The binding of procainamide hydrochloride to bovine serum albumin was investigated at different temperatures by using fluorescence spectroscopy and ultraviolet spectroscopy at pH 7.40. The experimental results showed a static quenching mechanism in the interaction of procainamide hydrochloride with bovine serum albumin. The binding constant and the number of binding sites are calculated according to the Stern–Volmer equation. The thermodynamic parameters ΔG 0, ΔH 0, and ΔS 0 calculated according to the van’t Hoff equation were observed to be −38.4 kJ mol−1, −66.8 J K−1 mol−1, and −18.5 kJ mol−1, respectively. The calculated distance between procainamide hydrochloride and the protein is evaluated according to the theory of Förster energy transfer. The results of fluorescence spectra and UV–Vis absorption spectra show that the secondary structure of the protein is changed in the presence of procainamide hydrochloride.
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