UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-23 11:46
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Conference: Bucharest University Faculty of Physics 2008 Meeting


Section: Electricity and Biophysics


Title:
Photooxidative stress on model membranes- studies by optical methods


Authors:
Marcela Elisabeta BARBINTA PATRASCU(1), Nicoleta Maria BADEA(2), Laura TUGULEA(1), Aurelia MEGHEA(2)


Affiliation:
(1)Faculty of Physics – University of Bucharest, Măgurele, 077125, Romania

(2) Faculty of Chemistry - University “POLITEHNICA” of Bucharest, Bucharest, 011061, Romania


E-mail
p_mareli@yahoo.com


Keywords:
liposomes,chlorophyll, photooxidative stress, antioxidants


Abstract:
Long exposure of living organisms to sunlight can produce seriously oxidative damage to membrane lipids, the lipid peroxidation being also one of the first stages during aging and many diseases such as cancer. Photophysical studies on oxidative stress were performed on liposomes as models of cell membranes. Different types of liposomes were prepared according to the thin-film hydration method with slight modifications. Small unilamellar liposomes obtained by sonication were exposed to oxidative stress induced by illumination with UV-VIS light from artificial light sources. Different liposoluble antioxidants were incorporated in the liposome bilayer during the lipid film preparation. The light-driven reactive oxygen species (ROS) effects on liposomal membranes were monitored by optical methods: UV-VIS absorption, fluorescence and chemiluminescence, exploiting the spectral properties of chlorophyll a (Chla) embedded into liposome bilayer (Chla/lipid molar ratio = 1/100). The irradiation of liposomes resulted in chlorophyll photobleaching and in a decrease in the intensity of fluorescence emission with a slight blue shift of the maximum wavelength. The interaction between Chla and the other liposome components resulted in changes in their absorption and emission fluorescence properties. The carotene containing liposomes display a slightly oxidative damage comparatively with the other ones, since carotene acts as an efficient quencher of singlet oxygen generated by irradiation. In addition, the carotene/Chla/α-tocopherol-acetate/DMPC system showed a good resistance to photooxidative stress because the carotene regenerates the tocopherol and also protects the chlorophyll a, similar events with those in photosynthetic organisms.