Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Mar 5;192:146-152. doi: 10.1016/j.saa.2017.11.017. Epub 2017 Nov 7.
Oxidative stress biomarkers, including glutathione (GSH) and related compounds, are involved in a variety of interactions enabling redox potential maintenance in living cells and protection against radicals. Since the oxidative stress is promoting and, in many cases, inducing serious illnesses, monitoring of GSH levels can aid in diagnostics and disease prevention. Herein, we report on the discovery of the formation of a supramolecular ensemble of GSH with fluorone black (9-phenyl fluorone, FB) which is optically active and enables sensitive determination of GSH by resonance elastic light scattering (RELS). We have found that supramolecular interactions of GSH with FB can be probed with spectroscopic, RELS, and electrochemical methods. Our investigations show that RELS intensity for FB solutions increases with GSH concentration while fluorescence emission of FB is not affected, as quenching begins only above 0.8mM GSH. The UV-Vis difference spectra show a positive peak at 383nm and a negative peak at 458nm, indicating a higher-energy absorbing complex in comparison to the non-bonded FB host. Supramolecular interactions of FB with GSH have also been corroborated by electrochemical measurements involving two configurations of FB-GSH ensembles on electrodes: (i) an inverted orientation on Au-coated quartz crystal piezoelectrode (Au@SG-FB), with strong thiolate bonding to gold, and (ii) a non-inverted orientation on glassy carbon electrode (GCE@FB-GS), with weak π-π stacking attachment and efficient charge mediation through the ensemble. The formation of a supramolecular ensemble with hydrogen bonding has also been confirmed by quantum mechanical calculations. The discovery of supramolecular FB-GSH ensemble formation enables elucidating the mechanisms of strong RELS responses, changes in UV-Vis absorption spectra, and the electrochemical reactivity. Also, it provides new insights to the understanding of the efficient charge-transfer in redox potential homeostasis which is likely based on an intermediate formation of a similar type of supramolecular ensembles.
氧化应激生物标志物，包括谷胱甘肽（GSH）和相关化合物，参与了各种相互作用，使活细胞中的氧化还原电位得以维持，并防止自由基的侵害。由于氧化应激会促进，而且在许多情况下会引发严重疾病，因此监测 GSH 水平可以帮助进行诊断和疾病预防。在此，我们报告了发现 GSH 与氟酮黑（9-苯基氟酮，FB）形成超分子聚集体的情况，该聚集体具有光学活性，能够通过共振弹性光散射（RELS）灵敏地测定 GSH。我们发现，GSH 与 FB 的超分子相互作用可以通过光谱学、RELS 和电化学方法进行探测。我们的研究表明，随着 GSH 浓度的增加，FB 溶液的 RELS 强度增加，而 FB 的荧光发射不受影响，因为仅在 0.8mM GSH 以上才开始猝灭。紫外可见差光谱显示在 383nm 处有一个正峰，在 458nm 处有一个负峰，表明与非键合的 FB 主体相比，形成了具有更高能量吸收的复合物。通过涉及 FB-GSH 聚集体在电极上的两种构型的电化学测量，也证实了 FB 与 GSH 的超分子相互作用：（i）在 Au 涂覆的石英晶体压电电极（Au@SG-FB）上的倒置取向，与金形成强硫醇键，以及（ii）在玻璃碳电极（GCE@FB-GS）上的非倒置取向，具有较弱的π-π堆积附着和通过聚集体进行的有效电荷中介。氢键形成的超分子聚集体也通过量子力学计算得到了证实。发现 FB-GSH 超分子聚集体的形成，使我们能够阐明强 RELS 响应、紫外可见吸收光谱变化和电化学反应性的机制。此外，它为理解氧化还原电位动态平衡中的有效电荷转移提供了新的见解，这可能基于类似类型的超分子聚集体的中间形成。
