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Methods

The BSA solution (0.1 mM) was prepared daily in Tris buffer (0.05 mol l-1, pH= 7.4) and treated at final concentration of 1.67× 10-5 M with different amounts of erlotinib hydrochloride to obtain final concentrations of 0, 0.2, 0.4, 0.8, 1, 2, 4, 6, 8, 20 and 42 µM receptively. The mixture was allowed to stand for 5 min and the fluorescence quenching spectra were recorded at 298, 303, 308 and 313 K.

Results

It was found that erlotinib hydrochloride caused the fluorescence quenching of BSA by the formation of a BSA-erlotinib hydrochloride complex. The mechanism of the complex formation was then analyzed by determination of the number of binding sites, apparent binding constant K, and calculation of the corresponding thermodynamic parameters such as the free energy (△ G), enthalpy (△ H) and entropy changes (△ S) at different temperatures. Results showed that binding of erlotinib hydrochloride to BSA …