Observing the mushroom-to-brush transition for kinesin proteins.

The height of polymers grafted to a surface is predicted to be constant at low densities ("mushroom" regime) and increase with the third root of the polymer surface density at high densities ("brush" regime). This mushroom-to-brush transition is explored with kinesin-1 proteins adhered to a surface at controlled densities. The kinesin height is measured by attaching fluorescently labeled microtubules to the kinesins and determining their elevation using fluorescence interference contrast microscopy.