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Title: Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine)

Abstract

In this work, we report on a photoionization study of the microhydration of the four DNA bases. Gas-phase clusters of water with DNA bases [guanine (G), cytosine (C), adenine (A), and thymine (T)] are generated via thermal vaporization of the bases and expansion of the resultant vapor in a continuous supersonic jet expansion of water seeded in Ar. The resulting clusters are investigated by single-photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for the DNA bases and the following water (W) clusters: G, GW{sub n} (n = 1-3); C, CW{sub n} (n = 1-3); A, AW{sub n} (n = 1,2); and T, TW{sub n} (n = 1-3). Appearance energies (AE) are derived from the onset of these PIE curves (all energies in eV): G (8.1 {+-} 0.1), GW (8.0 {+-} 0.1), GW{sub 2} (8.0 {+-} 0.1), and GW{sub 3} (8.0); C (8.65 {+-} 0.05), CW (8.45 {+-} 0.05), CW{sub 2} (8.4 {+-} 0.1), and CW{sub 3} (8.3 {+-} 0.1); A (8.30 {+-} 0.05), AW (8.20 {+-} 0.05), and AW{sub 2} (8.1 {+-} 0.1); T (8.90 {+-} 0.05); and TW (8.75 {+-} 0.05), TW{sub 2} (8.6 {+-} 0.1), andmore » TW{sub 3} (8.6 {+-} 0.1). The AEs of the DNA bases decrease slightly with the addition of water molecules (up to three) but do not converge to values found for photoinduced electron removal from DNA bases in solution.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
928432
Report Number(s):
LBNL-62328
R&D Project: 403101; BnR: KC0301020; TRN: US0804211
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A; Journal Volume: 111; Journal Issue: 31; Related Information: Journal Publication Date: 2007
Country of Publication:
United States
Language:
English
Subject:
37; ADENINES; CYTOSINE; DNA; EFFICIENCY; ELECTRONS; EVAPORATION; GUANINE; IONIZATION; MASS SPECTROSCOPY; PHOTOIONIZATION; REMOVAL; SYNCHROTRON RADIATION; THYMINE; WATER

Citation Formats

Belau, L., Wilson, K.R., Leone, S.R., and Musahid, Ahmed. Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine). United States: N. p., 2007. Web. doi:10.1021/jp0705929.
Belau, L., Wilson, K.R., Leone, S.R., & Musahid, Ahmed. Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine). United States. doi:10.1021/jp0705929.
Belau, L., Wilson, K.R., Leone, S.R., and Musahid, Ahmed. Mon . "Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine)". United States. doi:10.1021/jp0705929.
@article{osti_928432,
title = {Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine)},
author = {Belau, L. and Wilson, K.R. and Leone, S.R. and Musahid, Ahmed},
abstractNote = {In this work, we report on a photoionization study of the microhydration of the four DNA bases. Gas-phase clusters of water with DNA bases [guanine (G), cytosine (C), adenine (A), and thymine (T)] are generated via thermal vaporization of the bases and expansion of the resultant vapor in a continuous supersonic jet expansion of water seeded in Ar. The resulting clusters are investigated by single-photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for the DNA bases and the following water (W) clusters: G, GW{sub n} (n = 1-3); C, CW{sub n} (n = 1-3); A, AW{sub n} (n = 1,2); and T, TW{sub n} (n = 1-3). Appearance energies (AE) are derived from the onset of these PIE curves (all energies in eV): G (8.1 {+-} 0.1), GW (8.0 {+-} 0.1), GW{sub 2} (8.0 {+-} 0.1), and GW{sub 3} (8.0); C (8.65 {+-} 0.05), CW (8.45 {+-} 0.05), CW{sub 2} (8.4 {+-} 0.1), and CW{sub 3} (8.3 {+-} 0.1); A (8.30 {+-} 0.05), AW (8.20 {+-} 0.05), and AW{sub 2} (8.1 {+-} 0.1); T (8.90 {+-} 0.05); and TW (8.75 {+-} 0.05), TW{sub 2} (8.6 {+-} 0.1), and TW{sub 3} (8.6 {+-} 0.1). The AEs of the DNA bases decrease slightly with the addition of water molecules (up to three) but do not converge to values found for photoinduced electron removal from DNA bases in solution.},
doi = {10.1021/jp0705929},
journal = {Journal of Physical Chemistry A},
number = 31,
volume = 111,
place = {United States},
year = {Mon Jan 22 00:00:00 EST 2007},
month = {Mon Jan 22 00:00:00 EST 2007}
}
  • An ESR study of the relative distribution of ion radicals formed in DNA equilibrated with D{sub 2}O and {gamma}-irradiated at 77 K is presented. The ESR spectra of irradiated DNA and polynucleotides (poly(dG){center dot}poly(dC) and poly(dAdT){center dot}poly(dAdT)) were obtained and employed in a computer-assisted analysis for the individual ion-radical distribution. Analysis of spectra as a function of power allowed the separation of the spectra of the pyrimidine anions (T{sup {sm bullet}{minus}}, C{sup {sm bullet}{minus}}) from the spectra of the purine cations (G{sup {sm bullet}+}, A{sup {sm bullet}+}). The spectra of the mononucleotide ion radicals, dCMP{sup {sm bullet}{minus}}, dTMP{sup {sm bullet}{minus}},more » dGMP{sup {sm bullet}+}, and dAMP{sup {sm bullet}+}, were produced in 8 M LiCl glasses. In addition, the spectra of the ion radicals of all of the mononucleotide ion radicals except dAMP{sup +} were simulated by using hyperfine and g tensors from the literature. Basis spectra derived from (1) power saturation experiments, (2) polynucleotide and mononucleotide spectra, (3) spectra of mononucleotides alone, and (4) anisotropic simulations were used to fit the spectra of DNA by use of a linear least-squares analysis. Each of the four separate analyses confirms that the cytosine anion dominates the spectra of DNA at 100 K. Three analyses included the cationic composition, and they strongly favor the guanine cation over the adenine cation. An average of the authors results gives the DNA ion radicals' relative to abundances as ca. 77% C{sup {sm bullet}{minus}}, 23% T{sup {sm bullet}{minus}} for the anions and >90% G{sup {sm bullet}+} for the cations about equal amounts of anions and cations are present. No difference in results is found for DNA irradiated in frozen D{sub 2}O solutions or simply exchanged at 100% D{sub 2}O humidity.« less
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