Chemical-shift anisotropy crystallinity determination

Solid state NMR methods for the determination of intemuclear dipole-dipole couplings between homonuclear spin-1/2 nuclei have been presented by Gunne. " The methods considered are suitable for relatively dense dipolar networks which are still dominated by two-spin interactions. Symmetry derived pulse sequences with improved compensation against chemical shift anisotropies were found assuming a small isotropic chemical shift difference and using numerical calculations of the spin dynamics. It has been shown that a constant time procedure can be used to acquire reliable double quantum build up curves even in systems in which damping obscures oscillations in their symmetric build up curve. This technique has been demonstrated on four crystalline model com-... 

Solid state NMR spectroscopy was applied to measure the isotropic chemical shifts, chemical shift anisotropies and asymmetry parameters of three phosphorylated amino acids, O-phospho-L-serine, O-phospho-L-threonine and O-phospho-L-tyrosine. The CP buildup rates and longitudinal relaxation times of P and H were determined and compared with the values measured for a triphosphate bound to a crystalline protein. It was shown that the phosphorylated amino acids are well-suited model compounds, e.g. for the optimisation of experiments on crystalline proteins. In addition, from 2D exchange experiments on O-phospho-L-tyrosine the existence of an exchange between the two different conformations of the molecule was deduced. 

Computer simulations of selected spectra observed at 40.7 and 67.8 MHz in the crystalline phases are shown in Figure 7-14. The simulations included the effects of the chemical shift anisotropy (CSA) as well as the quadrupolar interaction. The chemical shifts and quadrupolar parameters of PDFS determined are shown together with those of 0-enriched cyclic tetramer DjEtg as the model compound of PDFS in Table 7-3. These include the quadrupolar coupling constant (Cq), the quadrupolar asymmetry parameter (tiq), the isotropic chemical shift ( i, ), cs = 33 - I833 - Sisol > 8ii - Ko > I822 - Sisol. the chemical shift... 

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