The effect of an applied electric field on the charge recombination kinetics in reaction centers reconstituted in planar lipid bilayers.
The effect of an applied electric field on the charge recombination kinetics in reaction centers reconstituted in planar lipid bilayers.
复制标题
施加的电场对平面脂质双层中重构的反应中心的电荷复合动力学的影响。
DOI：
10.1016/s0006-3495(85)83784-x
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发表时间：
1985
影响因子：
3.4
通讯作者：
Montal,M
中科院分区：
文献类型：
--
作者：
Gopher,A;Blatt,Y;Schönfeld,M;Okamura,MY;Feher,G;Montal,M
将来自光合细菌Rhodopophylla sphaeroides的反应中心（RC）并入由来自用纯化的RC重构的脂质体的单层制成的平面双层中。与还原的伯醌（QA-）和氧化的细菌叶绿素供体（D+）之间的电荷复合过程相关的光电流被测量为施加在双层上的电压（-150 mV小于V小于150 mV）的函数。当QA为天然泛醌（UQ）时，电荷复合不依赖于电压。当用蒽醌（AQ）代替UQ时，复合时间与外加电压V的关系为τ =8.5 × 10（-3）eV/0.175S。这些结果可以用一个简单的模型来解释，其中UQ-的电荷复合直接进行到D+，而AQ的电荷复合通过热激活的中间态D+I-QA发生，其中I是中间受体。电压依赖性由电场引起的状态D+I-QA和D+IQA-之间的能隙Δ G 0的变化引起。该模型得到了测量的电荷复合时间的温度依赖性的支持，对于具有AQ的RC，其给出了Δ G 0 =340 +/- 20 meV的值。相比之下，对于具有UQ作为主要受体的RC，Δ G 0足够大（约550 meV），使得即使在场的存在下，直接途径也占主导地位。电压依赖性表明，电子从I-到QA的转移是产电的。从电压对复合速率的依赖性的定量分析中得出结论，I和QA之间的距离的分量沿着膜的法线约为膜厚度的七分之一。这意味着从I到Q的电子转移至少贡献了D+和QA-之间电荷分离产生的电势的七分之一。
Reaction Centers (RCs) from the photosynthetic bacterium Rhodopseudomonas sphaeroides were incorporated in planar bilayers made from monolayers derived from liposomes reconstituted with purified RCs. The photocurrents associated with the charge recombination process between the reduced primary quinone (QA-) and the oxidized bacteriochlorophyll donor (D+) were measured as a function of voltage (-150 mV less than V less than 150 mV) applied across the bilayer. When QA was the native ubiquinone (UQ) the charge recombination was voltage independent. However, when UQ was replaced by anthraquinone (AQ), the recombination time depended on the applied voltage V according to the relation tau=8.5 X 10(-3) eV/0.175S. These results were explained by a simple model in which the charge recombination from UQ- proceeds directly to D+ while that from AQ occurs via a thermally activated intermediate state, D+I-QA, where I is the intermediate acceptor. The voltage dependence arises from an electric field induced change in the energy gap, delta G0, between the states D+I-QA and D+IQA-. This model is supported by the measured temperature dependence of the charge recombination time, which for RCs with AQ gave a value of delta G0=340 +/- 20 meV. In contrast, delta G0 for RCs with UQ as the primary acceptor, is sufficiently large (approximately 550 meV) so that even in the presence of the field, the direct pathway dominates. The voltage dependence shows that the electron transfer from I- to QA is electrogenic. From a quantitative analysis of the voltage dependence on the recombination rate it was concluded that the component of the distance between I and QA along the normal to the membrane is about one-seventh of the thickness of the membrane. This implies that the electron transfer from I to Q contributes at least one-seventh to the potential generated by the charge separation between D+ and QA-.