The investigation of the interaction between 5-iodouracil and human serum albumin by spectroscopic and modeling methods and determination of protein by synchronous fluorescence technique

The interaction of 5-iodouracil with human serum albumin (HSA) was investigated in aqueous solution by fluorescence quenching spectrum in combination with UV absorption spectrum and modeling method. The quenching mechanism and binding characteristics of 5-Iodouracil with HSA were obtained from the fluorescence measurement. The binding constants were calculated according to the Lineweaver-Burk equation at different temperatures. And the thermodynamic parameters, enthalpy change (AH) and entropy change (AS), were calculated by thermodynamic equations. The results showed that the hydrophobic interaction played a major role in the binding of 5-iodouracil with HSA. The binding distance was obtained according to Foster's non-radiative energy transfer theory. The effect of some normal ions on the binding constants was discussed. Modeling method was applied to elucidate the interaction mode between 5-iodouracil and HSA, which was agreed with the calculated result by thermodynamic method. Moreover, the synchronous fluorescence technique was successfully applied to quantify total protein in human body fluids including serum, urine, and saliva samples. The results showed that this method was stable, reliable, selective, sensitive, and practical for the determination of HSA. (c) 2007 Elsevier Inc. All rights reserved.