Quantification of dipolar couplings in biological solids is important for the understanding of dynamic processes. Under Magic Angle Spinning (MAS), order parameters are normally obtained by recoupling of anisotropic interactions involving the application of radio frequency pulses. We have recently shown that amide backbone order parameters can be estimated accurately in a spin-echo experiment in case the rotor spinning angle is slightly mis-calibrated. In this work, we apply this method to determine methyl order parameters in a deuterated sample of the SH3 domain of chicken α-spectrin in which the methyl containing side chains valine and leucine are selectively protonated.

定量生物固体中的偶极偶合对于理解动力学过程很重要。在“魔角旋转”（MAS）下，通常通过重新耦合涉及射频脉冲应用的各向异性相互作用来获得阶次参数。我们最近发现，在转子回旋角被稍微错误校准的情况下，可以在自旋回波实验中准确估算酰胺主链阶数参数。在这项工作中，我们应用此方法来确定鸡α-血影蛋白SH3结构域的氘代样品中的甲基顺序参数，在该样品中，含甲基的侧链缬氨酸和亮氨酸被选择性地质子化。