Polarization transfer in lipid membranes

Polarization transfer is a key experiment for the detection of insensitive nuclei by NMR. Transfer in liquids is often achieved through J-coupling usi ng the INEPT experiment, while in solids the dipolar coupling is used with cross polarization. Liquid crystals, including lipid membranes, are interme diate cases between solids and liquids. In the present article, we compare several transfer methods for lipid membranes spinning at the magic angle. I t is shown that the most commonly used cross polarization technique is, in most cases, advantageously replaced by refocused INEPT or even by the NOE e nhancement experiment, a method that is not normally used in that context. In principle, these enhancement techniques could be applied to other system s, including biological tissues and, more generally, soft matter systems th at are neither solid nor liquid by NMR standards. (C) 2000 Academic Press.