title: High desolvation temperature facilitates the ESI-source H/D exchange at non-labile sites of hydroxybenzoic acids and aromatic amino acids.
abstract: Hydrogen/deuterium exchange coupled with high-resolution mass spectrometry has become a powerful analytical approach for structural investigations of complex organic matrices. Here we report the 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 °C up to 400 °C. 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-dihydroxybenzoic 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 taking place in the sprayed droplets rather 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-acetylsalicylic acid. (2)H 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.
authors.affiliation: Lomonosov Moscow State University, Department of Chemistry, Leninskie Gory 1-3, 119991 Moscow, Russia. iperm@org.chem.msu.ru.
authors.forename: Alexander
authors.initials: A
authors.lastname: Zherebker
authors.affiliation: Skolkovo Institute of Science and Technology, Novaya St., 100, Skolkovo 143025, Russian Federation. ennikolaev@rambler.ru and Institute for Energy Problems of Chemical Physics Russian Academy of Sciences, Leninskij pr. 38 k.2, 119334 Moscow, Russia and Moscow Institute of Physics and Technology, 141700 Dolgoprudnyi, Moscow Region, Russia.
authors.forename: Yury
authors.initials: Y
authors.lastname: Kostyukevich
authors.affiliation: Emanuel Institute for Biochemical Physics Russian Academy of Sciences, Kosygina st. 4, 119334 Moscow, Russia and Institute for Energy Problems of Chemical Physics Russian Academy of Sciences, Leninskij pr. 38 k.2, 119334 Moscow, Russia and Moscow Institute of Physics and Technology, 141700 Dolgoprudnyi, Moscow Region, Russia.
authors.forename: Alexey
authors.initials: A
authors.lastname: Kononikhin
authors.affiliation: Lomonosov Moscow State University, Department of Chemistry, Leninskie Gory 1-3, 119991 Moscow, Russia. iperm@org.chem.msu.ru.
authors.forename: Vitaliy A
authors.initials: VA
authors.lastname: Roznyatovsky
authors.affiliation: Emanuel Institute for Biochemical Physics Russian Academy of Sciences, Kosygina st. 4, 119334 Moscow, Russia and Moscow Institute of Physics and Technology, 141700 Dolgoprudnyi, Moscow Region, Russia.
authors.forename: Igor
authors.initials: I
authors.lastname: Popov
authors.affiliation: Lomonosov Moscow State University, Department of Chemistry, Leninskie Gory 1-3, 119991 Moscow, Russia. iperm@org.chem.msu.ru.
authors.forename: Yuri K
authors.initials: YK
authors.lastname: Grishin
authors.affiliation: Lomonosov Moscow State University, Department of Chemistry, Leninskie Gory 1-3, 119991 Moscow, Russia. iperm@org.chem.msu.ru.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Perminova
authors.affiliation: Skolkovo Institute of Science and Technology, Novaya St., 100, Skolkovo 143025, Russian Federation. ennikolaev@rambler.ru and Emanuel Institute for Biochemical Physics Russian Academy of Sciences, Kosygina st. 4, 119334 Moscow, Russia and Institute for Energy Problems of Chemical Physics Russian Academy of Sciences, Leninskij pr. 38 k.2, 119334 Moscow, Russia and Moscow Institute of Physics and Technology, 141700 Dolgoprudnyi, Moscow Region, Russia.
authors.forename: Eugene
authors.initials: E
authors.lastname: Nikolaev