Dissociative electron transfer to and from pyrimidine cyclobutane dimers: An electrochemical study
Dissociative electron transfer to and from pyrimidine cyclobutane dimers: An electrochemical study
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DOI：
10.1039/b406923d
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发表时间：
2004-01-01
影响因子：
3.2
通讯作者：
Wille, U
中科院分区：
文献类型：
--
作者：
Boussicault, F;Kr端ger, O;Wille, U
用循环伏安法研究了几种模拟紫外线损伤DNA链的嘧啶环丁烷二聚体在极性溶剂(N，N-二甲基甲酰胺和乙腈)中的还原和氧化行为。分别向二聚体注入电子和从二聚体移除电子都会导致单体碱基的裂解和重整。研究了环丁烷基序的立体化学和取代方式对反应活性的影响。修复过程似乎总是以顺序的方式进行，初始形成二聚体离子自由基中间体，然后通过两个C-C键的均质裂解经历开环。测定了形成自由基阴离子和自由基阳离子状态的标准氧化还原电位。对简化模型化合物的量子计算揭示了发现碳-碳键的激发式均裂具有相当大的活化势垒的原因。讨论了这些关于光解酶对天然酶修复的机理研究的结果。
Cyclic voltammetry was used to study the reduction and oxidation behaviour of several pyrimidine cyclobutane dimers mimicking UV induced lesion in DNA strands in polar solvents (N, N-dimethylformamide and acetonitrile). Both electron injection and removal to and from the dimers, respectively, lead to their cleavage and reformation of the monomeric base. The influence of stereochemistry and substitution pattern at the cyclobutane motif on the reactivity has been studied. It appears that the repair process always proceeds in a sequential fashion with initial formation of a dimer ion radical intermediate, which then undergoes ring opening by homolytic cleavage of the two C - C bonds. Standard redox potentials for the formation of both radical anion and radical cation state of the dimers were determined. Quantum calculations on simplified model compounds reveal the reason for the finding that the exergonic homolytic cleavages of the carbon - carbon bonds are endowed with sizeable activation barriers. The consequences of these mechanistic studies on the natural enzymatic repair by photolyase enzyme are discussed.