荧光光谱法研究Ca^(2+)存在下左氧氟沙星与人血清白蛋白的结合作用

Study on the Binding Interaction of Levofloxacin with Human Serum Albumin in the Presence of Ca^(2+)by Fluorescence Spectrophotometry

目的:研究左氧氟沙星对人血清白蛋白以及在Ca^(2+)存在下左氧氟沙星与人血清白蛋白的结合作用。方法:通过荧光光谱法分析了左氧氟沙星对人血清白蛋白以及Ca^(2+)存在条件下左氧氟沙星对人血清白蛋白荧光淬灭光谱、同步荧光光谱,根据热力学方程讨论两者间主要的作用力类型。结果:在生理条件(pH=7.4,37℃)下,根据Stem-Volmer方程和荧光淬灭双倒数图,确定了左氧氟沙星对人血清白蛋白淬灭类型为静态淬灭,左氧氟沙星对人血清白蛋白的结合常数K=1.46×10~5L·mol^(-1),结合位点n=1.1,根据热力学方法确定作用力类型为疏水作用力;在Ca^(2+)存在条件下,淬灭类型和作用力类型不变,结合常数K=2.38×104L·mol^(-1),结合位点n=1.02。结论:在Ca^(2+)存在条件下,左氧氟沙星对人血清白蛋白的荧光淬灭减弱,结合常数和结合位点均变小。为研究左氧氟沙星的生物学效应,以及左氧氟沙星和Ca^(2+)对蛋白质构象的影响等提供了重要信息。

To investigate the binding interaction of levofloxacin with human serum albumin in the presence of Ca^2 ＋ by fluorescence speetrophotometry. Method： The interaction of levofloxaein with human serum albumin （HSA） in the presence of Ca^2 ＋ was studied by measuring fluorescence quenching spectra and synchronous fluorescence spectra. The type of binding force was estimated by the calculation of thermodynamic parameters. Result： After analyzing the fluorescence quenching data according to Stem-Volmer equation and double-reciprocal equation under physiological condition （pH = 7.4,37 ℃） , the type of fluorescence quenching of levofloxacin was static quenching,the binding constant was 1.46 × l0^5 L.mol^-1 and the binding site was 1.1. In the presence of Ca^2＋ ,the type of fluorescence quenching was unchanged with the binding constant of 2. 38 ×^104 L·mol^- 1 and the binding site of 1.02. The interaction between levofloxaein and HSA was both mainly driven by hydrophobic force with or without Ca^2＋. Conclusion： Ca^2＋ can decrease the combining constant and binding site of levofloxacin with HSA, and reduce the fluorescence quenching of levofloxacin with HSA. The re sults provide important information for the research of biological effects of levofloxacin and configuration modification of HSA by levofloxacin and Ca^2＋.