Competition between energy and proton transfer in ultrafast excited-state dynamics of an oligomeric fluorescent protein red kaede
Competition between energy and proton transfer in ultrafast excited-state dynamics of an oligomeric fluorescent protein red kaede
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DOI：
10.1021/jp064489f
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发表时间：
2006-11-16
影响因子：
3.3
通讯作者：
Tahara, Tahei
中科院分区：
文献类型：
--
作者：
Hosoi, Haruko;Mizuno, Hideaki;Tahara, Tahei
我们研究了飞秒和皮秒的时间分辨荧光动力学的四聚体荧光蛋白与红色发色团（红色Kaede），研究激发态动力学和四级结构的荧光蛋白之间的关系。从石珊瑚Trachyphyllia geoffroyi克隆的绿色Kaede经光转化获得红色Kaede。与其他典型的荧光蛋白一样，红色Kaede的发色团具有两种质子化状态，中性和平衡的阴离子形式。时间分辨荧光测量澄清，激发的中性形式给出了阴离子激发态的时间常数为13 ps，在pH 7.5。这个转换过程是由于荧光共振能量转移（FRET）从光激发的中性形式的基态阴离子的形式，位于一个相邻的亚基的四聚体。在不同pH下测量的时间分辨荧光数据显示，激发态质子转移（ESPT）也发生与300 ps的时间常数，因此，FRET和ESPT同时发生在荧光蛋白作为竞争过程。红色Kaede中的ESPT速率显著低于Aequorea GFP中的速率，这很可能是由于发色团周围的氢键网络不同。
We investigated femtosecond and picosecond time-resolved fluorescence dynamics of a tetrameric fluorescent protein Kaede with a red chromophore (red Kaede) to examine a relationship between the excited-state dynamics and a quaternary structure of the fluorescent protein. Red Kaede was obtained by photoconversion from green Kaede that was cloned from a stony coral Trachyphyllia geoffroyi. In common with other typical fluorescent proteins, a chromophore of red Kaede has two protonation states, the neutral and the anionic forms in equilibrium. Time-resolved fluorescence measurements clarified that excitation of the neutral form gives the anionic excited state with a time constant of 13 ps at pH 7.5. This conversion process was attributed to fluorescence resonance energy transfer (FRET) from the photoexcited neutral form to the ground-state anionic form that is located in an adjacent subunit in the tetramer. The time-resolved fluorescence data measured at different pH revealed that excited-state proton transfer (ESPT) also occurs with a time constant of 300 ps and hence that the FRET and ESPT take place simultaneously in the fluorescent protein as competing processes. The ESPT rate in red Kaede was significantly slower than the rate in Aequorea GFP, which highly likely arises from the different hydrogen bond network around the chromophore.