CHANGES IN PARTICLE-SIZE IN ACTOMYOSIN SUSPENSIONS DURING SUPERPRECIPITATION

Changes in the properties of native actomyosin suspensions, namely, tu rbidity, light scattering volume concentration, particle size, and par ticle size distribution have been studied during actomyosin superpreci pitation (SPP) in media of different compositions. Two sets of changes indicative of two types of SPP have been revealed. One, the ''immedia te'' type, is characterized by a rapid one-step increase in turbidity, the other, the ''spontaneous'' type, comprises a slow increase in tur bidity following a clarification phase. The mechanism of the increase in turbidity is suggested to be the same in both cases, an increase in the refraction index (density) of the particles. However, the mechani sms of dense particle formation are different. In the case of immediat e SPP particle density increases due to particle contraction, whereas during spontaneous SPP the dense particles arise by an orderly lateral association of myosin and actin filaments.