Computational and Experimental Study on the Interaction of Terbium (III) and Ytterbium (III) Complexes Containing 1,10-phenanthroline with Bovine Serum Albumin

In this work, the interaction of two synthesized complexes [Tb(phen)2Cl3.OH2] and [Yb(phen)2Cl3.OH2] (phen is 1,10-phenanthroline) with bovine serum albumin (BSA) were studied by UV-Vis, fluorescence, and molecular docking examinations. The experimental data indicated that these lanthanide complexes have a high binding affinity with BSA by effectively quenching the fluorescence of BSA via the static mechanism. The binding parameters, the type of interaction, the value of resonance energy transfer, and the binding distance between complexes and BSA were estimated from the analysis of fluorescence measurements and Förster theory. The thermodynamic parameters suggested that van der Waals interactions and hydrogen bonds play an important role in the binding mechanism. While the energy transfer from BSA molecules to these complexes occurs with high probability, the binding constants showed that the binding affinity ranked in the order Tb-complex > Yb-complex, which has been related to the radius of Ln3+ ion. Also, the results of competitive experiments and molecular docking calculations assessed the microenvironment residues around the bound mentioned complexes and represent site 3 of BSA, located in subdomain IB, as the most probable binding site for these complexes. The computational results kept in good agreement with experimental data.