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. 2021 Jul 28;23(29):15557-15563. doi: 10.1039/d1cp01517f.
The deactivation of singlet oxygen, the lowest electronic excited state of molecular oxygen, by proteins is usually described through the interaction of singlet oxygen with certain amino acids. Changes in accessibility of these amino acids influence the quenching rate and the phosphorescence kinetics of singlet oxygen. In the cellular environment, however, numerous proteins with covalently bound or encapsulated cofactors are present. These cofactors could also influence the deactivation of singlet oxygen, and these have received little attention. To confront this issue, we used cytochrome c (cyt c) and apocytochrome c (apocyt c) to illustrate how the heme prosthetic group influences the rate constant of singlet oxygen deactivation upon acidic pH-induced conformational change of cyt c. Photo-excited flavin mononucleotide (FMN) was used to produce singlet oxygen. Our data show that the heme group has a significant and measurable effect on singlet oxygen quenching when the heme is exposed to solvents and is therefore more accessible to singlet oxygen. The effect of amino acids and heme accessibility on the FMN triplet state deactivation was also investigated.
蛋白质使单线态氧（分子氧的最低电子激发态）失活通常通过单线态氧与某些氨基酸的相互作用来描述。这些氨基酸的可及性变化会影响单线态氧的猝灭速率和磷光动力学。然而，在细胞环境中，存在许多带有共价结合或封装辅因子的蛋白质。这些辅因子也可能影响单线态氧的失活，但它们很少受到关注。为了应对这个问题，我们使用细胞色素 c（cyt c）和脱细胞色素 c（apocyt c）来说明血红素辅基如何影响 cyt c 酸性 pH 诱导构象变化时单线态氧失活的速率常数。使用黄素单核苷酸（FMN）光激发来产生单线态氧。我们的数据表明，当血红素暴露于溶剂中并且更容易与单线态氧接触时，血红素对单线态氧猝灭有显著且可测量的影响。还研究了氨基酸和血红素可及性对 FMN 三重态失活的影响。
