Fascinating vesicles?

Abstract

Lipids are small amphiphatic molecules that can adopt a wide variety of aggregation states including micelles, lamellae and vesicles. In the vesicular state the lipids form a closed spherically bilayer. Such vesicles, or liposomes, play an important biological role in processes such as endo- and exo-cytosis, intracellular transport as well as providing nanoscale reaction vessels. Lipid vesicles are also used in drug delivery applications, and serve as model systems for experimental studies of cell processes. The length scales of vesicular systems in vivo ranges from nanometers to micrometers (whole cells). In this thesis we have pioneered the possibilities of simulating vesicular bilayer systems using molecular dynamics simulation (MD) techniques. We especially focus on the effect of membrane curvature on phase transitions and phase separations. For the first time we have been have been able to simulate so called 'raft' formation in lipid membranes. Rafts are liquid-ordered membrane domains consisting of a mixture of cholesterol and phospholipids. At present it is believed that such rafts, in combination with specific proteins, play an important role in cell signaling. On overall, this thesis shows that small liposomes possess interesting specific properties and are more than just curved membranes.