Figure 12.

Predicted X-ray patterns for an actin filament about 1 µm long deformed by crossbridge forces in the sarcomere lattice (Fig. 2 ▸ a) and with piecewise changes in the intermonomer spacing (Fig. 2 ▸ c). The X-ray diffraction patterns are shown for a relaxed and a nonuniformly stretched discontinuous helix with an intermonomer spacing predicted from MUSICO simulations of fully contracted frog muscle [Figs. 2 ▸(b) and 2 ▸(c) show only a part containing 111 units, but the patterns are calculated for the whole actin filament containing 364 monomers, forming a discontinuous helix with 13 monomers in six turns]. (a) The top half of the pattern from the equatorial line (red dotted line) to the third order of actin meridional reflections. (b) Details of the peak shifts between a relaxed and a stretched helix for the first, second and third meridional reflections. (c) The shifts in the profiles. The actin filament length is ∼1 µm and the other helix dimensions are the same as in Fig. 11 ▸.