Abstract：Studies on the binding mechanism between protein and small molecules could give us lots of useful information. For example, a detailed characterization of drug-protein binding properties was essential for understanding the function of delivery, hence, interest in the mechanism of the interaction between them has attracted much research using different methods. In the present paper, the interaction mechanism between meso-tetra-(3,5-dibromo-4-hydroxyphenyl) porphyrin [T(DBHP)P] and bovine serum albumin (BSA) was investigated using fluorescence method. Based on the mechanisms of fluorescence quenching of BSA caused by T(DBHP)P, the binding constants between T(DBHP)P and BSA were measured at different temperatures. The experiment showed that T(DBHP)P and BSA have strong interactions. The binding constants of the reaction at 27 and 48 ℃ were calculated by fluorescence method, respectively. The binding constants are K=1.30×106 L·mol-1 at 27 ℃, and K=6.32×105 L·mol-1 at 48 ℃. Because the binding constants decreased with increasing the temperature, the sort of quenching between T(DBHP)P and BSA was determined as static quenching. By the theory of Frster non-radiation energy transfer, the binding distance and the energy transfer efficiency at 27 ℃ between T(DBHP)P (accepter of energy) and BSA (donor of energy) were obtained to be 2.39 nm and 0.91, respectively. The binding distance was less than 7 nm, therefore, the interaction was similar to the non-radiation energy transfer, and the static quenching was further proved. According to the thermodynamic parameters, the main sorts of binding force between T(DBHP)P and BSA could be judged as electrostatic force when ΔG<0，ΔH<0 and ΔS>0. Using the synchronous fluorescence spectra, the effect of T(DBHP)P on the conformation of BSA was studied. The results indicated that the conformation of BSA was changed when T(DBHP)P was added, and the hydrophobic properties of the environment of residues in BSA decreased. It was proved that fluorescence quenching of BSA was induced by static quenching and non-radiation energy transfer.
Key words：BSA;T(DBHP)P;Binding constants;Energy transfer;Mechanisms of fluorescence quenching;Synchronous fluorescence spectra
颜梅,陈欣,孙舒婷,马洪敏,杜斌,魏琴*. 荧光光谱法研究二溴羟基卟啉与蛋白质的结合作用机理[J]. 光谱学与光谱分析, 2008, 28(06): 1322-1326.
YAN Mei,CHEN Xin,SUN Shu-ting,MA Hong-min,DU Bin,WEI Qin*. Study on Binding Mechanism of Meso-tetra-(3,5-Dibromo-4-Hydroxyphenyl) Porphyrin with Protein by Fluorescence Method. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(06): 1322-1326.
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