Ultrafast excited-state proton transfer dynamics in dihalogenated non-fluorescent and fluorescent GFP chromophores
Ultrafast excited-state proton transfer dynamics in dihalogenated non-fluorescent and fluorescent GFP chromophores
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DOI：
10.1063/1.5138666
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发表时间：
2020-01-14
影响因子：
4.4
通讯作者：
Fang, Chong
中科院分区：
文献类型：
--
作者：
Chen, Cheng;Zhu, Liangdong;Fang, Chong
绿色荧光蛋白（GFP）由于其光物理和光化学性质而使得无数生物成像进展成为可能。为了加深对这种光诱导过程的机械理解，通过将酚部分溴化或溴化成超光酸来工程化GFP发色团p-HBDI的新型衍生物，其在激发态的短寿命内在水溶液中有效地进行激发态质子转移（ESPT），而不是p-HBDI，其中没有观察到有效的ESPT。此外，我们通过p-HBDI骨架的构象锁定将激发态寿命从皮秒调整到纳秒，基本上将非荧光发色团转化为高荧光发色团。未锁定的超光酸进行无障碍ESPT没有太多的溶剂活性，而锁定的对应物表现出两个不同的溶剂参与的ESPT途径。飞秒瞬态吸收光谱的比较分析，这些解锁和锁定的超光酸揭示了ESPT率采用“倒置”的动力学行为的热力学驱动力增加后锁定的骨干。进一步的实验和理论研究有望揭示功能化GFP衍生物（例如，荧光开和关）。由AIP Publishing授权出版。
Green fluorescent protein (GFP) has enabled a myriad of bioimaging advances due to its photophysical and photochemical properties. To deepen the mechanistic understanding of such light-induced processes, novel derivatives of GFP chromophore p-HBDI were engineered by fluorination or bromination of the phenolic moiety into superphotoacids, which efficiently undergo excited-state proton transfer (ESPT) in aqueous solution within the short lifetime of the excited state, as opposed to p-HBDI where efficient ESPT is not observed. In addition, we tuned the excited-state lifetime from picoseconds to nanoseconds by conformational locking of the p-HBDI backbone, essentially transforming the nonfluorescent chromophores into highly fluorescent ones. The unlocked superphotoacids undergo a barrierless ESPT without much solvent activity, whereas the locked counterparts exhibit two distinct solvent-involved ESPT pathways. Comparative analysis of femtosecond transient absorption spectra of these unlocked and locked superphotoacids reveals that the ESPT rates adopt an "inverted" kinetic behavior as the thermodynamic driving force increases upon locking the backbone. Further experimental and theoretical investigations are expected to shed more light on the interplay between the modified electronic structure (mainly by dihalogenation) and nuclear motions (by conformational locking) of the functionalized GFP derivatives (e.g., fluorescence on and off). Published under license by AIP Publishing.