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AKB: Biologische Physik

AKB 40: Poster Session II

AKB 40.22: Poster

Mittwoch, 29. März 2006, 16:30–19:30, P3

Phase behaviour of DMPC and farnesol mixtures — •Maria Hanulova and Sergio S Funari — Hasylab at Desy, Notkestr. 85, D-22603 Hamburg

Farnesol is a 15carbon polyisoprenol derived from the mevalonate pathway. It regulates the cell cycle, post-translationally attaches to proteins and so helps protein sorting in cell membranes, inhibits neural channels, enhances drug penetration and sensitizes bacteria to antibiotics.

We studied the phase behaviour of DMPC (dimyristoyl phosphatidylcholine) and farnesol mixtures in the temperature range 5-80^∘C using X-ray diffraction and polarized optical microscopy. The mixtures were prepared in water or in buffer (10mM HEPES, 100mM NaCl, 1mM EDTA, pH 7.4).

Farnesol itself does not form ordered structures and does not mix with water, but incorporates into lipid membranes. DMPC + farnesol mixtures form lamellar phases at low temperatures. The gel-fluid transition is broader than in DMPC and occurs at lower temperatures. The DMPC ripple phase is suppressed. In the fluid state, we usually observed two coexisting lamellar phases, probably farnesol-rich and farnesol-poor domains.

In mixtures with farnesol contents up to 50 mol%, the lamellar phase persists till 80^∘C. Interestingly, at higher farnesol content the lamellar phase vanishes at 40-45^∘C and new ordered structures assemble on further heating. At about 60^∘C a cubic phase occurs and an additional hexagonal phase is seen above 70^∘C. The thermal behaviour nearly does not change for mixtures with 60 to 95 mol% farnesol.