Orientation and rotational dynamics of spin-labeled phalloidin bound to actin in muscle fibers.


We have used electron paramagnetic resonance spectroscopy (EPR) to investigate the orientational distribution of actin in thin filaments of glycerinated muscle fibers in rigor, relaxation, and contraction. A spin-labeled derivative of a mushroom toxin, phalloidin (PHSL), was bound to actin in the muscle fibers (PHSL-fibers). The EPR spectrum of unoriented… (More)