Cyanobacteriochromes are photoreceptors in cyanobacteria that exhibit a wide spectral coverage and unique photophysical properties from the photoinduced isomerization of a linear tetrapyrrole chromophore. Here, we integrate femtosecond-resolved fluorescence and transient-absorption methods and unambiguously showed the significant solvation dynamics occurring at the active site from a few to hundreds of picoseconds. These motions of local water molecules and polar side chains are continuously convoluted with the isomerization reaction, leading to a nonequilibrium processes with continuous active-site motions. By mutations of critical residues at the active site, the modified local structures become looser, resulting in faster solvation relaxations and isomerization reaction. The observation of solvation dynamics is significant and critical to the correct interpretation of often-observed multiphasic dynamic behaviors, and thus the previously invoked ground-state heterogeneity may not be relevant to the excited-state isomerization reaction.

蓝细菌色素是蓝细菌中的光感受器，其通过线性四吡咯发色团的光诱导异构化表现出宽光谱范围和独特的光物理性质。在这里，我们集成了飞秒分辨的荧光和瞬态吸收方法，并明确显示了在活性位发生的显着的溶剂化动力学过程，从几皮秒到几百皮秒。局部水分子和极性侧链的这些运动随着异构化反应而不断地回旋，从而导致具有连续活性位点运动的非平衡过程。通过在活性位点上关键残基的突变，修饰的局部结构变得更松散，导致更快的溶剂化弛豫和异构化反应。