Fraction of myosin motors attached to actin at peak force. (A) Axial profiles of the first layer line from demembranated trabeculae in relaxing (pCa 7.0; magenta) and rigor (pCa 9.0, no ATP; orange) conditions. Data added from four trabeculae. FReLoN detector with sample-to-detector distance, 1.6 m. Total exposure time, 160 ms. Temperature, 27 °C. Black and red continuous lines, double-Gaussian global fits to the axial layer-line profiles, with positions of myosin-layer 1 (ML1) and actin-layer 1 (AL1) as common parameters (continuous vertical gray lines). Dot-dashed lines and dashed lines are Gaussian components of the global fits for ML1 and AL1, respectively. (B) Axial profiles of the first layer line from intact trabeculae in diastole (green) and at PF (blue). Data added from four time-frames in diastole and around PF. Pilatus detector, sample-to-detector distance, 3.2 m. Total exposure time, 230 ms. Temperature, 26.4 °C. Black and red continuous lines, double-Gaussian fits to the axial profiles with positions of ML1 and AL1 constrained to the vertical gray lines from fits in A. Dot-dashed lines and dashed lines as in A.