ACTING ON ACTIN - THE ELECTRIC MOTILITY ASSAY

We have developed a novel technique which allows one to direct the two dimensional motion of actin filaments on a myosin coated sheet using a weak electric field parallel to the plane of motion. The filament ve locity can be increased or decreased, and even reversed, as a function of orientation and strength of the field. PMMA (poly(methylmethacryla te)) gratings, which act as rails for actin, allow one for the first t ime to explore three quadrants of the force velocity diagram. We discu ss effective friction, duty ratio and stall force at different myosin densities. A discontinuity in the velocity force relationship suggests the existence of dynamical phase transition.