A Fluorescence Quenching Study of the Interaction of Nebivolol Hydrochloride with Bovine and Human Serum Albumin

The interaction of nebivolol hydrochloride (NH), a beta(1)-blocker, with bovine serum albumin (BSA) has been investigated at different pH values using the fluorescence quenching technique. The effect of different temperatures was studied at physiological pH 7.4. The binding constants of NH with BSA at 288, 298, and 309 K were found to be 2.691 x 10(11), 1.38 x 10(10), and 6.27 x 10(8) M-1, respectively. From the Arrhenius plot, the thermodynamic parameters, Delta H-0 and Delta S-0, were estimated to be -204.48 kJ/mol and -491.42 J/mol x K, respectively. This indicates that Van der Waals interactions and hydrogen bonds play a major role in the reaction. The effect of some inorganic divalent cations (Cu2+, Ni2+, and Zn2+) on binding of NH to BSA was also studied at physiological pH 7.4. Conformational investigation of BSA was done using synchronous fluorescence, showing the change in the microenvironment of the tryptophan residues. Fluorescence quenching reactions of NH to human serum albumin (HSA) and to gamma-globulins were investigated and the binding parameters were obtained.