Abstract
Aim: To evaluate the binding interaction of diflunisal at active site of Human Serum Albumin (HSA), an important enzyme responsible for osteoarthritis disease.
Methodology: The gas phase molecule was optimized with B3LYP/6-311G** basis set, while a single point energy calculation was carried out for the molecule lifted from the active site. Bader's theory of atoms in molecules (AIM) was used to determine the electron density and Laplacian of electron density. The protein was assigned with polar hydrogens and Kollman charges. Iterated local search procedure was performed during docking, during this, both protein and ligand were considered as rigid. Among the ten poses, lowest binding energy pose was considered for further ligand protein interaction analysis and QTAIM studies.
Results: A close observation of the results shows that diflunisal has interactions in the binding sites IIA and IIIA of HSA as reported earlier. Two strong classical H-bonding interactions, three hydrophobic contacts with the amino acids VAL456, ALA194 andARG197, two close fluorine interactions, and two Pi-Sigma interactions have been observed. Apart from the H-bond interactions, the stability of HAS-Diflunisal complex was further empathized by five hyrdrophobic interactions framed between hydroxyl benzoic acid ring with ALA194, GLN459 and ARG197amino acid residue and difluorobenzene ring with ALA194 and VAL456.
Interpretation: The results of drug-likeness study showed that diflunisal is highly reactive and less toxic.