EVIDENCE FOR AN INCREASE IN WATER CONCENTRATION IN BILAYERS AFTER OXIDATIVE DAMAGE OF PHOSPHOLIPIDS INDUCED BY IONIZING-RADIATION

The two membrane fluorescent probes 2-dimethylamino-6-lauroyl-naphthal ene (Laurdan) and 2-dimethylamino-6-propionyl-naphthalene (Prodan) hav e been used to study the molecular basis of the damage induced in phos pholipid membranes by ionizing radiation. Laurdan and Prodan display a spectral sensitivity to the polarity of their environment, showing a red shift of both excitation and emission spectra with increase of the polarity of their environment. Owing to their chemical differences, t he two probes are anchored in the membrane with different strengths. I n aqueous environments Laurdan is not fluorescent while Prodan shows a ppreciable fluorescence. Laurdan and Prodan show an opposite response to oxidative damage produced in phospholipid bilayers by ionizing radi ation. The results support the model recently developed of water penet ration in the bilayer as a consequence of oxidative damage.