High desolvation temperature facilitates in ESI-source H/D exchange at non-labile sites of hydroxybenzoic acids and aromatic amino acidsстатья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 28 июня 2016 г.

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[1] High desolvation temperature facilitates in esi-source h/d exchange at non-labile sites of hydroxybenzoic acids and aromatic amino acids / Z. Alexander, K. Yury, K. Alexey et al. // The Analyst. — 2016. — Vol. 141. — P. 2426–2434. Hydrogen/Deuterium exchange coupled to high-resolution mass spectrometry has become a powerful analytical approach for structural investigations of complex organic matrices. Here we report feasibility of the site-specific H/D exchange of non-labile hydrogens directly in the electrospray ionization (ESI) source, which was facilitated by an increase in the desolvation temperature from 200 oC up to 400 oC. We have found that the exchanges at non-labile sites were observed only for the model compounds capable of keto-enol tautomeric transformations (e.g., 2,3-, 2,4-dihydroxy¬benzoic acids, gallic acid, DOPA), and only when water was used as a solvent. We hypothesized that the detected additional exchanges were induced by the presence of hydroxyls in the sprayed water droplets generated in the negative ESI mode. It was indicative of the exchange reactions rather taking place in the sprayed droplets than in the gas phase. To support this hypothesis, the H/D exchange experiments were run in deuterated water under base-catalyzed conditions for three model compounds, which showed the most intensive exchanges in the MS experiments: DOPA, 2,4-DHB, and 5-acetylsalycilic acid. 2H NMR spectroscopy has confirmed keto-enolic transformations of the model compounds leading to the specific labeling of the corresponding non-labile sites. We believe that the proposed technique will be useful for structural investigations of natural complex mixtures (e.g. proteins, humic substances) using site-specific H/D exchange. [ DOI ]

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