The dynamics of molecules in solution is usually quantified by the determination of timescale-specific amplitudes of motions. High-resolution nuclear magnetic resonance (NMR) relaxometry experiments—where the sample is transferred to low fields for longitudinal (T₁) relaxation, and back to high field for detection with residue-specific resolution—seeks to increase the ability to distinguish the contributions from motion on timescales slower than a few nanoseconds. However, tumbling of a molecule in solution masks some of these motions. Therefore, we investigate to what extent relaxometry improves timescale resolution, using the “detector” analysis of dynamics. Here, we demonstrate improvements in the characterization of internal dynamics of methyl-bearing side chains by carbon-13 relaxometry in the small protein ubiquitin. We show that relaxometry data leads to better information about nanosecond motions as compared to high-field relaxation data only. Our calculations show that gains from relaxometry are greater with increasing correlation time of rotational diffusion.

溶液中分子的动力学通常通过确定特定时间尺度的运动幅度来量化。高分辨率核磁共振 (NMR) 弛豫实验——将样品转移到低场进行纵向 ( T ₁) 松弛，并返回到高场以使用特定于残留物的分辨率进行检测 - 旨在提高区分运动的贡献的能力，时间尺度慢于几纳秒。然而，溶液中分子的翻滚掩盖了其中一些运动。因此，我们使用动力学的“检测器”分析来研究弛豫测量在多大程度上提高了时间尺度分辨率。在这里，我们展示了通过小蛋白泛素中的碳 13 弛豫测量法在表征含甲基侧链的内部动力学方面的改进。我们表明，与仅高场弛豫数据相比，弛豫数据可以提供关于纳秒运动的更好信息。我们的计算表明，随着旋转扩散相关时间的增加，来自弛豫测量的收益更大。