Department of Physics, University of California, San Diego, La Jolla, CA 92093.
Proc Natl Acad Sci U S A. 1986 Nov;83(21):8152-6. doi: 10.1073/pnas.83.21.8152.
Previous ENDOR studies on reaction centers from Rhodopseudomonas sphaeroides have shown the presence of two hydrogen-bonded protons associated with the primary, ubiquinone, acceptor Q(A). These protons exchange with deuterons from solvent (2)H(2)O. The effect of this deuterium substitution on the charge-recombination kinetics (BChl)(2) (+)Q(A) (-) --> (BChl)(2)Q(A) has been studied with a sensitive kinetic difference technique. The electron-transfer rate was found to increase with deuterium exchange up to a maximum Deltak/k of 5.7 +/- 0.3%. The change in rate was found to have an exchange time of 2 hr, which matched the disappearance of the ENDOR lines due to the exchangeable protons. These results indicate that these protons play a role in the vibronic coupling associated with electron transfer. A simple model for the isotope effect on electron transfer predicts a maximum rate increase of 20%, which is consistent with the experimental results.
先前关于来自球形红假单胞菌的反应中心的 EN-DOR 研究表明,存在两个与初级、泛醌、受体 Q(A) 相关的氢键质子。这些质子与溶剂 (2)H(2)O 中的氘交换。用灵敏的动力学差示技术研究了这种氘取代对电荷复合动力学 (BChl)(2) (+)Q(A) (-) --> (BChl)(2)Q(A) 的影响。发现电子转移速率随氘交换的增加而增加,最大 Deltak/k 为 5.7 +/- 0.3%。发现速率的变化具有 2 小时的交换时间,与由于可交换质子而消失的 EN-DOR 线相匹配。这些结果表明这些质子在与电子转移相关的声子耦合中起作用。一个简单的同位素效应对电子转移的影响的模型预测最大的速率增加 20%,这与实验结果一致。