Tikhonov Alexander N
Department of Biophysics, Faculty of Physics, M.V. Lomonosov, Moscow State University, Moscow, Russia.
Cell Biochem Biophys. 2017 Dec;75(3-4):421-432. doi: 10.1007/s12013-017-0797-2. Epub 2017 May 9.
This is a brief overview focused on the electron paramagnetic resonance applications to the study of the proton transport processes in chloroplasts. After brief description of structural and functional organization of the chloroplast electron transport chain, our attention is focused on the measurements of trans-thylakoid pH difference (ΔpH) with pH-sensitive spin-probes. The use of spin-probes is based either (i) on measuring the ΔpH-partitioning of spin-probes between the thylakoid lumen and external volume, or (ii) on monitoring changes in the electron paramagnetic resonance spectra of pH-sensitive nitroxide radicals located in the lumen. Along with the use of spin-probes, the intra-thylakoid pH (pH) can be determined by the "kinetic" method, which relies on the fact that the rate-limiting step in the chain of photosynthetic electron transfer (plastoquinol oxidation by the cytochrome b f complex) is controlled by pH. The results of ΔpH determinations in chloroplasts based on the use of pH-sensitive spin-probes and measurements of post-illumination reduction of photoreaction centers of Photosystem I are discussed in the context of the problem of energy coupling in laterally heterogeneous lamellar system of chloroplasts.
这是一篇简要综述，重点介绍电子顺磁共振在叶绿体质子传输过程研究中的应用。在简要描述叶绿体电子传输链的结构和功能组织后，我们将注意力集中在用对pH敏感的自旋探针测量类囊体膜两侧的pH差值（ΔpH）上。自旋探针的应用基于以下两种方法之一：（i）测量自旋探针在类囊体腔和外部体积之间的ΔpH分配；（ii）监测位于腔内的对pH敏感的氮氧化物自由基的电子顺磁共振谱的变化。除了使用自旋探针外，类囊体腔内pH（pHin）可通过“动力学”方法测定，该方法基于光合电子传递链（细胞色素b6f复合物氧化质体醌）中的限速步骤受pH控制这一事实。基于使用对pH敏感的自旋探针测定叶绿体ΔpH的结果以及光系统I光反应中心光照后还原的测量结果，将在叶绿体横向异质片层系统中的能量偶联问题背景下进行讨论。
