Faculty of Physics - University of Bucharest

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FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2001 Meeting

Section: Biophysics; Medical Physics

Title:

Liposomes with chlorophyll a

Authors:

Claudia Firanescu, Ioan Iacovache, Laura Tugulea

Affiliation:

Faculty of Physics, University of Bucharest

E-mail

Keywords:

Abstract:

Liposomes are membrane models used in studies of permeability and in drug transportation. Liposome preparation is based on the fact that the lipids form ordered structures spontaneously upon dispersion in aqueous media. Unilamellar liposomes are formed of planar bilayer sheets, which fold on themselves to form closed and sealed vesicles by exposure to sonic oscillations of the phospholipid suspension in aqueous media. Chlorophyll liposomes are especially used as models for the photosynthetic membranes. The special properties of chlorophyll a allow its use as a marker for physical and chemical studies on liposomes. The main goal of this experimental work was the to monitor the degradation in time of unilamellar liposomes with chlorophyll a: lipid oxidation and photooxidation of chlorophyll a and to use the chlorophyll a in obtaining information upon lipid dynamics. Unilamellar liposomes were obtained from multilamellar vesicles by the hand-shaken method and sonication for 30 minutes. The multilamellar vesicles were prepared using Chl a/lipid films (Dypalmitoyl phosphatidil choline - SIGMA), in the ratio of 1/100, which were dispersed in buffer solutions at different pH ( 6.2 - 7.6 ). The chlorophyll a was obtained in the laboratory by the chromatographic method. The UV and VIS spectra were recorded to observe the oxidation state of the chlorophyll and of the lipid. The fluorescence and polarization spectra were used in obtaining the transition temperature for different liposome solutions. A variation of the fluorescence intensity was observed in the phase transition of the lipid. It was also observed that there exists a connection between lipid oxidation and photooxidation of the chlorophyll, which allows the use of chlorophyll a in lipid oxidation studies.