Institute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gdańsk, Wita Stwosza 57, 80-308 Gdańsk, Poland.
Int J Mol Sci. 2021 Oct 28;22(21):11705. doi: 10.3390/ijms222111705.
The nature and mechanisms of interaction between two selected methyl benzoate derivatives (methyl -methoxy -methylaminobenzoate- and methyl -hydroxy -methylaminobenzoate-) and model transport protein bovine serum albumin (BSA) was studied using steady-state and time-resolved spectroscopic techniques. In order to understand the role of Trp residue of BSA in the -BSA and -BSA interaction, the effect of free Trp amino acid on the both emission modes (LE-locally excited ( and ) and ESIPT-excited state intramolecular proton transfer ()) was investigated as well. Experimental results show that the investigated interactions (with both BSA and Trp) are mostly conditioned by the ground and excited state complex formation processes. Both molecules form stable complexes with BSA and Trp (with 1:1 stoichiometry) in the ground and excited states. The binding constants were in the order of 10 M. The absorption- and fluorescence-titration experiments along with the time-resolved fluorescence measurements show that the binding of the and causes fluorescence quenching of BSA through the static mechanism, revealing a 1:1 interaction. The magnitude and the sign of the thermodynamic parameters, Δ, Δ, and Δ, determined from van't Hoff relationship, confirm the predominance of the hydrogen-bonding interactions for the binding phenomenon. To improve and complete knowledge of methyl benzoate derivative-protein interactions in relation to supramolecular solvation dynamics, the time-dependent fluorescence Stokes' shifts, represented by the normalized spectral response function , was studied. Our studies reveal that the solvation dynamics that occurs in subpicosecond time scale in neat solvents of different polarities is slowed down significantly when the organic molecule is transferred to BSA cavity.
采用稳态和时间分辨光谱技术研究了两种选定的苯甲酸甲酯衍生物（甲氧基甲氨基苯甲酸甲酯和羟基甲氨基苯甲酸甲酯）与模型转运蛋白牛血清白蛋白（BSA）之间的相互作用性质和机制。为了了解 BSA 中色氨酸残基在 -BSA 和 -BSA 相互作用中的作用，还研究了游离色氨酸氨基酸对两种发射模式（局部激发（LE）和激发态分子内质子转移（ESIPT））的影响。实验结果表明，所研究的相互作用（与 BSA 和色氨酸都有关）主要受基态和激发态络合过程的影响。两种分子都与 BSA 和色氨酸在基态和激发态下形成稳定的 1:1 配合物（与 BSA 和色氨酸都有关）。结合常数在 10 M 左右。吸收和荧光滴定实验以及时间分辨荧光测量表明，和的结合通过静态机制导致 BSA 的荧光猝灭，表明存在 1:1 的相互作用。从范特霍夫关系确定的热力学参数 Δ、Δ 和 Δ 的大小和符号证实了氢键相互作用对结合现象的优势。为了提高和完善与超分子溶剂化动力学有关的苯甲酸甲酯衍生物-蛋白质相互作用的知识，研究了时间相关的荧光斯托克斯位移，用归一化光谱响应函数 表示。我们的研究表明，在不同极性的纯溶剂中发生在皮秒时间尺度内的溶剂化动力学在将有机分子转移到 BSA 腔时显著减慢。
