[Mechano-chemical properties of actomyosin-ADP complexes in rabbit psoas muscle fibers].

The relaxing effect of vanadate on active contractile system is found to be completely absent from rigor skinned fibres with ADP even on their stretching up to the forces comparable with the active ones, though vanadate is likely to bind not very firmly with crossbridges not containing inorganic phosphate. Probable reasons of such distinction are considered. The complex actomyosin-ADP in the rigor fibres is supposed to have significantly lower free energy independently of its deformation than the one of the same composition in the active ones. Possible role of different actomyosin-ADP states in the mechanochemical cycle of crossbridge is discussed.