Single-molecule trapping and spectroscopy reveals photophysical heterogeneity of phycobilisomes quenched by Orange Carotenoid Protein
Single-molecule trapping and spectroscopy reveals photophysical heterogeneity of phycobilisomes quenched by Orange Carotenoid Protein
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DOI：
10.1038/s41467-019-09084-2
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发表时间：
2019-03-12
影响因子：
16.6
通讯作者：
Moerner, W. E.
中科院分区：
文献类型：
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作者：
Squires, Allison H.;Dahlberg, Peter D.;Moerner, W. E.
橙子类胡萝卜素蛋白（OCP）是一种胞质光传感器，在大多数蓝藻中负责光捕获过程的非光化学猝灭（NPQ）。在蓝绿光的光活化下，OCP与藻胆体天线复合物结合，提供激子陷阱以热耗散多余的能量。目前，OCP的结合位点和NPQ作用机理尚不清楚。使用反布朗电动势（ABEL）陷阱，我们分离单个藻胆体在自由溶液中，无论是在存在和不存在的激活OCP，直接确定OCP淬灭藻胆体的物理和异质性。令人惊讶的是，我们观察到两个不同的OCP猝灭状态，寿命为0.09 ns（未猝灭亮度的6%）和0.21 ns（亮度的11%）。光子通过藻胆体的激子转移的光子蒙特卡罗模拟表明，所观察到的淬灭状态是动力学一致的两个或一个绑定的OCP，分别强调在这个关键的光合单位的激发控制的额外机制。
The Orange Carotenoid Protein (OCP) is a cytosolic photosensor that is responsible for non-photochemical quenching (NPQ) of the light-harvesting process in most cyanobacteria. Upon photoactivation by blue-green light, OCP binds to the phycobilisome antenna complex, providing an excitonic trap to thermally dissipate excess energy. At present, both the binding site and NPQ mechanism of OCP are unknown. Using an Anti-Brownian ELectrokinetic (ABEL) trap, we isolate single phycobilisomes in free solution, both in the presence and absence of activated OCP, to directly determine the photophysics and heterogeneity of OCP-quenched phycobilisomes. Surprisingly, we observe two distinct OCP-quenched states, with lifetimes 0.09 ns (6% of unquenched brightness) and 0.21 ns (11% brightness). Photon-byphoton Monte Carlo simulations of exciton transfer through the phycobilisome suggest that the observed quenched states are kinetically consistent with either two or one bound OCPs, respectively, underscoring an additional mechanism for excitation control in this key photosynthetic unit.