Study of the interaction between quinocetone and bovine serum albumin by spectroscopic approaches

The fluorescence and ultraviolet spectroscopy were explored to study the interaction between quinocetone (QCT) and bovine serum albumin (BSA) at three different temperatures (288, 299 and 307 K) under imitated physiological conditions. The experimental results show that the fluorescence quenching mechanism between QCT and BSA is static quenching procedure at low QCT concentration, or a combined quenching (dynamic and static quenching) procedure at high concentrations. The binding constant (Ka), binding sites (n) and corresponding thermodynamic parameters (ΔH, ΔS, and ΔG) between QCT and BSA at different temperatures were obtained. According to the Förster non-radiation energy transfer theory, the average binding distance (r) between the donor (BSA) and the acceptor (QCT) was calculated to be 3.24 nm. The effect of QCT on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effect of some common metal ions Ni2+, Cu2+, Ca2+, and Mg2+ on the binding constants between QCT and BSA was examined.