Sarcomere Lattice Geometry Influences Cooperative Myosin Binding in Muscle
Figure 8
Maximal Force Varies with Lattice Stiffness
Contour plots of average steady-state force at maximal Ca2+ activation (pCa 4) across a range of mechanical lattice parameters are shown for the two-filament (A) and multi-filament (B,C) models. All simulation predictions adjust kxb over a range of [0.1–10] pN nm−1, shown on the abscissa of each panel. Simulations adjusting ka and kxb, while keeping km fixed at 6,060 pN nm−1 were done for both models (A,B). These simulations adjusted ka over a four-decade range (with respect to the original value of ka) using a scalar multiplier, X, that ranged from [−2 to 2] in log10 space, represented on the ordinate of (A) and (B). (C), however, is a different type of simulation performed only with the multi-filament model. This second type of simulation simultaneously scales the stiffness of both thick and thin filaments (kF) from their original values, using a similar range of X as (A) and (B). Colored-scale bars for force in pN are shown to the right of each panel; note the difference in scale between the two-filament predictions (A) and the multi-filament predictions (B,C). The maximum contour value (white solid circle) is 16, 963, and 933 pN for (A–C).