Authors:

Keriany Fuentes

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About Paper:

N-oxides are compounds wherein an oxygen atom is directly attached to the nitrogen atom of an amino group. They play crucial roles in metabolic pathways, including the metabolism of amino acids and in the biosynthesis of nitric oxide. Being able to unambiguously identify N-oxides would enhance our understanding of health, disease, and biological processes. However, the study of N-oxides is limited by the absence of analytical techniques for their identification in mixtures. Mass spectrometry is a powerful analytical technique that plays a crucial role in the identification and analysis of molecules, often directly in mixtures. Mass spectrometry separates ionized analytes based on their mass-to-charge ratio (m/z). In tandem mass spectrometry experiments, all the mixture components are first ionized. The analyte ion of interest is isolated and subjected to dissociation or gas-phase ion-molecule reactions (MS2 experiments). The product ions can then be isolated and subjected to further reactions (MS3 experiments). Gas-phase ion- molecule reactions of tris(dimethylamino)borane (TDMAB) have been used previously to identify and distinguish tertiary N-oxides from other types of compounds, such as amines and sulfoxides, by using MS3 experiments. Here, this work was expanded to include secondary N-oxides. Protonated secondary N-oxides react with TDMAB to form an adduct that has eliminated a dimethylamine molecule, just like tertiary N-oxides. However, when these product ions were subjected to collision-activated dissociation (CAD), diagnostic fragmentation reactions were detected. These reactions involved elimination of (CH3)2N-B=O (MW 71 Da) or both (CH3)2N-B=O (MW 71 Da) and dimethylimine (MW 43 Da).

Source:

Purdue University / 2023

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Co-authors:

Keriany Fuentes