Department of Biophysics, Medical School, University of Pecs, Szigeti Str. 12, 7624, Pecs, Hungary.
Laboratoire d'Optique et Biosciences, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128, Palaiseau, France.
Photochem Photobiol Sci. 2021 Mar;20(3):369-378. doi: 10.1007/s43630-021-00024-y. Epub 2021 Feb 22.
Tryptophan and tyrosine radical intermediates play crucial roles in many biological charge transfer processes. Particularly in flavoprotein photochemistry, short-lived reaction intermediates can be studied by the complementary techniques of ultrafast visible and infrared spectroscopy. The spectral properties of tryptophan radical are well established, and the formation of neutral tyrosine radicals has been observed in many biological processes. However, only recently, the formation of a cation tyrosine radical was observed by transient visible spectroscopy in a few systems. Here, we assigned the infrared vibrational markers of the cationic and neutral tyrosine radical at 1483 and 1502 cm (in deuterated buffer), respectively, in a variant of the bacterial methyl transferase TrmFO, and in the native glucose oxidase. In addition, we studied a mutant of AppABLUF blue-light sensor domain from Rhodobacter sphaeroides in which only a direct formation of the neutral radical was observed. Our studies highlight the exquisite sensitivity of transient infrared spectroscopy to low concentrations of specific radicals.
色氨酸和酪氨酸自由基中间体在许多生物电荷转移过程中起着至关重要的作用。特别是在黄素蛋白光化学中，可以通过超快可见和红外光谱的互补技术来研究短寿命反应中间体。色氨酸自由基的光谱性质已经得到很好的确立，并且在许多生物过程中已经观察到中性酪氨酸自由基的形成。然而，直到最近，在少数系统中通过瞬态可见光谱才观察到阳离子酪氨酸自由基的形成。在这里，我们在细菌甲基转移酶 TrmFO 的变体和天然葡萄糖氧化酶中分别分配了在 1483 和 1502 cm 处的阳离子和中性酪氨酸自由基的红外振动标记（在氘化缓冲液中）。此外，我们研究了来自球形红杆菌的 AppABLUF 蓝光传感器结构域的突变体，其中仅观察到中性自由基的直接形成。我们的研究强调了瞬态红外光谱对特定自由基低浓度的极高灵敏度。
