Liposomes from the thermophilic eubacterium Thermus SP. fluorescence polarization and permeability properties

• 1.1. The physical properties of liposomes prepared from total and polar lipid extracts of Thermus SPS 11 and SPS 17 grown at 50°C and at the optimal growth temperature (73–75°C) have been studied using 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization (P) and correlated to the permeability properties of the bilayers.
• 2.2. P data show the presence of a broad phase transition from a gel to a liquid-crystal phase for all liposomes studied. Liposomes from lipid fractions of Thermus SPS 11 and SPS 17 grown at 50°C were in a less fluid state than those of bacteria grown at the optimal growth temperature.
• 3.3. Comparing the permeabilities to ethyleneglycol, glycerol and erythritol of liposomes from lipid extracts of Thermus SPS 11 and SPS 17 grown at the two temperatures already mentioned, liposomes from lipid extracts of bacteria grown at 50°C were, in general, more permeable to ethyleneglycol and glycerol and less permeable to erythritol.
• 4.4. Liposomes from lipid fractions with higher carotenoid (CA) content were in a more rigid state within the whole range of temperatures studied, and their permeabilities to the three polyols were significantly lower than in the low-CA samples.