UNUSUAL THERMAL-STABILITY OF LIPOSOMES MADE FROM BIPOLAR TETRAETHER LIPIDS

The thermal stability of liposomes made from polar lipids of Sulfolobu s acidocaldarius, a thermoacidophilic archaebacterium, was studied. Wh ile two analogous nonarchaebacterial liposomes examined were unstable above 50 degrees C, liposomes made of the native tetraether lipids sho wed stability up to at least 80 degrees C. Incubation of the archaebac terial liposomes at 100 degrees C, under slight pressure, caused an ap proximate 15 % leakage after 60 minutes. Boiling, however, destroys th e integrity of the lipid membranes. The tetraether lipid vesicles are less permeable to solute molecules, such as carboxyfluorescein, than t he other lipid vesicles at any temperature. The permeability is also l ess temperature-sensitive than that for other lipids. (C) 1994 Academi c Press, Inc.