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Title:Probing The Conformational Landscape And Thermochemistry Of Dinucleotide Anions Via Helium Nanodroplet Infrared Action Spectroscopy
Author(s):Thomas, Daniel A
Contributor(s):von Helden, Gert; Meijer, Gerard; Greis, Kim; Lettow, Maike; Mucha, Eike; Chang, Rayoon
Abstract:When molecules are captured in a helium nanodroplet, the rate of cooling to an equilibrium temperature of ca. 0.4 K is faster than the rate of isomerization, resulting in “shock-freezing” that kinetically traps molecules in the local conformational minimum. This unique property enables the study of temperature-dependent conformational equilibria via infrared spectroscopy without the deleterious effects of spectral broadening at higher temperatures.\footnote{D. S. Skvortsov, A. F. Vilesov, \textit{J. Chem. Phys.} \textbf{2009}, \textit{130}, 151101.}$^{, }$\footnote{C. M. Leavitt \textit{et al.}, \textit{J. Phys. Chem. A} \textbf{2014}, \textit{118}, 9692-9700.} We utilize this approach to explore the equilibrium conformer populations of deprotonated dinucleotides, which have been shown previously by ion mobility spectrometry to exhibit a strong temperature dependence.\footnote{J. Gidden, M. T. Bowers, \textit{Eur. Phys. J. D} \textbf{2002}, \textit{20}, 409-419.} Dinucleotide anion species were generated by electrospray ionization, confined in a helium-buffer-gas ion trap at temperatures between 90 and 350 K, and entrained in traversing helium nanodroplets. The infrared spectra of the dinucleotide ions captured in nanodroplets show a strong dependence on pre-pickup ion temperature, consistent with the preservation of conformer populations prior to cooling in the helium nanodroplet. Non-negative matrix factorization was utilized to identify component conformer infrared spectra and thereby determine temperature-dependent conformer populations. Relative enthalpies and entropies of conformers were subsequently obtained from a van ’t Hoff analysis. These initial results demonstrate the promise of this technique to elucidate competing intramolecular interactions and experimentally measure thermochemical parameters for isolated biomolecular ions.\footnote{D. A. Thomas \textit{et al.}, \textit{Phys. Chem. Chem. Phys.} \textbf{2020}, \textit{22}, 18400-18413.}
Issue Date:2021-06-22
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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