Figure 4.

Aligned topographical profiles (parallel to the protofilament axis) of moving kinesin dimers, showing the 8 nm periodicity of the resting positions. (A) Displacements found for the 20 isolated moving kinesin dimers, recorded with different samples. Each event comprised 2 to 4 frames. Each curve represents a profile taken along the protofilament with kinesin bound. The position of the profiles from a single movie was referenced to fiduciary marks in the background to correct for drift. The x axis shows the axial displacement of the respective kinesin compared to the first or any of the previous frames. Most displacement distances were observed more than once, in which case the curves were averaged. Curves are plotted with a vertical offset for clarity. (B) Average of all profiles after subtracting the respective multiple of 8 nm. The heads, both bound to the MT and spaced 8 nm apart, can be clearly distinguished.