Order Parameters Based on DCs

InDIPSHIFT (dipolar chemical shift correlation) experiment [128,129], the H- C (or H- N) DC is available from fitting time domain data of the dipolar interaction evolved maximally over the one-rotor period. A motionaUy reduced DC strength is observed, if any sort of segmental motion occurs at the site of the DC measurements [130]. The segmental motion can be characterized by an order parameter S defined by. 

High-accuracy measurement of H, N DCs in the backbone of a per-deuterated sample of the a-spectrin SH3 domain was performed by means of a 3D DC experiment by introducing phase-inverted CP (CPPI) element in which H and rf fields are simultaneously phase-alternated every 10 ms 

In the solid state, relaxation measurements from the ns—fis blind spot is possible, although the detection of such motions in solution NMR is difficult due to overlapping of the range to overall tumbling motion [138]. In fact. 

N Ri measurements were performed for a microcrystalline U-[ C, N] Crh to study its site-specific backbone dynamics [139,140]. Substantial differences (up to a factor of 7) in Rj along the backbone were noted increased 

SH3 are sensitive to driven spin diffusion (PDSD), leading 

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It is very important to compare the solid-state order parameters based on DCs from LGCP measurements with solution-NMR order parameters from R-i relaxation and RDCs from a weakly oriented system for ubiquitin [138], because the solid-state order parameter is sensitive to motions that are on the submicrosecond scale, while the solution-NMR order parameter is sensitive to motions on the ps to ns time scale. Indeed, the solid-state NMR order parameter turns out to be generally smaller than the solution-NMR order parameter, and this inequality is easily rationalized by the difference in time scale. By contrast, many of the RDC-based order parameters are found to be very close to each other. 

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