Cytosine Iminyl Radical (cytN•) Formation via Electron-Induced Debromination of 5-Bromocytosine: A DFT and Gaussian 4 Study.

doi:10.1021/acs.jpca.7b04034

Paper

Cytosine Iminyl Radical (cytN•) Formation via Electron-Induced Debromination of 5-Bromocytosine: A DFT and Gaussian 4 Study.

Published Jun 16, 2017 · Anilesh Kumar, M. Sevilla

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Abstract

Halogen-substituted pyrimidines, such as 5-bromouracil and 5-iodouracil, have been used as radio therapeutic (RT) agents in cancer treatment. The radiosensitizing activity of 5-bromouracil is attributed to its reaction with electron which produce the highly reactive uracil-5-yl radical by dissociating the C5-Br bond. Using density functional methods and highly accurate Gaussian 4 (G4) theory, herein, we show that 5-bromocytosine (5-Brcyt) after reaction with electron, also, leads to the formation of cytosine-5-yl radical. However, our results show that this species can subsequently undergo a base-catalyzed tautomerization reaction to form the π-aminyl radical followed by a second tautomerization to the thermodynamically most stable σ-iminyl radical (cytN•). From the present theoretical calculations, we infer that the mechanism of the formation of cytN• by one-electron reduction of 5-Brcyt is straightforward and may take place in 5-Brcyt-labeled DNA in competition with the usual reactions expected for the cytosine-5-yl radical such as abstraction and water addition.

Study Snapshot

Electron-induced debromination of 5-bromocytosine leads to the formation of the thermodynamically most stable cytosine iminyl radical (cytN•), which may play a role in radiotherapeutic cancer treatment.

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Cytosine Iminyl Radical (cytN•) Formation via Electron-Induced Debromination of 5-Bromocytosine: A DFT and Gaussian 4 Study.

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