Studies on prenylquinones in green leaves

采用本研究开发的方法研究了叶片和叶绿体中烯丙基醌的分布和氧化还原水平。该方法首先在样品制备筒上快速提取醌类化合物，然后用双电极伏安检测器反相高效液相色谱分离检测。类囊体膜中半数以上的质体醌存在于脂质基质中，提示其具有移动电子和质子载体的作用。其余质体醌以粒子形式作为固定的电子/质子载体存在。在类囊体膜的各个部位，各衍生物与叶绿素的摩尔比几乎相同。叶绿醌集中在光系统I颗粒中，可能是氧化还原成分。在类囊体膜的各个部分，生育酚醌与叶绿素的比例几乎是恒定的，这表明它是一种强光对色素系统光损伤的保护剂。在菠菜叶片发育过程中，叶绿体醌- c与叶绿素的比值升高，泛素-9的比值降低。其他烯丙基醌的比例没有变化。在叶片发育过程中，呼吸系统作为ATP产生系统的作用部分被光合系统所取代。质体醌A.3光化学环氧化反应可制备质体醌C。光系统II中的初级光化学反应需要两个质体醌A分子。pH为7.8时，质体醌A在叶绿体中的氧化还原电位为+20 mV。

Distributions and redox levels of prenylquinones in leaves and chloroplasts were studied using the methods developed here. The method is consisted of rapid extraction of the quinones on the sample preparation cartridge, followed by the separation and detection with the reversed-phase high-performance liquid chromatography using the dual-electrodes voltanmetric detector.1. More than half of plastoquinones in thylakoid membranes were found in lipid matrix, suggesting its role as mobile electron and proton carrier. The rest of plastoquinones were in particles as fixed electron/proton carriers. The molar ratios of each derivatives to chlorophyll were almost the same in every part of thylakoid membrane. Phylloquinone was concentrated in photosytem I particle, possibly as a redox component. The ratio of tocopherolquinone to chlorophyll was almost constant in every portion of thylakoid membrane, suggesting its role as a protectant for the photoinjury of pigment systems by strong light.2. During the development of spinach leaves the ratio of plastoquinone-C to chlorophyll was increased, and of ubiquinone-9 was decreased. The ratios of the other prenylquinones were not changed. It seems that the role of the respiratory system as ATP producing system is partly replaced by the photosynthetic system in the course of leaf development. Plasstoquinone C might be produced by photochemical epoxydation of plastoquinone A.3. The primary photochemical reaction in Photosystem II required two plastoquinone A molecules.4. The redox potential of plastoquinone A in chloroplasts was +20 mV at pH 7.8.