International Tomography Center, Siberian Branch of the Russian Academy of Sciences and Novosibirsk State University, Novosibirsk, 630090, Russia.
Phys Chem Chem Phys. 2021 Apr 28;23(16):9715-9720. doi: 10.1039/d0cp06337a.
A novel method dubbed ZULF-TOCSY results from the combination of Zero and Ultra-Low Field (ZULF) with high-field, high-resolution NMR, leading to a generalization of the concept of total correlation spectroscopy (TOCSY). ZULF-TOCSY is a new building block for NMR methods, which has the unique property that the polarization is evenly distributed among all NMR-active nuclei such as 1H, 13C, 15N, 31P, etc., provided that they belong to the same coupling network, and provided that their relaxation is not too fast at low fields, as may occur in macromolecules. Here, we show that ZULF-TOCSY correlations can be observed for peptides at natural isotopic abundance, such as the protected hexapeptide Boc-Met-enkephalin. The analysis of ZULF-TOCSY spectra readily allows one to make sequential assignments, thus offering an alternative to established heteronuclear 2D experiments like HMBC. For Boc-Met-enkephalin, we show that ZULF-TOCSY allows one to observe all expected cross-peaks between carbonyl carbons and α-CH protons, while the popular HMBC method provides insufficient information.
一种名为 ZULF-TOCSY 的新方法源于零场和超低场（ZULF）与高场、高分辨率 NMR 的结合，导致了全相关光谱（TOCSY）概念的推广。ZULF-TOCSY 是 NMR 方法的一个新构建块，它具有独特的性质，即只要它们属于相同的偶联网络，并且在低场下的弛豫不是太快（如在大分子中可能发生的情况），则极化均匀地分布在所有 NMR 活性核（如 1H、13C、15N、31P 等）上。在这里，我们表明，对于天然丰度的肽，如 Boc-Met-enkephalin 保护的六肽，可以观察到 ZULF-TOCSY 相关。ZULF-TOCSY 谱的分析可以很容易地进行序列分配，从而为 HMBC 等已建立的异核 2D 实验提供了替代方法。对于 Boc-Met-enkephalin，我们表明 ZULF-TOCSY 允许观察到羰基碳和α-CH 质子之间的所有预期交叉峰，而流行的 HMBC 方法提供的信息不足。
