3D 14 N/1 H Double Quantum/1 H Single Quantum Correlation Solid-State NMR for Probing the Parallel and Anti-Parallel Beta-Sheet Arrangement of Oligo-Peptides at Natural Abundance.
3D 14 N/1 H Double Quantum/1 H Single Quantum Correlation Solid-State NMR for Probing the Parallel and Anti-Parallel Beta-Sheet Arrangement of Oligo-Peptides at Natural Abundance.
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3D 14 N/1 H 双量子/1 H 单量子相关固态 NMR，用于探测自然丰度下寡肽的平行和反平行 β 片层排列。
作者：
You;T. Asakura;Y. Nishiyama
寡肽和多肽的β(β)片状结构可以形成反平行(AP)和平行(P)形式，这是理解这种结构的一个重要特征。原则上，P-和AP-β-Sheet结构可以通过在对应的2D 1H双量子(DQ)/1H单量子(SQ)谱的对角线上存在(AP)或不存在(P)链间1HNH/1HNH关联来识别，这是由于这两种排列之间的链间距离不同。然而，1HNH/1HNH峰与1HNH3+/1HNH3+峰重叠，无论β-Sheet排列如何，1HNH3+/1HNH3+峰总是交叉峰。1HNH3+/1HNH3+峰干扰了1HNH3+/1HNH3+关联的存在/不存在的观察，并且1HNH3+和1HNH3+的归属并不总是可用的。这里介绍了在快速魔角旋转(70 kHz)下的3D14N/1Hdq/1Hsq关联固体核磁共振实验，以区分AP-和P-β-Sheet结构。14N维度允许将1HNH/1HNH峰与1HNH3+/1HNH3+峰区分开来，并明确指定了1HNH和1HNH3+。此外，1H和14N的高自然丰度使低聚丙氨酸(Ala3-6)的3D14N/1Hdq/1Hsq实验可以在4小时内完成，而不需要同位素标记。
The beta (β)-sheet structures of oligopeptides and polypeptides can be formed in anti-parallel (AP) and parallel (P) forms, which is an important feature to understand such structures. In principle, P- and AP-β-sheet structures can be identified by the presence (AP) or absence (P) of inter-strand 1 HNH /1 HNH correlations on a diagonal in the corresponding 2D 1 H double quantum (DQ)/1 H single quantum (SQ) spectrum due to the different inter-strand 1 HNH /1 HNH distances between the two arrangements. However, the 1 HNH /1 HNH peaks overlap with the 1 HNH3+ /1 HNH3+ peaks, which always give cross-peaks regardless of the β-sheet arrangement. The 1 HNH3+ /1 HNH3+ peaks disturb the observation of the presence/absence of 1 HNH /1 HNH correlations and the assignment of 1 HNH and 1 HNH3+ is not always available. Here, 3D 14 N/1 H DQ/1 H SQ correlation solid-state NMR experiments at fast magic angle spinning (70 kHz) are introduced to distinguish AP- and P-β-sheet structures. The 14 N dimension allows the distinction of 1 HNH /1 HNH peaks from 1 HNH3+ /1 HNH3+ peaks with clear assignments of 1 HNH and 1 HNH3+ . In addition, the high natural abundance of 1 H and 14 N enables 3D 14 N/1 H DQ/1 H SQ experiments of oligo-alanines (Ala3-6 ) in four hours without isotope labelling.