使用核磁技术分析复杂化合物结构，需采集多个二维核磁共振(2D NMR)图谱，通常实验耗时较长，不稳定且易分解的化合物可能因此发生结构变化，影响结构解析的准确性。为解决上述问题，该文探讨了基于NOAH(NMR by ordered acquisition using 1H-detection)快速采集 2D NMR的实验技术。实验结果表明，该技术通过共享恢复时间，不仅节省了约 60%的数据采集时间，同时提升了实验谱图的信噪比和分辨率，为化合物结构的快速鉴定和谱仪共享提供了有效方案。
Application of two-dimensional nuclear magnetic resonance using the NOAH technique
[Objective]Nuclear magnetic resonance(NMR)technology has emerged as a pivotal analytical tool for characterizing organic small molecules and drug molecular structures.Its applications span various fields,including chemistry,biomedicine,materials science,and food analysis.By providing detailed information about molecular structure,dynamics,and interactions,NMR helps researchers make informed decisions in drug development,quality control,and material characterization.In this respect,two-dimensional(2D)NMR plays a crucial role when it is necessary to clearly elucidate an unknown molecular structure,relying mainly on a series of 2D NMR experiments:correlation spectroscopy,total correlation spectroscopy,nuclear Overhauser effect spectroscopy,heteronuclear single quantum coherence,and heteronuclear multiple-bond correlation.By analyzing the distance and coupling between atoms in chemical bonds or space,2D NMR links the correlation between one-dimensional spectral peaks and further defines the attribution of one-dimensional spectral peaks,thereby resolving complex molecular structures.However,to obtain high-resolution 2D NMR spectra,the time domain must be sampled at equidistant time intervals,which consequently increases the time cost of data collection.For example,unstable compounds that are easily decomposed may undergo structural changes during long-term 2D NMR data collection,potentially leading to signal loss.Thus,the accuracy and reliability of structural analyses are compromised.In cases where the sample concentration is low or the natural abundance of nuclei is insufficient,it is often necessary to extend the acquisition time to ensure high-quality spectrograms,which consequently reduces the efficiency of the spectrometer.[Methods]In this paper,a fast 2D NMR acquisition method based on NOAH(NMR by ordered acquisition using 1H-detection)is proposed.Different from the traditional 2D NMR acquisition approach,the NOAH method employs a set of nested NMR super sequences founded upon 1H detection,which facilitate the orderly acquisition of NMR spectra with high sensitivity.By optimizing the sequence of data collection and sharing a recovery time(d1),several 2D NMR experiments related to both multiple homonuclear and heteronuclear processes can be completed in a relatively short time.Finally,a complete set of relevant data can be obtained in a single scan through the spatial coding of the NMR response.Data can be automatically collected and processed directly from within to generate individual 2D NMR experiment data.[Results]The 2D NMR data of Rifamycin-S was collected by NOAH-3_BSC pulse sequence combined with a high-field NMR spectrometer(700 MHz).The experimental results showed that the NOAH method can rapidly collect multiple homonuclear-and heteronuclear-related 2D NMR experiments in a short time.This not only reduces the time required for the experiment by 60%but also enhances the sensitivity and resolution of data compared with conventional 2D NMR and nonuniform sampling methods.[Conclusions]The NOAH method can effectively solve the structural changes and signal loss caused by long-term data acquisition of unstable and easily decomposed compounds.It provides a useful reference and a practical scheme for the rapid identification of compound structures,thereby improving the open sharing of future spectrometers.
two-dimensional nuclear magnetic resonanceNOAH techniqueRifamycin-S
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维普
