亚叶酸钙与DNA相互作用的热力学和光谱学研究

目的：研究DNA 与药物分子的相互作用机理。方法利用等温滴定微量热法（ITC）、紫外吸收光谱法（UV）和荧光光谱法研究了亚叶酸钙（CaFL）与小牛胸腺脱氧核糖核酸（ct‐DNA）在缓冲溶液中的结合反应。结果当药物分子与2类结合位点相结合时，标准吉布斯自由能（ΔG1°和ΔG2°）的变化几乎是一样的，然而，标准焓变（ΔH1°和ΔH 2°）却不相同，第1类结合发生在磷酸基团上，以焓驱动为主，而第2类结合则主要发生在碱基对形成的位点上，并显示为熵驱动为主的过程。结论热力学结果表明，ct‐DNA大分子上存在可结合FL2－阴离子的2类位点。

Thermodynamic and spectrographic study on DNA-calcium folinate complexation

Objective To study the interaction mechanism of DNA with drug. Methods The interaction of calcium folinate（CaFL） with calf thymus deoxyribonucleic acid（ct DNA） in aqueous buffer solution had been investigated by isothermal titration calorimetry（ITC）, ultraviolet absorption （UV） and fluorescence spectroscopy. Results There was only a subtle difference between changes in standard Gibbs free energy（ΔG1° and ΔG2° ） ,corresponding to the first and the second classes of binding processes. But the changes of standard enthalpy（ΔH1° and ΔH2°） were evidently different. One class of binding took place on phosphate groups, which was driven by enthalpy, while the other one took place at the sites formed by base pairs and appeared as an entropy driven process. The thermodynamic behavior of the DNA-drug supramolecular system had been discussed according to the spectra information. Conclusion Analysis of the thermodynamic data indicates that there are two classes of binding sites on the DNA molecules being able to coordinate with FL^2- anions.