Aspée A, Lissi E A
Department of Chemistry, Faculty of Chemistry and Biology, University of Santiago, Casilla 40, Correo 33, Santiago, Chile.
Luminescence. 2000 Sep-Oct;15(5):273-82. doi: 10.1002/1522-7243(200009/10)15:5<273::AID-BIO591>3.0.CO;2-M.
When amino acids are incubated in the presence of a free radical source [2,2'-azobis(2-amidinopropane) dihydrocloride], only tyrosine (Tyr) and tryptophan (Trp) produce significant chemiluminescence. The relationship between the observed light intensity, the rate of the oxidation process and the substrate concentration is complex and can not be explained in terms of the formation of excited states in termination processes involving two peroxyl radicals (Russell's mechanism). The observed increase in light emission with the incubation time, for both Trp and Tyr, would indicate the participation of more than one reaction product as intermediates in the pathways leading to the production of excited molecules. However, the fact that after product accumulation a high proportion of the observed luminescence is quenched by Trolox addition, implies that the main chemiluminescent process must involve the interaction of product(s) and free radicals. From the effect of added Ebselen, it is proposed that hydroperoxides and peroxides, formed along the reaction path, are the intermediates whose accumulation leads to the observed increase in chemiluminescence with elapsed time. The observed time profiles and the proposed mechanism strongly resemble those associated with the oxidation of complex biological systems, suggesting that protein oxidation could be one of the main sources of chemiluminescence in biological oxidations.
当氨基酸在自由基源[2,2'-偶氮二(2-脒基丙烷)二盐酸盐]存在的情况下进行孵育时，只有酪氨酸（Tyr）和色氨酸（Trp）会产生显著的化学发光。观察到的光强度、氧化过程的速率与底物浓度之间的关系很复杂，无法用涉及两个过氧自由基的终止过程中激发态的形成（拉塞尔机制）来解释。对于Trp和Tyr，观察到的发光随孵育时间的增加，这表明在导致激发分子产生的途径中，有不止一种反应产物作为中间体参与其中。然而，在产物积累后，观察到的大部分发光会被添加的生育三烯酚淬灭，这一事实意味着主要的化学发光过程必定涉及产物与自由基的相互作用。从添加依布硒啉的效果来看，有人提出在反应过程中形成的氢过氧化物和过氧化物是中间体，它们的积累导致观察到的化学发光随时间增加。观察到的时间曲线和提出的机制与复杂生物系统氧化相关的情况非常相似，这表明蛋白质氧化可能是生物氧化中化学发光的主要来源之一。
