Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
Department of Pharmaceutical Analysis & State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China.
J Biomol NMR. 2021 Mar;75(2-3):133-142. doi: 10.1007/s10858-021-00362-0. Epub 2021 Mar 20.
A unique aspect of NMR is its capacity to provide integrated insight into both the structure and intrinsic dynamics of biomolecules. Chemical exchange phenomena that often serve as probes of dynamic processes in biological macromolecules can be quantitatively investigated with chemical exchange saturation transfer (CEST) experiments. H-decoupling sidebands, however, always occur in the profiles of CHD C-CEST experiments when using the simple CW (continuous wave) method, which may obscure the detection of minor dips of excited states. Traditionally, these sidebands are manually eliminated from the profiles before data analysis by removing experimental points in the range of H-decoupling field strength ±50 Hz away from the major dips of the ground state on either side of the dips. Unfortunately, this may also eliminate potential minor dips if they overlap with the decoupling sidebands. Here, we developed methods that use pseudo-continuous waves with variable RF amplitudes distributed onto ramps for H decoupling. The new methods were thoroughly validated on Bruker spectrometers at a range of fields (H frequencies of 600, 700, and 850 MHz, and 1.1 GHz). By using these methods, we successfully removed the sidebands from the NMR profiles of CHD C-CEST experiments.
NMR 的一个独特之处在于，它能够提供对生物分子结构和固有动力学的综合洞察。化学交换现象通常可作为生物大分子动态过程的探针，可通过化学交换饱和转移 (CEST) 实验进行定量研究。然而，在使用简单的 CW（连续波）方法进行 CHD C-CEST 实验时，H 去耦边带总是出现在 CHD C-CEST 实验的谱图中，这可能会掩盖对激发态小凹陷的检测。传统上，通过从 H 去耦场强度范围为±50 Hz 的实验点中去除谱图的边带，在数据分析之前手动从谱图中去除这些边带，这些实验点位于激发态的主要凹陷的任一侧的±50 Hz 范围内。不幸的是，如果这些实验点与去耦边带重叠，这也可能消除潜在的小凹陷。在这里，我们开发了使用具有可变 RF 幅度的伪连续波在斜坡上进行 H 去耦的方法。在一系列磁场（600、700 和 850 MHz 以及 1.1 GHz 的 H 频率）的布鲁克光谱仪上对新方法进行了彻底验证。通过使用这些方法，我们成功地从 CHD C-CEST 实验的 NMR 谱图中去除了边带。
