Actin-myosin interaction in oriented F-actin filament system.

The decorated actin technique combined with the spin label method was used to study the interaction of skeletal muscle actin and myosin in synthetic filament system. If follows from the orientation dependence of the EPR spectra of the rigidly attached spin label in F-action filaments that the spin-label is sensitive to the dynamic state of the filaments. The interaction of myosin heads with actin reduces the intrinsic order of the F-actin filaments.

Study of force development in resting and activated muscles during velocity dependent stretching.

The time course in force development of gastrocnemius muscles isolated from frog (Rama esculenta) were investigated under the effect of stretching with different velocity and time characteristics. Time course of stretching were linear, parabolic and exponential. It was found that the changes in force development of both resting and activated muscles depend on the time characteristics of the stretching applied.

The study of nitroxide radical active esters as spin labels on muscle protein actin.

Nitroxide radical active esters were used to label the muscle protein actin and to study the orientation dependence of the EPR spectra of the labelled protein. It is concluded that the labels are located at least at two different sites of the protein with strong polar environment and different mobilities. The EPR spectrum of the strongly immobilized labels exhibits orientation dependence, the N--O bond axis of the spin labels is nearly perpendicular to the long axis of the F-actin threads, and the labels undergo a rapid rotational motion about an axis directed perpendicular to the filament axis.