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在298.15 K下,应用等温滴定量热法和圆二色谱法研究了氧化苦参碱(OMT)与牛血清白蛋白(BSA)的相互作用,并讨论了二者结合过程热力学性质的改变.研究结果表明,BSA大分子上存在可结合OMT分子的两类位点.OMT分子与第一类位点相结合时,结合过程的平衡常数、标准摩尔焓变和标准摩尔吉布斯自由能变分别为K1=(2.14±0.31)×105,ΔH1=(-1.07±0.50)kJ·mol-1,ΔG1=(-30.4±0.4)kJ·mol-1,最大可结合位点数为N1=(10.0±0.2),该过程是以熵驱动为主的焓熵协同驱动过程.OMT分子与第二类位点相结合时,K2=(6.84±0.32)×103,ΔH2=(1.91±0.03)kJ·mol-1,ΔG2=(-21.9±0.4)kJ·mol-1,N2=(25.0±0.3),该过程是熵驱动过程.圆二色谱测试结果表明,两类结合过程中,OMT与BSA的相互作用均导致了蛋白质二级结构构象及不同结构单元相对含量的变化.
The interaction between oxymatrine (OMT) and bovine serum albumin (BSA) was studied by isothermal titration calorimetry and circular dichroism at 298.15 K, and the thermodynamic properties of the combined process were discussed. The results indicate that there are two types of sites on the BSA macromolecules that can bind to OMT molecules. When the OMT molecules are combined with the first type of sites, the equilibrium constant, standard molar enthalpy of change, and standard molar Gibbs free energy change are respectively K1 = (2.14 ± 0.31) × 105, ΔH1 = (-1.07 ± 0.50) kJ·mol-1, ΔG1 = (-30.4 ± 0.4) kJ·mol-1, and the maximum number of binding sites is N1 = (10.0 ± 1) 0.2) This process is based on the entropy-driven coevolution drive process. When OMT molecules are combined with the second type of sites, K2=(6.84±0.32)×103 and ΔH2=(1.91±0.03)kJ·mol -1, ΔG2 = (-21.9 ± 0.4) kJ·mol-1, N2 = (25.0 ± 0.3), the process is an entropy-driven process. The circular dichroism test results show that, in the two types of bonding process, the mutuality of OMT and BSA The effects all lead to the conformation of protein secondary structure and the relative content of different structural units.