Mechanism of resonant electron emission from the deprotonated GFP chromophore and its biomimetics.
Mechanism of resonant electron emission from the deprotonated GFP chromophore and its biomimetics.
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DOI：
10.1039/c6sc05529j
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发表时间：
2017-04-01
期刊：
影响因子：
8.4
通讯作者：
Fielding HH
中科院分区：
文献类型：
--
作者：
Bochenkova AV;Mooney CRS;Parkes MA;Woodhouse JL;Zhang L;Lewin R;Ward JM;Hailes HC;Andersen LH;Fielding HH
通过揭示紫外共振电子发射的机理，我们证明了GFP仿生材料对光氧化更稳定。绿色荧光蛋白（GFP），广泛用于生物成像，是已知的经历光诱导氧化还原转化。电子转移被认为是通过其发色团的激发态共振发生的；然而，对发色团的电子入口态的详细了解仍然缺失。在这里，我们使用光电子能谱和高级量子化学计算表明，在紫外激发后，发色团阴离子中的超快电子动力学通过与开放连续体强耦合的激发形状共振进行。这种状态的影响贯穿整个355-315 nm激发范围，从第一个边界跃迁以上到更高的连续层开口以下。通过解开光剥离通道中的电子动力学，我们为位于348 nm的电子门户态的绝热位置提供了重要的参考，并发现了文献中报道的奇怪的大宽度光电子能谱的来源。通过对GFP发色团进行化学修饰，我们发现分离阈值和入口态的位置，以及潜在的激发态动力学，可以系统地改变。这使得GFP发色团的固有电子发射特性得以微调，并对其功能具有重要意义，这表明仿生GFP发色团对光氧化更稳定。
By uncovering the mechanism of UV resonant electron emission, we show that the GFP biomimetics are more stable to photooxidation. The Green Fluorescent Protein (GFP), which is widely used in bioimaging, is known to undergo light-induced redox transformations. Electron transfer is thought to occur resonantly through excited states of its chromophore; however, a detailed understanding of the electron gateway states of the chromophore is still missing. Here, we use photoelectron spectroscopy and high-level quantum chemistry calculations to show that following UV excitation, the ultrafast electron dynamics in the chromophore anion proceeds via an excited shape resonance strongly coupled to the open continuum. The impact of this state is found across the entire 355–315 nm excitation range, from above the first bound–bound transition to below the opening of higher-lying continua. By disentangling the electron dynamics in the photodetachment channels, we provide an important reference for the adiabatic position of the electron gateway state, which is located at 348 nm, and discover the source of the curiously large widths of the photoelectron spectra that have been reported in the literature. By introducing chemical modifications to the GFP chromophore, we show that the detachment threshold and the position of the gateway state, and hence the underlying excited-state dynamics, can be changed systematically. This enables a fine tuning of the intrinsic electron emission properties of the GFP chromophore and has significant implications for its function, suggesting that the biomimetic GFP chromophores are more stable to photooxidation.