin in the presence of actin-binding proteins or multivalent ions is studied in microchannel devices using FRET microscopy.