Gliding velocities of actin filaments on ventricular and M. soleus β-/slow myosin purified from the same animal or the same M. soleus tissue. (A) On BSA-coated coverslips M. soleus myosin molecules moved actin filaments with 0.263 µm/s (±0.005 µm/s SE, n = 5 assay chambers, left) or 0.273 µm/s (±0.005 µm/s SE, n = 3 assay chambers, right) significantly slower than ventricular myosin purified from the same animals (1.004 ± 0.062 µm/s SE, n = 6 assay chambers and 1.077 ± 0.016 µm/s SE, n = 3 assay chambers, respectively). No significant differences were detected between M. soleus and ventricular myosin preparations from both animals (P = 0.3036 and P = 0.3379, respectively). (B) From one animal, M. soleus myosin was extracted in two preparations, and no significant difference regarding gliding velocity was observed (0.282 ± 0.019 µm/s SE, n = 10 assay chambers; 0.269 ± 0.011 µm/s SE, n = 4 assay chambers; P = 0.5926). Data points represent mean gliding velocities of individual assay chambers, while bars represent mean values ± SE.