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Issue 25, 2007
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Anion photoelectron imaging of deprotonated thymine and cytosine

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We report the anion photoelectron spectra of deprotonated thymine and cytosine at 3.496 eV photodetachment energy using velocity-mapped imaging. The photoelectron spectra of both species exhibit bands resulting from detachment transitions between the anion ground state and the ground state of the neutral radical. Franck–Condon simulations identify the anion isomers that contribute to the observed photoelectron spectrum. For both thymine and cytosine, the photoelectron spectra are consistent with anions formed by removal of a proton from the N atom that normally attaches to the sugar in the nucleotide (N1). For deprotonated thymine, the photoelectron spectrum shows a band due to a ring breathing vibration excited during the photodetachment transition. The electron affinity for the dehydrogenated thymine radical is determined as 3.250 ± 0.015 eV. For deprotonated cytosine, the photoelectron spectrum lacks any resolved structure and the electron affinity of the dehydrogenated cytosine radical is determined to be 3.037 ± 0.015 eV. By combining the electron affinity with previously measured gas phase acidities of thymine and cytosine, we determine the bond dissociation energy for the N–H bond that is broken.

Graphical abstract: Anion photoelectron imaging of deprotonated thymine and cytosine

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The article was received on 28 Feb 2007, accepted on 05 Apr 2007 and first published on 03 May 2007

Article type: Paper
DOI: 10.1039/B703045B
Phys. Chem. Chem. Phys., 2007,9, 3291-3297

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    Anion photoelectron imaging of deprotonated thymine and cytosine

    B. F. Parsons, S. M. Sheehan, T. A. Yen, D. M. Neumark, N. Wehres and R. Weinkauf, Phys. Chem. Chem. Phys., 2007, 9, 3291
    DOI: 10.1039/B703045B

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