Sokolov V S, Block M, Stozhkova I N, Pohl P
Frumkin Institute of Electrochemistry RAS, Moscow, Russia.
Biophys J. 2000 Oct;79(4):2121-31. doi: 10.1016/S0006-3495(00)76459-9.
The adsorption of a membrane-impermeable photosensitizer to only one membrane leaflet is found to trigger a localized photodynamic reaction; i.e., the amount of carbonyl cyanide m-chlorophenylhydrazone (CCCP) molecules damaged in the leaflet facing the photosensitizer is roughly identical to the total amount of CCCP inactivated. Whereas the latter quantity is assessed from the drop in membrane conductivity G, the former is evaluated from the photopotential phi that is proportional to the interfacial concentration difference of the uncoupler. Localized photodestruction is encountered by CCCP diffusion to the site of photodamage. A simple model that accounts for both photoinhibition and diffusion predicts the dependence of the photopotential on light intensity, buffer capacity, and pH of the medium. It is concluded that only a limited amount of the reactive oxygen species responsible for CCCP photodamage diffuses across the membrane. If the concentration of reactive oxygen species is decreased by addition of NaN(3) or by substituting aqueous oxygen for argon, phi is inhibited. If, in contrast, their life time is increased by substitution of H(2)O for D(2)O, phi increases.
发现一种不能透过膜的光敏剂仅吸附在一个膜小叶上会引发局部光动力反应；也就是说，在面向光敏剂的小叶中被破坏的羰基氰化物间氯苯腙（CCCP）分子数量与失活的CCCP总量大致相同。后者的量通过膜电导率G的下降来评估，而前者则根据与解偶联剂界面浓度差成正比的光电势φ来评估。CCCP扩散到光损伤部位会导致局部光破坏。一个兼顾光抑制和扩散的简单模型预测了光电势对光强度、缓冲容量和介质pH值的依赖性。得出的结论是，导致CCCP光损伤的活性氧物种只有有限的量会扩散穿过膜。如果通过添加NaN₃或用氩气替代水中的氧气来降低活性氧物种的浓度，φ会受到抑制。相反，如果通过用D₂O替代H₂O来延长它们的寿命，φ会增加。
