光受体蛋白主要通过吸收自然光触发下游的信号传导，从而调节生物体的功能，目前在光遗传学中有重要应用。含BLUF域蛋白是一种重要的光受体蛋白，由于它的黄素辅基的异咯嗪环具有刚性，其光化学过程不涉及大的生色团结构变化，这一点与其它光受体蛋白（例如光敏色素和视紫质）不同。在光受体蛋白AppA的BLUF域中，黄素辅基超快光化学的研究存在着一定的争议，而后续引发的蛋白质结构重排过程的动力学研究尚未开展。本项目拟通过结合超快光谱学和定点突变技术，设计相应的蛋白突变体，分别解析AppA的BLUF域中两个不同的超快电子转移反应通道的动力学。进一步，本项目拟通过结合超快光谱学和定点标记技术，研究Trp104在重排过程中的结构异构动力学机理。通过系统解析AppA的BLUF域的光化学过程，有望在光受体蛋白动态机理解析领域取得突破，对于将来开发新的光遗传学分子工具具有启发意义。

Photoreceptors absorb light to trigger downstream signals and then modulate biological functions. Recently photoreceptors have found their important applications in optogenetics. BLUF (Blue Light receptors Using FAD) domain-containing proteins are one type of important photoreceptors. The BLUF protein photochemistry is unique in that only small chromophore structural changes are involved due to the rigidity of the flavin isoalloxazine ring, which differs from other photoreceptors such as phytochromes and rhodopsins. Currently there are a lot of controversies in the research of the ultrafast flavin photochemistry in BLUF protein AppA. Besides, research on the kinetics of the flavin photochemistry triggering downstream protein rearrangement has not been carried out. We propose to combine ultrafast spectroscopy and site-directed mutagenesis to differentiate the two different reaction pathways in AppA BLUF domain. Taking one step further, we propose to combine ultrafast spectroscopy and site-specific isotope labeling to investigate the structural rearrangement of Trp 104 following the flavin photocycle. By systematically analyzing the molecular mechanism of AppA BLUF domain, the proposed research will advance our understanding of the molecular dynamics of photoreceptors and shed light on designing new molecular tools for optogenetics.