Department of Biophysics, Faculty of Science, P. J. Šafárik University in Košice, Jesenná 5, 041 54 Košice, Slovakia.
Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia.
Phys Chem Chem Phys. 2022 Jun 1;24(21):13317-13324. doi: 10.1039/d2cp01281b.
Singlet oxygen refers to the nonradical metastable excited state of molecular oxygen that readily oxidizes various cellular components. Its behavior in different biological systems has been studied for many years. Recently, we analyzed the effect of singlet oxygen quenching by heme cofactor in cytochrome (cyt ). Here, we have exploited this effect in the investigation of conformational differences in the molten globule states of cyt induced by different sodium anions, namely sulfate, chloride and perchlorate. The high efficiency of heme toward quenching singlet oxygen enabled us to use this property for the analysis of the otherwise experimentally difficult-to-determine parameter of heme upon exposure to solvents as highly similar conformational states of cyt in the molten globule states are induced by different salts at acidic pH. Our results from singlet oxygen quenching experiments correlate well with other spectroscopic methods, such as circular dichroism and fluorescence measurements, and suggest increasing availability of heme in the order: perchlorate < chloride < sulfate. Based on our findings we propose that singlet oxygen phosphorescence measurements are useful in determining the differences in the protein conformation of their heme regions, particularly regarding the relative heme exposure to the solvent.
单线态氧是指分子氧的非自由基亚稳态激发态，它容易氧化各种细胞成分。多年来，人们一直在研究它在不同生物系统中的行为。最近，我们分析了细胞色素（cyt）中血红素辅因子对单线态氧的猝灭作用。在这里，我们利用这一效应研究了不同的钠离子，即硫酸盐、氯化物和高氯酸盐，诱导的细胞色素（cyt）的无规卷曲状态下构象差异。血红素对单线态氧的高效猝灭作用使我们能够利用这一特性来分析血红素在暴露于溶剂时的实验上难以确定的参数，因为在酸性 pH 下，不同的盐诱导的细胞色素（cyt）的无规卷曲状态具有非常相似的构象。我们的单线态氧猝灭实验结果与圆二色性和荧光测量等其他光谱方法很好地相关，并表明血红素的可用性按以下顺序增加：高氯酸盐<氯化物<硫酸盐。基于我们的发现，我们提出单线态氧磷光测量可用于确定其血红素区域的蛋白质构象差异，特别是关于血红素相对于溶剂的相对暴露程度。
