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首页> 外文期刊>Biochemistry >Photoinduced electron transfer in singly labeled thiouredopyrenetrisulfonate cytochrome c derivatives
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Photoinduced electron transfer in singly labeled thiouredopyrenetrisulfonate cytochrome c derivatives

机译：单标记的硫代尿嘧啶氢磺酸磺酸盐细胞色素c衍生物中的光诱导电子转移

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摘要

A novel method for initiation of intramolecular electron transfer reactions in cytochrome c is reported. The method is based on photoexcitation of covalently attached thiouredopyrenetrisulfonate (TUPS) by the third harmonic frequency of a Nd:YAG laser (355 nm), the reaction that generates the low-potential triplet state of the dye with high quantum efficiency. TUPS derivatives of horse heart cytochrome c singly labeled at specific lysine residues were prepared and purified to homogeneity by ion-exchange high-pressure liquid chromatography. Eight derivatives were characterized by determination of the location of the modification, reduction potentials, and measurement of enzymatic activity with cytochrome oxidase. Transient absorption spectroscopy was used to directly measure the rate constants for the electron transfer reaction from the photoexcited triplet state of TUPS to the oxidized heme group and the back reaction from the ferrous heme to the oxidized dye. For all singly labeled derivatives, the rate constants for heme reduction were 1 or 2 orders of magnitude larger than for its reoxidation, consistent with the greater thermodynamic driving force for the oxidation reaction. Analysis of the variation of electron-transfer rates with the distance separating the dye and the heme reveals a value of coupling decay constant (beta) of 0.46 A-1. Rapid and effective photoreduction of cytochrome c makes it a useful tool for fast initiation of electron transfer in the reductive direction within complexes of cytochrome c with other redox proteins.
机译：报道了一种在细胞色素c中引发分子内电子转移反应的新方法。该方法是基于Nd：YAG激光的三次谐波频率（355 nm）对共价连接的硫脲基吡咯烷磺酸盐（TUPS）进行光激发，该反应产生具有高量子效率的染料低电势三重态。制备了在特定赖氨酸残基上单独标记的马心脏细胞色素TUPS衍生物，并通过离子交换高压液相色谱纯化至同质。通过确定修饰的位置，还原电位和使用细胞色素氧化酶测量酶活性来表征八种衍生物。瞬态吸收光谱法用于直接测量从TUPS的光激发三重态到氧化血红素基团的电子转移反应的速率常数，以及从亚铁血红素到氧化染料的逆反应的速率常数。对于所有单标记的衍生物，血红素还原的速率常数比其再氧化的速率常数大1或2个数量级，这与氧化反应的更大的热力学驱动力一致。分析电子传输速率随染料和血红素之间的距离的变化，发现耦合衰减常数β为0.46 A-1。细胞色素c的快速有效的光还原使其成为在细胞色素c与其他氧化还原蛋白复合物内沿还原方向快速启动电子转移的有用工具。

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