Cano Kristin E, Thrippleton Michael J, Keeler James, Shaka A J
Department of Chemistry, University of California, Irvine, CA 92697-2025, USA.
J Magn Reson. 2004 Apr;167(2):291-7. doi: 10.1016/j.jmr.2003.12.017.
A simple and robust method to suppress zero-quantum coherence (ZQC) in NMR experiments, in a single scan and with very high suppression ratio, is described. It is an appreciable improvement on a previous technique by Thrippleton and Keeler [Angew. Chem. Int. Ed. 42 (2003) 3938]. The method, called a z-filter cascade, preserves longitudinal, or z-magnetization, with high efficiency. Losses depend mostly on T1 relaxation but not T2 relaxation mechanisms. At the same time, suppression of ZQC can be essentially complete in a single scan. The time duration of the z-filter cascade scales inversely to representative chemical shift differences between the coupled spins, and is typically a few tens of milliseconds. The high efficiency of the zero-quantum suppression and excellent retention of the desired z-magnetization, in a single scan without resort to phase cycling or difference spectroscopy, makes the z-filter cascade a useful new pulse sequence building block for a whole range of NMR experiments. In cases where unwanted residual ZQC may have previously contributed to baseline " t1-noise" in two-dimensional NMR spectra, the z-filter cascade can deliver a noteworthy improvement in spectral quality.
本文描述了一种简单且可靠的方法，可在核磁共振（NMR）实验中单次扫描就以非常高的抑制率抑制零量子相干（ZQC）。这是对Thrippleton和Keeler之前的一项技术[《德国应用化学》国际版42 (2003) 3938]的显著改进。该方法称为z滤波器级联，能高效保留纵向磁化或z磁化。损失主要取决于T1弛豫，而非T2弛豫机制。同时，在单次扫描中ZQC的抑制基本可以完全实现。z滤波器级联的持续时间与耦合自旋之间的代表性化学位移差成反比，通常为几十毫秒。零量子抑制的高效率以及在单次扫描中无需借助相位循环或差谱法就能出色地保留所需的z磁化，使得z滤波器级联成为一系列NMR实验中一个有用的新型脉冲序列构建模块。在二维NMR谱中，若之前不需要的残余ZQC可能导致基线“t1噪声”，则z滤波器级联可显著提高谱图质量。
