[Change in the size of particles in actomyosin suspensions during superprecipitation]

Changes in the properties of natural actomyosin suspensions, such as turbidity, light scattering, volume concentration, particle size and particle size distribution during superprecipitation (SPP) of actomyosin in media of different compositions have been investigated. Two sets of changes indicating the existence of two SPP types--the "immediate" SPP characterized by a rapid one-step rise in turbidity and the "spontaneous" SPP, when the slow increase in turbidity follows the clear phase, have been revealed. In both cases the mechanism of the increase in the suspension turbidity is assumed to be similar and is conditioned by an increase in the refraction index (density) of the particles; however, the ways of formation of dense particles are different. During the "immediate" SPP, the particle density increases due to particle striction, whereas during the "spontaneous" SPP dense particles are formed as a result of ordered lateral association of myosin and actin filaments.