Bicelles and micelles
Bicelles and micelles are lipid phases spontaneously formed in water environment. While micelles are approximately spherical in shape, bicelles form disk-like structures of variable diameter. The central part of a bicelle is made of long-chain phospholipids forming a regular bilayer which is surrounded by a rim of short-chain phospholipids that shields the long-chain lipid tails from water. Size of a single aggregate depends on molar ratio of core and chemical structure of rim molecules. Bicelles are suitable models of membrane systems and are useful for the physicochemical and biochemical studies of membrane proteins. Since bicelles are magnetically orientable, they are widely used in NMR structural studies of phospholipids and proteins. The main aim of our studies is to elucidate the dynamical structure of a single bicelle aggregate and to obtain information on lipid/lipid and lipid/water interactions. The bilayer properties are compared with data from micelle and lipid bilayer phases. The use of bicelles as model systems in MD simulations allows for significant reduction of artifacts related to periodic boundary conditions.