Gliding velocities of actin filaments on ventricular and M. soleus β-/slow myosin. (A) On a BSA-coated assay chamber surface M. soleus β-/slow myosin molecules purified from native tissue moved actin filaments with 0.279 µm/s (±0.011 µm/s SE, n = 19 assay chambers), while native tissue derived ventricular β-/slow myosin moved actin filaments with 0.872 µm/s (±0.047 µm/s SE, n = 21). (B) On a nitrocellulose-coated assay chamber surface immobilized M. soleus β-/slow myosin molecules moved actin filaments with 0.101 µm/s (±0.007 µm/s SE, n = 7, 2 mM MgATP, T = 23°C). Under the same conditions, ventricular β-/slow myosin moved actin filaments with 0.200 µm/s (±0.010 µm/s SE, n = 6). Data points represent mean gliding velocities of individual assay chambers, while bars represent mean values ± SE. Data could be described by normal distributions (intrinsic curves).