Abstract: The effect of taurine on the microenvironment and conformation of human serum albumin (HSA) are studied using fluorescence spectroscopy and ultraviolet absorption spectroscopy. The results show that HSA can be quenched regularly by taurine through a static quenching mechanism at different temperatures, with quenching rate constants greater than 2.0×1010 L·M−1 ·s −1 . The binding constant increases with the increase of temperature, and the number of binding sites also increases, approaching to 0.5. The thermodynamic parameters enthalpy change is less than 0, entropy change is greater that 0, and free energy change is less than 0, indicating that the binding process is spontaneous and the main force is electrostatic attraction. According to Forster's non-radiative energy transfer theory, the binding distance between taurine and HSA is estimated to be 2.645, indicating that there is non-radiative energy transfer. The results of this study indicate that taurine can affect the microenvironment of HSA and change the spatial conformation of HSA. This mechanism may be the essential source of taurine's ability to protect hepatocyte and improve the structure and function of portal vein.

Key words: spectroscopy, static quenching, fluorescence spectroscopy, taurine, nonradioactive energy transfer