Complex influence of cytochalasin B on actin polymerization

In the presence of very low concentrations (about 2 x 10-7 ᴍ) of cytochalasin B (CB) the time course of actin polymerization is much more sigmoidal when followed by viscosity measurements than when followed by light scattering measurements. This suggests that under these conditions actin polymers do not immediately reach their final length but only via short ”bent“ polymers which can be detected only by light scattering but not by viscosity measurements. At higher CB concentrations (about equimolar to those of actin) CB reduces the average degree of polymerization and favors the nucleation step necessary for polymerization