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利用紫外光谱法和荧光光谱法研究了苋菜红的解离常数及其与牛血清白蛋白(BSA)的结合行为。应用荧光猝灭现象和Frster理论,考察了不同环境温度和酸度下苋菜红与牛血清白蛋白的结合常数和结合位点,并对其热力学常数进行了研究。苋菜红的解离常数pKa为10.43,与牛血清白蛋白间主要存在的是疏水作用和静电作用,二者间的结合距离为3.83 nm。结合过程中静态猝灭和非辐射能量转移是导致牛血清白蛋白荧光猝灭的原因。通过同步荧光光谱和荧光探针技术证明与苋菜红作用后的BSA分子二级结构发生了变化,苋菜红与其在亚结构域IIA(Site I)发生了结合。研究结果将为苋菜红在环境和生物体内的吸收、分布、代谢等行为的探索提供一定的理论基础。
The dissociation constant of amaranth and its binding to bovine serum albumin (BSA) were studied by ultraviolet spectroscopy and fluorescence spectroscopy. Using fluorescence quenching and Färster theory, the binding constants and binding sites of amaranth and bovine serum albumin were investigated under different ambient temperatures and acidities. The thermodynamic constants were also studied. The dissociation constant pKa of amaranth was 10.43. The main interaction between amaranth and bovine serum albumin was hydrophobicity and electrostatic interaction, the binding distance between them was 3.83 nm. Static quenching and non-radiative energy transfer during binding are responsible for the fluorescence quenching of bovine serum albumin. The secondary structure of BSA after the interaction with amaranth was observed by synchronous fluorescence spectroscopy and fluorescent probe technique. Amaranth was associated with its binding site IIA (Site I). The results will provide a theoretical basis for the exploration of the absorption, distribution and metabolism of amaranth in environment and living body.