Two-dimensional magic-angle spinning

Massiot, D., B. Touzo, D. Trumeau, J. P. Coutures, J. Virlet, P. Florian and P. J. Grandinetti. 1996. Two-dimensional magic-angle spinning isotropic reconstruction sequences for quadrupolar nuclei. Solid State Nucl. Magn. Reson. 6, 73-83. 

Asakura, T., Ashida, J., Yamane, T., Kameda, T., Nakazawa, Y., Ohgo, K., and Komatsu, K. (2001). A repeated beta-turn structure in poly(Ala-Gly) as a model for silk I of Bombyx mod silk fibroin studied with two-dimensional spin-diffusion NMR under off magic angle spinning and rotational echo double resonance. / Mol. Biol. 306, 291-305. 

Fig. 10. The pulse sequence for the WISE experiment.21 This two-dimensional experiment separates H wideline spectra according to the isotropic l3C chemical shift of the 13C each H is bonded to. An initial H 90° pulse creates transverse H magnetization that is allowed to evolve in t. A short cross-polarization step then transfers the remaining H magnetization to the nearest 13C spin, i.e. the bonded one. The resulting 13C transverse magnetization is then allowed to evolve in ti under magic-angle spinning, where an FID is recorded.

Fig. 14. The pulse sequence for recording the double-quantum 2H experiment.37 The entire experiment is conducted under magic-angle spinning. This two-dimensional experiment separates 2H spinning sideband patterns (or alternatively, static-like 2H quadrupole powder patterns) according to the 2H double-quantum chemical shift, so improving the resolution over a single-quantum experiment. In addition, the doublequantum transition frequency has no contribution from quadrupole coupling (to first order) so, the double-quantum spectrum is not complicated by spinning sidebands. Details of molecular motion are then extracted from the separated 2H spinning sideband patterns by simulation.37 All pulses in the sequence are 90° pulses with the phases shown (the first two pulses are phase cycled to select double-quantum coherence in q). The r delay is of the order 10 gs. The q period is usually rotor-synchronized.

Fig. 15. The pulse sequence for the 13C 2H correlation experiment.38 This two-dimensional experiment, conducted under magic-angle spinning, separates 2H line-shapes according to the 13C isotropic chemical shift of nearby l3C spins, i.e. the bonded l3C in practice. The narrow black pulses are 90° pulses wide ones are 180° pulses. The 2H pulses are placed symmetrically within the rotor period.

Fig. 18. The pulse sequence used for the two-dimensional NOESY experiment for measuring H- H cross-relaxation rates in soft polymers. The entire experiment is conducted under magic-angle spinning. Gradient pulses are used to remove unwanted coherences, as this allows for much faster experiments than phase cycling.

In summary, for this area to move forward, methods need to be introduced to provide information additional to 2H lineshapes when studying more complex systems. Calculations such as those just described are one real possibility experimental possibilities include use of magic-angle spinning 2H NMR, and using the full anisotropy of 2H 7j measurements and 13C NMR. A very nice illustration of the use of several different techniques in a motional study examined the slow alkane motions in a urea/alkane inclusion compound via 2H relaxation measurements, selective inversion experiments and two-dimensional 2H exchange.125... 

Szeverenyi, N. M., Sullivan, M. J. and Maciel, G. E. (1982). Observation of spin exchange by two-dimensional Fourier transform carbon-13 cross- polarization— magic angle spinning. / Magn. Reson., 47,462-75. [141]... 

Baltisberger JH, Xu Z, Stebbins JF, Wang SH, Pines A (1996) Triple-quantum two-dimensional Al magic-angle spinning nuclear magnetic resonance spectroscopic study of aluminosilicate and aluminate crystals and glasses. J Am Chem Soc 118 7209-7214... 

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