The binding of caffeine to human serum albumin (HSA) under physiological conditions has been stud-ied by the methods of fluorescence,UV-vis absorbance and circular dichroism (CD) spectroscopy. The mechanism of quenching of HSA fluorescence by caffeine was shown to involve a dynamic quenching procedure. The number of binding sites n and apparent binding constant Kb were measured by the fluorescence quenching method and the thermodynamic parameters △H,△G,△S were calculated. The results indicate that the binding is mainly enthalpy-driven,with van der Waals interactions and hydrogen bonding playing major roles in the reaction. The distance r between donor (HSA) and acceptor (caffeine) was obtained according to the Frster theory of non-radiative energy transfer. Synchronous fluorescence,CD and three-dimensional fluorescence spectroscopy showed that the microenvironment and conformation of HSA were altered during the reaction.
在模拟生理条件下,用荧光光谱法结合圆二色谱法研究了吲哚美辛(IM)与牛血清白蛋白(BSA)的相互作用。实验结果表明,IM对BSA的猝灭机制属于形成复合物的静态猝灭过程,由修正的Stern-Volmer方程求出不同温度下相应的结合常数分别为11.87×104、8.351×104、6.110×104 L.mol-1。利用范特霍夫方程及结合常数的数据分别计算体系的焓变、熵变和吉布斯自由能变。焓变值(-42.54 kJ.mol-1)和熵变值(-45.65J.mol-1.K-1)表明,氢键和van der Waals是IM与BSA之间缔合作用的主要作用力。圆二色谱、三维荧光光谱的研究结果显示,在与IM结合后,BSA中α-螺旋的含量减少,说明在与IM结合反应过程中,BSA的微环境和构型发生了改变。
