[Estimating the length of actomyosin cross-bridge contraction]

In the work by Yanagida et al. (1985) the distance was measured by which the myosin cross-bridge moved along the actin filament during one cycle of ATP hydrolysis. This distance, in the opinion of the authors, must be equal to the length of the cross-bridge power stroke. However the measured distance (60 divided by 68 nm) was considerably greater than the cross-bridge power stroke measured earlier by other methods. In the present paper it is shown on the basis of the kinetic theory of muscle contraction of V. I. Deshcherevsky that the distance, the cross-bridge passed during one cycle of ATP hydrolysis must be nearly 5 times greater than the cross-bridge power stroke. The estimation of the length of the cross-bridge power stroke from the Yanagida's et al. data on the basis of the kinetic model gives 12 divided by 14 nm which is in a good accordance with the results obtained earlier.