Dynamic Structural Effects on the Second-Harmonic Generation of Tryptophane-Rich Peptides and Gramicidin A,The Journal of Physical Chemistry B

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Dynamic Structural Effects on the Second-Harmonic Generation of Tryptophane-Rich Peptides and Gramicidin A
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-03-23 , DOI: 10.1021/acs.jpcb.0c00643
Jakob Seibert ₁ , Benoît Champagne ₂ , Stefan Grimme ₁ , Marc de Wergifosse ₁

Affiliation

Peptide chains can model endogenous biotags for applications in second-harmonic imaging microscopy. Such structures are flexible which may strongly affect their structure–property relationship. Here, we explore quantum-mechanically the conformational space of a set of tryptophan-rich model peptides. This has become feasible because of the recently proposed meta-dynamics method based on efficient tight-binding (TB) calculations. The TB version of the simplified time-dependent density functional theory (sTD-DFT-xTB) method is used to evaluate the first hyperpolarizability (β). These new tools enable us to calculate nonlinear optical properties for systems with several thousand atoms and/or to screen large structure ensembles. First, we show that the indole chromophore in tryptophan residues dominates the β response of these systems. Their relative orientation mostly determines the global β tensor and affects the static β response. The results underline the importance of finding low-energy conformers for modeling β of flexible molecules. Additionally, we compare calculated and extrapolated experimental static β. The sTD-DFT-xTB method is capable of providing reliable second-harmonic generation values for tryptophan-rich systems at a fraction of the computational cost of the commonly used TD-DFT/TD-HF levels of theory.

中文翻译：

动态结构效应对富含色氨酸的肽和农杆菌肽A的二次谐波产生

肽链可以模拟内源性生物标签，用于二次谐波成像显微镜。这样的结构是灵活的，可能会严重影响它们的结构-财产关系。在这里，我们用量子力学方法研究了一组富含色氨酸的模型肽的构象空间。由于最近提出的基于有效紧密结合（TB）计算的元动力学方法，这已变得可行。简化的时变密度泛函理论（sTD-DFT- x）的TB版本TB）方法用于评估第一个超极化率（β）。这些新工具使我们能够计算具有数千个原子的系统的非线性光学特性和/或筛选大型结构体。首先，我们表明色氨酸残基中的吲哚发色团主导了这些系统的β反应。它们的相对方向主要决定整体β张量并影响静态β反应。结果强调了寻找低能量构象体以建模柔性分子β的重要性。此外，我们比较了计算得出的和外推的实验静态β。sTD-DFT- x TB方法能够为富含色氨酸的系统提供可靠的二次谐波生成值，而其计算成本只是常用的TD-DFT / TD-HF理论水平的一小部分。

更新日期：2020-03-24

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