Bukhov N G, Karapetian N V
Mol Biol (Mosk). 1978 Jul-Aug;12(4):868-78.
The functioning of the acceptor part of photosystem I was studied by temperature dependence of time course of light induced absorbtion changes at 700 nm of digitonin chloroplast fragments, enriched by photosystem I. Partial irreversibility of P700 photooxidation at low temperatures and appearance of two components (rapid and slow) in the time course of P700+ dark reduction reflect the contribution of different acceptors in electron transport. Thermoinactivation of fragments incubation at acid pH or treatment by glutaraldehyde cause complete inhibition of irreversible P700 photooxidation and slow dark reduction of P700+ at -170 degrees. The slow component of P700+ reduction and irreversible photooxidation of P700 are ascribed to contribution of secondary ferredoxin acceptors. The accurence of rapid component of P700+ dark reduction in light induced signal of treated fragments indicate that this component is due to recombination of reduced primary acceptor and P700+. Because only one electron transport takes at -170 degrees, the occurence of rapid and slow components in dark decay kinetics of P700+ suggests, that secondary acceptors of some reaction centers are incapable to reduction at -170 degrees. The shape of temperature dependence curve of the slow P700+ reduction component is interpreted as an indication of the tunneling electron transport.
通过对富含光系统I的洋地黄皂苷叶绿体片段在700nm处光诱导吸收变化的时间进程的温度依赖性研究了光系统I受体部分的功能。低温下P700光氧化的部分不可逆性以及P700 +暗还原时间进程中两个成分（快速和慢速）的出现反映了不同受体在电子传递中的作用。在酸性pH下孵育片段或用戊二醛处理导致在-170℃下不可逆的P700光氧化和P700 +的缓慢暗还原完全受到抑制。P700 +还原的慢速成分和P700的不可逆光氧化归因于次级铁氧还蛋白受体的作用。处理过的片段的光诱导信号中P700 +暗还原快速成分的出现表明该成分是由于还原的初级受体和P700 +的重组。因为在-170℃下仅发生一次电子传递，P700 +暗衰减动力学中快速和慢速成分的出现表明，一些反应中心的次级受体在-170℃下不能还原。慢速P700 +还原成分的温度依赖性曲线形状被解释为隧道电子传递的指示。
