Nonphotochemical quenching mechanisms regulate light harvesting in oxygenic photosynthesis. Measurement techniques for nonphotochemical quenching have typically focused on downstream effects of quenching, such as measuring reduced chlorophyll fluorescence. Here, to directly measure a species involved in quenching, we report snapshot transient absorption (TA) spectroscopy, which rapidly tracks carotenoid radical cation signals as samples acclimate to excess light. The formation of zeaxanthin radical cations, which is possible evidence of zeaxanthin–chlorophyll charge-transfer (CT) quenching, was investigated in spinach thylakoids. Together with fluorescence lifetime snapshot data and time-resolved high-performance liquid chromatography (HPLC) measurements, snapshot TA reveals that Zea^•+ formation is closely related to energy-dependent quenching (qE) in nonphotochemical quenching. Quantitative and dynamic information on CT quenching discussed in this work give insight into the design principles of photoprotection in natural photosynthesis.

中文翻译：

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高光适应性类囊体膜中类胡萝卜素自由基阳离子的瞬态瞬态吸收光谱。

非光化学猝灭机制调节氧光合作用中的光收集。非光化学猝灭的测量技术通常集中在猝灭的下游效应，例如测量减少的叶绿素荧光。在这里，为了直接测量涉及淬灭的物质，我们报告了快照瞬态吸收（TA）光谱，当样品适应过量的光时，该光谱可快速跟踪类胡萝卜素自由基阳离子信号。在菠菜类囊体中研究了玉米黄质自由基阳离子的形成，这可能是玉米黄质–叶绿素电荷转移（CT）猝灭的证据。结合荧光寿命快照数据和时间分辨高效液相色谱（HPLC）测量，快照TA揭示了Zea ^•+在非光化学猝灭中，形成与能量依赖猝灭（qE）密切相关。这项工作中讨论的有关CT猝灭的定量和动态信息使人们对天然光合作用中的光保护设计原理有了深刻的了解。