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Electron-transfer induced repair of 6-4 photoproducts in DNA: a computational study
Uppsala University, Sweden.
Örebro University, Sweden.
University of Siena, Italy.
2007 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, no 12, 2351-2361 p.Article in journal (Refereed) Published
Abstract [en]

The mechanism employed by DNA photolyase to repair 6-4 photoproducts in UV-damaged DNA is explored by means of quantum chemical calculations. Considering the repair of both oxetane and azetidine lesions, it is demonstrated that reduction as well as oxidation enables a reversion reaction by creating anionic or cationic radicals that readily fragment into monomeric pyrimidines. However, on the basis of calculated reaction energies indicating that electron transfer from the enzyme to the lesion is a much more favorable process than electron transfer in the opposite direction, it is suggested that the photoenzymic repair can only occur by way of an anionic mechanism. Furthermore, it is shown that reduction of the oxetane facilitates a mechanism involving cleavage of the C−O bond followed by cleavage of the C−C bond, whereas reductive fragmentation of the azetidine may proceed with either of the intermonomeric C–N and C–C bonds cleaved as the first step. From calculations on neutral azetidine radicals, a significant increase in the free-energy barrier for the initial fragmentation step upon protonation of the carbonylic oxygens is predicted. This effect can be attributed to protonation serving to stabilize reactant complexes more than transition structures.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2007. Vol. 111, no 12, 2351-2361 p.
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-96773DOI: 10.1021/jp0676383OAI: diva2:643318
Available from: 2013-08-26 Created: 2013-08-26 Last updated: 2013-09-03Bibliographically approved

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Durbeej, Bo
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