Efficient solid-state NMR methods for measuring heteronuclear dipolar couplings in unoriented lipid membrane systems

Abstract

Recently (Dvinskikh et al., J. Magn. Reson., 2003, 164, 165 and Dvinskikh et al., J. Magn. Reson., 2004, 168, 194), some of us introduced two efficient solid-state NMR techniques for the determination of heteronuclear dipolar couplings under magic-angle spinning (MAS). These two-dimensional (2D) recoupling methods have been applied previously to simple amino acids, and to columnar systems with high positional and orientational order. In this work, we show that the 2D MAS sequences produce unparalleled ¹H–¹³C dipolar resolution in unoriented lipid membranes. The recoupling experiments were applied to hydrated dimyristoylphosphatidylcholine (DMPC) in the liquid-crystalline L_α phase, and the results agreed well with previous NMR investigations using specifically deuterated phospholipids.