Fig. 3.

Contractile activity of single C2.7 cells in response to the myosin inhibitor blebbistatin. Contractile activity was expressed as the ratio of the maximal traction force after addition of blebbistatin F([Blebb]) and the maximal force without blebbistatin (F _max = 297 nN). F([Blebb])/F _max decreased with blebbistatin concentration. The inhibitory constant (Ki ∼ 2.8 μM) was in excellent agreement with the Ki values found for mouse cardiac muscles as well as for the ATPase activity of nonmuscle myosin II (24, 25).