Surzhikova Darya P, Sukovatyi Lev A, Nemtseva Elena V, Esimbekova Elena N, Slyusareva Evgenia A
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, 660041 Krasnoyarsk, Russia.
Biophysics Department, Siberian Federal University, 660041 Krasnoyarsk, Russia.
Micromachines (Basel). 2023 Jul 18;14(7):1442. doi: 10.3390/mi14071442.
In this work, we considered the influence of viscogenic agents (glycerol, sucrose) as well as the temperature on the fluorescent characteristics of fluorescein at pH 6.5 in order to describe the acid-base status of local environment in terms of a spectrally detectable dianion-anion equilibrium. The protolytic equilibrium of fluorescein was found to depend on the solvent viscosity in a complex way. Whereas in the presence of sucrose the ratiometric signal of fluorescein (I/I) remains rather unchanged, the addition of glycerol (up to 40% /) results in the increase of the signal (up to 19%), that can be attributed to the different mechanisms of cosolvents effects on dye molecules in the ground state. Molecular dynamics of the dye in the presence of glycerol and sucrose revealed that the cosolvents preferentially interact with fluorescein monoanion and dianion, displacing water molecules from the local environment which in turn reduces the average number of the hydrogen bonds between xanthene ring of the dye and water molecules. The ratiometric signal demonstrates linear growth with the temperature in the range of 10-80 °C regardless of the presence of viscogenic agents. A linear correlation between the temperature sensitivity of the ratiometric signal and the change in the molar enthalpy of the proton dissociation reaction in buffer and viscous media was determined.
在这项工作中，我们考虑了致粘剂（甘油、蔗糖）以及温度对pH 6.5条件下荧光素荧光特性的影响，以便根据可光谱检测的二价阴离子-阴离子平衡来描述局部环境的酸碱状态。发现荧光素的质子解离平衡以复杂的方式依赖于溶剂粘度。在存在蔗糖的情况下，荧光素的比率信号（I/I）保持相当不变，而添加甘油（高达40%/）会导致信号增加（高达19%），这可归因于共溶剂对基态染料分子的不同作用机制。在甘油和蔗糖存在下染料的分子动力学表明，共溶剂优先与荧光素单阴离子和二价阴离子相互作用，将水分子从局部环境中取代，这反过来又减少了染料的呫吨环与水分子之间氢键的平均数量。无论是否存在致粘剂，比率信号在10-80°C范围内随温度呈线性增长。确定了比率信号的温度敏感性与缓冲液和粘性介质中质子解离反应的摩尔焓变化之间的线性相关性。
