Contribution of the actomyosin motor to the temperature-dependent translational diffusion of water by cytoplasmic streaming in Elodea canadensis cells

Summary. The extent to which the actomyosin motor responsible for cytoplasmic streaming contributes to the translational diffusion of water in Elodea canadensis cells was studied by a nuclear magnetic resonance (NMR) spin-echo technique. The relative contribution of the actomyosin motor was determined from the corresponding apparent diffusion coefficient by the Einstein–Smolukhovsky relation. It is equal to the difference between the diffusional displacements of the cytoplasmic and the bulk water (X). The NMR data show that the temperature dependence of X is humpshaped, which is characteristic of enzyme reactions. At the same time, the apparent diffusion coefficient of cytoplasmic water increases with an increase in temperature. The most significant contribution of the actomyosin motor to X is observed at temperatures below 20°C. Within the temperature range of 20 to 33°C, X changes only slightly, and a further increase in temperature reduces X to zero.