叶酸属于B族维生素，作为生物体内转移一碳单位酶系中的辅酶，与其他维生素相互作用，共同维持体内红细胞的稳定，对氨基酸之间的转化、细胞的分裂生长，蛋白质合成的反应都有重要意义。药物半衰期、峰浓度和反应速度常数是研究药代动力学的重要参数，实验运用荧光分光光度计和停流光谱分析仪研究了仿生环境下牛血清白蛋白和叶酸反应的动力学参数，为叶酸相关的药物代谢参数提供参考。结果表明：利用Stern‐Volmer方程处理荧光猝灭实验数据，得到25，30和37℃下叶酸对牛血清白蛋白内源荧光的静态猝灭常数分别为2.455×1010，4.900×1010和6.427×1010 L・mol-1・s-1；动力学反应速率常数的计算结果表明不同温度、pH值和缓冲介质下BSA和叶酸反应的速率常数都大于100 mol・L -1・s-1，阐明了BSA与叶酸之间的猝灭机理是通过形成复合物的静态猝灭过程；生理温度下，牛血清白蛋白浓度与其初始浓度满足二级反应公式，相关系数为0.9987，药代半衰期 t1／2为0.059 s ；反应的表观速率常数随着叶酸浓度的增加呈线性增加趋势，且叶酸催化牛血清白蛋白荧光猝灭的速率常数 kcat ＝3.174×105 mol・L -1・s-1。此外还测定了不同缓冲介质下牛血清白蛋白与叶酸相互作用的表观速率常数和反应速率常数，以此来探讨生理介质对于二者反应的影响，为确定临床用药方案、预测药物的疗效和毒性以及合理用药有着重要意义。%As a kind of coenzyme of one‐carbon enzymes in vivo ,folic acid belongs to B vitamins ,which can interact with other vitamins and has great significance for converting among amino acids ,dividing growth of cells and protein synthesis reactions . Half‐life ,concentration and reaction rate constant of drugs are important parameters in pharmacokinetic study .In this paper ,by utilizing fluorescence spectrophotometer and stopped‐flow spectrum analyzer ,reaction kinetic parameters between bovine serum albumin(BSA) and folic acid in a bionic system have been investigated ,which provide references for parameters of drug metabo‐lism related to folic acid .By using Stern‐Volmer equation dealing with fluorescence quenching experiments data ,we concluded that under 25 ,30 ,and 37 ℃ ,the static quenching constants of folic acid to intrinsic fluorescence from bovine serum albumin were 2.455 × 1010 ,4.900 × 1010 and 6.427 × 1010 L・mol-1 ・s-1 respectively ;The results of kinetic reaction rate have shown that the reaction rate of BSA and folic acid are greater than 100 mol・ L -1 ・ s-1 at different temperatures ,pH and buffering media ,illustrating that the quenching mechanism between BSA and folic acid is to form composite static quenching process .Re‐action concentration of bovine serum albumin and its initial concentration were equal to the secondary reaction formula ,and the correlation coefficient was 0 .998 7 ,while the half‐life (t1/2 ) was 0.059 s at physiological temperature .With the increase of folic acid concentration ,the apparent rate constant of this reaction had a linear increasing trend ,the BSA fluorescence quenching rate constant catalyzed by folic acid was 3.174 × 105 mol・L -1 ・s-1 .Furthermore ,with different buffer ,the apparent rate constant and reaction rate constant of BSA interacting with folic acid were detected to explore the influence on the reaction under physio‐logical medium ,which is of great significance to determine the clinical regimen ,forecast the efficacy and toxicity of drugs and ra‐tional drug .
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