Unit for Nano Science & Technology, Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, India.
Sci Rep. 2013;3:1580. doi: 10.1038/srep01580.
Fluorescent proteins undergoing green to red (G/R) photoconversion have proved to be potential tools for investigating dynamic processes in living cells and for photo-localization nanoscopy. However, the photochemical reaction during light induced G/R photoconversion of fluorescent proteins remains unclear. Here we report the direct observation of ultrafast time-resolved electron transfer (ET) during the photoexcitation of the fluorescent proteins EGFP and mEos2 in presence of electron acceptor, p-benzoquinone (BQ). Our results show that in the excited state, the neutral EGFP chromophore accepts electrons from an anionic electron donor, Glu222, and G/R photoconversion is facilitated by ET to nearby electron acceptors. By contrast, mEos2 fails to produce the red emitting state in the presence of BQ; ET depletes the excited state configuration en route to the red-emitting fluorophore. These results show that ultrafast ET plays a pivotal role in multiple photoconversion mechanisms and provide a method to modulate the G/R photoconversion process.
荧光蛋白的绿色到红色（G/R）光致变色已被证明是研究活细胞动态过程和光定位纳米显微镜的潜在工具。然而，荧光蛋白的光诱导 G/R 光致变色过程中的光化学反应仍不清楚。在这里，我们报告了在存在电子受体对苯醌（BQ）的情况下，对荧光蛋白 EGFP 和 mEos2 的光激发过程中进行超快时间分辨电子转移（ET）的直接观察。我们的结果表明，在激发态下，中性 EGFP 发色团从阴离子电子供体 Glu222 接受电子，并且 ET 有助于附近的电子受体促进 G/R 光致变色。相比之下，在 BQ 存在的情况下，mEos2 无法产生红色发射状态；ET 在向红色荧光团的过程中耗尽激发态构型。这些结果表明超快 ET 在多种光致变色机制中起着关键作用，并提供了一种调节 G/R 光致变色过程的方法。
