Toward understanding optical properties of amyloids: a reaction path and nonadiabatic dynamics study,Journal of the American Chemical Society

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Toward understanding optical properties of amyloids: a reaction path and nonadiabatic dynamics study
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-09-23 , DOI: 10.1021/jacs.0c07134
Luca Grisanti _{1,

2} , Marin Sapunar ₃ , Ali Hassanali ₂ , Nađa Došlić ₃

Affiliation

Amyloids have unique structural, chemical and optical properties. Although much theoretical effort has been directed toward understanding amyloid nucleation, the understanding of their optical properties has remained rather limited. In particular, the photophysical mechanisms leading to near UV excitation and characteristic blue-green luminescence in amyloid systems devoid of aromatic amino acids have not been resolved. We use ab initio static calculations and nonadiabatic dynamics simulations to study the excited electronic states of model amyloid-like peptides. We show that their photophysics is essentially governed by the multitude of nπ* states with excitation localized on the amide groups. The strong stabilization of the nπ* states with respect to the amide group deplanarization and the concomitant increase of the oscillator strength makes excitation in the near UV possible. With respect to emission, our dynamics simulations revealed that the amyloid cross β arrangement effectively hinders the nonradiative relaxation channels operative in functional proteins. Finally, we show that after relaxation of the photoexcited peptides toward the minimum of the different nπ* states, fluorescence takes place in the visible (green) part of the electromagnetic spectrum.

中文翻译：

了解淀粉样蛋白的光学特性：反应路径和非绝热动力学研究

淀粉样蛋白具有独特的结构、化学和光学特性。尽管许多理论工作都致力于理解淀粉样蛋白成核，但对其光学特性的理解仍然相当有限。特别是，在不含芳香族氨基酸的淀粉样蛋白系统中导致近紫外激发和特征性蓝绿色发光的光物理机制尚未得到解决。我们使用从头算静态计算和非绝热动力学模拟来研究模型淀粉样肽的激发电子态。我们表明，它们的光物理本质上受大量 nπ* 状态的控制，激发位于酰胺基团上。nπ* 状态在酰胺基团去平面化方面的强稳定性和振荡器强度的伴随增加使得在近紫外线下激发成为可能。关于发射，我们的动力学模拟表明，淀粉样蛋白交叉 β 排列有效地阻碍了在功能蛋白质中起作用的非辐射弛豫通道。最后，我们表明在光激发肽向不同 nπ* 状态的最小值松弛后，在电磁波谱的可见（绿色）部分发生荧光。

更新日期：2020-09-23

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