Study on silver ions binding to β-lactoglobulin

The drug-resistant pathogen phenomenon, resulting in infections and deaths that are increasingly difficult to treat, requires research into searching new potential antimicrobial agents. The presented study is focused on the investigation of impact of silver ions (Ag⁺ ions) to β-lactoglobulin (βLG) structure and mechanism formation of silver-β-lactoglobulin nanocomposites, that could find potential applications in medicine. To determine the physicochemical characteristics of silver ion binding, kinetics and isothermal models were used. The presence of functional groups involved in the binding process was investigated by spectroscopic methods (FTIR-ATR, Raman spectroscopy). The binding ability and nanocomplexes formation was determined by instrumental analyses (SEM, TEM, EDX). Based on the obtained results, the binding of Ag⁺ ions to βLG were heterogeneous in nature consisting of three main steps: rapid sorption of Ag⁺ ions on the βLG surface, intramolecular diffusion of Ag⁺ ions, and chemical equilibrium. Microscopic studies showed a change in the surface morphology of βLG and the appearance of silver nanoparticles. Spectroscopic studies indicated that acidic (Glu^-, Asp^-) and Lys, Tyr, Met amino groups play a key role in the formation of the AgβLG nanocomplex. Finally, molecular dynamics (MD) and density functional theory (DFT) calculated studies as a comparative and complementary method have proven contribution of respective amino acids in the binding process.