Figure 1. Unstained frozen-hydrated MTs stabilized with DCX and Taxol.

Electron cryo-micrograph was obtained with a 120 kV microscope (Tecnai T12, FEI). Straight and curved MTs with a uniform diameter (13-PF architecture) are darker than ice (vitrified buffer). Some polymers are bundled, flattened or otherwise disrupted. In intact MTs, PFs are visible by glancing along their length and their number can be deduced from the striation pattern (so called moiré pattern) [8]. MT edges appear darker due to the presence of several PFs in the projection.