Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra
Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra
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DOI：
10.1021/jp0519722
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发表时间：
2005-07-07
影响因子：
2.9
通讯作者：
Arai, T
中科院分区：
文献类型：
--
作者：
Murakami, M;Maeda, K;Arai, T
利用磁场效应（MFE）对瞬态吸收（TA）光谱研究了黄素腺嘌呤二核苷酸（FAD）分子在光照射下的分子内电子转移反应中间体动力学。MFE的存在时间和MFE的作用谱与溶液的pH有很强的相关性。MFE作用谱表明黄素部分存在自由基对与阳离子形式的三重态激发态相互转化。通过MFE作用谱和TA的衰变动力学分析确定了三重态和自由基对的所有速率常数。得到的相互转换值表明，阳离子自由基的形成促进了反向电子转移反应到三重态激发态。此外，通过不同pH下MFE的时间谱研究了自旋弛豫和复合的速率常数，得到了这两个因子的剧烈变化，并可以用在pH > 2.5下形成堆叠构象引起的SOC（自旋轨道耦合）诱导的反向电子转移来解释。
The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.