Influence of the Electrochemical Properties of the Bacteriochlorophyll Dimer on Triplet Energy-Transfer Dynamics in Bacterial Reaction Centers.
Influence of the Electrochemical Properties of the Bacteriochlorophyll Dimer on Triplet Energy-Transfer Dynamics in Bacterial Reaction Centers.
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细菌叶绿素二聚体的电化学性质对细菌反应中心三重态能量传递动力学的影响。
DOI：
10.1021/acs.jpcb.8b07985
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Woodbury,NealW
中科院分区：
文献类型：
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作者：
Mandal,Sarthak;Espiritu,Eduardo;Akram,Natalie;Lin,Su;Williams,JoAnnC;Allen,JamesP;Woodbury,NealW
能量学、蛋白质动力学和电子耦合是控制光合细菌反应中心（RC）中电子和能量传递的关键因素。在这里，我们研究了一系列突变体RC中P+ HA自由基对电荷重组、三重态形成以及随后从细菌叶绿素二聚体（P）三重态到类胡萝卜素的三重态能量转移的速率和机制途径（L131 LH + M160 LH（D1）、L131 LH + M197 FH（D2）和L131 LH + M160 LH + M197 FH（T1））。在这些突变体中，P的电子结构被扰动，并且由于P和引入的残基之间的氢键的增加，P/P+中点电位系统地增加。高分辨率，宽带，瞬态吸收光谱的飞秒到微秒的时间尺度上显示，电荷复合率增加和三重态能量转移率下降，在这些突变体相对于野生型（WT）。电荷复合率的增加与P+ HA-能级的增加和P/P+中点电位的增加有关。另一方面，突变体中三重态能量传递速率的降低可以用3 P能量的降低和P细菌叶绿素中电子自旋密度分布的移动来解释。三重态能量传递速率的顺序为WT > L131 LH + M197 FH> L131 LH + M160 LH> L131 LH + M160 LH + M197 FH，在室温和77 K下。一个显着的温度依赖性的速率观察所有的RC样品。与该过程相关的活化能在突变体中相对于WT增加，这与由于P和引入的残基之间添加氢键而导致的较低的3 P能量一致。
Energetics, protein dynamics, and electronic coupling are the key factors in controlling both electron and energy transfer in photosynthetic bacterial reaction centers (RCs). Here, we examine the rates and mechanistic pathways of the P+HA–radical-pair charge recombination, triplet state formation, and subsequent triplet energy transfer from the triplet state of the bacteriochlorophyll dimer (P) to the carotenoid in a series of mutant RCs (L131LH + M160LH (D1), L131LH + M197FH (D2), and L131LH + M160LH + M197FH (T1)) ofRhodobacter sphaeroides. In these mutants, the electronic structure of P is perturbed and the P/P+midpoint potential is systematically increased due to addition of hydrogen bonds between P and the introduced residues. High-resolution, broad-band, transient absorption spectroscopy on the femtosecond to microsecond timescale shows that the charge recombination rate increases and the triplet energy transfer rate decreases in these mutants relative to the wild type (WT). The increase of the charge recombination rate is correlated to the increase in the energy level of P+HA–and the increase in the P/P+midpoint potential. On the other hand, the decrease in rate of triplet energy transfer in the mutants can be explained in terms of a lower energy of3P and a shift in the electron spin density distribution in the bacteriochlorophylls of P. The triplet energy-transfer rate follows the order of WT > L131LH + M197FH > L131LH + M160LH > L131LH + M160LH + M197FH, both at room temperature and at 77 K. A pronounced temperature dependence of the rate is observed for all of the RC samples. The activation energy associated to this process is increased in the mutants relative to WT, consistent with a lower3P energy due to the addition of hydrogen bonds between P and the introduced residues.