Solid state 2H NMR

It will be useful to outline the basic features of solid state 2H NMR spectra. Deuteron is a spin 7= 1 nucleus possessing an electric quadrupole moment. The EFG interacts with the electric quadrupole moment to produce a frequency shift. Frequencies of the symmetric line shape centred around the Larmor frequency 0, which depend on the relative orientation of an external magnetic field B0 and the EFG tensor, are given by1 7 

2H NMR spectra are profoundly influenced by motions.1 7 It is possible to calculate the powder spectra in the presence of any type of motion by taking into account the geometry, and amplitudes and rates of motions involved.80,81 Consider a C-2H bond which can jump between three equivalent sites, 

If a C-2H bond diffuses uniformly over the surface of a cone having semiangle 6C, we have 

Then averaged quadrupolar splitting is given by82 

Although 2H NMR line shapes provide information about the type of motions, it contains no further information about the rates when the motion is faster than QCC. However, 7j enables us to evaluate the correlation times 

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Local Dynamics in Polypeptides Studied by Solid State 2H NMR Side Chain Dynamics of Poly(Y-benzyl L-glutamate) and Racemic Poly(Y-benzyl glutamate)... 

Solid state 2H NMR parameters are almost exclusively governed by the quadrupole interaction with the electric field gradient (EFG) tensor at the deuteron site.1 8 The EFG is entirely intramolecular in nature. Thus molecular order and mobility are monitored through the orientation of individual C-2H bond directions. Therefore, 2H NMR is a powerful technique for studying local molecular motions. It enables us to discriminate different types of motions and their correlation times over a wide frequency range. Dynamics of numerous polymers has been examined by solid state 2H NMR.1 3,7,9 Dynamic information on polypeptides by NMR is however limited,10 26 although the main-chain secondary structures of polypeptides in the solid have been extensively evaluated by 13C and 15N CP/MAS NMR.27,28... 

In this review we focus on the detailed side chain dynamic of PBLG and racemic PBG deuterated at several positions in a side chain by means of solid state 2H NMR. The brief description of the 2H NMR parameters used... 

The first account is on Phase Incremented Pulses in NMR with Applications by S. Zhang, this is followed by Advances in NMR Studies of Liquid Crystals by R. Y. Dong, H. C. Bertram and H. J. Anderson report on Applications of NMR in Meat Science , NMR Characterization of Mechanical Waves is covered by G. Madelin, N. Baril, J. D. de Certaines, J.-M. Francone and E. Thiaudiere, the next account is on Aspects of Coherence Transfer in High Molecular Weight Proteins by P. Permi, the final chapter is on Local Dynamics in Polypeptides studied by Solid State 2H NMR by T. Hiraoki, S. Kitazawa and A. Tsutsumi. 

FIGURE 45. Orientation and conformation of retinal in bR, constructed from the individual methyl group orientations that have been determined by solid-state 2H NMR. The angles 6 of the C—CD3 bond vectors with respect to the membrane normal (N) were evaluated for Cis (37°), C49 (40°) and C20 (32°) from the zero-tilt spectra shown in Figure 44 and with the aid of line-shape simulation of the tilt series in Figure 42 and 43. Reprinted with permission from Reference 57. Copyright (1994) American Chemical Society... 

From the solid-state 2H NMR spectra of tert-butyl alcohol sorbed within samples of HZSM-5 catalysts, it was concluded that the geometry of the isolated molecule is unperturbed when bound to the active site (8g, h). Since the critical dimension of the ter/-butyl alcohol (ca. 6.8 A) significantly exceeds the channel diameter of the catalyst (ca. 5.5 A), it follows that this reactant molecule must be accommodated at channel intersections [where there is a free diameter of ca. 9 A (70)], and that, therefore, the Bronsted active sites are themselves located at such intersections, as illustrated in Figs. 4 and 5. 

Batchelder, L. S., Sullivan, C. E., Jelinski, L. W., and Torchia, D. A. (1982). Characterization of leucine side-chain reorientation in collagen fibrils by solid state 2H NMR. Proc. Natl. Acad. Sci. 79, 386—389. 

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