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A New Mechanism Towards Understanding the Origin of DNA Oxidation Biomarkers Under Hypoxia Condition -- a Theoretical Perspective
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  • Shuang Zhao,
  • Shan Jiang,
  • Min Wang,
  • Chunyan Cao,
  • Xin Wan
Shuang Zhao
Bohai University
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Shan Jiang
Bohai University
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Min Wang
Bohai University
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Chunyan Cao
Bohai University
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Xin Wan
Bohai University
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Peer review status:UNDER REVIEW

18 Jun 2020Submitted to International Journal of Quantum Chemistry
19 Jun 2020Assigned to Editor
19 Jun 2020Submission Checks Completed
25 Jun 2020Reviewer(s) Assigned

Abstract

Reactivity of thymine peroxy radical in DNA and its fate under hypoxia or oxygen-less conditions are studied at the M06-2X/6-31+G(d,p) level. The spaciously most accessible H2’ can be abstracted by C6-peroxy radical in an intranucleotidyl manner with the estimated barriers of 18.8 ~ 21.1 kcal/mol. The calculations show that C6-peroxy radical has a highly more reactivity towards C(sp3)-H abstraction reactions than its relative C6-yl, which is a counter-intuitive case. The formed hydroperoxide with the C6-OaObH2’ constituent can fast transfer ObH2’ group to C2’ radical in an intranucleotidyl manner with a low barrier (ca. 13.2 kcal/mol) and very strong heat release. The results show that the formed hydroperoxide product is unstable so that it could be quickly transformed into other species and thus is very hard to be experimentally observed. Afterwards, H2’ can be again abstracted by C6-oxyl radical to result in formation of thymine glycol which is the main products. The parallel C5-C6 bond scission reaction leads to formation of the precursor for 5-hydroxy-5-methylhydantion. The two competitive reactions have very low barriers. Based on our present calculations, the new radical reaction paths to formation of the DNA oxidation products are suggested under hypoxia or oxygen-less conditions, which is different from the previously suggested paths under high oxygen concentration surroundings.