Fig. 5 Decoration of actin filaments with myosin S1. (a). S1-decorated actin filament displays a helical rope-like appearance; the asymmetry of individual turns of a helix allows to determine polarity: the thicker part of a turn is directed to the pointed end of a filament (direction of the arrowhead). (b), part of an actin filament bundle from a REF-52 fibroblast after S1 decoration; polarity of some filaments is indicated by arrowheads. Bars, 0.1 µm