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Title: Can an Excess Electron Localise on a Purine Moiety in the Adenine-thymine Watson-Crick Base Pair? A Computational Study

Abstract

The electron affinity and the propensity to electron-induced proton transfer (PT) of hydrogen-bonded complexes between the Watson–Crick adenine–thymine pair (AT) and simple organic acid (HX), attached to adenine in the Hoogsteen-type configuration, were studied at the B3LYP/6-31+G** level. Although the carboxyl group is deprotonated at physiological pH, its neutral form, COOH, resembles the peptide bond or the amide fragment in the side chain of asparagine (Asn) or glutamine (Gln). Thus, these complexes mimic the interaction between the DNA environment (e.g., proteins) and nucleobase pairs incorporated in the biopolymer. Electron attachment is thermodynamically feasible and adiabatic electron affinities range from 0.41 to 1.28 eV, while the vertical detachment energies of the resulting anions span the range of 0.39 –2.88 eV. Low-energy activation barriers separate the anionic minima: aHX(AT) from the more stable single-PT anionic geometry, aHX(AT)-SPT, and aHX(AT)-SPT from the double-PT anionic geometry, aHX(AT)-DPT. Interaction between the adenine of the Watson–Crick AT base pair with an acidic proton donor probably counterbalances the larger EA of isolated thymine, as SOMO is almost evenly delocalized over both types of nucleic bases in the aHX(AT) anions. Moreover, as a result of PT the excess electron localizes entirely on adenine. Thus, in DNA interacting withmore » its physiological environment, damage induced by low-energy electrons could begin, contrary to the current view, with the formation of purine anions, which are not formed in isolated DNA because of the greater stability of anionic pyrimidines.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1012313
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Quantum Chemistry, 107(12):2224-2232; Journal Volume: 107; Journal Issue: 12
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 60 APPLIED LIFE SCIENCES; ADENINES; AFFINITY; AMIDES; ANIONS; ASPARAGINE; CONFIGURATION; DNA; ELECTRON ATTACHMENT; ELECTRONS; GEOMETRY; GLUTAMINE; ORGANIC ACIDS; PEPTIDES; PROTEINS; PROTONS; PURINES; PYRIMIDINES; STABILITY; THYMINE; Environmental Molecular Sciences Laboratory

Citation Formats

Mazurkiewicz, Kamil, Haranczyk, Maciej, Gutowski, Maciej S., and Rak, Janusz. Can an Excess Electron Localise on a Purine Moiety in the Adenine-thymine Watson-Crick Base Pair? A Computational Study. United States: N. p., 2007. Web. doi:10.1002/qua.21359.
Mazurkiewicz, Kamil, Haranczyk, Maciej, Gutowski, Maciej S., & Rak, Janusz. Can an Excess Electron Localise on a Purine Moiety in the Adenine-thymine Watson-Crick Base Pair? A Computational Study. United States. doi:10.1002/qua.21359.
Mazurkiewicz, Kamil, Haranczyk, Maciej, Gutowski, Maciej S., and Rak, Janusz. Tue . "Can an Excess Electron Localise on a Purine Moiety in the Adenine-thymine Watson-Crick Base Pair? A Computational Study". United States. doi:10.1002/qua.21359.
@article{osti_1012313,
title = {Can an Excess Electron Localise on a Purine Moiety in the Adenine-thymine Watson-Crick Base Pair? A Computational Study},
author = {Mazurkiewicz, Kamil and Haranczyk, Maciej and Gutowski, Maciej S. and Rak, Janusz},
abstractNote = {The electron affinity and the propensity to electron-induced proton transfer (PT) of hydrogen-bonded complexes between the Watson–Crick adenine–thymine pair (AT) and simple organic acid (HX), attached to adenine in the Hoogsteen-type configuration, were studied at the B3LYP/6-31+G** level. Although the carboxyl group is deprotonated at physiological pH, its neutral form, COOH, resembles the peptide bond or the amide fragment in the side chain of asparagine (Asn) or glutamine (Gln). Thus, these complexes mimic the interaction between the DNA environment (e.g., proteins) and nucleobase pairs incorporated in the biopolymer. Electron attachment is thermodynamically feasible and adiabatic electron affinities range from 0.41 to 1.28 eV, while the vertical detachment energies of the resulting anions span the range of 0.39 –2.88 eV. Low-energy activation barriers separate the anionic minima: aHX(AT) from the more stable single-PT anionic geometry, aHX(AT)-SPT, and aHX(AT)-SPT from the double-PT anionic geometry, aHX(AT)-DPT. Interaction between the adenine of the Watson–Crick AT base pair with an acidic proton donor probably counterbalances the larger EA of isolated thymine, as SOMO is almost evenly delocalized over both types of nucleic bases in the aHX(AT) anions. Moreover, as a result of PT the excess electron localizes entirely on adenine. Thus, in DNA interacting with its physiological environment, damage induced by low-energy electrons could begin, contrary to the current view, with the formation of purine anions, which are not formed in isolated DNA because of the greater stability of anionic pyrimidines.},
doi = {10.1002/qua.21359},
journal = {International Journal of Quantum Chemistry, 107(12):2224-2232},
number = 12,
volume = 107,
place = {United States},
year = {Tue Apr 17 00:00:00 EDT 2007},
month = {Tue Apr 17 00:00:00 EDT 2007}
}