High dynamic-angle spinning

Since the fourth-rank anisotropic broadening can be removed by sample rotation at an angle of 30.6° or 70.1° with respect to high-resolution spectra corresponding to the removal of the residual second-rank quadrupolar broadening can be achieved by the methods of double rotation (DOR) [163] and dynamic-angle spin-... 

In another related article Jerschow has reviewed new high-resolution NMR techniques for the study of quadrupolar nuclei. This article also includes theoretical description of the NMR techniques. A number of topics that are often left out in other review articles, such as nuclear quadrupole resonance, overtone spectroscopy and the ionic model for the calculation of electric field gradients, have also been considered. In addition, high-resolution techniques, such as double rotation, dynamic-angle spinning, MQ MAS, and satellite transition MAS have also been reviewed. 

D. E. Warschawski, J. D. Gross and R. G. Griffin, Effects of membrane peptide dynamics on high-resolution magic-angle spinning NMR, J. Chim.-Phys. Phys. Biol., 1998, 95, 460-466. 

In general, multiple pulse techniques sufficiently average the dipolar interactions, compress the chemical shift scale, but they do not affect heteronuclear dipolar interactions and the chemical shift anisotropy. A combination of both multiple pulse techniques and magic angle spinning, so-called CRAMPS (Combined Rotational And Multiple Pulse Spectroscopy) is found to yield satisfactory results in the solid state H NMR of solids 186). The limitations of all these techniques, from the analytical point of view, arises from the relatively small chemical shift range (about 10 ppm) as compared with some other frequently studied nuclei. However, high resolution H NMR of solids is useful in studies of molecular dynamics. 

The 2,2,6,6-tetramethylpiperidinoxyl radical (TEMPO) was first prepared in 1960 by Lebedev and Kazarnovskii by oxidation of its piperidine precursor.18 The steric hindrance of the NO bond in TEMPO makes it a highly stable radical species, resistant to air and moisture. Paramagnetic TEMPO radicals can be employed as powerful spin probes for elucidating the structure and dynamics of both synthetic and biopolymers (e.g., proteins and DNA) by ESR spectroscopy.19 Unlike solid-phase 1H-NMR where magic angle spinning is required in order to reduce the anisotropic effects in the solid-phase environment, solid-phase ESR spectroscopy can be conducted without specialized equipment. Thus, we conducted comparative ESR studies of various polymers with persistent radical labels, and we also determined rotational correlation times as a function of... 

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