Many studies have shown that glutathione (GSH) and cysteine (Cys)/homocysteine (Hcy) levels are interrelated in biological systems. To unravel the complicated biomedical mechanisms by which GSH and Cys/Hcy are involved in various disease states, probes that display distinct signals in response to GSH and Cys/Hcy are highly desirable. In this work, we report a rhodol thioester (1) that responds to GSH and Cys/Hcy with distinct fluorescence emissions in neutral media. Probe 1 reacts with Cys/Hcy to form the corresponding deconjugated spirolactam via a tandem native chemical ligation (NCL) reaction. This intramolecular spirocyclization leads to the “quinone–phenol” transduction of rhodol dyes, and an excited-state intramolecular proton transfer (ESIPT) process between the phenolic hydroxyl proton and the aromatic nitrogen in the benzothiazole unit occurs upon photoexcitation, thus affording 2-(2′-hydroxyphenyl) benzothiazole (HBT) emission (454 nm). In the case of the tripeptide GSH, only transthioesterification takes place removing the intramolecular photo-induced electron transfer (PET) process caused by the electron deficient 4-nitrobenzene moiety giving rise to a large fluorescence enhancement at the rhodol emission band (587 nm). The simultaneous detection of GSH and Cys/Hcy is attributed to the significantly different rates of intramolecular S,N-acyl shift of their corresponding thioester adducts derived from 1. The utility of probe 1 has been demonstrated in various biological systems including serum and cells.
许多研究表明,
谷胱甘肽 (GSH) 和半胱
氨酸 (Cys)/同型半胱
氨酸 (Hcy)
水平在
生物系统中是相互关联的。为了揭示 GSH 和 Cys/Hcy 参与各种疾病状态的复杂
生物医学机制,非常需要能够响应 GSH 和 Cys/Hcy 发出不同信号的探针。在这项工作中,我们报道了一种
对甲酚硫酯 (1),它可以在中性介质中响应 GSH 和 Cys/Hcy,并发出明显的荧光发射。探针 1 通过串联天然
化学连接 (NCL) 反应与 Cys/Hcy 反应形成相应的去共轭螺内酰胺。这种分子内螺环化导致
对甲酚染料的“醌-
苯酚”转导,并且在光激发下
酚羟基质子和
苯并噻唑单元中的芳香族氮之间发生激发态分子内质子转移(ESI
PT)过程,从而提供2-( 2'-羟基苯基)
苯并噻唑 (HBT) 发射 (454 nm)。就三肽 GSH 而言,仅发生转
硫酯化,消除了由缺电子 4-
硝基苯部分引起的分子内光诱导电子转移 (PET) 过程,从而在
对甲氨基酚发射带 (587 nm) 处产生较大的荧光增强。 GSH 和 Cys/Hcy 的同时检测归因于源自 1 的相应
硫酯加合物的分子内 S,N-酰基转移速率显着不同。探针 1 的实用性已在包括血清和细胞在内的各种
生物系统中得到证明。