Phase Transition of Lipids Membranes Determination: Comparison of Different Methods

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In this work we compare results of phase transition temperature measurements by different methods: microcalorimetry and fluorescence spectroscopy. For this purpose, we prepared the series of lipid mixtures consisting of cationic and zwitterionic lipids with different lipid ratios. Measurements of phase transition temperature by steady-state fluorescence spectroscopy can be utilized prodan and its derivative laurdan. These fluorescence probes are sensitive to the polarity of local environment due to partial charge separation between the 2-dimethylamino and the 6-carbonyl residues forming dipole moment, which causes solvent reorientation upon excitation. This solvent reorientation consumes energy and decreases the probe's excited state energy resulting in continuous red shift of the probe's emission spectrum. Thus, this shift in laurdan and prodan emission spectra indicates the increased concentration of water within the bilayer and its increased mobility.The laurdan in compared to prodan contains lauric acid tail, therefore is anchored within the hydrophobic core. Thus, these two probes should be localized in different zones of bilayer and give complex information of water penetration. Comparison of obtained results from the microcalorimetry and the fluorescence spectroscopy may be concluded that they are mutually similar.

Lipid, membrane, phase transition temperature, laurdan, fluorescence, microcalorimetry

BURDÍKOVÁ, J.; MRAVEC, F.; TÜRKEOVÁ, I.; DOSKOČIL, L.; PEKAŘ, M.

26. 4. 2016

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