[A study of the effect of low alpha-tocopherol concentrations on the dynamical parameters of microsomal membranes by...

The effect of alpha-tocopherol (alpha-tp) prepared in solvents of different polarity in a wide range of concentrations (10(-4) M - 10(-25) M) on lipid phase structural characteristics of microsomal membranes isolated from mouse liver cells has been investigated in vitro. Structural changes in membranes were detected on a Bruker-200D ESR-spectrometer (Germany) by the method of spin probes. Changes in the rigidity of surface lipid bilayer regions (8 A) and microviscosity of deep membrane layers (20 A) were studied using the stable nitroxyl radicals 5- and 16-doxylstearic acids, correspondingly. As a result, nonlinear multimodal dose dependences were obtained. It was demonstrated that the physiological (10(-4) M - 10(-9) M) and ultralow doses of alpha-tocopherol up to "apparent" concentrations (10(-11) M - 10(-25) M) increased the rigidity of surface lipid bilayer regions and microviscosity in the depth of membrane. Additionally, these doses of alpha-tp induced an increase in the number of thermoinduced structural transitions in deep lipid bilayer regions. The effect at "apparent" concentrations (< 10(-18) M) has only been observed in polar alpha-tocopherol solutions. The results obtained are statistically reliable with a significance level of 95%.