Gas-phase protonation thermochemistry of adenosine

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Author(s) Touboul, David, Bouchoux, Guy, Zenobi, Renato
Publication Type Journal Items, Publication Status: Published
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Title Gas-phase protonation thermochemistry of adenosine
Author(s) Touboul, David
Bouchoux, Guy
Zenobi, Renato
Journal or Series Title The journal of physical chemistry. B
Volume Number 112
Issue Number 37
Start Page 11716
End Page 11725
ISSN 1520-6106
Publisher American Chemical Society
Publication Place Washington, DC
Publication Date 2008
Abstract The goal of this work was to obtain a detailed insight on the gas-phase protonation energetic of adenosine using both mass spectrometric experiments and quantum chemical calculations. The experimental approach used the extended kinetic method with nanoelectrospray ionization and collision-induced dissociation tandem mass spectrometry. This method provides experimental values for proton affinity, PA(adenosine) = 979 +/- 1 kJ.mol(-1), and for the "protonation entropy", Delta S-p degrees(adenosine) = S degrees(adenosineH(+)) - S degrees(adenosine) = -5 +/- 1 5 J . mol(-1) . K-1. The corresponding gas-phase basicity is consequently equal to: GB(adenosine) = 945 2 kJ . mol(-1) at 298K. Theoretical calculations conducted at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) level, including 298 K enthalpy correction, predict a proton affinity value of 974 kJ.mol(-1) after consideration of isodesmic proton transfer reactions with pyridine as the reference base. Moreover, computations clearly showed that N3 is the most favorable protonation site for adenosine, due to a strong internal hydrogen bond involving the hydroxyl group at the 2' position of the ribose sugar moiety, unlike observations for adenine and 2'-deoxyadenosine, where protonation occurs on NI. The existence of negligible protonation entropy is confirmed by calculations (theoretical Delta S-p degrees(adenosine) similar to -2/-3 J.mol(-1).K-1) including conformational analysis and entropy of hindered rotations. Thus, the calculated protonation thermochemical properties are in good agreement with our experimental measurements. It may be noted that the new PA value is similar to 10 kJ . mol(-1) lower than the one reported in the National Institute of Standards and Technology (NIST) database, thus pointing to a correction of the tabulated protonation thermochemistry of adenosine.
DOI 10.1021/jp804786e
Additional Notes Received 30 May 2008, Revised 10 July 2008, Publication Date (Web) 23 August 2008
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03430
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NEBIS System Number 001807682
Source Database ID PP-41462
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  author = "Touboul, David and Bouchoux, Guy and Zenobi, Renato",
  title = "{G}as-phase protonation thermochemistry of adenosine",
  journal = "The journal of physical chemistry. B",
  year = 2008,
  volume = "112",
  number = "37",
  pages = "11716--11725",

E-Citations record created: Thu, 01 Apr 2010, 23:01:44 CET