Chang Yongxin, Qin Haijuan, Wang Xue, Li Xiaopei, Li Minmin, Yang Hang, Xu Kuoxi, Qing Guangyan
Institute of Functional Organic Molecular Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, P. R. China.
Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China.
ACS Sens. 2020 Aug 28;5(8):2438-2447. doi: 10.1021/acssensors.0c00619. Epub 2020 Jul 23.
Molecular configuration strongly impacts on its functions; however, due to complicated and diverse configuration as well as easy and rapid conversion among various configurations, research of molecular configuration is extremely difficult. If the free rotation of a molecule could be "slowed down" or even "frozen" by an external stimulus, such as ultralow temperature, then one configuration of the molecule could be captured and characterized relatively easily. Here, we show that the rotation of a hemicyanine-labeled 2-(2'-hydroxyphenyl)-4-methyloxazole (H-HPMO) molecule could be specifically and reversibly restricted by sequential additions of copper ion (Cu) and pyrophosphate (PO), reflecting as remarkable fluorescence quenching and recovery, which could be directly observed by naked eyes. Binding affinity tests and cryogenic H NMR indicate that Cu forms intensive coordinate bonds with phenolic hydroxyl, oxazole, and methoxyl groups of HPMO, which strongly restricts the free rotations of these groups and blocks charge transfer. This study provides a precise, rapid, visible, reversible, and low-cost method to monitor the molecular configuration, indicating the broad application prospects of near-infrared fluorescent sensors in configuration analysis, biosensing, and drug-substrate complexation.
分子构型对其功能有强烈影响；然而，由于分子构型复杂多样且能在各种构型之间轻易快速转换，分子构型的研究极其困难。如果分子的自由旋转能够通过外部刺激（如超低温）“减慢”甚至“冻结”，那么分子的一种构型就能够相对容易地被捕获和表征。在此，我们表明，通过依次添加铜离子（Cu）和焦磷酸（PO），半花菁标记的2-(2'-羟基苯基)-4-甲基恶唑（H-HPMO）分子的旋转能够被特异性且可逆地限制，表现为显著的荧光猝灭和恢复，这能够直接用肉眼观察到。结合亲和力测试和低温核磁共振表明，Cu与HPMO的酚羟基、恶唑基和甲氧基形成强配位键，这强烈限制了这些基团的自由旋转并阻断了电荷转移。本研究提供了一种精确、快速、可见、可逆且低成本的监测分子构型的方法，表明近红外荧光传感器在构型分析、生物传感和药物-底物络合方面具有广阔的应用前景。
