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Ring Opening of the Cyclobutane in a Thymine Dimer Radical Anion

机译:胸腺嘧啶二聚体自由基阴离子中环丁烷的开环

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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.gamma-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.
机译:水合电子(e_(aq)〜-)与胸腺嘧啶二聚体2和胸苷的反应已通过辐射解法和产物研究相结合进行了研究,并通过BB1K-HMDFT计算得到了解决。胸腺嘧啶二聚体2可提供t_(1/2)<35 ns的胸苷(5)自由基。理论上,理论研究表明,自旋密度和电荷分布均位于两个胸腺嘧啶环中的自由基阴离子3,经历环丁烷的快速部分离子分裂,半衰期为几ps。该模型与体内通过光解酶对胸腺嘧啶二聚体修复的观察结果相吻合。胸腺嘧啶二聚体2的γ射线辐解表明,单电子还原和随后的环丁烷环裂解不是通过自由基链机理进行的,也就是说,在该模型反应中,T〜(-·)无法将电子转移至胸腺嘧啶二聚体2。

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