Babcock G T, Sauer K
Biochim Biophys Acta. 1975 Feb 17;376(2):315-28. doi: 10.1016/0005-2728(75)90024-9.
A rapid, light-induced reversible component in Signal II is observed upon inhibition of oxygen evolution in broken spinach chloroplasts. The inhibitory treatments used include Tris washing, heat, treatment with chaotropic agents, and aging. This new Signal II component is in a 1 : 1 ratio with Signal I (P700). Its formation corresponds to a light-induced oxidation which occurs in less than 500 mus. The subsequent decay of the radical results from a reduction which occurs more rapidly as this free radical component is complete following a single 10-mus flash, and it occurs with a quantum efficiency similar to that observed for Signal I formation. Red light is more effective than far-red light in the generation of this species, and, in preilluminated chloroplasts, 3-(3,4-dichlorophenyl)-1,1-dimethylurea blocks its formation. Inhibition studies show that the decline in oxygen evolution parallels the activation of this Signal II component. These results are interpreted in terms of a model in which two pathways, one involving water, the other involving the rapid Signal II component, compete for oxidizing equivalents generated by Photosystem II. In broken chloroplasts this Signal II pathway is deactivated and water is the principal electron donor. However, upon inhibition of oxygen evolution, the Signal II pathway is activated.
在破碎的菠菜叶绿体中，当氧释放受到抑制时，观察到信号II中存在一种快速的、光诱导的可逆成分。所使用的抑制处理包括Tris洗涤、加热、用离液剂处理和老化。这种新的信号II成分与信号I（P700）的比例为1:1。其形成对应于在不到500微秒内发生的光诱导氧化。自由基随后的衰减是由还原引起的，随着这个自由基成分在单次10微秒闪光后完成，还原过程更快发生，并且其发生的量子效率与信号I形成时观察到的相似。在产生这种物质方面，红光比远红光更有效，并且在预照光的叶绿体中，3-(3,4-二氯苯基)-1,1-二甲基脲会阻止其形成。抑制研究表明，氧释放的下降与这种信号II成分的激活平行。这些结果根据一个模型来解释，在该模型中，两条途径，一条涉及水，另一条涉及快速信号II成分，竞争由光系统II产生的氧化当量。在破碎的叶绿体中，这种信号II途径失活，水是主要的电子供体。然而，当氧释放受到抑制时，信号II途径被激活。
