Spectroscopic Studies on the Binding of Phenazopyridine Hydrochloride and Bovine Serum Albumin
ZHOU Hong1, CHEN Chang-yun1, XIE An-jian2
1. Department of Chemistry, Nanjing Xiaozhuang College, Nanjing 210017, China 2. College of Chemistry and Chemical Engineering，Anhui University，Hefei 230039，China
Abstract：The binding of phenazopyridine hydrochloride and bovine serum albumin under physiological conditions was studied by spectroscopic method. The quenching mechanism of the fluorescence of bovine serum albumin by phenazopyridine hydrochloride was studied with fluorescence and absorption spectroscopy. The binding constant Kb and the number of binding sites n were determined at different temperatures according to Scatchard equation, and the main binding force was discussed by thermodynamic equations. The effect of the drug on bovine serum albumin conformation was also studied by using synchronous fluorescence spectroscopy. The quenching mechanism of phenazopyridine hydrochloride to bovine serum albumin is static quenching and non-radiation energy transfer. The binding constants Kb at 15, 25 and 37 ℃ are 2.47×107, 9.15×106 and 4.36×106mol-1 with one binding site, respectively. The thermodynamic parameters of the reaction are ΔH=-71.2 kJ·mol-1, and ΔS=124.8 J·mol-1·K-1. Binding phenazopyridine hydrochloride to bovine serum albumin is a spontaneous inter-molecular interaction in which entropy increases and Gibbs free energy decreases. The binding distance r between phenazopyridine hydrochloride and bovine serum albumin is 1.61 nm according to Frster theory of non-radiation energy transfer. The binding force is electrostatic interaction. Phenazopyridine hydrochloride can be deposited and transported by serum protein in vivo. Phenazopyridine hydrochloride does affect the serum protein conformation.
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