Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA.
A.N. Belozersky Institute of Physical-Chemical Biology, Moscow State University, Moscow, Russia.
Biochim Biophys Acta Bioenerg. 2018 Dec;1859(12):1288-1301. doi: 10.1016/j.bbabio.2018.09.367. Epub 2018 Sep 19.
This work aims to fully elucidate the effects of a trehalose glassy matrix on electron transfer reactions in cyanobacterial Photosystem I (PS I). Forward and backward electron transfer rates from A and A to F and charge recombination rates from A, A, A, F, and [F/F] to P were measured in P-F/F complexes, P-F cores, and P-A cores, both in liquid and in a trehalose glassy matrix at 11% humidity. By comparing CONTIN-resolved kinetic events over 6 orders of time in increasingly simplified versions of PS I at 480 nm, a wavelength that reports primarily A/A oxidation, and over 9 orders of time at 830 nm, a wavelength that reports P reduction and A oxidation, assignments could be made for nearly all of the resolved kinetic phases. Trehalose-embedded PS I samples demonstrated partially arrested forward electron transfer. The fractions of complexes in which electron transfer did not proceed beyond A, A and F were 53%, 16% and 22%, respectively, with only 10% of electrons reaching the terminal F/F clusters. The ~10 μs and ~150 μs components in both liquid and trehalose-embedded PS I were assigned to recombination between A and P and between A and P, respectively. The kinetics and amplitudes of these resolved kinetic phases in liquid and trehalose-embedded PS I samples could be well-fitted by a kinetic model that allowed us to calculate the asymmetrical contribution of the A and A quinones to the electrochromic signal at 480 nm. Possible reasons for these effects are discussed.
本工作旨在充分阐明海藻糖玻璃基质对蓝细菌光系统 I（PS I）中电子转移反应的影响。在 11%相对湿度下的液态和海藻糖玻璃基质中，通过测量 P-F/F 复合物、P-F 核心和 P-A 核心中 A 和 A 到 F 的正向和反向电子转移速率以及 A、A、A、F 和[F/F]到 P 的电荷复合速率，在 P-F/F 复合物、P-F 核心和 P-A 核心中，均在液态和海藻糖玻璃基质中进行了测量。通过比较 6 个时间阶的 CONTIN 解析动力学事件，在 480nm 处，主要报告 A/A 氧化的波长，以及在 830nm 处，主要报告 P 还原和 A 氧化的波长，在 PS I 的简化版本中，进行了 9 个时间阶的比较，可以对几乎所有解析的动力学阶段进行分配。海藻糖嵌入 PS I 样品表现出部分停止的正向电子转移。电子转移未超过 A、A 和 F 的复合物分数分别为 53%、16%和 22%，只有 10%的电子到达终端 F/F 簇。在液态和海藻糖嵌入 PS I 中，约 10μs 和 150μs 组分分别被分配到 A 和 P 之间以及 A 和 P 之间的复合。通过一个动力学模型，可以很好地拟合液态和海藻糖嵌入 PS I 样品中这些解析动力学阶段的动力学和幅度，该模型允许我们计算 480nm 处 A 和 A 醌的电致变色信号的不对称贡献。讨论了这些影响的可能原因。
