KINETICS OF RADIATION-INDUCED AND CYTOCHROME-C-INDUCED MODIFICATIONS IN LIPOSOMES ANALYZED BY FT-RAMAN SPECTROSCOPY

Fourier transform Raman spectroscopy on artificial lipid membranes was used to study radiation-induced peroxidation processes as a function of time after radiation exposure. The time dependent intensity changes of the Raman lines of various C=C bondings were compared to results o btained by measuring conjugated dienes and by the thiobarbituric acid test for malondialdehydes. The results show that mainly the cis C=C bo nds of the lipid chains are involved and, therefore, indicate that gam ma-radiation induces conformational changes in the lipid chain while t he mobility of the lipid chains is reduced. New Raman bands can be ass igned to aldehyde products induced at the end of the peroxidation proc ess. The immediate decrease of the =CH vibration lines was directly co rrelated with the formation of conjugated C=C double bonds suggesting that these vibration lines are in contrast to the C=C lines solely Ram an active, when isolated C=C bonds are present. Cytochrome c (ox.) inc orporated into the bilayer of the artificial membranes induced autooxi dation processes not influenced by gamma-radiation. It was observed th at cytochrome c (ox.)-induced changes of the relative intensity of the C=C bonds differ from those induced by gamma-radiation. These results of cytochrome c together with the inhibitory effects of the antioxida nt alpha-tocopherol suggest that the radical species involved in the c ytochrome c induced process might be different from the free radicals involved in the gamma-radiation-induced process. (C) 1997 Elsevier Sci ence B.V.