Fluorescent probes are commonly used in studying G protein-coupled receptors in living cells; however their application to the whole animal receptor imaging is still challenging. To address this problem, we report the design and the synthesis of the first near-infrared emitting fluorogenic dimer with environment-sensitive folding. Due to the formation of non-fluorescent H-aggregates in an aqueous medium, the near-infrared fluorogenic dimer displays a strong turn-on response (up to 140-fold) in an apolar environment and exceptional brightness: 56% quantum yield and ≈444 000 M⁻¹ cm⁻¹ extinction coefficient. Grafted on a ligand of the oxytocin receptor, it allows the unprecedented background-free and target-specific imaging of the naturally expressed receptor in living mice.

中文翻译：

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近红外荧光二聚体可实现活小鼠内源性 GPCR 的无背景成像

荧光探针常用于研究活细胞中的 G 蛋白偶联受体；然而，它们在整个动物受体成像中的应用仍然具有挑战性。为了解决这个问题，我们报告了第一个具有环境敏感折叠的近红外发射荧光二聚体的设计和合成。由于在水性介质中形成非荧光 H 聚集体，近红外荧光二聚体在非极性环境中显示出强烈的开启响应（高达 140 倍）和异常亮度：56% 量子产率和 ≈ 444 000 M ^-1 cm ^-1消光系数。移植到催产素受体的配体上，它允许对活体小鼠中自然表达的受体进行前所未有的无背景和目标特异性成像。