engleski

EPR Investigation of Cell Membrane Fluidity upon External Oxidative Stimulus

The perturbation of the physical state of the membrane triggered by the external oxidative stimulus has been studied on the sperm cells which were chosen as a model system. The electron paramagnetic resonance (EPR) spectroscopy was applied and three different nitroxides bearing paramagnetic group on the 5th, 7th and 13th carbon of the stearic acid acyl chain were used to probe different regions of the membrane. The theoretical simulations of the experimental spectra indicate distinct domains in the intact cell plasma membrane where local steric constrains impose different degrees of motional averaging experienced by the reporter group. Upon the external oxidative stimulus the spectral changes were proportional to the accumulated oxidation products and were detected only for the reporter group residing close to the lipid-water interface. The EPR spectra reveal that the motion of the motion of the reporter group has slowed down in the oxidised cells and that the oxidatively modified membrane shows up as a more rigid structure as compared to the native state. The results also indicate that the oxidation-induced spectral changes are supressed in the presence of gangliosides.

membrane fluidity ; EPR ; oxidation ; gangliosides ; sperm cells

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