We develop a rapid "stroboscopic" fluorescence induction method, using the fast repetition rate fluorometry (FRRF) technique, to measure changes in the quantum yield of light emission from chlorophyll in oxygenic photosynthesis arising from competition with primary photochemical charge separation (P680* ➔ P680+QA-). This method determines the transit times of electrons that pass through PSII during the successive steps in the catalytic cycle of water oxidation/O2 formation (S states) and plastoquinone reduction in any oxygenic phototroph (in vivo or in vitro). We report the first measurements from intact living cells, illustrated by a eukaryotic alga (Nannochloropsis oceanica). We demonstrate that S state transition times depend strongly on the redox state of the PSII acceptor side, at both QB and the plastoquinone pool which serve as the major locus of regulation of PSII electron flux. We provide evidence for a kinetic intermediate S3' state (lifetime 220 μs) following formation of S3 and prior to the release of O2. We compare the FRRF-detected kinetics to other previous spectroscopic methods (optical absorbance, EPR, and XES) that are applicable only to in vitro samples.

中文翻译：

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通过“频闪”荧光法测定活生物体中光合作用水氧化的光驱动步骤的实时动力学。

我们开发了一种快速的“频闪”荧光诱导方法，使用快速重复速率荧光法（FRRF）技术来测量与主要光化学电荷分离竞争引起的光合作用中叶绿素的光发射量子产率的变化（P680 *➔P680） + QA-）。该方法确定了在任何氧化性养分（体内或体外）的水氧化/ O2形成（S状态）和质体醌还原催化循环的后续步骤中，穿过PSII的电子的传输时间。我们报告从完整的活细胞，由真核藻（Nannochloropsis oceanica）说明的首次测量。我们证明了S状态的转变时间很大程度上取决于PSII受体一侧的氧化还原状态，在QB和质体醌库中，它们是PSII电子通量调节的主要场所。我们提供了S3形成之后和O2释放之前的动力学中间S3'状态（寿命为220μs）的证据。我们将FRRF检测到的动力学与仅适用于体外样品的其他以前的光谱方法（光学吸收，EPR和XES）进行了比较。