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首页> 外文期刊>Applied Magnetic Resonance >CIDEP Created by the Quenching of Photo-Excited Tryptophan at Protein Surface: A Challenge to CIDEP Probing of Protein Structural Changes
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CIDEP Created by the Quenching of Photo-Excited Tryptophan at Protein Surface: A Challenge to CIDEP Probing of Protein Structural Changes

机译：CIDEP由光激发色氨酸在蛋白质表面的淬灭而创建：对CIDEP探测蛋白质结构变化的挑战

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摘要

Quenching of the triplet excited state of molecular tryptophan by nitroxide radical in 1,4-dioxane and water solutions was investigated by means of time-resolved electron paramagnetic resonance (EPR) and Fourier-transform (FT)-EPR. The chemically induced dynamic electron polarization (CIDEP) signals with net emissive phase were recorded at these quenching events and were analyzed through radical-triplet pair mechanism. The CIDEP time profiles were well reproduced by Bloch and kinetic equations, assuming radical-triplet pair mechanism with the appropriate quenching rate constants. From a comparison of the simulation and the experiment, CIDEP enhancement factor in 1,4-dioxane was determined to be −30 × P eq, where P eq is the spin polarization of nitroxide at thermal equilibrium. Net emissive CIDEP was also observed by FT-EPR measurements on the nitroxide quenching of the triplet excited state of tryptophan residue in α-lactalbumin. Magnitude of CIDEP created in α-lactalbuminitroxide system depends on the pH condition of α-lactalbumin solution, which is related to protein folding dynamics. We argue the CIDEP mechanism at the α-lactalbumin surface and propose a possibility of a novel CIDEP method to probe a protein surface and structural changes.
机译：通过时间分辨电子顺磁共振（EPR）和傅里叶变换（FT）-EPR研究了1,4-二恶烷和水溶液中亚硝酸根对分子色氨酸三重激发态的猝灭。在这些猝灭事件中记录了具有净发射相的化学诱导动态电子极化（CIDEP）信号，并通过自由基-三重态对机理进行了分析。假设自由基-三重态对机制具有适当的淬灭速率常数，则通过Bloch和动力学方程可以很好地再现CIDEP时间曲线。通过模拟和实验的比较，确定1,4-二恶烷中CIDEP增强因子为−30×P eq ，其中P eq 为自旋极化热平衡下的氮氧化物含量通过FT-EPR测量，α-乳清蛋白中色氨酸残基三重激发态的氮氧化物猝灭也观察到净发射CIDEP。在α-乳白蛋白/氮氧化物系统中产生的CIDEP的大小取决于α-乳白蛋白溶液的pH条件，这与蛋白质折叠动力学有关。我们争论α-乳白蛋白表面的CIDEP机制，并提出了一种新颖的CIDEP方法来探测蛋白质表面和结构变化的可能性。

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