Figure 4.

Cross-bridge kinetics in myofibril preparations

A, maximal tension on average did not differ between R403Q and HCM_smn myofibrils. B, myofibrils from R403Q(1) showed a significant decrease in maximal tension compared to the other R403Q patients and HCM_smn patients (*P = 0.02 vs. HCM_smn, ^#P = 0.019 vs. R403Q(2) and ⁺P = 0.003 vs. R403Q(3)). C, slow k_rel (∼g_app∼tension cost) was significantly higher in R403Q myofibrils compared to HCM_smn (*P < 0.0001). D, this increase was visible in myofibrils of all R403Q patients compared to HCM_smn (R403Q(1)(2) *P < 0.0001 and R403Q(3) *P = 0.001). In addition, slow k_rel was significantly higher in myofibrils of R403Q(1) compared to R403Q(2)(^#P = 0.006) and R403Q(3)(⁺P = 0.001). Data are represented as individual myofibril preparations ± SEM and N = number of patients, n = number of individual muscle strips. ^aData from Belus et al. (2008).