Influence of the Antileprosy Drug, DDS, on the Phase Transitions in Lyotropic, Mixed Lipid-Water Systems

Abstract

Abstract DSC investigation of the chain melting (CM), chain ordering (CO) and ice-water transitions in mixed lipid model membranes of DPPC-DPPE-water (weight ratio of DPPC to DPPE being 2:1) have been carried out and the effect of the drug, DDS, on these, have been studied. The water to lipid weight ratio, X, was in the range 0.5 ≤ × < 3.0 and the molar ratio, Rm of DDS to lipid was 0, 0.05 and 0.3. A mixture of phases (I and II) has been observed to exist in both the drug-free and drug-doped systems. The drug induces a decrease in the CM/CO transition temperatures of phase I, indicating that the DDS molecules enter the acyl chain region in this phase. From the X-dependences of the ice-water transition enthalpies, ΔHjw and ΔHwi, it has been deduced that the water of hydration for mixed lipids is significantly higher than that for either DPPC or DPPE. Our results have been explained in the light of a model picturing phase I to consist predominantly of DPPC molecules and phase II to be an admixture of DPPC ...