Fluorescent probes for sensing fundamental properties of biomolecular environment, such as polarity and hydration, help to study assembly of lipids into biomembranes, sensing interactions of biomolecules and imaging physiological state of the cells. Here, we summarize major efforts in the development of probes based on two photophysical mechanisms: (i) an excited-state intramolecular charge transfer (ICT), which is represented by fluorescent solvatochromic dyes that shift their emission band maximum as a function of environment polarity and hydration; (ii) excited-state intramolecular proton transfer (ESIPT), with particular focus on 5-membered cyclic systems, represented by 3-hydroxyflavones, because they exhibit dual emission sensitive to the environment. For both ICT and ESIPT dyes, the design of the probes and their biological applications are summarized. Thus, dyes bearing amphiphilic anchors target lipid membranes and report their lipid organization, while targeting ligands direct them to specific organelles for sensing their local environment. The labels, amino acid and nucleic acid analogues inserted into biomolecules enable monitoring their interactions with membranes, proteins and nucleic acids. While ICT probes are relatively simple and robust environment-sensitive probes, ESIPT probes feature high information content due their dual emission. They constitute a powerful toolbox for addressing multitude of biological questions.

中文翻译：

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基于电荷和质子转移的荧光探针用于探测生物分子环境

用于感测生物分子环境的基本特性（例如极性和水合）的荧光探针有助于研究脂质组装成生物膜、感测生物分子的相互作用以及对细胞的生理状态进行成像。在这里，我们总结了基于两种光物理机制的探针开发方面的主要努力：（i）激发态分子内电荷转移（ICT），其以荧光溶剂化变色染料为代表，其发射带最大值作为环境极性的函数而变化和水合作用； （ii）激发态分子内质子转移（ESIPT），特别关注以3-羟基黄酮为代表的五元循环系统，因为它们表现出对环境敏感的双发射。对于 ICT 和 ESIPT 染料，总结了探针的设计及其生物学应用。因此，带有两亲锚的染料靶向脂质膜并报告其脂质组织，同时靶向配体将它们引导至特定细胞器以感知其局部环​​境。插入生物分子中的标记、氨基酸和核酸类似物能够监测它们与膜、蛋白质和核酸的相互作用。虽然 ICT 探头是相对简单且坚固的环境敏感探头，但 ESIPT 探头由于其双重发射而具有高信息含量。它们构成了解决众多生物学问题的强大工具箱。