Cysteine is an important amino acid that is related to human health and food safety. How to effectively detect Cys in food has received widespread attention. Compared with other methods, fluorescent probes have the advantages of simple operation, high sensitivity, and good selectivity. Therefore, a selective fluorescence probe 2 for Cys in food was designed and synthesized. Probe 2 employed the acrylate group as a thiol-recognition site for Cys, which endowed probe 2 with better selectivity for Cys over Hcy and GSH. The recognition pathway underwent Michael addition, intramolecular cyclization, and concomitant release of the piperideine-based fluorophore, along with a chromogenic change from yellow to orange. This pathway was supported by ¹H NMR analysis and DFT calculations. In addition, probe 2 displays a linear response to Cys concentrations (0–30 μM), low detection limit (0.89 μM), and large Stokes shift (125 nm). Overall, probe 2 showed great application potential for the quantitative determination of Cys in water, milk, cucumber, pear and tomato.

中文翻译：

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一种具有大斯托克斯位移的新型荧光探针，用于比色和选择性检测水、牛奶、黄瓜、梨和番茄中的半胱氨酸

半胱氨酸是一种重要的氨基酸，关系到人类健康和食品安全。如何有效检测食品中的Cys受到广泛关注。与其他方法相比，荧光探针具有操作简单、灵敏度高、选择性好等优点。因此，设计并合成了食品中Cys的选择性荧光探针2 。探针2采用丙烯酸酯基团作为Cys的硫醇识别位点，这使得探针2对Cys的选择性优于Hcy和GSH。识别途径经历了迈克尔加成、分子内环化和伴随的基于哌啶的荧光团的释放，以及从黄色到橙色的显色变化。该途径得到¹ H NMR 分析和 DFT 计算的支持。此外，探针2显示出对 Cys 浓度 (0–30 μM) 的线性响应、低检测限 (0.89 μM) 和大斯托克斯位移 (125 nm)。总体而言，探针2在水、牛奶、黄瓜、梨和番茄中半胱氨酸的定量测定方面显示出巨大的应用潜力。