Bilokin' Mykhailo D, Shvadchak Volodymyr V, Yushchenko Dmytro A, Duportail Guy, Mély Yves, Pivovarenko Vasyl G
Organic Chemistry Department, Chemistry Faculty, National Taras Shevchenko University of Kyiv, Kyiv, 01601, Ukraine.
J Fluoresc. 2009 May;19(3):545-53. doi: 10.1007/s10895-008-0443-x. Epub 2008 Nov 20.
3-Hydroxyquinolones (3HQs) are a new class of water soluble dual fluorescence probes that can monitor both polarity and basicity (H-bond accepting ability) parameters. Both parameters play an important role in proteins and lipid membranes. Nevertheless, no method exists actually to measure the basicity parameter separately from the polarity. To achieve this aim, we synthesized 2-benzofuryl-3-hydroxy-4(1H)-quinolone (3HQ-Bf) and characterized its photophysical properties by UV, steady-state and time-resolved fluorescence spectroscopy. Due to its extended conjugation and totally planar conformation, 3HQ-Bf is characterized by a high fluorescence quantum yield. In solution, this dye shows an excited state intramolecular proton transfer (ESIPT) reaction resulting in two tautomer bands in the emission spectra. The ESIPT reaction can be considered as irreversible and is governed by rate constants from 0.6 to 8 x 10(9) s(-1), depending on the solvent. The analysis of the spectral properties of 3HQ-Bf in a series of organic solvents revealed a marginal sensitivity to the solvent polarity, but an exquisite sensitivity to solvent basicity, as shown by the linear dependence of the logarithm of the emission bands intensity ratio, log(I(N*)/I(T*)), as well as the absorption or emission maxima wavenumbers as a function of the solvent basicity parameter. This probe may find useful applications through coupling to a protein ligand, for characterizing the H-bond acceptor ability at the ligand binding site as well as for studying the basicity changes of lipid membranes during their chemo- and thermotropic conversions.
3-羟基喹诺酮（3HQs）是一类新型的水溶性双荧光探针，可监测极性和碱性（氢键接受能力）参数。这两个参数在蛋白质和脂质膜中都起着重要作用。然而，目前实际上不存在将碱性参数与极性分开测量的方法。为了实现这一目标，我们合成了2-苯并呋喃基-3-羟基-4（1H）-喹诺酮（3HQ-Bf），并通过紫外、稳态和时间分辨荧光光谱对其光物理性质进行了表征。由于其共轭扩展和完全平面构象，3HQ-Bf具有高荧光量子产率。在溶液中，这种染料表现出激发态分子内质子转移（ESIPT）反应，导致发射光谱中出现两个互变异构体带。ESIPT反应可被视为不可逆反应，其速率常数在 0.6 至8×10⁹ s⁻¹之间，具体取决于溶剂。对3HQ-Bf在一系列有机溶剂中的光谱性质分析表明，其对溶剂极性的敏感性较低，但对溶剂碱性极为敏感，这表现为发射带强度比log（I（N*）/I（T*））的对数以及吸收或发射最大值波数与溶剂碱性参数的线性关系。通过与蛋白质配体偶联，该探针可能会有有用的应用，用于表征配体结合位点的氢键接受能力，以及研究脂质膜在化学和热致转变过程中的碱性变化。
