Sein Julien, Giraud Nicolas, Blackledge Martin, Emsley Lyndon
Laboratoire de Chimie (UMR 5182 CNRS/ENS Lyon), Ecole Normale Supérieure de Lyon, 69364 Lyon, France.
J Magn Reson. 2007 May;186(1):26-33. doi: 10.1016/j.jmr.2007.01.010. Epub 2007 Jan 20.
The influence of the (15)N CSA on (15)N longitudinal relaxation is investigated for an amide group in solid proteins in powder form under MAS. This contribution is determined to be typically 20-33% of the overall longitudinal relaxation rate, at 11.74 and 16.45 T, respectively. The improved treatment is used to analyze the internal dynamics in the protein Crh, in the frame of a motional model of diffusion in a cone, using the explicit average sum approach. Significant variations with respect to the determined dynamics parameters are observed when properly accounting for the contribution of (15)N CSA fluctuations. In general, the fit of experimental data including CSA led to the determination of diffusion times (tau(w)) which are longer than when considering only an (15)N-(1)H dipolar relaxation mechanism. CSA-Dipole cross-correlation is shown to play little or no role in protonated solids, in direct contrast to the liquid state case.
在变温固体核磁共振条件下，研究了粉末状固体蛋白质中酰胺基团的(^{15}N)化学位移各向异性（CSA）对(^{15}N)纵向弛豫的影响。在11.74T和16.45T场强下，该贡献分别占总纵向弛豫率的20%-33%。采用改进的处理方法，在锥形扩散运动模型框架下，使用显式平均和方法分析了蛋白质Crh的内部动力学。当适当考虑(^{15}N) CSA波动的贡献时，观察到动力学参数的显著变化。一般来说，包含CSA的实验数据拟合得到的扩散时间((\tau_w))比仅考虑(^{15}N-^{1}H)偶极弛豫机制时更长。与液态情况形成直接对比的是，CSA-偶极交叉相关在质子化固体中几乎没有作用。
