An Orthogonal-Pattern Absorption-Mode 2D J -Resolved NMR Spectroscopy for Analyses on Complex Samples

Abstract

Despite the powerfulness for revealing molecular structures and compositions, conventional 2D J -resolved nuclear magnetic resonance (NMR) experiments are generally exposed to crowded NMR resonances, distorted peak lineshapes, strong coupling artifacts, and inhomogeneous broadening effects, thus rendering its potential applications restricted. Herein, we propose a general NMR method to circumvent these complications and record absorption-mode 2D J -resolved spectra, in which pure chemical shifts and J couplings are presented in two orthogonal dimensions. Thereby, this method facilitates peak assignments at congested spectral regions and implements high-resolution measurements on the desired structural information of J couplings and chemical shifts, even under nonideal magnetic field conditions. Experimental results on samples of a biomolecule and clinical antibiotics demonstrate its suitability and effectiveness for analyzing complex samples exhibiting crowded resonances or strong coupling responses under adverse magnetic field conditions. More importantly, it is available for directly probing heterogeneous biological samples containing intrinsic susceptibility variations and abundant metabolites. In addition, a multiband version is further developed to enhance the spectral sensitivity by collecting signals from multiple spatial slices. This proposed technique is applicable to common commercial liquid NMR spectrometers without special requirements on instrument hardwares and sample pretreatments. Consequently, this study permits composition measurements and multiplet structure analyses on complex samples even in inhomogeneous magnetic fields, thus showing interesting prospects for future chemical and biological applications.