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. Author manuscript; available in PMC: 2011 Jul 6.
Published in final edited form as: Annu Rev Biophys. 2011 Jun 9;40:169–186. doi: 10.1146/annurev-biophys-042910-155359

Figure 2.

Figure 2

The helical structure of F-actin derived from cryo-electron microscopy (16). The molecules are arranged on a single helix with 13 molecules repeating in almost exactly six left-handed turns. The rise per molecule is 2.76 nm and the twist per molecule is –166.6±0.6°(for simplicity of drawing, in the figure the value -166.15 has been used to make the structure repeat exactly after 13 residues). Because -166° is close to 180° the structure takes on the appearance of a two-start right-handed long-pitch helix.