Effect of temperature and pH on interaction between bovine serum albumin and cetylpyridinium bromide: Fluorescence spectroscopic approach

The fluorescence spectroscopic technique has been efficiently employed to investigate the interaction between bovine serum albumin (BSA) and cetylpyridinium bromide (CPB) under different pH and temperature conditions. The binding constant, number of binding sites, thermodynamic parameters such as ΔG, ΔH, ΔS, and nature of binding forces between BSA and CPB were obtained by measuring the steady state fluorescence quenching of BSA by CPB. The experimental results showed that the fluorescence quenching of BSA by CPB was a result of the formation of CPB–BSA complex. The static quenching was confirmed from the Stern–Volmer quenching constant at different temperatures. The effect of CPB on the conformation of BSA was analyzed using synchronous and three-dimensional fluorescence spectroscopy. pH dependence complex formation between BSA–CPB is due to the interaction between cationic side chain of CPB and the net charge developed on BSA. The distance ‘r’ between BSA and CPB was obtained according to the fluorescence resonance energy transfer.