Triplet photosensitization mechanism of thymine by an oxidized nucleobase: from a dimeric model to DNA environment†,Physical Chemistry Chemical Physics

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Triplet photosensitization mechanism of thymine by an oxidized nucleobase: from a dimeric model to DNA environment†
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2018-10-03 00:00:00 , DOI: 10.1039/c8cp04866e
Antonio Francés-Monerris _{1,

2,

3,

4} , Cécilia Hognon _{1,

2,

3,

4} , Miguel A. Miranda _{5,

6,

7,

8} , Virginie Lhiaubet-Vallet _{5,

6,

7,

8} , Antonio Monari _{1,

2,

3,

4}

Affiliation

Nucleic acids are constantly exposed to external agents that can induce chemical and photochemical damage. In spite of the great advances achieved in the last years, some molecular mechanisms of DNA damage are not completely understood yet. A recent experimental report (I. Aparici-Espert et al., ACS Chem. Biol. 2018, 13, 542) proved the ability of 5-formyluracil (ForU), a common oxidatively generated product of thymine, to act as an intrinsic sensitizer of nucleic acids, causing single strand breaks and cyclobutane pyrimidine dimers in plasmid DNA. In the present contribution, we use theoretical methodologies to study the triplet photosensitization mechanism of thymine exerted by ForU in a model dimer and in DNA environment. The photochemical pathways in the former system are described combining the CASPT2 and TD-DFT methods, whereas molecular dynamics simulations and QM/MM calculations are employed for the DNA duplex. It is unambiguously shown that the ¹n,π* state localised in ForU mediates the population of the triplet manifold, most likely the ³π,π* state centred in ForU, whereas the ³π,π* state localized in thymine can be populated via triplet–triplet energy transfer given the small energy barrier of <0.23 eV determined for this pathway.

中文翻译：

胸腺嘧啶的三重态光敏机理：被氧化的核碱基：从二聚体模型到DNA环境†

核酸经常暴露于外部试剂中，这些外部试剂会引起化学和光化学损伤。尽管最近几年取得了巨大进步，但DNA损伤的某些分子机制尚未完全被理解。最近的实验报告（I. Aparici-Espert等人，ACS化学生物学2018，13，542）证明了5-甲氧基尿嘧啶（ForU）（胸腺嘧啶的一种常见的氧化产物）作为核酸的内在敏化剂的作用，引起了质粒DNA中的单链断裂和环丁烷嘧啶二聚体。在目前的贡献中，我们使用理论方法来研究ForU在模型二聚体和DNA环境中对胸腺嘧啶的三重态光敏机理。结合CASPT2和TD-DFT方法描述了前者系统中的光化学途径，而DNA双链体则采用了分子动力学模拟和QM / MM计算。它明确地表明，^1个N，π*在ForU局域态介导的三重歧管的人口，最有可能的³ π，π*状态ForU中心，而³ π，π*中的胸腺嘧啶局部状态可以填充经由给定<0.23电子伏特的小能量势垒的三重态-三线态能量传递判断，此通路。

更新日期：2018-10-03

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