Virtual decoupling to break the simplification versus resolution trade-off in nuclear magnetic resonance of complex metabolic mixtures

The heteronuclear single quantum correlation (HSQC) experiment developed by Bodenhausen and Ruben (1980) in the early days of modern nuclear magnetic resonance (NMR) is without a doubt one of the most widely used experiments, with applications in almost every aspect of NMR including metabolomics. Acquiring this experiment, however, always implies a trade-off: simplification versus resolution. Here, we present a method that artificially lifts this barrier and demonstrate its application towards metabolite identification in a complex mixture. Based on the measurement of clean in-phase and clean anti-phase (CLIP/CLAP) HSQC spectra (Enthart et al., 2008), we construct a virtually decoupled HSQC (vd-HSQC) spectrum that maintains the highest possible resolution in the proton dimension. Combining this vd-HSQC spectrum with a J-resolved spectrum (Pell and Keeler, 2007) provides useful information for the one-dimensional proton spectrum assignment and for the identification of metabolites in Dreissena polymorpha (Prud'homme et al., 2020).

Virtual decoupling to break the Simplification Versus Resolution Trade Off in NMR of Complex Metabolic Mixtures

The HSQC experiment developed by Bodenhausen and Ruben (Bodenhausen and Ruben, 1980) in the early days of modern NMR is without a doubt one of the most widely used experiments, with applications in almost every aspect of NMR including metabolomics. Acquiring this experiment however always implies a trade-off: simplification versus resolution. Here, we present a method that artificially lifts this barrier, and demonstrate its application towards metabolite identification in a complex mixture. Based on the measurement of CLean In-Phase and CLean Anti-Phase (CLIP/CLAP) HSQC spectra (Enthart et al., 2008), we construct a virtually decoupled HSQC (vd-HSQC) spectrum that maintains the highest possible resolution in the proton dimension. Combining this vd-HSQC spectrum with a J-resolved spectrum (Pell and Keeler, 2007) provides useful information for the one-dimensional proton spectrum assignment and for the identification of metabolites in Dreissena polymorpha (Prud’homme et al., 2020).

Characterization of the Structure of 2-(4-methyl-2 Phenyl-4, 5-dihydrooxazol-4-ylmethyl)-isoindole-1, 3-dione by 1D, COSY and HSQC 2D NMR Spectroscopy

The identity of the 2-(4-Methyl-2-phenyl-4,5-dihydrooxazol-4-ylmethyl)-isoindole-1,3-dione, previously synthesized in our laboratory, was proven without doubt by means of 1D and 2D NMR spectroscopy. Two-dimensional NMR spectroscopy played a major role. The analysis of the 2D-COSY spectrum of isoindoline-1,3-dione derivative shows a perfect correlation between neighboring protons. Thus, a correlation was noted between the protons of the phthalimide, H(8) and H(9) on the one hand and H(8') and H(9') on the other hand. The analysis of the 2D-HSQC spectrum of the studied compound indicates a faultless correlation between protons and adjacent carbons, and no correlation in the case of all quaternary carbons.

CHARACTERIZATION OF ALGINATE PREPARED FROM BROWN SEAWEEDS IN THUA THIEN-HUE PROVINCE, VIETNAM

The characterization of alginate prepared from brown seaweeds in TT-Hue province of Vietnam was investigated. Composition and the sequential structure of alginate were determined by 1HNMR, 13C-NMR, TOCSY, 1H-1H COSY, and 1H-13C-HSQC spectrum. It is found that alginate with molecular weight around 101 KDa is composed of homopolymeric regions of M and G blocks, interspersed with very small amount of regions of alternating structure of MG block. This information is essential for application guideline of alginate in TT-Hue province.