Photo processes on self-associated cationic porphyrins and plastocyanin complexes 1. Ligation of plastocyanin tyrosine 83 onto metalloporphyrins and electron-transfer fluorescence quenching.
Photo processes on self-associated cationic porphyrins and plastocyanin complexes 1. Ligation of plastocyanin tyrosine 83 onto metalloporphyrins and electron-transfer fluorescence quenching.
复制标题
自缔合阳离子卟啉和质体蓝素复合物的光过程 1. 将质体蓝素酪氨酸 83 连接到金属卟啉上并进行电子转移荧光猝灭。
DOI：
10.1021/jp054712t
复制
发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Rodgers,MichaelAJ
中科院分区：
文献类型：
--
作者：
Anula,HewaM;Myshkin,Eugene;Guliaev,Anton;Luman,Charles;Danilov,EvgenyO;Castellano,FelixN;Bullerjahn,GeorgeS;Rodgers,MichaelAJ
本文研究了菠菜质体蓝素的阴离子表面对接位点与阳离子金属卟啉（其中酪氨酸83（Y83）部分位于对接位点的正下方）四（N-甲基-4-吡啶基）卟啉（Pd（II）TMPyP 4+和Zn（II）TMPyP 4+）之间形成的自缔合复合物的光谱性质。Zn（II）TMPyP 4 +/质体蓝素自组装复合物的荧光猝灭现象也被发现。观察到的红移的Soret和Q带的紫外可见光谱，约。9 nm的Pd（II）TMPyP 4 +/质体蓝素和约. 6 nm的Zn（II）TMPyP 4 +/plastocyanin复合物，解释了激子理论耦合Gouterman模型。因此，自缔合质体蓝素/阳离子卟啉复合物的Y83残基的羟基苯基末端与这些金属卟啉的中心金属原子的电荷转移连接有牵连。此外，Pd（II）TMPyP 4+与Y83突变体质体蓝素（Y83 F-PC）系统之间的基态光谱结合研究证明，质体蓝素的Y83部分在此类离子对复合物的形成中发挥了关键作用。差示吸收光谱和Job’s作图表明，在低离子强度缓冲液、1 mM KCl和1 mM磷酸盐缓冲液（pH 7.4）中，阳离子卟啉与邻近Y83残基的质体蓝素阴离子片之间的静电吸引导致了基态自缔合1：1络合物的形成，该络合物具有显著的高结合常数（Pd（II）TMPyP 4+和锌变体的K值分别为（8.0 ± 1.1）× 105 M ~（-1）和（2.7 ± 0.8）× 106 M ~（-1））。分子模拟计算支持形成1：1的自缔合复合物之间的卟啉和质体蓝素的平均距离约为。在卟啉和Y83的质量中心之间的约9 μ m处，Y83恰好位于蛋白质表面上的阴离子表面对接位点的后面。光激发单重态的Zn（II）TMPyP 4+淬灭的Y83残基的自相关质体蓝素在静态机制证明了稳态和时间分辨荧光实验。即使当所有的卟啉络合（超过97%），观察到显着的残留荧光从复合物，这样的猝灭的振幅的单重态的未络合的物种是极大地模糊。
The spectroscopic properties of the self-associated complexes formed between the anionic surface docking site of spinach plastocyanin and the cationic metalloporphyrins, in which the tyrosine 83 (Y83) moiety is placed just below the docking site, tetrakis(N-methyl-4-pyridyl)porphyrin (Pd(II)TMPyP4+and Zn(II)TMPyP4+), have been studied and reported herein. The fluorescence quenching phenomenon of the self-assembled complex of Zn(II)TMPyP4+/plastocyanin has also been discovered. The observed red-shifting of the Soret and Q-bands of the UV−visible spectra, ca. 9 nm for Pd(II)TMPyP4+/plastocyanin and ca. 6 nm for the Zn(II)TMPyP4+/plastocyanin complexes, was explained in terms of exciton theory coupled with the Gouterman model. Thus, the hydroxyphenyl terminus of the Y83 residue of the self-associated plastocyanin/cationic porphyrin complexes was implicated in the charge-transfer ligation with the central metal atoms of these metalloporphyrins. Moreover, ground-state spectrometric-binding studies between Pd(II)TMPyP4+and the Y83 mutant plastocyanin (Y83F-PC) system proved that Y83 moiety of plastocyanin played a critical role in the formation of such ion-pair complexes. Difference absorption spectra and the Job's plots showed that the electrostatic attractions between the cationic porphyrins and the anionic patch of plastocyanin, bearing the nearby Y83 residue, led to thepredominantformation of a self-associated 1:1 complexin the ground-state with significantly high binding constants (K= (8.0 ± 1.1) × 105M-1and (2.7 ± 0.8) × 106M-1for Pd(II)TMPyP4+and zinc variant, respectively) in low ionic strength buffer, 1 mM KCl and 1 mM phosphate buffer (pH 7.4). Molecular modeling calculations supported the formation of a 1:1 self-associated complex between the porphyrin and plastocyanin with an average distance of ca. 9 Å between the centers of mass of the porphyrin and Y83 positioned just behind the anionic surface docking site on the protein surface. The photoexcited singlet state of Zn(II)TMPyP4+was quenched by the Y83 residue of the self-associated plastocyanin in a static mechanism as evidenced by steady-state and time-resolved fluorescence experiments. Even when all the porphyrin was complexed (more than 97%), significant residual fluorescence from the complex was observed such that the amplitude of quenching of the singlet state of uncomplexed species was enormously obscured.