Analytical Sciences

Binding of Human Serum Albumin to N-(p-Ethoxy-phenyl)-N′-(1-naphthyl)thiourea and Synchronous Fluorescence Determination of Human Serum Albumin

Fengling CUI,* Junli WANG,* Yanrui CUI,* Jianping LI,* Yan LU,* Jing FAN,* and Xiaojun YAO**

*School of Chemistry and Environmental Science, Key Laboratory for Environmental Pollution Control Technology of Henan Province, Henan Normal University, Xinxiang 453007, People's Republic of China
**Department of Chemistry, Lanzhou University, Lanzhou 730000, People's Republic of China

The binding of N-(p-ethoxy-phenyl)-N′-(1-naphthyl)thiourea (EPNT) to human serum albumin (HSA) was investigated under simulative physiological conditions by fluorescence spectra in combination with UV absorption spectroscopy and a molecular modeling method. A strong fluorescence quenching reaction of EPNT to HSA was observed, and the quenching mechanism was suggested to be static quenching according to the Stern-Volmer equation. The binding constants (K) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), were calculated according to relevant fluorescent data and the vant' Hoff equation. This indicated that a hydrophobic interaction was a predominant intermolecular force for stabilizing the complex, which is in agreement with the results of molecule modeling study. The effects of energy transfer and other ions on the binding constant were considered. In addition, synchronous fluorescence technology was successfully applied to the determination of HSA added into the EPNT solution.

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