592343.fig.008
Figure 8: Predicted gamma distributed for the two myosin isoforms under varying MgATP conditions at 37°C. (a) The parameter values estimated for the -MyHC demonstrate an increasing shape parameter and prolonged as MgATP was reduced. The resulting looks more Gaussian in shape rather than exponential as MgATP was reduced. This would be consistent with a longer rigor state prior to MgATP binding and detachment of the myosin crossbridge. (b) The distributions for -MyHC represent longer compared to -MyHC. Again, a longer rigor state would arise with lower MgATP. (c, d) In the -MyHC at 5 mM MgATP, the release of , release of ADP, and binding of ATP occur in relatively quick succession. The time periods that represent the and ADP states, however, would not be affected by MgATP availability. With the reduction in MgATP concentration, the rigor state would be prolonged as detected in the viscoelastic mechanics. (e, f). In the -MyHC, the ADP state is longer than that in the -MyHC and the rigor state is more dramatically prolonged with decreasing MgATP compared to -MyHC.