Mixtures of phospholipid and detergents are known to undergo transformation between micelle and vesicle forms under proper conditions. The transformation process occurs within a narrow range of compositions of detergent and phospholipid and seems to involve intermediate structures which are quite different from either the vesicles or micelles which exist at the two extreme boundaries of the transition region. Little is known about the characteristics of the transitions in the transition region and the properties of the transitions forms. This project involves the study of several detergent- phospholipid systems by differential scanning calorimetry at compositions particularly close to the transition region between micelles and vesicles. Lipids in aqueous mixtures of phospholipids and detergent are thought to exist in several different structural forms dependent upon the composition and conditions in solution. At low mole ratios of detergent to lipid unilamellar vesicles form, while at high ratios micellar structures prevail. The transition between these limiting structures is a fundamental problem that has implications for several important areas relating to the physical and chemical behavior of phospholipids. The results of this project could be significant for a better understanding of membrane reconstitution methods, vesicular drug delivery methods and the mechanisms of lipid transport in biliary mixtures of bile salts and phospholipids.
