The interaction of caffeine with bovine serum albumin （BSA） under physiological condition was investigated by fluorescence, UV-vis absorption and circular dichroism （CD） spectroscopy. Fluorescence data revealed that the fluorescence quenching of BSA by caffeine was a result of the formation of BSA-caffeine complex. The binding constants Ka at different temperatures and corresponding thermodynamic parameters △H, △G and △S were calculated. The spectroscopic measurements and the thermodynamic parameters suggested that van der Waals interaction and hydrogen bonds were the predominant intermolecular forces to stabilize the complex. The conformational change of BSA induced by caffeine has been analyzed by means of CD and synchronous fluorescence spectroscopy. Furthermore, it is observed from the probe of competitive experiments that the binding location of caffeine with BSA could be the same as warfarin binding site I of BSA, which was also revealed by fluorescence anisotropy.
Wu, QiongJiang, FengleiLi, ChaohongHu, YanjunLiu, Yi
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.
