可逆荧光探针用于亚硫酸根与双氧水检测的机制研究

Mechanism Study on Reversible Fluorescent Probes for the Detection of Sulfite and Hydrogen Peroxide

摘要: 亚硫酸根($S{O}_3^{2-}$ )与双氧水(H₂O₂)作为生物体内重要的活性氧与活性硫物种，其浓度变化与多种生理病理过程密切相关。开发高选择性、高灵敏度的检测方法对生物医学研究具有重要意义。本文通过理论计算系统研究了两种可逆荧光探针(probe-a和probe-b)检测$S{O}_3^{2-}$ 与H₂O₂的作用机制。结果表明，probe-a分子的最高占据分子轨道(HOMO)与最低未占据分子轨道(LUMO)均匀分布于整个分子结构，表现出明显的局域激发特性，在激发后产生较强的红色荧光(振子强度f = 0.86)；而probe-b经$S{O}_3^{2-}$ 作用后，HOMO与LUMO发生空间分离，分别定位于SO₃基团和分子主体部分，呈现典型的电荷转移激发特性，导致荧光强度显著减弱(振子强度f = 0.01)。平均局部离子化能(ALIE)分析证实，probe-b中SO₃基团具有强还原反应活性，是与H₂O₂发生氧化还原反应的关键位点。电子转移热图清晰展示了两种探针在激发过程中的电荷分布变化，为理解荧光响应机制提供了直接的理论依据。该研究不仅揭示了可逆荧光探针的设计原理，还为开发新型活性物种检测探针提供了重要的参考。

Abstract: Sulfite ($S{O}_3^{2-}$ ) and hydrogen peroxide (H₂O₂), as important reactive oxygen species and reactive sulfur species in organisms, their concentration changes are closely related to various physiological and pathological processes. Developing detection methods with high selectivity and sensitivity is of great significance for biomedical research. In this paper, the action mechanism of two reversible fluorescent probes (probe-a and probe-b) for the detection of $S{O}_3^{2-}$ and H₂O₂ was systematically studied by theoretical calculations. The results showed that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of probe-a molecule are uniformly distributed in the entire molecular structure, showing obvious local excitation characteristics, and strong red fluorescence is generated after excitation (oscillator strength f = 0.86). After probe-b is acted on by $S{O}_3^{2-}$ , HOMO and LUMO are spatially separated, locating in the SO₃ group and the main molecular part respectively, showing typical charge transfer excitation characteristics, leading to a significant decrease in fluorescence intensity (oscillator strength f = 0.01). Average Local Ionization Energy (ALIE) analysis confirmed that the SO₃ group in probe-b has strong reductive reaction activity and is the key site for redox reaction with H₂O₂. The electron transfer heat map clearly shows the changes in charge distribution of the two probes during the excitation process, providing a direct theoretical basis for understanding the fluorescence response mechanism. This study not only reveals the design principle of reversible fluorescent probes, but also provides an important reference for the development of new probes for the detection of reactive species.