On the Conflicting Estimations of Pigment Site Energies in Photosynthetic Complexes: A Case Study of the CP47 Complex.
On the Conflicting Estimations of Pigment Site Energies in Photosynthetic Complexes: A Case Study of the CP47 Complex.
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DOI：
10.4137/aci.s32151
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Jankowiak R
中科院分区：
文献类型：
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作者：
Reinot T;Chen J;Kell A;Jassas M;Robben KC;Zazubovich V;Jankowiak R
我们重点关注阐明光合复合物（PSC）位点能量的问题，以便对文献中传播的相互矛盾的估计提出一些真正的担忧。作为一个例子，我们对从菠菜光系统 II 的广泛研究的 CP47 天线复合体的光谱拟合中提取的位点能量进行了严格的评估，尽管许多一般性评论也适用于其他 PSC。 CP47 中叶绿素 (Chl) a 的正确值对于理解其激子结构、群体动态和激发能量途径至关重要。为了证明这一点，我们提出了一个案例研究，其中同时拟合多个光谱（吸收、发射、圆二色性和非共振烧孔光谱）表明几组参数可以很好地拟合光谱。重要的是，我们表明，假设许多先前研究的 CP47 样品是完整和不稳定蛋白质的混合物，则可以解释文献中报道的非共振烧孔光谱中的可变发射最大值（690-695 nm）和样品依赖性漂白。 CP47 复合物不稳定的亚群似乎可能以 Chl29 的 131-酮基和 PsbH 蛋白亚基之间的氢键减弱为特征，尽管不能完全排除其他可能性，如本工作中所讨论的。简要讨论了我们的研究结果可能产生的影响。
We focus on problems with elucidation of site energies for photosynthetic complexes (PSCs) in order to raise some genuine concern regarding the conflicting estimations propagating in the literature. As an example, we provide a stern assessment of the site energies extracted from fits to optical spectra of the widely studied CP47 antenna complex of photosystem II from spinach, though many general comments apply to other PSCs as well. Correct values of for chlorophyll (Chl) a in CP47 are essential for understanding its excitonic structure, population dynamics, and excitation energy pathway(s). To demonstrate this, we present a case study where simultaneous fits of multiple spectra (absorption, emission, circular dichroism, and nonresonant hole-burned spectra) show that several sets of parameters can fit the spectra very well. Importantly, we show that variable emission maxima (690–695 nm) and sample-dependent bleaching in nonresonant hole-burning spectra reported in literature could be explained, assuming that many previously studied CP47 samples were a mixture of intact and destabilized proteins. It appears that the destabilized subpopulation of CP47 complexes could feature a weakened hydrogen bond between the 131-keto group of Chl29 and the PsbH protein subunit, though other possibilities cannot be entirely excluded, as discussed in this work. Possible implications of our findings are briefly discussed.