Malkin R, Bearden A J
Department of Cell Physiology, University of California, Berkeley, Calif. 94720.
Proc Natl Acad Sci U S A. 1973 Feb;70(2):294-7. doi: 10.1073/pnas.70.2.294.
Electron paramagnetic resonance (EPR) spectroscopy has revealed a new free-radical signal produced by illumination of spinach chloroplasts at 77 degrees K. This signal is observed only when an oxidant (ferricyanide) is added to the chloroplast suspension in the dark before illumination. The EPR signal is produced at 77 degrees K by illumination with 645-nm monochromatic light capable of activating Photosystem II but not with 715-nm illumination capable of activating Photosystem I. Furthermore, since the signal shows a relative increase in chloroplast fragments enriched in Photosystem II but is absent in chloroplast fragments enriched in Photosystem I, we conclude that this new EPR signal is associated with the primary photoact of Photosystem II in chloroplasts. On the basis of the measured EPR parameters (g = 2.0026 +/- 0.0002, linewidth = 8 G), it is suggested that the signal may be associated with the reaction-center chlorophyll of Photosystem II.
电子顺磁共振(EPR)光谱揭示了菠菜叶绿体在77K温度下光照产生的一种新的自由基信号。只有在黑暗中光照前向叶绿体悬浮液中添加氧化剂(铁氰化物)时,才会观察到这种信号。该EPR信号是在77K温度下用能够激活光系统II的645nm单色光照射产生的,而用能够激活光系统I的715nm光照则不会产生。此外,由于该信号在富含光系统II的叶绿体片段中相对增加,而在富含光系统I的叶绿体片段中不存在,我们得出结论,这种新的EPR信号与叶绿体中光系统II的初级光化学作用有关。根据测量的EPR参数(g = 2.0026 +/- 0.0002,线宽 = 8 G),表明该信号可能与光系统II的反应中心叶绿素有关。