Centre de RMN à Très Hauts Champs, UMR 5280 CNRS/Ecole Normale Supérieure de Lyon, University of Lyon, 5 rue de la Doua, 69100 Villeurbanne, France.
Chemphyschem. 2012 Jun 18;13(9):2405-11. doi: 10.1002/cphc.201200099. Epub 2012 Apr 23.
A double-zero quantum (DZQ)-refocused INADEQUATE experiment is introduced for J-based NMR correlations under ultra-fast (60 kHz) magic angle spinning (MAS). The experiment records two spectra in the same dataset, a double quantum-single quantum (DQ-SQ) and zero quantum-single quantum (ZQ-SQ) spectrum, whereby the corresponding signals appear at different chemical shifts in ω(1). Furthermore, the spin-state selective excitation (S(3)E) J-decoupling block is incorporated in place of the second refocusing echo of the INADEQUATE scheme, providing an additional gain in sensitivity and resolution. The two sub-spectra acquired in this way can be treated separately by a shearing transformation, producing two diagonal-free single quantum (SQ-SQ)-type spectra, which are subsequently recombined to give an additional sensitivity enhancement, thus offering an improvement greater than a factor of two as compared to the original refocused INADEQUATE experiment. The combined DZQ scheme retains transverse magnetization on the initially polarized (I) spin, which typically exhibits a longer transverse dephasing time (T(2)') than its through-bond neighbour (S). By doing so, less magnetization is lost during the refocusing periods in the sequence to give even further gains in sensitivity for the J correlations. The experiment is demonstrated for the correlation between the carbonyl (CO) and alpha (CA) carbons in a microcrystalline sample of fully protonated, [(15)N,(13)C]-labelled Cu(II),Zn(II) superoxide dismutase, and its efficiency is discussed with respect to other J-based schemes.
引入了一种基于双零量子（DZQ）重聚焦的 INADEQUATE 实验，用于超快（60 kHz）魔角旋转（MAS）下基于 J 的 NMR 相关。该实验在同一个数据集记录两个谱，一个双量子-单量子（DQ-SQ）谱和零量子-单量子（ZQ-SQ）谱，相应的信号在 ω(1) 中出现在不同的化学位移处。此外，自旋态选择性激发（S(3)E）J 去耦块被合并到 INADEQUATE 方案的第二个重聚焦回波中，提供了灵敏度和分辨率的额外增益。以这种方式获得的两个子谱可以通过剪切变换分别处理，产生两个无对角的单量子（SQ-SQ）型谱，然后重新组合以提供额外的灵敏度增强，与原始重聚焦 INADEQUATE 实验相比，灵敏度提高了两倍以上。组合的 DZQ 方案保留了初始极化（I）自旋上的横向磁化，其横向退相时间（T(2)′）通常比其键间邻居（S）长。通过这样做，在序列中的重聚焦期间损失的磁化较少，从而为 J 相关提供了更高的灵敏度增益。该实验在完全质子化的、[(15)N，(13)C]-标记的 Cu(II)、Zn(II)超氧化物歧化酶的微结晶样品中羰基（CO）和α（CA）碳之间的相关性进行了演示，并讨论了其相对于其他 J 基方案的效率。
