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Studies on the Interaction of Flavones and Serum Albumin in the Prescence of Metal Ions and Its Application in Analytical Chemistry

Author: LiZuo
Tutor: HuXiaoRong
School: Chengdu University of Technology
Course: Analytical Chemistry
Keywords: Flavonoid Bovine serum albumin Metal Ions FluorescenceSpectrometry Spectrophotometry
CLC: O657.3
Type: Master's thesis
Year: 2013
Downloads: 36
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Abstract

Serum albumin is the most abundant protein in blood plasma. Flavonoids have a wide range of pharmacological activities. In this thesis, the interaction between three flavonoids binding to bovine serum albumin (BSA) at pH7.4was studied by using fluorescence quenching, UV-vis absorption spectroscopic techniques. The quenching constant, binding constant, thermodynamic binding parameter, reaction force between molecules and the effects of metal ions on the interactions were studied in detail.The following results were obtained:The interaction between apigenin and BSA in the prescence of different metal ions was investigated by fluorescence spectrometry. The fluorescence of BSA was quenched by apigenin, and the quenching mechanism was a static quenching process. When appropriate amount of metal ions was added to the mixture of apigenin and BSA, the quenching constant, binding constant, number of binding site decreased. The quenching mechanism of BSA by apigenin was not changed in the prescence of different metal ions. The main binding force was still electrostatic force. For example, when the equal amouts of apigenin and Cu2+were added to BSA, the fluorescence was quenched more severely than only adding apigenin or Cu2+, and the binding constant was decreased with the increase of Cu2+concentration. From ultraviolet absorption spectrum, it can be infered that apigenin and BSA formed a new substance. The ternary system was different from apigenin-BSA. The analysis indicated that the reason of metal ions on the interaction between apigenin and BSA was metal-apigenin complex formation, or the competiton between metal ions and apigenin.The interaction between baicalein and BSA in the prescence of different metal ions was investigated by fluorescence spectrometry. The fluorescence of BSA was quenched by baicalein, and the quenching mechanism was a static quenching process. When appropriate amount of metal ions was added to the mixture of baicalein and BSA, the quenching constant, binding constant, number of binding site decreased. The quenching mechanism of BSA by baicalein was not changed in the prescence of different metal ions. The main binding force was still hydrophobic force. For example, when the equal amouts of baicalein and Fe3+were added to BSA, the fluorescence was quenched more severely than only adding baicalein or Fe3+, and the binding constant was decreased with the increase of Fe3++concentration. From ultraviolet absorption spectrum, it can be infered that baicalein and BSA formed a new substance. The ternary system was different from baicalein-BSA. The analysis indicated that the reason of metal ions on the interaction between baicalein and BSA was metal-baicalein complex formation, or the competiton between metal ions and baicalein.The interaction between anthocyanin and BSA was studied by fluorescence spectrometry. The anthocyanin was extracted from the red cabbage and purified by the XD-2macroporous resin. The results revealed that anthocyanin caused the fluorescence quenching of BSA through a static quenching procedure. The binding constant was1.09×106L·mol-1at311K, exhibiting a strong binding force. This process was spontaneous. It indicated that anthocyanin and BSA was hydrophobic force (ΔH>0, ΔS>0). The effect of metal ions (i.e., Ni2+, Zn2+, Cu2+, Fe3+, Mn2+, and Mg2+) on the interaction characteristics between anthocyanin and BSA was investigated, such as the change of quenching mechanism of fluorescence, the interaction forces, the association constant, and the binding site. It turned out that the quenching mechanism of BSA by anthocyanin was not changed, and the binding constant was increased in the prescence of different metal ions. Different metal ions have different influence on the binding force of anthocyanin-BSA. The binding force was changed from hydrophobic force to electrostatic force in the prescence of Mg2+, and changed from hydrophobic force to hydrogen bonds and van der Waals forces in the prescence of Ni2+and Cu+. The bnding force was not changed in the prescence of Zn2+, Fe3+, and Mn2+.In the acetic acid sodium buffer system (pH4.7), Fe (Ⅲ) and anthocyanins formed stable complexes. We use ultra-violet spectrophotometry and fluorescence spectrometry to study the complex. Subsequently, a new method for the determination of Fe (Ⅲ) was established by using absorption spectrometry. The maximum absorption wavelength of the Fe (Ⅲ)-anthocyanin complexwas610nm in acetic acid sodium buffer system, with the existence of cationic surfactant CTMAB. The molar absorption coefficient of the complex was6.16×103L·mol-1cm-1. A linear relationship between the absorbance signal and the concentration of Fe(Ⅲ) was observed in the range of2-10mg·L-1(r=0.9997). The quantitative detection limit was0.91μ·mL-1. The proposed method was successfully applied to the determination of Fe (Ⅲ) in certified reference material(super mafic rocks DZE-2), with recoveries from93.8%to105.3%. The relative standard deviation is1.65%.

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