The microscopic structure of an aqueous lysozyme solution at different concentrations was investigated using molecular dynamics simulations. The aim of the study was to analyse the structural and thermodynamic properties of aqueous lysozyme solutions at different concentrations in the presence of chloride counterions. By comparing a system containing one lysozyme molecule with two systems, each containing four lysozyme molecules, at two different concentrations, the effect of concentration on the spatial distribution of water molecules around the protein and on intermolecular interactions between protein molecules was investigated. The effect of concentration on the mobility of protein molecules was also specifically investigated. The simulations were performed using the GROMACS software package. The stability and structural characteristics of the systems were evaluated based on temperature, pressure, potential energy, and radius of gyration, while protein–water and protein–protein interactions were investigated through hydrogen-bond analysis and radial pair distribution functions. The mobility of protein molecules was evaluated using the diffusion coefficient.
The results showed that a change in concentration within the investigated range does not significantly affect the global structure of lysozyme or its hydration environment, as the radius of gyration, hydrogen bonds, and protein–water radial pair distribution functions were comparable at different concentrations. At a higher concentration, more pronounced changes in the spatial organization of protein molecules were observed, accompanied by a decrease in their diffusion coefficient. Thus, the effect of concentration is manifested primarily in protein–protein interactions and the mobility of protein molecules.
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