The interaction between mefloquine (MEF), the antimalarial drug, and human serum albumin (HSA), the main carrier protein in blood circulation, was explored using fluorescence, absorption, and circular dichroism spectroscopic techniques. Quenching of HSA fluorescence with MEF was characterized as static quenching and thus confirmed the complex formation between MEF and HSA. Association constant values for MEF-HSA interaction were found to fall within the range of 3.79-5.73 × 104 M-1 at various temperatures (288, 298, and 308 K), which revealed moderate binding affinity. Hydrogen bonds and hydrophobic interactions were predicted to connect MEF and HSA together in the MEF-HSA complex, as deduced from the thermodynamic data (ΔS = +133.52 J mol-1 K-1 and ΔH = +13.09 kJ mol-1 ) of the binding reaction and molecular docking analysis. Three-dimensional fluorescence spectral analysis pointed out alterations in the microenvironment around aromatic amino acid (tryptophan and tyrosine) residues of HSA consequent to the addition of MEF. Circular dichroic spectra of HSA in the wavelength ranges of 200-250 and 250-300 nm hinted smaller changes in the protein's secondary and tertiary structures, respectively, induced by MEF binding. Noncovalent conjugation of MEF to HSA bettered protein thermostability. Site marker competitive drug displacement results suggested HSA Sudlow's site I as the MEF binding site, which was also supported by molecular docking analysis.

中文翻译：

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抗疟药甲氟喹与人血清白蛋白的联合模式：光谱和对接方法的见解

使用荧光、吸收和圆二色光谱技术探索了抗疟药甲氟喹 (MEF) 和人血清白蛋白 (HSA)（血液循环中的主要载体蛋白）之间的相互作用。用 MEF 淬灭 HSA 荧光的特点是静态淬灭，从而证实了 MEF 和 HSA 之间的复合物形成。发现 MEF-HSA 相互作用的关联常数值在不同温度（288、298 和 308 K）下落在 3.79-5.73 × 104 M-1 的范围内，这表明结合亲和力适中。从热力学数据（ΔS = +133.52 J mol-1 K-1 和 ΔH = +13.09 kJ mol-1 ）推断，氢键和疏水相互作用将 MEF-HSA 复合物中的 MEF 和 HSA 连接在一起。结合反应和分子对接分析。三维荧光光谱分析指出加入 MEF 后 HSA 的芳香族氨基酸（色氨酸和酪氨酸）残基周围的微环境发生了变化。HSA 在 200-250 和 250-300 nm 波长范围内的圆二向色光谱分别暗示了 MEF 结合诱导的蛋白质二级和三级结构的较小变化。MEF 与 HSA 的非共价结合改善了蛋白质的热稳定性。位点标记竞争性药物置换结果表明 HSA Sudlow 的位点 I 作为 MEF 结合位点，这也得到了分子对接分析的支持。HSA 在 200-250 和 250-300 nm 波长范围内的圆二向色光谱分别暗示了 MEF 结合诱导的蛋白质二级和三级结构的较小变化。MEF 与 HSA 的非共价结合改善了蛋白质的热稳定性。位点标记竞争性药物置换结果表明 HSA Sudlow 的位点 I 作为 MEF 结合位点，这也得到了分子对接分析的支持。HSA 在 200-250 和 250-300 nm 波长范围内的圆二向色光谱分别暗示了 MEF 结合诱导的蛋白质二级和三级结构的较小变化。MEF 与 HSA 的非共价结合改善了蛋白质的热稳定性。位点标记竞争性药物置换结果表明 HSA Sudlow 的位点 I 作为 MEF 结合位点，这也得到了分子对接分析的支持。