| Regional Biophysics Meeting 2005, March 16-20, Zreče, Slovenia | [MembBiophys] |
The binding of photosensitizers to the target cells is a crucial step in photodynamic diagnosis and therapy. Based on the distribution of different porphyrins in the hydrophilic and hydrophobic phases one can decide if it makes them a good candidate to affect the cell membrane integrity by photodynamic effect. Due to this, the photophysical properties of porphyrinoid sensitizers in microheterogeneous systems, such as liposomes, are of extreme interest. Site-selective fluorescence spectroscopy was applied first on such a system. One component, small unilamellar vesicles (SUV) formed by different phosphatidylcholines (DMPC, DPPC, DSPC) with the incorporated mesoporphyrin (MP) and with a newly synthesized porphyrin were studied. Throughout the duration of the experiment, liposomes were checked by dynamic light-scattering after each step of the preparation. In the case of MP, based on the line narrowing spectra, the inhomogeneous distribution function (IDF) could be determined, and used to characterize the distribution of MP in liposomes. Double character of these functions revealed two different type of binding sites for the MP in the system. This is in good agreement with earlier suggestions. Decomposition of the IDF-s into Gaussian distributions and the analysis of the fit results served as evidence for that probably one kind of the binding sites for the MP is between the two lipid-layers and the other along the hydrocarbon chains.
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