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目的:研究咖啡因、茶碱、可可碱3种甲基黄嘌呤类生物碱与牛血清白蛋白(BSA)结合反应的荧光光谱行为,了解其与蛋白质结合的信息。方法:采用荧光光谱法研究25℃和37℃时3种生物碱不同浓度对BSA的荧光猝灭作用,通过Stern-Volmer曲线和Perrin曲线线性拟合计算得到动态猝灭常数和静态猝灭常数,判断猝灭机制;计算结合常数、结合位点数及热力学函数ΔH、ΔS、ΔG,判断其结合作用力模型。结果:随着3种生物碱浓度升高,BSA内源荧光强度有规律地降低;随温度的升高,静态猝灭常数和结合常数均降低,而3种生物碱与BSA的结合常数差别较大,但结合位点数均接近1;ΔG<0,ΔH<0,ΔS>0。结论:3种生物碱能较显著猝灭BSA的荧光,且机制均为静态猝灭,与白蛋白之间均存在以疏水相互作用为主的结合作用;3种结构相近的生物碱与BSA的相互作用存在差异。
AIM: To study the fluorescence spectra of caffeine, theophylline and theobromine in the binding reaction of three methylxanthines alkaloids with bovine serum albumin (BSA), and to understand the binding of protein to protein. Methods: Fluorescence spectroscopy was used to study the fluorescence quenching of BSA at different concentrations of three alkaloids at 25 ℃ and 37 ℃. The dynamic quenching constants and static quenching constants were calculated by linear fitting of Stern-Volmer curve and Perrin curve. Determine the quenching mechanism; calculate the binding constants, the number of binding sites and thermodynamic functions ΔH, ΔS, ΔG, to determine the binding force model. Results: With the increase of the concentration of three alkaloids, the endogenous fluorescence intensity of BSA decreased regularly. The static quenching constants and binding constants of BSA decreased with increasing temperature, but the binding constants of the three alkaloids were lower than that of BSA Large, but the number of binding sites are close to 1; ΔG <0, ΔH <0, ΔS> 0. CONCLUSION: Three kinds of alkaloids can significantly quench the fluorescence of BSA, and the mechanism is static quenching. The binding interaction between albumin and albumin is mainly hydrophobic interaction. The three alkaloids with similar structure are similar to those of BSA There are differences in interaction.