The effects of experimental conditions of fluorescence quenching on the binding parameters of apigenin to bovine serum albumin by response surface methods

A fluorescence quenching technique is often used to study interactions between small molecules and serum albumin. However, the results are quite different by using spectroscopic techniques on the same drug-protein interaction research and they may be affected by different conditions (e.g. working solution of pH and ionic strength). In this research, using apigenin as an example, the effect of experimental conditions of fluorescence quenching on the binding parameters of drug to bovine serum albumin was investigated using a response surface method (RSM). The effect of pH, the concentration of NaCl and the concentration Mg2+ on the quenching constant (K-SV), the apparent association constant (K-a) and the number of binding sites (n) was studied by single-factor experiments with pH, [NaCl] and [Mg2+] as independent variables and K-SV, K-a and n as response values. Prediction models were fit to a quadratic polynomial regression equation and the results showed that both K-SV and n displayed a second-order model, whereas Ka displayed linear relation dependence on pH, [NaCl] and [Mg2+]. Under these experimental conditions, [NaCl] was the most significant (p < 0.05) impact factor on K-SV and K-a, whereas n was most affected by pH (p < 0.05). Copyright (c) 2013 John Wiley & Sons, Ltd.