[论文解读] Roles of pigment arrangement in light-harvesting phycobiliproteins revealed by recombinant techniques combined with two-dimensional electronic spectroscopy

Masaaki Tsubouchi, Takatoshi Fujita+2 more|arXiv (Cornell University)|Jan 28, 2026

Photosynthetic Processes and Mechanisms被引用 0

一句话总结

该研究使用重组藻胆红素蛋白和二维电子光谱来分离色素贡献，并显示色素-蛋白相互作用，而非单一外周色素，主要塑造光捕获藻胆红素蛋白中的超快能量弛豫与相干性。

ABSTRACT

We developed methods for protein synthesis and performed two-dimensional electronic spectroscopy (2D-ES) to examine the influence of pigment arrangement on the photoexcitation dynamics of light-harvesting proteins in phycobilisome. We synthesized allophycocyanin (APC), C-phycocyanin (CPC), and mutant CPC lacking the \b{eta}153 phycocyanobilin (PCB) pigment by an Escherichia coli expression system. The number of pigments in the mutant CPC is identical to that in the wild-type APC, and their spatial arrangements are similar. The absorption and fluorescence spectra of the mutant CPC closely resemble those of the wild-type CPC rather than the wild-type APC, indicating that pigment spatial arrangement is not a primary factor in determining the excited-state energy structure. The 2D-ES measurements show that the wild-type CPC retains broad positive signals at 1 ps, signifying incomplete relaxation and persistence of excited vibronic states, unlike APC, which vibrationally relaxes to the bottom of the potential energy surface within the same timeframe. The mutant CPC behaves similarly to the wild-type CPC in the 2D-ES, reinforcing that the pigment number or arrangement is not a dominant factor. Instead, the local pigment-protein interaction governs the electronic structure and relaxation dynamics. Structural analysis reveals that the bent structure of PCB in CPC's α-chain versus the planar structure of PCB in APC. The bent PCB in CPC reduces the degree of π-conjugation, and exhibits excited-state properties distinct from those of the planar structure of PCB in APC. This finding highlights a critical role of the electronic structure governed by the local interaction in ultrafast energy relaxation.

研究动机与目标

• 研究色素排列如何影响光捕获藻胆红蛋白蛋白中的超快激发动力学。
• 使用缺少β153 PCB的突变 CPC 来分离外周色素（β153 PCB）的贡献。
• 评估动力学变化是否来自色素-色素激子耦合还是色素-蛋白相互作用。
• 阐明 APC 与 CPC 的作用及局部蛋白环境在能量弛豫与相干中的作用。

提出的方法

• 构建重组的藻胆红蛋白蛋白（APC）和C-藻胆红蛋白蛋白（CPC），包括β153 PCB缺失的 CPC 突变体。
• 记录吸收和荧光光谱以评估光谱贡献与色素之间的激子耦合。
• 应用二维电子光谱（2D-ES）研究超快弛豫和相干动力学。
• 比较野生型 CPC、β153 缺失 CPC 与 APC，以分离色素特异效应与色素-蛋白相互作用。
• 用色素几何、振动电子结构和局部蛋白环境来解释动力学。

实验结果

研究问题

• RQ1 β153 藻胆红素色素在 CPC 中的光谱与动力学贡献是什么？
• RQ2 超快弛豫动力学的变化是否源自色素-色素激子耦合还是色素-蛋白相互作用？
• RQ3 在能量弛豫与相干方面，APC 与 CPC 如何因其局部蛋白环境而不同？
• RQ4 色素-蛋白相互作用在多大程度上调节色素几何和振动电子结构以控制能量弛豫？

主要发现

• 移除β153色素主要消除了其光谱贡献，但未显著改变α84与β84色素之间的激子耦合。
• 时域二维-ES显示野生型 CPC 与β153 缺失 CPC 的超快动力学相似。
• APC 与 CPC 的差异主要来自于色素-蛋白相互作用，这些相互作用调节色素几何与振动电子结构。
• 局部蛋白环境在控制这些光能植物中的能量弛豫与相干性方面极为重要。