Solid-state NMR spectroscopy is invaluable in the study of non-crystalline solids. We have been particularly interested in the application of experiments based on the cross polarization-magic angle spinning (CPMAS) technique. Applications have centered on elucidation of local conformation within a synthetic nine-amino acid sequence found in the amyloid protein of Alzheimer's disease. This work has been an application of the rotational resonance (RR) technique, in which spin diffusion between widely resolved resonances is enhanced by input of rotor energy. More basic work has included development of an experiment in which RR occurs between spectral resonances at scaled chemical shift onsets. In addition, we have developed which is essentially a CPMAS version of TOCSY, in which chemical shifts of heteronuclei are scaled to zero, eliminating (in the sense of average Hamiltonian theory) the Zeeman energy barrier to spin diffusion. We call this experiment DICSY, for dipolar correlation spectroscopy. Both this and the scaled RR experiment are based on design and analysis of appropriate multiple-pulse scaling sequences.
