Squires Allison H, Wang Quan, Dahlberg Peter D, Moerner W E
Department of Chemistry, Stanford University, Stanford, California 94305-4401, USA.
J Chem Phys. 2022 Feb 21;156(7):070901. doi: 10.1063/5.0079042.
Single-molecule fluorescence spectroscopy allows direct, real-time observation of dynamic photophysical changes in light harvesting complexes. The Anti-Brownian ELectrokinetic (ABEL) trap is one such single-molecule method with useful advantages. This approach is particularly well-suited to make detailed spectroscopic measurements of pigment-protein complexes in a solution phase because it enables extended-duration single-molecule observation by counteracting Brownian motion. This Perspective summarizes recent contributions by the authors and others that have utilized the unique capabilities of the ABEL trap to advance our understanding of phycobiliproteins and the phycobilisome complex, the primary light-harvesting apparatus of cyanobacteria. Monitoring the rich spectroscopic data from these measurements, which include brightness, fluorescence lifetime, polarization, and emission spectra, among other measurable parameters, has provided direct characterization of pigments and energy transfer pathways in the phycobilisome, spanning scales from single pigments and monomeric phycobiliproteins to higher order oligomers and protein-protein interactions of the phycobilisome complex. Importantly, new photophysical states and photodynamics were observed to modulate the flow of energy through the phycobilisome and suggest a previously unknown complexity in phycobilisome light harvesting and energy transport with a possible link to photoadaptive or photoprotective functions in cyanobacteria. Beyond deepening our collective understanding of natural light-harvesting systems, these and future discoveries may serve as inspiration for engineering improved artificial light-harvesting technologies.
单分子荧光光谱法能够直接实时观察光捕获复合物中动态的光物理变化。抗布朗电动（ABEL）阱就是这样一种具有实用优势的单分子方法。这种方法特别适合对溶液相中的色素 - 蛋白质复合物进行详细的光谱测量，因为它通过抵消布朗运动实现了长时间的单分子观察。本观点综述了作者及其他人员最近的研究成果，这些研究利用ABEL阱的独特功能，增进了我们对藻胆蛋白和藻胆体复合物（蓝细菌的主要光捕获装置）的理解。监测这些测量中丰富的光谱数据，包括亮度、荧光寿命、偏振和发射光谱等其他可测量参数，直接表征了藻胆体中色素和能量转移途径，涵盖了从单个色素和单体藻胆蛋白到藻胆体复合物的高阶寡聚体及蛋白质 - 蛋白质相互作用等不同尺度。重要的是，观察到新的光物理状态和光动力学调节了通过藻胆体的能量流动，并表明藻胆体光捕获和能量传输中存在先前未知的复杂性，这可能与蓝细菌中的光适应或光保护功能有关。除了加深我们对自然光捕获系统的总体理解之外，这些以及未来的发现可能会为设计改进的人工光捕获技术提供灵感。
