Simultaneously enhancing spectral resolution and sensitivity in heteronuclear correlation NMR spectroscopy.
Simultaneously enhancing spectral resolution and sensitivity in heteronuclear correlation NMR spectroscopy.
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DOI：
10.1002/anie.201305709
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发表时间：
2013-10-25
影响因子：
16.6
通讯作者：
Morris, Gareth A.
中科院分区：
文献类型：
--
作者：
Paudel, Liladhar;Adams, Ralph W.;Kiraly, Peter;Aguilar, Juan A.;Foroozandeh, Mohammadali;Cliff, Matthew J.;Nilsson, Mathias;Sandor, Peter;Waltho, Jonathan P.;Morris, Gareth A.
描述了一种实时获取纯位移异核单量子相关 (HSQC) NMR 谱的方法。由双线性旋转去耦 (BIRD)[1, 2] 重聚焦元件序列组成的窗口采集方案用于通过重聚焦 JHH 调制采集数据块，同时通过宽带异核去耦抑制 JXH。所得光谱显示 F2 分辨率和信噪比均得到提高。标量自旋-自旋（J）耦合为分子结构阐明提供了有价值的信息，但它引起的多重态结构在光谱分辨率方面非常昂贵。在 1HNMR 光谱中，多重峰通常是单线宽度的许多倍。通过宽带去耦来抑制异核耦合（JXH）是常规方法，[3-7]，但直到最近同核宽带去耦的实验方法才变得实用。这些“纯位移”或“化学位移分辨”或“δ分辨”方法[8-19]可以使分辨率提高接近一个数量级，远远超过静态磁场增加所实际预期的任何增益。然而，与传统测量相比，所有这些方法都或多或少地受到灵敏度降低的影响。在这里，我们描述了一种获得纯位移异核单量子相关 (HSQC) 光谱的实验方法，其中使用 BIRD 脉冲序列元件 [1] 进行实时同去耦，在直接检测 (1H) 维度上实现了首次同时分辨率和信号增强。（同模耦合先前已在 HSQC 实验中进行过描述，但仅在间接 (13C) 中进行了描述。 [20]）HSQC 实验是最广泛使用的 NMR 方法，用于关联直接键合的 13C-1H 对的化学位移。在其传统的[21]形式中，它显示出F2中的质子多重结构，这限制了复杂物质光谱的分辨率。最近的研究表明[17,22,23]，可以将目前使用的纯位移方法（依赖于将短周期解耦信号的单独测量拼接在一起）扩展到实时采集，其中通过在采集单个自由感应衰变期间应用适当的自旋操作，定期重新聚焦同核耦合。这种 J 重聚焦序列元件通常设计为宽带的，与经典的选择性 [24, 25] 或带选择性 [26] 同去耦不同；对于 HSQC，J 重聚焦使用 BIRD 脉冲序列元件和硬（非选择性）1808 脉冲。 BIRD 序列元件[1]，顾名思义，最初用于宽带同核解耦，直到最近，[12] 几乎专门用于异核二维实验的间接维度中的解耦。[27]这里，BIRD序列和硬1808脉冲的组合效应是仅反转那些不直接耦合到13C的质子，从而重新集中后面的质子和直接耦合（键合）到13C且其信号记录在HSQC中的质子之间的耦合效应。 BIRD 方法的巨大优势在于，与 Zangger-Sterk 类型的方法相比，[8,9,22,23]它不会带来额外的灵敏度损失；事实上，敏感性普遍增加。 BIRD序列元件已经被非常有效地用于获得纯位移1H-13C HSQC谱，[16]和强耦合的纯位移1D质子谱
A method for acquiring pure shift heteronuclear single quantum correlation (HSQC) NMR spectra in real time is described. A windowed acquisition scheme consisting of trains of bilinear rotation decoupling (BIRD)[1, 2] refocusing elements is used to acquire chunks of data with refocused JHH modulation while suppressing JXH with broadband heteronuclear decoupling. The resultant spectra show both enhanced resolution in F2 and enhanced signal-to-noise ratio. Scalar spin–spin (J) coupling provides valuable information for molecular structure elucidation, but the multiplet structure it causes is very expensive in terms of spectral resolution. In 1HNMR spectroscopy, multiplets are often many times the width of a single line. It is routine to suppress heteronuclear couplings (JXH) by broadband decoupling,[3–7] but only recently have experimental methods for homonuclear broadband decoupling become practical. These “pure shift” or “chemical-shift resolved” or “δ-resolved” methods [8–19] can give resolution improvements approaching an order of magnitude, far in excess of any gains to be realistically expected from increases in the static magnetic field. However, all of these methods suffer to a greater or lesser extent from reduced sensitivity compared to conventional measurements. Here we describe an experimental method for obtaining pure shift heteronuclear single quantum correlation (HSQC) spectra, in which real-time homodecoupling using the BIRD pulse sequence element [1] leads to the first simultaneous resolution and signal enhancement in the directly detected (1H) dimension.(Homodecoupling has previously been described for the HSQC experiment, but only in the indirect (13C) dimension.[20])The HSQC experiment is the most widely used NMR method for correlating the chemical shifts of directly-bonded 13C–1H pairs. In its conventional [21] form, it shows proton multiplet structure in F2, which limits resolution in the spectra of complex species. It has recently been shown [17, 22, 23] that it is possible to extend the pure shift methods currently used, which rely on stitching together separate measurements of short periods of decoupled signal, to real-time acquisition, in which homonuclear couplings are periodically refocused, by applying appropriate spin manipulations during the acquisition of a single free-induction decay. Such J-refocusing sequence elements are generally designed to be broadband, as distinct from classical selective [24, 25] or band-selective [26] homodecoupling; in the case of HSQC, J-refocusing uses a BIRD pulse sequence element and a hard (nonselective) 1808 pulse. The BIRD sequence element,[1] which, as its name suggests, was originally intended for broadband homonuclear decoupling, has, until recently,[12] been used almost exclusively for decoupling in the indirect dimension of heteronuclear 2D experiments.[27] Here, the combined effect of the BIRD sequence and the hard 1808 pulse is to invert only those protons not directly coupled to 13C, thus refocusing the effects of couplings between the latter protons and protons that are directly coupled (bonded) to 13C and whose signals are recorded in HSQC. The great advantage of the BIRD method here is that, in contrast to Zangger–Sterk type methods,[8, 9, 22, 23] it incurs no extra sensitivity penalty; indeed, the sensitivity is generally increased. The BIRD sequence element has already been very effectively used to obtain pure shift 1H-13C HSQC spectra,[16] and pure shift 1D proton spectra of strongly coupled
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影响因子：
16.6
作者：
Meyer, N. Helge;Zangger, Klaus
通讯作者：
Zangger, Klaus
影响因子：
4.9
作者：
Nilsson, Mathias;Morris, Gareth A.
通讯作者：
Morris, Gareth A.
影响因子：
2.2
作者：
Lupulescu, Adonis;Olsen, Gregory L.;Frydman, Lucio
通讯作者：
Frydman, Lucio
影响因子：
2
作者：
Giraud, Nicolas;Joos, Marc;Merlet, Denis
通讯作者：
Merlet, Denis
影响因子：
16.6
作者：
Aguilar, Juan A.;Faulkner, Stephen;Morris, Gareth A.
通讯作者：
Morris, Gareth A.