Effect of 2-(4-fluorophenylamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole on the molecular organisation and structural properties of the DPPC lipid multibilayers.

Interactions and complex formation between lipids and biologically active compounds are crucial for better understanding of molecular mechanisms occurring in living cells. In this paper a molecular organisation and complex formation of 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) in DPPC multibilayers are reported. The simplified pseudo binary phase diagram of this system was created based on the X-ray diffraction study and fourier transform infrared spectroscopic data. The detailed analysis of the refraction effect indicates a much higher concentration of FABT in the polar zones during phase transition. Both the lipid and the complex ripple after cooling. It was found that FABT occupied not only the hydrophilic zones of the lipid membranes but also partly occupied the central part of the non polar zone. The infrared spectroscopy study reveals that FABT strongly interact with hydrophilic (especially PO(2)(-)) and hydrophobic (especially "kink" vibrations of CH(2) group). The interactions of FABT molecules with these groups are responsible for changes of lipid multibilayers observed in X-ray diffraction study.