Interaction of singlet oxygen and superoxide radical anion with guanine and formation of its mutagenic modification 8-oxoguanine

Mishra, P. C. ; Singh, A. K. ; Suhai, S. (2005) Interaction of singlet oxygen and superoxide radical anion with guanine and formation of its mutagenic modification 8-oxoguanine International Journal of Quantum Chemistry, 102 (3). pp. 282-301. ISSN 0020-7608

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/qua.202...

Related URL: http://dx.doi.org/10.1002/qua.20272

Abstract

Formation of 8-oxoguanine (8OG) from guanine in biological systems is known to cause lethal mutation and cancer. It has been suggested earlier, on the basis of experimental studies, that the oxygen molecule in its lowest singlet excited state (1O2) plays an important role in the formation of 8OG. In order to understand the possible mechanisms in this context, B3LYP/6-31+G and MP2/6-31+G calculations were carried out on the structures and stabilities of different molecules and complexes involved in the formation of 8OG. All the molecules, complexes, and transition states studied in the present report were solvated in aqueous media. Guanine has been found to make a strong complex with 1O2 with the latter species located above the imidazole ring plane, and the complex of guanine with 3O2 is much weaker than that with 1O2. Transition state calculations were carried out to study formation of 7,8-dihydro,8-hydroxyguanine (8OHG) and 2-oxo-imidazole. It has been shown that 8OG can be formed in two different ways: (i) due to interaction of the radical cation of guanine with O2_ where 8OHG complexed with 1O2 would occur as an intermediate, and (ii) due to interaction of guanine with 1O2 leading to the formation of guanine hydroperoxide that would react with a water molecule in the presence of two 1O2 molecules serving as a source of energy to overcome the barrier. It is shown that because the interaction strengths of 3O2 and 1O2 with other molecules, e.g., guanine, are very different, a crossing of their potential energy surfaces takes place in both gas phase and aqueous media, as a result of which the lifetime of 1O2 is strongly decreased.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
Keywords:Mutation; Cancer; 8-Oxoguanine; 7,8-Dihydro,8-hydroxyguanine; Singlet Oxygen; Oxygen Superoxide Radical Anion
ID Code:54107
Deposited On:11 Aug 2011 11:47
Last Modified:11 Aug 2011 11:47

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