[Preservation of differences in the degree of polymerization of actin, isolated at different stages of ontogenesis after its purification].

Actin preparation from skeletal muscles of new-born, 10 days old and adult rabbits, containing less than or equal to 5% of inactivated actin and 1-2% of other myofibrillar proteins, were studied by means of flow birefringence and viscosimetry. It is found, that, like earlier studied crude preparations, purified actin preparations, isolated at different ontogenesis stages, differ in their intrinsic viscosity and extinction angle. These differences retain after the additional trypsin treatment. Non-polymerizing fraction of Straub F-actins, isolated from rabbit muscles of all ontogenesis stages studied, practically does not affect the polymerization in the course of ontogenesis, which is due to changes in its stucture.