Phospholipid studies of marine organisms: 26. Interactions of some marine sterols with 1-stearoyl-2-oleoyl phosphatidylcholine (SOPC) in model membranes.

The thermotropic behavior of multilamellar vesicles (MLV) composed of different mole fractions of various marine sterols and 1-stearoyl-2-oleoyl phosphatidylcholine (SOPC) was examined by differential scanning calorimetry (DSC), and was compared to pure SOPC as well as their mixtures with cholesterol. The marine sterols investigated were capable of interacting with the phospholipid bilayers. Upon addition of marine sterols, the apparent transition temperature (Tm) of SOPC decreased significantly. Desmosterol (cholesta-5,24-dien-3 beta-ol) had the least interaction with SOPC, as reflected by the larger delta H values of its mixtures with the phospholipid. Fucosterol (24-ethylcholesta-5,24(28)-dien-3 beta-ol) showed a non-linear trend as the mole percent of the sterol increased. Mixtures of sutinasterol (24R-24-ethyl-26,26-dimethylcholesta-7,25(27)-dien-3 beta-ol) with SOPC had similar enthalpy values to cholesterol. The shape of the SOPC/marine sterol endotherm and their delta H values were not identical when liposomes prepared by dialysis were compared to MLV.