Axial and Radial Forces of Cross-Bridges Depend on Lattice Spacing
Figure 7
Changes in cross-bridge resting geometry with the power stroke.
(A)–(C) show, schematically, the change in the rest lengths and angles of the single and multi-spring cross-bridges. The rest length and angle of the 2sXB's extensional and torsional springs are set, in both the pre- and post-power stroke states so as to match the tip position of the 2sXB in each condition to that of the 4sXB (in Table 1). The change in the unstressed radial distance from the thick filament to the tip of the multi-spring cross-bridges that occurs with the power stroke is particularly visible in (B) and (C) when compared to the single spring cross-bridge (A). The effects of the universal joint attaching the springs of the 4sXB and the 2sXB to the globular domain, and the globular domain's own fixed angle to the thin filament, are shown by the continued radial orientation of the globular domain after the power stroke occurs.