We describe the utility of small nutation angle (acute; <90°) 1H radiofrequency pulses for efficient manipulation of magnetization in selectively [13CH3]-labeled methyl groups of otherwise deuterated proteins. Focusing primarily on NMR applications that target either fast (pico-to-nanosecond) motions of the methyl group three-fold rotation axis, or slow (micro-to-millisecond) processes associated with chemical exchange, we show that significant simplification of the 13CH3 spin-system and, as a consequence, of NMR pulse schemes, may be achieved in certain cases by the proper choice of the flip-angle of the 1H acute-angle pulse. In other instances, appropriate adjustment of acute-angle 1H pulses permits optimization of the sensitivity of NMR experiments. The results of acute-angle pulse based NMR experiments are validated by comparison with well-established NMR techniques for the characterization of fast dynamics of methyl-containing side-chains and chemical exchange processes.

中文翻译：

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小章动角 1H 脉冲在蛋白质中含甲基侧链动力学的 NMR 研究中的效用


我们描述了小章动角（急性;<90°）1H 射频脉冲在选择性 [13CH3] 标记的甲基中有效操纵磁化的效用其他氘代蛋白。主要关注针对甲基三倍旋转轴的快速（皮秒到纳秒）运动或与化学交换相关的慢速（微到毫秒）过程的 NMR 应用，我们表明，在某些情况下，通过适当选择 1H 锐角脉冲的翻转角度，可以实现 13CH3 自旋系统的显着简化，因此，可以实现 NMR 脉冲方案。在其他情况下，适当调整锐角 1H 脉冲可以优化 NMR 实验的灵敏度。通过与成熟的 NMR 技术进行比较，验证了基于锐角脉冲的 NMR 实验结果，以表征含甲基侧链的快速动力学和化学交换过程。