Photocurrents from photosystem II in a metal oxide hybrid system: Electron transfer pathways.
Photocurrents from photosystem II in a metal oxide hybrid system: Electron transfer pathways.
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DOI：
10.1016/j.bbabio.2016.03.004
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发表时间：
2016-09
期刊：
影响因子：
--
通讯作者：
Fantuzzi A
中科院分区：
文献类型：
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作者：
Brinkert K;Le Formal F;Li X;Durrant J;Rutherford AW;Fantuzzi A
我们已经研究了光系统II（PSII），水氧化酶，从细长热聚球藻分离，当固定在纳米结构的二氧化钛铟锡氧化物电极（TiO 2/ITO）产生的光电流的性质。我们调查的光电流从PSII时，固定为单层与多层，在存在和不存在的抑制剂，结合到网站的可交换的醌（QB）和存在和不存在的外源性移动的电子载体（介质）的特性。研究结果表明，电子转移发生从第一醌（QA）直接到电极表面，但通过纳米结构的金属氧化物的电子转移是限速步骤。氧化还原介体通过将电子从纳米结构半导体表面带到ITO电极表面而不是从PSII来增强光电流。这是通过使用不能接受来自PSII的电子的介体的光电流增强来证明的。这个电子转移模型也解释了文献中使用类似和相关系统报道的异常现象。TiO 2中电子转移步骤的缓慢速率是由于电子注入到半导体材料中的能级低于导带。这限制了本混合电极的有用性。克服这种动力学限制的策略进行了讨论。在PSII金属氧化物混合系统中，直接电子转移发生从QA到电极表面。通过纳米结构的TiO 2的电子转移是限速的。氧化还原介体可以通过将电子从TiO 2半导体带到电极表面来克服限制。
We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidizing enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absence of an inhibitor that binds to the site of the exchangeable quinone (QB) and in the presence and absence of exogenous mobile electron carriers (mediators). The findings indicate that electron transfer occurs from the first quinone (QA) directly to the electrode surface but that the electron transfer through the nanostructured metal oxide is the rate-limiting step. Redox mediators enhance the photocurrent by taking electrons from the nanostructured semiconductor surface to the ITO electrode surface not from PSII. This is demonstrated by photocurrent enhancement using a mediator incapable of accepting electrons from PSII. This model for electron transfer also explains anomalies reported in the literature using similar and related systems. The slow rate of the electron transfer step in the TiO2 is due to the energy level of electron injection into the semiconducting material being below the conduction band. This limits the usefulness of the present hybrid electrode. Strategies to overcome this kinetic limitation are discussed. In PSII metal oxide hybrid systems, direct electron transfer occurs from QA to the electrode surface. Electron transfer through the nanostructured TiO2 is rate-limiting. Redox mediators can overcome the limitation by taking electrons from the TiO2 semiconductor to the electrode surface.