Ilani A, Woodle M, Mauzerall D
Photochem Photobiol. 1989 May;49(5):673-9. doi: 10.1111/j.1751-1097.1989.tb08440.x.
Both photoinitiated (thermodynamically downhill) and photodriven (thermodynamically uphill) electron transfer reactions across lipid bilayers are sensitized by magnesium octaethyl porphyrin (MgOEP). It is shown that the reaction mechanism is via reduction of photoexcited MgOEP at the reducing (ascorbate) side of the bilayer and the charge carrier is likely the neutral protonated MgOEP anion. The MgOEP cation (or its neutral form) does not contribute to charge passage across the bilayer even though it is readily formed at the acceptor (ferricyanide or methyl viologen) side of the membrane. Photoelectric measurements on planar bilayers show that the time constant for reduction of excited MgOEP is about 10 microseconds with 10 mM ascorbate. The membrane transport of the mediator appears to be rate limiting when the reaction is photoinitiated and the interfacial reaction appears to be limiting when the reaction is photodriven. The quantum yield of the process is about 0.1 in the latter case and about 0.02 in the former. The former yield is increased to about 0.15 in the presence of a redox mediator, duroquinone. In these systems, the magnesium porphyrin is both sensitizer and trans membrane redox mediator.
通过脂质双层的光引发（热力学上的下坡反应）和光驱动（热力学上的上坡反应）电子转移反应均由八乙基卟啉镁（MgOEP）敏化。结果表明，反应机制是通过双层还原侧光激发的MgOEP的还原，电荷载体可能是中性质子化的MgOEP阴离子。MgOEP阳离子（或其中性形式）对跨双层的电荷传递没有贡献，尽管它很容易在膜的受体（铁氰化物或甲基紫精）侧形成。对平面双层的光电测量表明，在含有10 mM抗坏血酸盐的情况下，激发态MgOEP还原的时间常数约为10微秒。当反应是光引发时，介质的膜传输似乎是速率限制因素；当反应是光驱动时，界面反应似乎是限制因素。在后一种情况下，该过程的量子产率约为0.1，在前一种情况下约为0.02。在氧化还原介质杜醌存在下，前一种产率提高到约0.15。在这些系统中，卟啉镁既是敏化剂又是跨膜氧化还原介质。
