TY - JOUR
T1 - Tautomerization lowers the activation barriers for N-glycosidic bond cleavage of protonated uridine and 2′-deoxyuridine
AU - Wu, R. R.
AU - Rodgers, M. T.
N1 - Publisher Copyright:
© the Owner Societies 2016.
PY - 2016
Y1 - 2016
N2 - The gas-phase conformations of protonated uridine, [Urd+H]+, and its 2′-deoxy form, protonated 2′-deoxyuridine, [dUrd+H]+, have been examined in detail previously by infrared multiple photon dissociation action spectroscopy techniques. Both 2,4-dihydroxy tautomers and O4 protonated conformers of [Urd+H]+ and [dUrd+H]+ were found to coexist in the experiments with the 2,4-dihydroxy tautomers dominating the population. In the present study, the kinetic energy dependence of the collision-induced dissociation behavior of [Urd+H]+ and [dUrd+H]+ are examined using a guided ion beam tandem mass spectrometer to probe the mechanisms and energetics for activated dissociation of these protonated nucleosides. The primary dissociation pathways observed involve N-glycosidic bond cleavage leading to competitive elimination of protonated or neutral uracil. The potential energy surfaces (PESs) for these N-glycosidic bond cleavage pathways are mapped out via electronic structure calculations for the mixture of 2,4-dihydroxy tautomers and O4 protonated conformers of [Urd+H]+ and [dUrd+H]+ populated in the experiments. The calculated activation energies (AEs) and heats of reaction (ΔHrxns) for N-glycosidic bond cleavage at both the B3LYP and MP2(full) levels of theory are compared to the measured values. The agreement between experiment and theory indicates that B3LYP provides better estimates of the energetics of the species along the PESs for N-glycosidic bond cleavage than MP2, and that the 2,4-dihydroxy tautomers, which are stabilized by strong hydrogen-bonding interactions, predominantly influence the observed threshold dissociation behavior of [Urd+H]+ and [dUrd+H]+.
AB - The gas-phase conformations of protonated uridine, [Urd+H]+, and its 2′-deoxy form, protonated 2′-deoxyuridine, [dUrd+H]+, have been examined in detail previously by infrared multiple photon dissociation action spectroscopy techniques. Both 2,4-dihydroxy tautomers and O4 protonated conformers of [Urd+H]+ and [dUrd+H]+ were found to coexist in the experiments with the 2,4-dihydroxy tautomers dominating the population. In the present study, the kinetic energy dependence of the collision-induced dissociation behavior of [Urd+H]+ and [dUrd+H]+ are examined using a guided ion beam tandem mass spectrometer to probe the mechanisms and energetics for activated dissociation of these protonated nucleosides. The primary dissociation pathways observed involve N-glycosidic bond cleavage leading to competitive elimination of protonated or neutral uracil. The potential energy surfaces (PESs) for these N-glycosidic bond cleavage pathways are mapped out via electronic structure calculations for the mixture of 2,4-dihydroxy tautomers and O4 protonated conformers of [Urd+H]+ and [dUrd+H]+ populated in the experiments. The calculated activation energies (AEs) and heats of reaction (ΔHrxns) for N-glycosidic bond cleavage at both the B3LYP and MP2(full) levels of theory are compared to the measured values. The agreement between experiment and theory indicates that B3LYP provides better estimates of the energetics of the species along the PESs for N-glycosidic bond cleavage than MP2, and that the 2,4-dihydroxy tautomers, which are stabilized by strong hydrogen-bonding interactions, predominantly influence the observed threshold dissociation behavior of [Urd+H]+ and [dUrd+H]+.
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U2 - 10.1039/c6cp03620a
DO - 10.1039/c6cp03620a
M3 - Article
C2 - 27536972
AN - SCOPUS:84985003673
SN - 1463-9076
VL - 18
SP - 24451
EP - 24459
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 35
ER -