Primary radical pair P+H- lifetime in Rhodobacter sphaeroides with blocked electron transfer to QA.: Effect of o-phenanthroline
Primary radical pair P+H- lifetime in Rhodobacter sphaeroides with blocked electron transfer to QA.: Effect of o-phenanthroline
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DOI：
10.1021/jp075184j
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发表时间：
2008-02-14
影响因子：
3.3
通讯作者：
Pajzderska, Maria
中科院分区：
文献类型：
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作者：
Gibasiewicz, Krzysztof;Pajzderska, Maria
采用时间分辨率接近1 ns的瞬态吸收光谱研究了球形红杆菌R-26反应中心中电子从H-向Q(a)转移被阻断的初级自由基对P+H-的衰变。电子转移中的阻滞是通过两种方式实现的：减少或去除Q(A)。我们发现在这两种情况下P+H衰变的动力学非常不同。多指数衰减与仪器响应函数的卷积允许在Q(A)减少的色团中以及在Q(A)减少或去除（含或不含邻菲罗啉）但相对振幅可变的孤立反应中心中分辨出多达三个< 1-，3-4-和9-12-ns寿命的动力学成分。去除Q(A)或在分离的反应中心加入邻菲罗啉，相对于最快的衰变相，最慢的衰变相的振幅增加。在这些观察的基础上，我们提出反应中心采用三种构象状态，它们具有不同的P+H-衰变动力学特征。这些构象状态似乎是由Q(A)位点附近的电荷控制的，这是由Q(A)还原和邻菲罗啉介导的Q(A)位点附近质子化的影响所揭示的。
Transient absorption spectroscopy with a time resolution of similar to 1 ns was applied to study the decay of the primary radical pair P+H- in Rhodobacter sphaeroides R-26 reaction centers with blocked electron transfer from H- to Q(A). The block in the electron transfer was realized in two ways: by either reducing or removing Q(A). We found very different kinetics of the P+H- decay in these two cases. Convolution of the multiexponential decay with the instrument response function allowed resolution of as many as three kinetic components of < 1-, 3-4-, and 9-12-ns lifetimes in chromatophores with Q(A) reduced and in isolated reaction centers both with Q(A) either reduced or removed (with or without o-phenanthroline) but with variable relative amplitudes. Removing Q(A) or adding o-phenanthroline to isolated reaction centers increased the amplitude of the slowest decay phase relative to that of the fastest phase. On the basis of these observations, we propose that reaction centers adopt three conformational states characterized by different decay kinetics of P+H-. These conformational states appear to be controlled by the charges in the vicinity of the Q(A) site as revealed by the effects of Q(A) reduction and o-phenanthroline-mediated protonation of the sites close to Q(A).