The slow component of Photosystem II luminescence. A process with distributed rate constant
The slow component of Photosystem II luminescence. A process with distributed rate constant
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光系统 II 发光的慢速成分。
DOI：
10.1016/0005-2728(82)90140-2
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
J. Dennery
中科院分区：
文献类型：
--
作者：
J. Lavorel;J. Dennery
光系统II发光的慢相在光照结束几秒钟后开始，通常被报道遵循二级动力学，因此被归因于双等分子复合反应，即具有相同浓度的反应物(空穴和电子)的双分子反应。我们认为，考虑到光合作用装置的限制，双分子假说是不太可能的。相反，我们建议反应实体，本质上是单分子的，在一个速率常数k的范围内连续分布。结果表明：(1)k分布假设直接导致文献中所报道的二级动力学定律，假设初始k分布是指数分布，以及(2)一类广泛的k分布(连续的，跨越k值的大区间)倾向于成为kat的指数函数。我们从实验上重新研究了叶绿素和菠菜叶绿体的发光慢相，并对其衰变进行了数值分析。最好的描述是byl(T)=L(0)(1+k1t+k2t2)−1。对应的初始分布是指数型的(其最大值位于接近但不是atk=0)。这种动力学类型在许多实验条件下是不变的(光强度、解偶联器等)。在双等分子假说的框架下，这将有望改变动力学类型。如果k分布的想法是正确的，这意味着在这个时间范围内的发光揭示了一系列未指明来源的运动状态。我们可能只能得出结论，上述状态至少在S大约100年内是稳定的，并且它们主要与放氧系统无关。
The slow phase of Photosystem II luminescence, starting a few seconds after the end of illumination, has often been reported to follow second-order kinetics and was consequently ascribed to a biequimolecular recombination reaction, i.e., a bimolecular reaction with equal concentrations of reactants (holes and electrons). We argue that, given the constraints of the photosynthetic apparatus, the biequimolecular hypothesis is very unlikely. We propose instead that the reacting entities, inherently monomolecular, are continuously distributed over a range of rate constants,k. It is shown that (1) thek-distribution hypothesis results directly in second-order kinetic laws as reported in the literature, provided that the initialkdistribution is exponential and (2) a broad class ofkdistributions (continuous, spanning a large interval ofkvalues) tend to become an exponential function ofkat long times. We have reinvestigated experimentally the slow phase of luminescence inChlorellaand spinach chloroplasts and submitted its decay to numerical analysis. The best description is given byL(t) =L(0)(1 +k1t+k2t2)−1. The corresponding initial distribution is of exponential type (with its maximum located close to but not atk= 0). This kinetic type is invariant under a number of experimental conditions (light intensity, uncouplers, etc.) which, in the frame of the biequimolecular hypothesis, would be expected to change the kinetic type. If the idea of thekdistribution is correct, it means that luminescence in this time range reveals a continuum of kinetic states of unspecified origin. We may only conclude that the above states are stable for at least about 100 s and that they are not primarily associated with the O2-evolving system.