Modern nuclear magnetic resonance (NMR) methods like carbon relaxation dispersion in the rotating frame (13C-R1ρ) and proton chemical exchange saturation transfer (1H-CEST) are key methods to investigate molecular recognition in biomacromolecules and to detect molecular motions on the µs to s timescale, revealing transient conformational states. Changes in kinetics can be linked to binding, folding, or catalytic events. Here, we investigated whether these methods allow detection of changes in the dynamics of a small, highly selective peptide catalyst during recognition of its enantiomeric substrates. The flexible tetrapeptide Boc-l-(π-Me)-His-AGly-l-Cha-l-Phe-OMe, used for the monoacetylation of cycloalkane-diols, is probed at natural abundance using 13C-R1ρ and 1H-CEST. Indeed, we detected differences in dynamics of the peptide upon interaction with the diol. Importantly, these differ depending on the enantiomer of the substrate used. These enantiospecific influences of the substrates on the dynamics of the peptide are rationalized using computational techniques. We find that even though one enantiomer reacts faster, as confirmed by reaction monitoring, the other is more tightly bound in DCM (as confirmed by 1H-saturation transfer difference (STD) measurements). These findings provide insights into the recognition of the substrates and explain the selectivity differences observed between the solvents toluene and DCM.

中文翻译：

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研究对映选择性肽催化酰化反应的相互作用动力学


现代核磁共振 （NMR） 方法，如旋转坐标系中的碳弛豫分散 （13C-R1ρ） 和质子化学交换饱和转移 （1H-CEST），是研究生物大分子中分子识别和检测 μs 到 s 时间尺度上的分子运动的关键方法，揭示瞬态构象状态。动力学的变化可能与结合、折叠或催化事件有关。在这里，我们研究了这些方法是否允许检测小的、高选择性的肽催化剂在识别其对映体底物过程中的动力学变化。使用 13C-R1ρ 和 1H-CEST 以自然丰度探测用于环烷烃-二醇单乙酰化的柔性四肽 Boc-l-（π-Me）-His-AGly-l-Cha-l-Phe-OMe。事实上，我们在与二醇相互作用时检测到肽动力学的差异。重要的是，这些因所用底物的对映异构体而异。底物对肽动力学的这些对映体特异性影响使用计算技术进行了合理化。我们发现，即使一种对映异构体反应更快，如反应监测所证实的那样，另一种对映异构体在 DCM 中的结合更紧密（通过 1H 饱和转移差 （STD） 测量证实）。这些发现为识别底物提供了见解，并解释了在溶剂甲苯和 DCM 之间观察到的选择性差异。