In this work the binding of artificial sweetener aspartame with human serum albumin (HSA) was studied at physiological pH. Binding studies of aspartame (APM) with HSA are useful to understand APM -HSA interaction, mechanism and providing guidance for the application and design of new and more efficient artificial sweeteners. The interaction was investigated by spectrophotometric, spectrofluorometric competition experiment and circular dichroism (CD) techniques. The results indicated that the binding of APM to HSA caused fluorescence quenching of HSA through static quenching mechanism with binding constant 1.42 × 10+4 M-1 at 298 K and the number of binding sites is approximately one. Thermodynamic parameters, enthalpy changes (ΔH) and entropy changes (ΔS) were calculated to be -41.20 kJ mol-1 and -58.19 J mol-1 K-1, respectively, according to van't Hoff equation, which indicated that reaction is enthalpically driven. Quenching of the fluorescence of HSA was found to be a static quenching process. The binding constants and number of binding sites were obtained at three different temperatures (298, 308 and 318 K). Combining above results and those of spectrofluorometric competition experiment and circular dichroism (CD), indicated that APM binds to HSA via Sudlow's site I. Furthermore, the study of molecular docking on HSA binding also indicated that APM can strongly bind to the site I (subdomain IIA) of HSA mainly by hydrophobic interaction and hydrogen bond interactions exist between APM and HSA.

中文翻译：

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阿斯巴甜与人血清白蛋白相互作用的光谱研究

在这项工作中，研究了人工甜味剂阿斯巴甜与人血清白蛋白 (HSA) 在生理 pH 值下的结合。阿斯巴甜 (APM) 与 HSA 的结合研究有助于了解 APM -HSA 的相互作用、机制，并为新的、更有效的人造甜味剂的应用和设计提供指导。通过分光光度计、分光荧光计竞争实验和圆二色性 (CD) 技术研究了相互作用。结果表明，APM与HSA的结合通过静态猝灭机制引起HSA的荧光猝灭，在298 K时结合常数为1.42×10+4 M-1，结合位点数约为1。计算得到的热力学参数、焓变 (ΔH) 和熵变 (ΔS) 分别为 -41.20 kJ mol-1 和 -58.19 J mol-1 K-1，根据范特霍夫方程，这表明反应是由焓驱动的。发现 HSA 的荧光猝灭是一个静态猝灭过程。在三种不同的温度（298、308 和 318 K）下获得了结合常数和结合位点的数量。结合上述结果与荧光竞争实验和圆二色性 (CD) 的结果，表明 APM 通过 Sudlow 位点 I 与 HSA 结合。此外，对 HSA 结合的分子对接研究也表明 APM 可以与位点 I（子域）结合IIA)的HSA主要通过疏水相互作用和APM与HSA之间存在氢键相互作用。在三种不同的温度（298、308 和 318 K）下获得了结合常数和结合位点的数量。结合上述结果与荧光竞争实验和圆二色性 (CD) 的结果，表明 APM 通过 Sudlow 位点 I 与 HSA 结合。此外，对 HSA 结合的分子对接研究也表明 APM 可以与位点 I（子域）结合IIA)的HSA主要通过疏水相互作用和APM与HSA之间存在氢键相互作用。在三种不同的温度（298、308 和 318 K）下获得了结合常数和结合位点的数量。结合上述结果与荧光竞争实验和圆二色性（CD）的结果，表明 APM 通过 Sudlow 位点 I 与 HSA 结合。此外，对 HSA 结合的分子对接研究也表明 APM 可以与位点 I（子域）结合IIA)的HSA主要通过疏水相互作用和APM与HSA之间存在氢键相互作用。