Solution and Solid-State NMR of Lipids

Lipid structure and dynamics are of first importance for cellular function. Lipids such as phosphatidyl inositol (PtdIns) are essential in signaling pathways, as they are recognition sites at the membrane surface. Their head-group or chain structure appears to be crucial for such a signaling role. Other lipids such as cholesterol and sphingomyelin are key molecules in maintaining membrane integrity and are the building blocks of membrane domains, such as “rafts.” It is essential to have techniques that can decipher both the structure and dynamics of various classes of lipids. With its liquid-state and solid-state facets, NMR is a very powerful tool for such a determination. We show that lipids extracted from membranes and dissolved in organic solvents can reveal their molecular structure when observed with multinuclear one-dimensional or two-dimensional NMR. We also show that multinuclear solid-state NMR provides information on the nature of the membrane phase (lamellar, hexagonal, isotropic, etc.), its dynamics (fluid or gel, or liquid ordered with cholesterol), and the molecular structure of embedded lipids when using the magic angle spinning apparatus. Typical examples of relatively simple experiments are shown both with liquid- and solid-state NMR of lipids.