NMR spectroscopy of lipid bilayers

Knowledge of lipid structure and dynamics in a membranous environment is of first importance for deciphering cellular function. Sterols and sphingolipids are key molecules in maintaining membrane integrity and are the building blocks of membrane domains, such as "rafts". Phosphatidyl inositols are crucial in signalling pathways as they are recognition sites at the membrane surface. Other lipids such as Phosphatidylethanolamines, Cardiolipins, or diacylglycerols are essential in fusion processes. It is fundamental to have techniques that can resolve the structure and dynamics of various classes of lipids in a membrane environment. Solid state NMR with its high resolution and wide line facets is a very powerful tool for such determinations. Here it is shown that multinuclear solid state NMR provides information on the nature of the membrane phase (bicelle, lamellar, hexagonal, micelle, cubic, etc.), its dynamics (fluid or gel, or liquid-ordered with cholesterol), and the molecular structure of embedded lipids when using the magic angle sample spinning (MAS) apparatus. Typical examples of relatively simple experiments are shown both with high resolution MAS and wide line NMR of lipids. Relaxation time measurements are also described to measure lipid motional processes from the picosecond to the second timescale.