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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Electron transfer from A_0~- to A1 in Photosystem I from Chlamydomonas reinhardtii occurs in both the A and B branch with 25-30-ps lifetime
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Electron transfer from A_0~- to A1 in Photosystem I from Chlamydomonas reinhardtii occurs in both the A and B branch with 25-30-ps lifetime

机译：莱茵衣藻在光系统I中从A_0〜-到A1的电子转移同时发生在A和B分支中，寿命为25-30 ps

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摘要

We have recorded transient absorption kinetics at 390 nm with picosecond resolution in order to observe electron transfer from the reduced primary acceptor, A_0~-, to the secondary acceptor, A_(l5) in wild type and mutated Photosystem I from Chlamydomonas reinhardtii. In the mutants, the methionine axial ligand to the primary electron acceptor in either the A- or B-branch of electron transfer cofactors, was replaced with histidine. Both of the mutations reduced the formation of a positive signal at 390 nm, characteristic of A_1~- to a level approximately half of that observed in wild type Photosystem I. It is concluded that in the mutated branch of Photosystem I, electron transfer from A_0~- to A1 does not occur. The absorption kinetics resulting from subtraction of either of the mutants' traces from that of wild type is interpreted to reflect the kinetics of A- or B-side electron transfer from A_0~- to A1 in the the wild type Photosystem I. Each of these traces could be fitted with a monoexpoenential decay characterized by the same amplitude and 25-30-ps lifetime. The almost identical effect of both mutations on A_1~- formation confirm a similar engagement of both the A- ad B-branches in electron transfer to A1 in Photosystem I from C. reinhardtii. This observation is in contrast to the unidirectional electron transfer concluded from the studies on similar mutants of cyanobacterial Photosystem I.1 Thus, this contribution provides further evidence for functional differences between these two model Photosystems.
机译：我们已经记录了在390 nm处具有皮秒分辨率的瞬态吸收动力学，目的是观察电子从还原型初级受体A_0〜-到野生型次级受体A_（l5）以及莱茵衣藻突变的光系统I的电子转移。在突变体中，电子转移辅助因子的A或B分支中主要电子受体的蛋氨酸轴向配体被组氨酸取代。这两个突变都将在390 nm处形成正信号（A_1〜-的特征）降低到在野生型光系统I中观察到的水平的一半左右。结论是，在光系统I的突变分支中，电子从A_0转移~~不会出现A1。从野生型减去任一突变体的痕迹产生的吸收动力学被解释为反映了野生型光系统I中A侧或B侧电子从A_0〜-转移至A1的动力学。迹线可以装有以相同幅度和25-30ps寿命为特征的单指数衰减。两种突变对A_1〜-形成的几乎相同的影响证实了两个A-ad B分支都参与了雷氏梭菌在光系统I中电子转移到A1的过程。该观察结果与对蓝细菌光系统I.1的类似突变体的研究得出的单向电子转移相反。因此，这一贡献为这两个模型光系统之间的功能差异提供了进一步的证据。

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