Stark Spectroscopy and Reaction Dynamics in a Single Cell

连续测量了表达GFP-tudor融合蛋白的HeLa细胞的荧光寿命图像。寿命图像显示在整个细胞中均匀分布;然而，在用无血清培养基处理并暴露于正常空气后，细胞显示荧光寿命降低。这些结果表明，在应力下荧光寿命变短。活细胞中荧光寿命的变化归因于GFP发色团周围的蛋白质腔中产生的局部电场的变化。为了研究电场对GFP的光激发动力学的影响，在PVA中测量了GFP的荧光寿命的场诱导变化，并且发现GFP的荧光寿命被电场降低，这表明蛋白质腔内部产生的电场影响GFP的荧光寿命。在HeLa细胞以及负载BCECF的盐生盐杆菌中的荧光寿命图像结果表明，荧光寿命成像技术（FLIM）可以在活体内检测细胞内的pH值，电场可以有效地形成盐细菌的聚集体，但盐细菌的局部电场在聚集体形成后仍保持不变。

Fluorescence lifetime images of HeLa cells expressing GFP-tudor fusion protein have been continuously measured. The lifetime image displays a uniform distribution throughout cells; however, the cells exhibit the decrease in fluorescence lifetime after the treatment with serum-free medium and exposure to normal air. These results indicate that the fluorescence lifetime becomes shorter under the stress. The change in fluorescence lifetime in living cells has been attributed to a change in local electric field produced in the protein cavity surrounding the GFP chromophore. To investigate the electric field effects on the photoexcitation dynamics of GFP, field-induced change in fluorescence lifetime of GFP was measured in PVA, and the fluorescence lifetime of GFP is found to be reduced by an electric field, suggesting that the electric field produced inside the protein cavity affects the fluorescence lifetime of GFP.The fluorescence lifetime images in HeLa cells as well as in Halobacterium salinarum loaded with BCECF have been measured with varying intracellular pH. The results indicate that intracellular pH of a living cell can be evaluated in vivo by fluorescence lifetime imaging (FLIM).Aggregates of the halobacteria are effectively formed by an electric field, but the local fields in halosbacteria remain unchanged even after the formation of the aggregates.