超快光谱研究嗜热菌叶绿素 a 蛋白天线复合物 Fenna-Matthews-Olson(FMO)定向突变体中的能量转移

Ultrafast Spectroscopic Investigation of Energy Transfer in Site-Directed Mutants of the Fenna-Matthews-Olson (FMO) Antenna Complex from Chlorobaculum tepidum.

机构信息

Department of Biology, ‡Department of Chemistry, and §Photosynthetic Antenna Research Center, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130, United States.

出版信息

J Phys Chem B. 2017 May 11;121(18):4700-4712. doi: 10.1021/acs.jpcb.7b01270. Epub 2017 Apr 28.

Abstract

Ultrafast transient absorption (TA) and time-resolved fluorescence (TRF) spectroscopic studies were performed on several mutants of the bacteriochlorophyll (BChl) a-containing Fenna-Matthews-Olson (FMO) complex from the green sulfur bacterium Chlorobaculum tepidum. These mutants were generated to perturb a particular BChl a site and determine its effects on the optical spectroscopic properties of the pigment-protein complex. Measurements conducted at 77 K under both oxidizing and reducing conditions revealed changes in the dynamics of the various spectral components as compared to the data set from wild-type FMO. TRF results show that under reducing conditions all FMO samples decay with a similar lifetime in the ∼2 ns range. The oxidized samples revealed varying fluorescence lifetimes of the terminal BChl a emitter, considerably shorter than those recorded for the reduced samples, indicating that the quenching mechanism in wild-type FMO is still present in the mutants. Global fitting of TA data yielded similar overall results, and in addition, the lifetimes of early decaying components were determined. Target analyses of TA data for select FMO samples generated kinetic models that better simulate the TA data. A comparison of the lifetime of excitonic components for all samples reveals that the mutations affect mainly the early kinetic components, but not that of the lowest energy exciton, which reflects the flexibility of energy transfer in FMO.

摘要

超快瞬态吸收(TA)和时间分辨荧光(TRF)光谱研究了来自绿硫细菌 Chlorobaculum tepidum 的菌叶绿素(BChl)a 含有 Fenna-Matthews-Olson(FMO)复合物的几种突变体。这些突变体是为了干扰特定的 BChl a 位点,并确定其对色素蛋白复合物光学光谱性质的影响而产生的。在 77 K 下进行的氧化和还原条件下的测量与野生型 FMO 的数据集相比,显示出各种光谱分量的动力学变化。TRF 结果表明,在还原条件下,所有 FMO 样品的衰减寿命均在 ∼2 ns 范围内相似。氧化样品显示出末端 BChl a 发射器的荧光寿命变化很大,明显短于还原样品记录的寿命,表明野生型 FMO 中的猝灭机制仍然存在于突变体中。TA 数据的全局拟合得到了相似的总体结果,并确定了早期衰减成分的寿命。对选定的 FMO 样品的 TA 数据进行目标分析生成了更好地模拟 TA 数据的动力学模型。对所有样品的激子成分寿命的比较表明,突变主要影响早期动力学成分,而不是最低能量激子的寿命,这反映了 FMO 中能量转移的灵活性。

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