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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study
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Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study

机译：电子转移诱导的DNA中6-4光产物的修复：计算研究

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摘要

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.
机译：通过量子化学计算探索了DNA光解酶修复紫外线损伤的DNA中6-4个光产物的机理。考虑到氧杂环丁烷和氮杂环丁烷损伤的修复，已证明还原和氧化通过产生易于裂解为单体嘧啶的阴离子或阳离子基团，可以实现还原反应。然而，基于计算出的反应能量，表明电子从酶到病灶的转移比反方向的电子转移更为有利，表明光酶的修复只能通过阴离子机理进行。此外，已经表明，氧杂环丁烷的还原促进了一种机制，该机制涉及C-O键的断裂，然后C-C键的断裂，而氮杂环丁烷的还原性断裂可能是第一步进行的C-N和C-C键之间的断裂。通过对中性氮杂环丁烷自由基的计算，可以预料到在羰基氧的质子化之后，初始裂解步骤的自由能垒会显着增加。该作用可归因于质子化比过渡结构更能稳定反应物配合物。

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