Unilamellar vesicle interaction studies

Interactions of apolipoproteins with PL are essential for the assembly of lipoproteins, stabilization of lipoprotein structures, and expression and modulation of apolipoprotein functions. The main experimental approaches for the study of apolipoprotein interactions with PL have used isolated, exchangeable apolipoproteins in conjunction with aggregated lipids dispersed in water or spread at the air-water interface. The aggregated lipid states include lipid monolayers, various types of liposomes (small unilamellar vesicles, large unilamellar vesicles, multilamellar vesicles), and emulsions. All these lipid systems consist of or include PL, especially PC. 

The formation of GUVs in the presence of the various additives under various stress conditions has been studied quantitatively. The presence of CAB in the molten globule state at pH 4 was observed to favor the formation of the larger size of giant unilamellar vesicles. The hydrophobic interaction between vesicles membranes and proteins was found to be a key factor for the formation. 

Preliminary experiments with 6-CF loaded mixed vesicles of dipalmitoylphosphat-idylcholine (DPPC) and diacetylenic lipid (22) exhibit only a very slow release of 6-CF after the addition of phopholipase A2. Reasons for this may be headgroup interactions which decrease the enzymatic activity or the fact that multilamellar vesicles were used for this study. Further experiments will be carried out with giant liposomes (visible under the light microscope) which are unilamellar and provide a higher enclosure percentage and low surface curvature (see 4.3.2). 

Measurement of the influence of different micellar environments on proton transfer from excited states of 3-hydroxyflavone allows estimates to be made of micelle concentrations from measurement of the tautomer emission yield. Proton transfer reactions of benzimidazole excited singlet states have also been studied in ionic micelles. Magnetic fields are found to affect the behaviour of radicals generated by the photodissociation of benzil in micellar media. The starburst dendrites which are formed by anionic macromolecules in interaction with both anionic and cationic surfactants have been examined by pyrene fluorescence. Benzo[k]fluoranthrene fluorescence has served as a probe of the effects of metal salts on bile salt aggregation. The incorporation and distribution of benzoquinone into liposomes containing amphilic Zn(II) porphyrin has been followed by its effect on the quenching of the excited state °. A comparison of the photochromism of spirobenzpyran derivatives in unilamellar surfactant vesicles and solvent cast surfactant films has also been reported. ... 

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