Intermolecular interaction of fosinopril with bovine serum albumin (BSA): The multi-spectroscopic and computational investigation

The intermolecular interaction of fosinopril, an angiotensin converting enzyme inhibitor with bovine serum albumin (BSA), has been investigated in physiological buffer (pH7.4) by multi-spectroscopic methods and molecular docking technique. The results obtained from fluorescence and UV absorption spectroscopy revealed that the fluorescence quenching mechanism of BSA induced by fosinopril was mediated by the combined dynamic and static quenching, and the static quenching was dominant in this system. The binding constant, K-b, value was found to lie between 2.69x10(3) and 9.55x10(3)M(-1) at experimental temperatures (293, 298, 303, and 308K), implying the low or intermediate binding affinity between fosinopril and BSA. Competitive binding experiments with site markers (phenylbutazone and diazepam) suggested that fosinopril preferentially bound to the site I in sub-domain IIA on BSA, as evidenced by molecular docking analysis. The negative sign for enthalpy change (H-0) and entropy change (S-0) indicated that van der Waals force and hydrogen bonds played important roles in the fosinopril-BSA interaction, and 8-anilino-1-naphthalenesulfonate binding assay experiments offered evidence of the involvements of hydrophobic interactions. Moreover, spectroscopic results (synchronous fluorescence, 3-dimensional fluorescence, and Fourier transform infrared spectroscopy) indicated a slight conformational change in BSA upon fosinopril interaction.