Background: Tau protein is believed to be stationary while bound to microtubules. Results: Tau molecules can diffuse along microtubules over distances up to several micrometers. Conclusion: Tau diffusion on microtubules is a novel mechanism for Tau dispersion in cells. Significance: Modulation of Tau binding and diffusion on microtubules by local modifications of microtubules can provide a tool to target Tau to specific cellular compartments.

protofilaments. Previous experiments to characterize the stiffness of microtubules have generally relied on heterogeneous ensembles of microtubules with different structures, complicating the interpretation and comparison of stiffness measurements. We report on a kinesin-driven microtubule gliding experiment that simultaneously determines the stiffness and protofilament number (diameter) of individual microtubules, allowing us to distinguish stiffness for microtubules of 12-14 protofilaments (including two different 14 protofilament lattice structures). The scaling of our stiffness measurements are consistent with previous theories connecting protofilament number to stiffness, but also suggest an alternate correlation between stiffness and protofilament superhelical pitch.