Molecular Biomimetics, Department of Chemistry-Ångström, Uppsala University, P.O. Box 523, 751 20 Uppsala, Sweden.
Molecular Biomimetics, Department of Chemistry-Ångström, Uppsala University, P.O. Box 523, 751 20 Uppsala, Sweden.
Biochim Biophys Acta Bioenerg. 2023 Nov 1;1864(4):148994. doi: 10.1016/j.bbabio.2023.148994. Epub 2023 Jun 23.
An alternative charge separation pathway in Photosystem II under the far-red light was proposed by us on the basis of electron transfer properties at 295 K and 5 K. Here we extend these studies to the temperature range of 77-295 K with help of electron paramagnetic resonance spectroscopy. Induction of the S state multiline signal, oxidation of Cytochrome b and Chlorophyll was studied in Photosystem II membrane preparations from spinach after application of a laser flashes in visible (532 nm) or far-red (730-750 nm) spectral regions. Temperature dependence of the S state signal induction after single flash at 730-750 nm (T ~ 240 K) was found to be different than that at 532 nm (T ~ 157 K). No contaminant oxidation of the secondary electron donors cytochrome b or chlorophyll was observed. Photoaccumulation experiments with extensive flashing at 77 K showed similar results, with no or very little induction of the secondary electron donors. Thus, the partition ratio defined as (yield of Y/CaMnO-cluster oxidation):(yield of Cytb/Chl/Car oxidation) was found to be 0.4 at under visible light and 1.7 at under far-red light at 77 K. Our data indicate that different products of charge separation after far-red light exists in the wide temperature range which further support the model of the different primary photochemistry in Photosystem II with localization of hole on the Chl molecule.
我们基于 295 K 和 5 K 时的电子转移特性，提出了在远红光下光系统 II 中存在另一种电荷分离途径。在这里，我们借助电子顺磁共振波谱学，将这些研究扩展到了 77-295 K 的温度范围。在可见（532nm）或远红（730-750nm）光谱区域应用激光闪光后，我们研究了菠菜光系统 II 膜制剂中 S 态多线信号的诱导、细胞色素 b 和叶绿素的氧化。在 730-750nm 处单闪光后 S 态信号诱导的温度依赖性（T240K）与在 532nm 处（T157K）不同。未观察到次级电子供体细胞色素 b 或叶绿素的污染物氧化。在 77K 时进行广泛闪光的光积累实验也得到了类似的结果，次级电子供体几乎没有或很少被诱导。因此，在 77K 下，定义为（Y/CaMnO-团簇氧化的产率）：（细胞色素 b/叶绿素/类胡萝卜素氧化的产率）的分配比在可见光下为 0.4，在远红光下为 1.7。我们的数据表明，在宽温度范围内，远红光后电荷分离的产物不同，这进一步支持了光系统 II 中存在不同初级光化学的模型，其中空穴定位于叶绿素分子上。
