Structure and Dynamics in Amphiphilic Bilayers: NMR and MD simulation Studies
Abstract: Popular Abstract in English Drizzle a thin stream of olive oil into water. The oil splashes into tiny little drops first, and in a fraction of a second, they emerge from bulk to the surface, and then coalesce to form a thin layer. This phenomenon relates to the molecular properties of the liquids. Olive oil is composed, in a large extent, of molecules with a fierce name, triglycerides, which are built by a glycerol group and three fatty acid chains attached to it. Although glycerol alone dissolves in water, the fatty acid chains are insoluble which renders the olive oil immiscible in water. Lecithins are natural molecules very similar to triglycerides, except for one of the fatty acid groups that is replaced by a water-soluble chain. Thus, when lecithins are mixed with water, a part of the molecules wants to be hydrated but their fatty acid chains will force their way to avoid any occasional contact with the water molecules (scientific studies indicate that rather water wants to avoid fat but that's another story). This love/hate duality makes lecithin molecules to adopt a position that pleases both parties: they self-assemble into a two molecule thick bilayer film, with the insoluble parts forming an inner core of fat, and the water soluble parts directing outwards to the aqueous medium. This thesis concerns how lecithins and other molecules with a similar love/hate duality towards water, behave within a fluid bilayer. Focus is put on applying and developing methods to find out how they displace themselves and how fast they move. The studies were carried out by combining two types of techniques. One uses an intrinsic property of particles called spin which can be accessed in a truly ingenious way by nuclear magnetic resonance (NMR) spectroscopy. The second method dismisses the real molecules, and instead calculates, through the single use of computers, how the molecules should move, in order to ultimately generate an atomic-detail computer animation of the bilayer. If one can already watch the molecules in the computer why to worry with performing experiments then? This thesis delves around this and other related questions, and represents a little contribution as part of a wide effort to make the movies better.
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