Ring Opening of the Cyclobutane in a Thymine Dimer Radical Anion

✍ Scribed by Chryssostomos Chatgilialoglu; Maurizio Guerra; Panagiotis Kaloudis; Chantal Houée-Lévin; Jean-Louis Marignier; Vijay N. Swaminathan; Thomas Carell

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 476 KB
• Volume: 13
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200700807

✦ Synopsis

Abstract

The reactions of hydrated electrons (e~aq~^−^) with thymine dimer 2 and thymidine have been investigated by radiolytic methods coupled with product studies, and addressed computationally by means of BB1K‐HMDFT calculations. Pulse radiolysis revealed that one‐electron reduction of the thymine dimer 2 affords the radical anion of thymidine (5) with t~1/2~<35 ns. Indeed, the theoretical study suggests that radical anion 3, in which the spin density and charge distribution are located in both thymine rings, undergoes a fast partially ionic splitting of the cyclobutane with a half‐life of a few ps. This model fits with the in vivo observation of thymine dimer repair in DNA by photolyase. γ‐Radiolysis of thymine dimer 2 demonstrates that the one‐electron reduction and the subsequent cleavage of the cyclobutane ring does not proceed by means of a radical chain mechanism, that is, in this model reaction the T^−.^ is unable to transfer an electron to the thymine dimer 2.