Solvent effect on excited state potential energy surfaces of Thioflavin T. Qualitatively different results by TDDFT and SA‐2‐CASSCF methods,Journal of Computational Chemistry

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Solvent effect on excited state potential energy surfaces of Thioflavin T. Qualitatively different results by TDDFT and SA‐2‐CASSCF methods
Journal of Computational Chemistry ( IF 3.4 ) Pub Date : 2020-06-09 , DOI: 10.1002/jcc.26358
Vitali I Stsiapura ₁

Affiliation

Thioflavin T (ThT) is a viscosity‐sensitive fluorescent dye and its emission intensity undergoes a significant enhancement upon binding to DNA or amyloid fibrils. This fluorescence light‐up feature has been attributed earlier to restriction of structural rearrangements in the excited state that are coupled to an intramolecular charge transfer (ICT) reaction. In this work TDDFT (using B3LYP and CAM‐B3LYP functionals) and SA‐2‐CASSCF calculations were carried out to obtain relaxed excited‐state potential energy surfaces (PES) along twisting φ and wagging δ angles that describe mutual orientation of benzothiazole (BTZ) and dimethylaniline (DMA) fragments in ThT. For isolated ThT molecule both methods predict that during structural rearrangements of the initially excited Franck‐Condon state, besides twisting along CC bond which connects BTZ and DMA fragments, a considerable wagging motion is expected to occur. Account for solvent effect using polarized continuum model showed qualitative differences in the excited state PES features calculated by SA‐2‐CASSCF and TDDFT methods. Single‐reference TDDFT calculations failed to describe solvation of TICT state and predicted increase of its energy in more polar media.

中文翻译：

溶剂对硫磺素 T 激发态势能面的影响。TDDFT 和 SA-2-CASSCF 方法的定性不同结果

硫磺素 T (ThT) 是一种粘度敏感的荧光染料，与 DNA 或淀粉样蛋白原纤维结合后，其发射强度显着增强。这种荧光点亮特性早先归因于激发态结构重排的限制，这些重排与分子内电荷转移 (ICT) 反应耦合。在这项工作中，进行了 TDDFT（使用 B3LYP 和 CAM-B3LYP 泛函）和 SA-2-CASSCF 计算，以获得沿着描述苯并噻唑（BTZ）相互取向的扭曲 φ 和摆动 δ 角的松弛激发态势能面（PES） ) 和 ThT 中的二甲基苯胺 (DMA) 片段。对于分离的 ThT 分子，两种方法都预测在最初激发的 Franck-Condon 状态的结构重排期间，除了沿着连接 BTZ 和 DMA 片段的 CC 键扭曲外，预计还会发生相当大的摆动。使用极化连续介质模型考虑溶剂效应表明，SA-2-CASSCF 和 TDDFT 方法计算的激发态 PES 特征存在质的差异。单参考 TDDFT 计算未能描述 TICT 状态的溶剂化和预测其能量在更多极性介质中的增加。

更新日期：2020-06-09

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