Zanetti-Polzi Laura, Aschi Massimiliano, Amadei Andrea, Daidone Isabella
Department of Physical and Chemical Sciences, University of L'Aquila , via Vetoio (Coppito 1), 67010 L'Aquila, Italy.
Department of Chemical and Technological Sciences, University of Rome "Tor Vergata" , Via della Ricerca Scientifica, 00185 Rome, Italy.
J Phys Chem Lett. 2017 Jul 20;8(14):3321-3327. doi: 10.1021/acs.jpclett.7b01575. Epub 2017 Jul 7.
Flavoproteins, containing flavin chromophores, are enzymes capable of transferring electrons at very high speeds. The ultrafast photoinduced electron-transfer (ET) kinetics of riboflavin binding protein to the excited riboflavin was studied by femtosecond spectroscopy and found to occur within a few hundred femtoseconds [ Zhong and Zewail, Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 11867-11872 ]. This ultrafast kinetics was attributed to the presence of two aromatic rings that could transfer the electron to riboflavin: the side chains of tryptophan 156 and tyrosine 75. However, the underlying ET mechanism remained unclear. Here, using a hybrid quantum mechanical-molecular dynamics approach, we perform ET dynamics simulations taking into account the motion of the protein and the solvent upon ET. This approach reveals that ET occurs via a major reaction channel involving tyrosine 75 (83%) and a minor one involving tryptophan 156 (17%). We also show that the protein environment is designed to ensure the fast quenching of the riboflavin excited state.
含有黄素发色团的黄素蛋白是能够以非常高的速度转移电子的酶。通过飞秒光谱研究了核黄素结合蛋白与激发态核黄素之间超快的光诱导电子转移（ET）动力学，发现其在几百飞秒内发生[Zhong和Zewail，《美国国家科学院院刊》2001年，98卷，11867 - 11872页]。这种超快动力学归因于两个能够将电子转移至核黄素的芳香环的存在：色氨酸156和酪氨酸75的侧链。然而，潜在的电子转移机制仍不清楚。在此，我们使用量子力学 - 分子动力学混合方法，进行了考虑电子转移时蛋白质和溶剂运动的电子转移动力学模拟。该方法揭示电子转移通过一个涉及酪氨酸75的主要反应通道（83%）和一个涉及色氨酸156的次要反应通道（17%）发生。我们还表明蛋白质环境旨在确保核黄素激发态的快速猝灭。
