Figure 4. The mechanical properties of the multi-half-sarcomere framework depend on the stiffness of the inter-myofibrillar links.

A) The black line in the top panel shows the experimental force record for the pCa 4.5 condition from Fig 1. The red lines show the force and mean sarcomere length (averaged perpendicular to the filaments) records for the multi-half-sarcomere simulations from Fig 3. The green lines show simulations performed with a model that is identical with the sole exception of k _im which is equal to zero. B) Computer-rendered striation patterns for the simulations drawn in red in Panel A with finite k _im. Thick filaments are drawn in black. M-lines are yellow. Z-disks are magenta. The Z-disks are all in register but the M-lines are sometimes misaligned. Only ∼1/5 of the length of the framework is shown in the diagram for clarity. C) As for Panel B but drawn for the simulations with k _im equal to zero. The Z-disks are also misaligned. A movie showing how the striation patterns change during the length perturbation is included as Supporting Information (Video S1).