Abstract

With the aim of achieving bioactive anticancer metal-based drugs, a new lanthanum(III) complex using tyrosine amino acid was synthesized and characterized. The anticancer activities of La(Tyr)(3)(OH2)(3) complex against MCF-7 cell lines were studied and revealed that it can inhibit breast cancer cell lines with the IC50 value of 21 mu M following 72 h exposure. The interaction of the La(III) complex with two model proteins, bovine serum albumin (BSA) and beta-lactoglobulin (beta-LG), was studied using biophysical as well as computational techniques. The fluorescence studies showed that the interaction of the La(III) complex with whey proteins caused strong fluorescence quenching of both proteins through static quenching mechanism and the La(III) complex interacted with BSA and beta-LG with moderate binding affinity (K (BSA-La complex) = 0.50(+/- 0.1) x 10(4) M- 1 and K (beta-LG-La complex) = 0.15(+/- 0.1) x 10(3) M- 1 at 310 K). According to the obtained thermodynamic parameters, hydrogen bonds and van der Waals interactions play a major role for BSA-complex and beta-LG-complex associations. UV-Vis results showed that the binding of prepared La(III) complex to each protein induced conformational changes in the protein. The distances of the La(III) complex with the proteins were calculated using Forster energy transfer theory and proved the existence of energy transfer between two proteins and prepared La(III) complex with a high probability. UV-Vis absorption studies indicated that the binding of the La(III) to BSA and beta-LG may induce conformational and micro-environmental changes of the proteins. The docking results indicate that the La(III) complex bind to residues located in the site II of BSA and second site of beta-LG.