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Tautomerism in the guanyl radical
Chryssostomos Chatgilialoglu1, Clara Caminal, Alessio Altieri
1ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy. chrys@isof.cnr.it
Journal of the American Chemical Society
|October 19, 2006
Summary
Researchers identified two tautomers of one-electron-oxidized guanine, formed via protonation of 8-haloguanine electron adducts. This study advances understanding of guanine oxidation products and their properties.
Area of Science:
- Physical Chemistry
- Chemical Kinetics
- Computational Chemistry
Background:
- Understanding the tautomers of one-electron-oxidized guanine is crucial for comprehending DNA damage and repair mechanisms.
- Previous studies have not fully characterized the transient species formed during guanine oxidation.
Purpose of the Study:
- To elucidate the structure and properties of tautomers of one-electron-oxidized guanine.
- To investigate the reaction mechanisms and kinetics of electron adduct formation and decay in 8-substituted guanine derivatives.
Main Methods:
- Pulse radiolysis technique to measure reaction rate constants of hydrated electrons with 8-substituted guanine derivatives.
- Radiolytic methods coupled with product studies to investigate the fate of electron adducts.
- Time-dependent Density Functional Theory (TD-DFT) calculations (TD-B3LYP/6-311G**//B1B95/6-31+G**) for computational analysis.
Main Results:
- Two distinct tautomers of one-electron-oxidized guanine (iminic 7 and aminic 3 forms) were identified as short-lived intermediates.
- Rate constants for electron transfer reactions correlated with inductive and resonance effects of substituents.
- Computational studies revealed the mechanism of bromide ion (Br-) ejection from 8-bromoguanine adducts and identified tautomerization as a water-assisted process.
Conclusions:
- The study successfully describes two key tautomers of one-electron-oxidized guanine, providing insights into their formation and decay pathways.
- The findings contribute to a deeper understanding of the chemical behavior of oxidized guanine species, relevant to radiation chemistry and biological processes.
