Figure 6: Cross-bridge duty ratio ( ) during unloaded sliding of regulated thin filaments reconstituted with HcTn and either α-GS-Tm WT, α-GS-Tm D175N, or α-GS-Tm E180G is lower than for unregulated F-actin. Duty ratio was estimated using the method of Uyeda et al. [61] by varying HMM density (ρ) as described in Materials and Methods (see Section 2.8). Estimates of were obtained by applying the band model and were normalized to the value obtained for WT at the same ρ. Bars indicate average normalized for all ρ ( ); error bars indicate S.D. Duty ratios for all three types of regulated thin filaments were significantly lower than for unregulated F-actin (** ) but were not statistically different from each other ( ).