Figure 3. Summary of isometric tension and stiffness.

(A) Active isometric tension of the actin-filament reconstituted cardiac muscle fibers in the absence of Tm/Tn (T_a). (B) Isometric tension of the reconstituted fibers in the presence of Tm/Tn. In (A) and (B), tension was measured and normalized to T₀ (initial tension of native fibers before extraction, T₀=26.9±1.1 KPa, N=41). T_HC (high Ca²⁺ tension at pCa 4.66) and T_LC (low Ca²⁺ tension at pCa 8) were measured from the absolute baseline. T_act=T_HC−T_LC. (C) Stiffness (Y) of the reconstituted fibers in the presence of Tm/Tn. Subscripts HC, LC, and act corresponds to those of tension. Rigor was induced from fully reconstituted and Ca²⁺ activated fibers by washing out ATP, but Y_LC was not subtracted. Other than the absolute baseline, all experiments were performed at 25°C. *Significantly different from WT actin (p<0.05).