McLaughlin Conor, Assmann Mariana, Parkes Michael A, Woodhouse Joanne L, Lewin Ross, Hailes Helen C, Worth Graham A, Fielding Helen H
Department of Chemistry , University College London , 20 Gordon Street , London WC1H 0AJ , UK . Email:
Chem Sci. 2017 Feb 1;8(2):1621-1630. doi: 10.1039/c6sc03833f. Epub 2016 Nov 7.
Green fluorescent protein (GFP) continues to play an important role in the biological and biochemical sciences as an efficient fluorescent probe and is also known to undergo light-induced redox transformations. Here, we employ photoelectron spectroscopy and quantum chemistry calculations to investigate how the phenoxide moiety controls the competition between electron emission and internal conversion in the isolated GFP chromophore anion, following photoexcitation with ultraviolet light in the range 400-230 nm. We find that moving the phenoxide group from the position to the position enhances internal conversion back to the ground electronic state but that adding an additional OH group to the chromophore, at the position, impedes internal conversion. Guided by quantum chemistry calculations, we interpret these observations in terms of torsions around the C-C-C bridge being enhanced by electrostatic repulsions or impeded by the formation of a hydrogen-bonded seven-membered ring. We also find that moving the phenoxide group from the position to the position reduces the energy required for detachment processes, whereas adding an additional OH group to the chromophore at the position increases the energy required for detachment processes. These results have potential applications in tuning light-induced redox processes of this biologically and technologically important fluorescent protein.
绿色荧光蛋白（GFP）作为一种高效的荧光探针，在生物和生物化学科学中继续发挥着重要作用，并且已知会发生光诱导的氧化还原转变。在此，我们采用光电子能谱和量子化学计算方法，来研究在400 - 230 nm范围内用紫外光进行光激发后，苯氧基团如何控制孤立的GFP发色团阴离子中电子发射与内转换之间的竞争。我们发现，将苯氧基团从 位置移至 位置会增强回到基态电子态的内转换，但在 发色团的 位置添加一个额外的OH基团会阻碍内转换。在量子化学计算的指导下，我们根据围绕C - C - C桥的扭转因静电排斥而增强或因形成氢键七元环而受阻来解释这些观察结果。我们还发现，将苯氧基团从 位置移至 位置会降低离解过程所需的能量，而在 发色团的 位置添加一个额外的OH基团会增加离解过程所需的能量。这些结果在调节这种具有生物学和技术重要性的荧光蛋白的光诱导氧化还原过程方面具有潜在应用。
