Nuclear magnetic resonance dipolar interaction

Hansen, M. R., Hanson, R, and Rardi, A. (2000). Eilamentous bacteriophage for aligning RNA, DNA, and proteins for measurement of nuclear magnetic resonance dipolar coupling interactions. Methods EnzymoL, 317, 220-240. 

As we shall see, each of these two terms, one for each nucleus, describes a second-rank scalar interaction between the electric field gradient at each nucleus and the nuclear quadrupole moment. De Santis, Lurio, Miller and Freund [44] included two other terms which involve the nuclear spins. One is the direct dipolar coupling of the 14N nuclear magnetic moments, an interaction which we discussed earlier in connection with the magnetic resonance spectrum of D2 its matrix elements were given in equation (8.33). The other is the nuclear spin-rotation interaction, also discussed in connection with H2 and its deuterium isotopes. It is represented by the term... 

Nuclear magnetic resonance spectra of these compounds are highly informative in this regard. The lineshapes of the Sn and resonances are dominated by the coupling of the nuclei with the unpaired electron spins. This interaction results in large resonance shifts arising from both the Fermi contact and the pseudo-contact (dipolar) interaction. 

Oas TG, GriffinRG, Levitt MH (1988) Rotary resonance recoupling of dipolar interactions in solid-state nuclear magnetic resonance spectroscopy. J Chem Phys 89 692-695... 

M. Mvmowitz, R. Griffin, G. Bodenhausen, T. Huang, Two-dimensional rotational spin-echo nuclear magnetic resonance in solids correlation of chemical shift and dipolar interactions, J. Am. Chem. Soc. 103 (1981) 2529—2533. 

Nuclear magnetic resonance (NMR) is a technique of considerable versatility in polymer science. It is used universally as a probe of chemical configurations, it provides information on the dynamics and relaxation times of a polymer system and it offers a route to the determination of orientation parameters, the exact route depending on the particular nuclei employed. In principle quadrupolar, dipolar, shielding tensor and indirect spin coupling interactions can all be employed " however, in practice only the first two have any universal appeal. Dipolar coupling using proton NMR offers the simplest approach in terms of material preparation and will be considered first. 

In a nuclear magnetic resonance measurement in solution, the direct dipolar interaction Xo actually disappears because, due to rapid molecular motion, the interspin (internuclear) vectors are rapidly space-averaged within the time-scale of a measurement. Hence, the terms Xs and Xj are detectable as sharp lines or splittings in a high-resolution spectrum of H or and they can be related to detailed molecular structure or conformation of the substance investigated. In a solid, on the contrary, the directions of the internuclear vectors are stationary even if they are distributed randomly in space. Then, X gives a very wide linewidth to the zeroth-order absorption line and completely masks all lines due to Xs and Xj. 

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