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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Reaction of Protonated Tyrosine with Electronically Excited Singlet Molecular Oxygen (a1Δg): An Experimental and Trajectory Study
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Reaction of Protonated Tyrosine with Electronically Excited Singlet Molecular Oxygen (a1Δg): An Experimental and Trajectory Study

机译：质子化酪氨酸与电子激发单线态分子氧（a1Δg）的反应：实验和轨迹研究

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摘要

Reaction of protonated tyrosine with the lowest electronically excited singlet state of molecular oxygen, 1O2 (a1Δg), is reported over the center-of-mass collision energy (Ecol) range from 0.1 to 3.0 eV, using an electrosprayionization, guided-ion-beam scattering instrument, in conjunction with ab initio electronic structure calculations and direct dynamics trajectory simulations. Only one product channel is observed, corresponding to generation of hydrogen peroxide via transfer of two hydrogen atoms from protonated tyrosine. Despite being exoergic, the reaction is in competition with physical quenching of 1O2 and is very inefficient. At low Ecol, the reaction may be mediated by intermediate complexes and shows strong inhibition by collision energy. At high Ecol, the reaction efficiency drops to 1% and starts to have contribution from a direct mechanism. Quasi-classical trajectory simulations were performed to probe the mechanism at high collision energies. Analysis of trajectories shows that, at Ecol of 3.0 eV, a small fraction of hydrogen peroxide (25%) is produced via a direct, concerted mechanism where two hydrogen atoms are transferred simultaneously, but most hydrogen peroxide (75%) is formed by dissociation of hydroperoxide intermediates. According to ab initio calculations and trajectory simulations, collisions also lead to formation of various endoperoxides, and dissociation of endoperoxides may play a role in physical quenching of 1O2. The apparatus and experimental techniques are described in detail.
机译：据报道，质子化酪氨酸与分子氧的最低电子激发单重态1O2（a1Δg）的反应在质量中心碰撞能量（Ecol）为0.1到3.0 eV的范围内，使用电喷雾，引导离子束散射仪，结合从头算起的电子结构计算和直接动力学轨迹模拟。仅观察到一个产物通道，其对应于通过质子化酪氨酸转移两个氢原子产生过氧化氢。尽管放热，该反应与1O2的物理淬灭竞争，并且效率很低。在低Ecol下，该反应可能由中间配合物介导，并显示出被碰撞能量的强烈抑制作用。在高Ecol下，反应效率下降至1％，并且开始由直接机理做出贡献。进行了准经典轨迹模拟，以探讨在高碰撞能量下的机理。轨迹分析表明，在3.0 eV的Ecol下，通过直接协调的机制产生了小部分过氧化氢（25％），其中两个氢原子同时转移，但是大多数过氧化氢（75％）是通过解离形成的氢过氧化物中间体。根据从头算和轨迹模拟，碰撞还会导致形成各种内过氧化物，并且内过氧化物的离解可能在1O2的物理淬灭中起作用。详细描述了仪器和实验技术。

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