Cryo-EM image analysis of actin I and II.

<p>(<b>A</b>) Electron cryo-micrographs of actin I and II (left and right, respectively). Side-by-side average power spectrum of actin I and II. (<b>B</b>) Representative class averages from k-means clustering. Center: Histograms of measured cross-over distances reveal a larger half pitch for actin I. (<b>C</b>) Eigen images 1–2 from actin I and II k-means clustering reveal a constant pitch of the one-start helix, whereas Eigen images 3–4 confirm the difference in cross-over distance of actin I and II.