Pulsed-field-gradient NMR with magic-angle spinning: Diffusion studies and NMR microscopy of heterogeneous materials

High-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy is a well-established tool for studying heterogeneous systems, especially semi-solid materials such as lipid membranes [1-4], drug delivery systems, cell suspensions [5,6], biopsy samples [7], molecules adsorbed in zeolites [8,9], and resin-bound molecules [10]. In such systems MAS sufficiently suppresses the otherwise disturbing anisotropic interactions such as magnetic susceptibility, chemical shift anisotropy or even dipolar coupling. At already modest rotation frequencies, well-resolved 1H-NMR spectra can be observed, and the straightforward application of NMR methods commonly used for liquid samples is possible.