[Structural changes in the myelin sheath membranes detectable by using the nonpolar probe perylene. A fluorescence polarization study]

Perylene as a fluorescent probe has been used to investigate membranes of the myelin sheath of surviving nerve fibres. Fluorescence polarization (P) of perylene was measured in stained nerve fibres, and their dependence on the angle (AD) between the geometrical axis of the fibre and electrical vector of exciting light was studied. The dependence of AD on the temperature showed that P (90 degrees) decreased gradually when the temperature increased at heating within the range of 0-32 degrees. A model of the prove movement in the lipid matrix is described. This model considers the rotation around the axis perpendicular to the plane of the perylene molecule only. Comparison of the results of model calculations and the experimental data allows to estimate the value of energy of viscosity activation. It proved to be 20-25 kcal/mol. Possible causes of such a high value of the kinetic barrier are discussed.