Docking Studies on the Binding Properties of Methotrexate to Human Serum Albumin

Human serum albumin (HSA) is one of the main endogenous vehicles for biodistribution of molecules by blood plasma. Association constants and thermodynamic parameters for the interaction of HSA with Methotrexate were studied by docking. Docking studies provide remarkable information on binding sites of drugs, estimating the binding energies of each drug conformation with corresponding scores and functions. Docking study suggests that Methotrexate is able to interact with HSA by means of hydrogen bonds with one lysine , two arginine ,one Asparagine and one Glutamine residues, whereas the carbonyl group is inserted in a hydrophobic pocket, close to Trp-214.The Estimated of Gibbs free energies( ΔG° (kcal/mol)) is equal to -12.6 for the best model. The negative values of ΔG° indicate a spontaneous process. The association constant value (Ka ≈ 109 L•mol−1) is favorable for its efficient biodistribution by blood plasma. Studies using molecular modeling were performed to analyze the main intermolecular interactions between the Methotrexat and the amino acid residues present in the subdomain IIA interaction cavity.